Video transmission system, transmitting device, display device, video transmission method, and program

Abstract

A video transmission system (1) includes a delivery device (100), a display device (200), and a control unit (300). The delivery device comprises a delivery unit that divides a second video stream of a second bit rate into a plurality of transmission packets and delivers the transmission packets to the display device. The display device comprises a decoding unit (212) that uses the plurality of transmission packets to decode a display video, a display unit (213) that displays the display video, and a determination unit (214) that determines whether packet loss has occurred. When it is indicated that packet loss has occurred (i), the control unit controls encoding by the encoding unit so as to reduce the second bit rate, and when it is continually indicated for a prescribed period of time that packet loss has not occurred (ii), the control unit causes the delivery unit to deliver a plurality of dummy packets together with the plurality of transmission packets to the display device via a network.

Description

[Technical field]

[0001] The present disclosure relates to a video transmission system, a transmitting device, a display device, a video transmission method, and a program. [Background technology]

[0002] Patent document 1 discloses an IP gateway device that automatically measures the traffic conditions of an IP network by sending pseudo RTP packets for bandwidth measurement and calculating the loss rate, and performs channel restrictions on incoming and outgoing voice data communicated via the IP network based on the measurement results. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-171293 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a video transmission system and the like that can appropriately adjust the bit stream of a video stream to be transmitted in accordance with the communication bandwidth of a network. [Means for solving the problem]

[0005] A video transmission system in the present disclosure is a video transmission system including a transmitting device that transmits a video stream, a display device that receives the video stream and displays a video represented by the video stream and is separate from the transmitting device, and a control unit, wherein the transmitting device includes an encoding unit that encodes the first video stream such that a first video stream having a first bit rate becomes a second bit rate that is equal to or lower than the first bit rate, and generates a second video stream, and a transmitting unit that divides the second video stream into a plurality of transmission packets and transmits a plurality of packets including the plurality of transmission packets to the display device via a network, and the display device includes a receiving unit that receives the plurality of packets, The display device includes a decoding unit that generates the second video stream using the plurality of transmission packets and decodes a display image from the second video stream, a display unit that displays the display image, and a judgment unit that judges whether or not packet loss has occurred based on the plurality of packets received by the receiving unit, wherein the control unit (i) controls the encoding by the encoding unit to reduce the second bit rate when the judgment result by the judgment unit indicates that packet loss has occurred, and (ii) causes the transmitting unit to transmit a plurality of dummy packets together with the plurality of transmission packets via the network to the display device when the judgment result indicates that packet loss has not occurred for a predetermined consecutive period of time.

[0006] Further, a transmitting device in the present disclosure is a transmitting device included in a video transmission system including a transmitting device that transmits a video stream, a display device that receives the video stream and displays a video represented by the video stream and is separate from the transmitting device, and a control unit, the transmitting device including: an encoding unit that encodes the first video stream so that a first video stream having a first bit rate becomes a second bit rate that is lower than the first bit rate, thereby generating a second video stream; and a transmitting unit that divides the second video stream into a plurality of transmission packets and transmits a plurality of packets including the plurality of transmission packets to the display device via a network, wherein the control unit (i) controls the encoding by the encoding unit to reduce the second bit rate when a determination result of whether or not packet loss has occurred in the display device indicates that packet loss has occurred, and (ii) causes the transmitting unit to transmit a plurality of dummy packets together with the plurality of transmission packets to the display device via the network when the determination result indicates that packet loss has not occurred for a predetermined consecutive period of time.

[0007] Further, a display device according to the present disclosure is a display device included in a video transmission system including a transmitting device that transmits a video stream, a display device that receives the video stream and displays a video represented by the video stream and is separate from the transmitting device, and a control unit, the display device including: a receiving unit that receives a plurality of packets including a plurality of transmission packets from the transmitting device via a network; a decoding unit that generates a second video stream using the plurality of transmission packets and decodes a display video from the second video stream; a display unit that displays the display video; and a determination unit that determines whether or not a packet loss has occurred based on the plurality of packets received by the receiving unit. the plurality of transmission packets are generated by the transmitting device by dividing the second video stream having a second bit rate equal to or less than the first bit rate, the second video stream having a second bit rate generated by encoding a first video stream having a first bit rate, and the control unit (i) controls the encoding by the transmitting device to reduce the second bit rate when a determination result by the determination unit indicates that packet loss has occurred, and (ii) causes the transmitting device to transmit a plurality of dummy packets together with the plurality of transmission packets to the display device via the network when the determination result indicates that no packet loss has occurred for a predetermined consecutive period of time.

[0008] Further, a video transmission method in the present disclosure is a video transmission method by a video transmission system including a transmitting device that transmits a video stream, a display device that receives the video stream and displays a video represented by the video stream and is separate from the transmitting device, and a control unit, in which the transmitting device encodes the first video stream such that a first video stream having a first bit rate becomes a second bit rate that is equal to or lower than the first bit rate, generates a second video stream, divides the second video stream into a plurality of transmission packets, and transmits a plurality of packets including the plurality of transmission packets to the display device via a network, and the display device encodes the plurality of packets. the control unit receives a plurality of transmission packets, generates the second video stream using the plurality of transmission packets, decodes a display video from the second video stream, displays the display video, and determines whether or not packet loss has occurred based on the plurality of received packets, wherein the control unit (i) controls the encoding by the transmitting device to reduce the second bit rate when the determination result by the display device indicates that packet loss has occurred, and (ii) causes the transmitting device to transmit a plurality of dummy packets together with the plurality of transmission packets to the display device via the network when the determination result indicates that no packet loss has occurred for a predetermined consecutive period of time.

[0009] Furthermore, these general or specific aspects may be realized by a system, a method, an integrated circuit, a computer program, or a recording medium such as a computer-readable CD-ROM, or may be realized by any combination of a system, a method, an integrated circuit, a computer program, and a recording medium. Effect of the Invention

[0010] The video transmission system and the like according to the present disclosure can appropriately adjust the bit stream of the video stream to be transmitted in accordance with the communication bandwidth of the network. [Brief description of the drawings]

[0011] [Figure 1]FIG. 1 is a diagram illustrating an outline of a video transmission system according to an embodiment. [Diagram 2] FIG. 2 is a diagram illustrating an example of a hardware configuration of a video transmission system according to an embodiment. [Diagram 3] FIG. 3 is a diagram illustrating an example of a functional configuration of a video transmission system according to an embodiment. [Figure 4] FIG. 4 is a diagram showing the relationship between the communication state of wireless communication and the control of the encoding rate. [Diagram 5] FIG. 5 is a diagram for explaining the control of the encoding rate by the control unit. [Figure 6] FIG. 6 is a diagram for explaining a case where a packet loss occurs in packets of a video stream. [Figure 7] FIG. 7 is a diagram for explaining control for giving priority to transmitting packets of a video stream over dummy packets. [Figure 8] FIG. 8 illustrates an example of the configuration of an IP header. [Figure 9] FIG. 9 is a diagram showing the transition of the number of packet losses when a plurality of transmission packets are transmitted with priority over dummy packets. [Figure 10] FIG. 10 is a flowchart showing an example of viewing control in the display device. [Figure 11] FIG. 11 is a flowchart showing an example of adaptive rate control in the display device. [Figure 12] FIG. 12 is a flowchart showing an example of transmission control in the transmitting device. [Figure 13] FIG. 13 is a flowchart showing an example of adaptive rate control in the transmitting device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A video transmission system according to an embodiment of the present disclosure includes a transmitting device that transmits a video stream, a display device that receives the video stream and displays a video represented by the video stream and is separate from the transmitting device, and a control unit, wherein the transmitting device includes an encoding unit that encodes the first video stream at a first bit rate to a second bit rate that is equal to or lower than the first bit rate, and generates a second video stream, and a transmitting unit that divides the second video stream into a plurality of transmission packets and transmits a plurality of packets including the plurality of transmission packets to the display device via a network, and the display device includes a receiving unit that receives the plurality of packets. a decoding unit that generates the second video stream using the plurality of transmission packets and decodes a display image from the second video stream; a display unit that displays the display image; and a judgment unit that judges whether or not packet loss has occurred based on the plurality of packets received by the receiving unit, wherein the control unit (i) controls the encoding by the encoding unit to reduce the second bit rate when the judgment result by the judgment unit indicates that packet loss has occurred, and (ii) causes the transmitting unit to transmit a plurality of dummy packets together with the plurality of transmission packets to the display device via the network when the judgment result indicates that packet loss has not occurred for a predetermined consecutive period of time.

[0013] According to this, when packet loss occurs in the display device, the control unit determines that the communication bandwidth between the transmitting device and the display device is insufficient for transmitting the video stream, and controls the encoding by the encoding unit of the transmitting device to reduce the second bit rate. Therefore, the transmitting device can reduce the bit rate of the video stream in accordance with the communication bandwidth, and can transmit the video stream from the transmitting device to the display device without loss.

[0014] Furthermore, when the display device indicates that no packet loss has occurred for a predetermined period of time, the control unit determines that the communication bandwidth is sufficient for transmitting the video stream, and causes the transmitting device to transmit a plurality of dummy packets together with a plurality of transmission packets to the display device. This causes the transmitting device to transmit data to the display device with a bit rate that is larger by the amount of the dummy packets. Thus, it is possible to determine that there is more room in the communication bandwidth than before the dummy packets were transmitted.

[0015] Therefore, the bit stream of the video stream to be transmitted can be appropriately adjusted according to the communication bandwidth of the network.

[0016] Furthermore, the control unit may control the encoding by the encoding unit so as not to change the second bit rate when the determination result indicates that no packet loss has occurred for a predetermined consecutive period of time.

[0017] As a result, the transmitting device transmits data with a bit rate that is larger by the amount of the dummy packets to the display device. Therefore, it is possible to measure that there is more room in the communication band than before the dummy packets were transmitted. In addition, since dummy packets may be lost when the communication band narrows and packet loss occurs, it is possible to transmit multiple packets from the transmitting device to the display device without missing any video stream.

[0018] In addition, when the transmitting unit is transmitting the multiple dummy packets and the determination result indicates that no packet loss has occurred for the specified period of time, the control unit may control the encoding by the encoding unit to increase the second bit rate.

[0019] As a result, if it is determined that the communication bandwidth is sufficient for transmitting the video stream during dummy packet transmission, the second bit rate is increased, so that the video quality can be improved if there is sufficient communication bandwidth.

[0020] Furthermore, when the control unit controls the encoding by the encoding unit to increase the second bit rate, the control unit may increase the second bit rate by an amount equivalent to a transmission rate of the plurality of dummy packets.

[0021] As a result, if it is determined during transmission of dummy packets that the communication bandwidth is sufficient for transmitting the video stream, the second bit rate is increased by the transmission rate of the multiple dummy packets, thereby improving the video quality when there is sufficient communication bandwidth.

[0022] In addition, when the transmission unit is transmitting the multiple dummy packets and the determination result indicates that packet loss has occurred, the control unit may cause the transmission unit to transmit the multiple packets not including the dummy packets to the display device via the network.

[0023] As a result, if it is determined during dummy packet transmission that the communication bandwidth between the transmitting device and the display device is insufficient for transmitting the video stream, transmission control is performed so that dummy packets are not sent, thereby reducing the transmission bit rate without degrading the video quality.

[0024] In addition, when the determination result indicates that packet loss has occurred when the transmitting unit is transmitting the multiple dummy packets, the control unit may further control the encoding by the encoding unit so as not to change the second bit rate.

[0025] As a result, if it is determined during transmission of dummy packets that the communication bandwidth between the transmitting device and the display device is insufficient for transmitting the video stream, encoding control is performed so as not to change the second bit rate, while transmission control is performed so as not to transmit dummy packets, thereby reducing the transmission bit rate without degrading the quality of the video.

[0026] Furthermore, when transmitting the plurality of dummy packets together with the plurality of transmission packets, the transmission unit may transmit the plurality of transmission packets with priority over the dummy packets.

[0027] Therefore, when the communication band becomes narrow and packet loss occurs, dummy packets are preferentially lost, so that the video stream can be transmitted from the transmitting device to the display device without any loss.

[0028] Furthermore, when transmitting the plurality of dummy packets, the transmission unit may transmit the plurality of dummy packets at a fixed transmission rate.

[0029] This makes it possible to adjust the transmission rate at which data is transmitted from the transmitting device by transmitting dummy packets or stopping the transmission of dummy packets.

[0030] In addition, these general or specific aspects may be realized by a transmitting device, a display device, an integrated circuit, a computer program, or a non-transitory recording medium such as a computer-readable CD-ROM, or may be realized by any combination of a transmitting device, a display device, an integrated circuit, a computer program, and a non-transitory recording medium.

[0031] Hereinafter, the embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters or duplicate explanation of substantially the same configuration may be omitted. This is to avoid the following explanation becoming unnecessarily redundant and to facilitate understanding by those skilled in the art.

[0032] The inventor(s) provide the accompanying drawings and the following description to enable those skilled in the art to fully understand the present disclosure, and do not intend for them to limit the subject matter described in the claims.

[0033] (Embodiment) Hereinafter, the embodiment will be described with reference to FIGS. 1 to 13. FIG.

[0034] [1-1. Configuration] FIG. 1 is a diagram illustrating an outline of a video transmission system according to an embodiment.

[0035] As shown in Fig. 1, the video transmission system 1 includes a transmitting device 100 that transmits a video stream, and a display device 200 that receives the video stream transmitted by the transmitting device 100 and displays the video represented by the video stream. The transmitting device 100 may obtain an audio stream corresponding to the video stream together with the video stream. The transmitting device 100 may obtain an encoded stream including the video stream and the audio stream. The display device 200 may receive the encoded stream and display the video of the video stream included in the encoded stream, as well as output the audio of the audio stream included in the encoded stream.

[0036] The transmitting device 100 acquires a video stream. The transmitting device 100 may be connected to an antenna (not shown), for example, and may acquire the video stream from a broadcast wave received by the antenna. The transmitting device 100 may acquire the video stream via a communication network, such as the Internet. The transmitting device 100 may acquire the video stream by playing video data stored in a recording medium, for example. Here, the recording medium may be, for example, a non-volatile memory, such as a hard disk drive (HDD) or a solid state drive (SSD), or an optical disk, such as a Blu-ray (registered trademark) disc (BD) or a digital versatile disc (DVD). When acquiring an encoded stream, the transmitting device 100 may acquire the encoded stream from the same source as in the case of acquiring the video stream described above.

[0037] The transmitting device 100 compresses the acquired video stream (hereinafter referred to as "first video stream") at an encoding rate according to the effective communication bandwidth of the network, and transmits the compressed video stream (hereinafter referred to as "second video stream") to the display device 200. The first video stream may be, for example, a video stream having a resolution of 4K or 8K.

[0038] The display device 200 is a device separate from the transmission device 100. The display device 200 is a device that is previously associated with the transmission device 100 as a destination of a video stream transmitted by the transmission device 100. The display device 200 is also previously associated with the transmission device 100 as a source that transmits a control signal to the transmission device 100.

[0039] The transmitting device 100 and the display device 200 can communicate with each other through a network. The transmitting device 100 transmits the second video stream to the display device 200 through the network. The display device 200 receives the second video stream from the transmitting device 100 through the network. The transmitting device 100 and the display device 200 may communicate with each other through wireless communication such as wireless LAN, or through wired communication such as wired LAN. The transmitting device 100 and the display device 200 may communicate with each other through wireless communication of a communication standard other than wireless LAN, or through wired communication of a communication standard other than wired LAN. The transmitting device 100 and the display device 200 may communicate with each other directly through a network not via other devices, or may communicate with each other indirectly through a network via other devices such as an access point. In the following, a case where the transmitting device 100 and the display device 200 communicate with each other directly through wireless communication not via other devices will be described as an example.

[0040] Fig. 2 is a diagram illustrating an example of a hardware configuration of a video transmission system according to an embodiment. Specifically, Fig. 2 is a diagram illustrating an example of a hardware configuration of each of a transmission device 100 and a display device 200.

[0041] <Hardware configuration of the transmitting device> As shown in FIG. 2, the transmitting device 100 includes a controller 101, a flash memory 102, a buffer memory 103, a tuner 104, an encoder 105, a network IF (Interface) 106, and a power supply 107.

[0042] The controller 101 is a control circuit that outputs various control instructions to the flash memory 102, the buffer memory 103, the tuner 104, the encoder 105, the network IF 106, and the power supply 107 in order to execute predetermined processing on the obtained first video stream. The controller 101 is a processing circuit for realizing the functions of the transmitting device 100.

[0043] Furthermore, the controller 101 may execute various processes in addition to outputting control instructions. For example, the controller 101 may have a function as a decoder that decodes the encoded stream acquired from the tuner 104 and acquires a first video stream by decoding. When the encoded stream is multiplexed (i.e., when the encoded stream includes a first video stream and a first audio stream), the controller 101 may demultiplex the encoded stream and decode the video encoded stream and audio encoded stream obtained by the demultiplexing into the first video stream and the first audio stream, respectively.

[0044] Furthermore, the controller 101 may divide the second video stream obtained by the encoder 105 into a plurality of transmission packets, and transmit a plurality of packets including the plurality of transmission packets to the display device 200 using the network IF 106. At this time, the controller 101 may also divide the first audio stream into a plurality of transmission packets, similar to the second video stream, and transmit them to the display device 200 using the network IF 106.

[0045] The controller 101 may be realized by a general-purpose processor such as a CPU that executes a predetermined control program, or may be realized by a dedicated circuit. The controller 101 may include multiple processors, may include multiple dedicated circuits, or may include a processor and a dedicated circuit.

[0046] A predetermined control program is stored in the flash memory 102. The flash memory 102 may include a plurality of recording media.

[0047] The buffer memory 103 is a volatile storage area used as a work area when the controller 101 executes a program. The buffer memory 103 is, for example, a RAM (Random Access Memory). The buffer memory 103 may be included in the controller 101.

[0048] The tuner 104 converts an analog signal constituting a broadcast wave received by an antenna (not shown) into an encoded stream, which is a digital signal, and outputs the encoded stream obtained by the conversion to the controller 101 .

[0049] The encoder 105 encodes the obtained first video stream and outputs the encoded second video stream. The encoder 105 generates the second video stream, for example, by encoding the first video stream so that it becomes a bit stream specified by the controller 101. The encoder 105 may encode the first video stream so that the intraframe encoding rate or the interframe encoding rate becomes a bit stream specified by the controller 101.

[0050] Furthermore, the encoder 105 may encode the first video stream into a bit stream specified by the controller 101 by reducing the resolution of each frame of the first video stream, that is, by performing a process of compressing each frame. Furthermore, the encoder 105 may encode the first video stream into a bit stream specified by the controller 101 by reducing the frame rate of the first video stream. The encoder 105 may encode the first video stream into a bit stream specified by the controller 101 by performing a process on the first video stream that combines a process of compressing each frame and a process of reducing the frame rate.

[0051] The bit rate specified by the controller 101 may be the same as the bit rate of the primary video stream. In this case, the encoder 105 may output the primary video stream as is.

[0052] The network IF 106 is a communication interface for transmitting data to and from the display device 200. The network IF 106 may be, for example, an interface for wireless communication such as a wireless LAN interface. The network IF 106 may be, for example, a wireless LAN (Local Area Network) interface conforming to the IEEE802.11a, b, g, n, ac, and ax standards.

[0053] The power supply 107 receives power from an external power supply such as a commercial power supply or an external battery, and supplies power to the components inside the transmission device 100 .

[0054] <<Hardware configuration of the display device>> The display device 200 also includes a controller 201 , a flash memory 202 , a buffer memory 203 , a display device 204 , a speaker 205 , a network IF (Interface) 206 , an input IF 207 , and a power supply 208 .

[0055] The controller 201 is a control circuit that outputs various control instructions to the flash memory 202, the buffer memory 203, the display device 204, the speaker 205, the network IF 206, the input IF 207, and the power supply 208 in order to execute a process of receiving a plurality of transmission packets in which the second video stream has been packetized, a process of displaying a video for display based on the received plurality of transmission packets, etc. The controller 201 is a processing circuit for realizing the functions of the display device 200.

[0056] Furthermore, the controller 201 may execute various processes in addition to outputting control instructions. The controller 201 may have a function as a decoder that generates a second video stream from a plurality of transmission packets received by the network IF 206 and decodes a display video from the second video stream. When the plurality of transmission packets includes data of the second video stream and data of the first audio stream, the controller 201 may further have a function as a decoder that generates a first audio stream from the plurality of transmission packets and decodes an output audio from the first audio stream.

[0057] The controller 201 may be realized by a general-purpose processor such as a CPU that executes a predetermined control program, or may be realized by a dedicated circuit. The controller 201 may include multiple processors, may include multiple dedicated circuits, or may include a processor and a dedicated circuit.

[0058] A predetermined control program is stored in the flash memory 202. The flash memory 202 may include a plurality of recording media.

[0059] The buffer memory 203 is a volatile storage area used as a work area when the controller 201 executes a program. The buffer memory 203 is, for example, a RAM (Random Access Memory). The buffer memory 203 may be included in the controller 201.

[0060] The display device 204 displays a display image obtained from the second video stream output by the controller 201. The display device 204 is, for example, a liquid crystal display or an organic EL (Electro-Luminescence) display.

[0061] The speaker 205 outputs an output sound obtained from the first audio stream output by the controller 201 .

[0062] The network IF 206 is a communication interface for transmitting data to and from the transmitting device 100. The network IF 206 may be, for example, an interface for wireless communication such as a wireless LAN interface. The network IF 206 may be, for example, a wireless LAN (Local Area Network) interface conforming to at least one of the standards of IEEE802.11a, b, g, n, ac, and ax.

[0063] The input IF 207 is an interface for receiving input from a user. The input IF 207 may be a pointing device such as a mouse, a touch pad, a touch panel, or a trackball, or may be a keyboard. The input IF 207 may also be a receiving unit that receives a control signal output from a remote control (not shown) that receives an input from a user in response to the input received by the remote control.

[0064] The power supply 208 receives power from an external power source such as a commercial power source or an external battery, and supplies power to the components inside the transmitting device 100 .

[0065] Fig. 3 is a diagram showing an example of a functional configuration of a video transmission system according to an embodiment. Specifically, Fig. 3 is a diagram showing an example of a functional configuration of each of a transmission device 100 and a display device 200.

[0066] <Functional configuration of the transmitting device> As shown in FIG. 3, the transmission device 100 includes, as its functional components, an acquisition unit 111, a control unit 112, and a communication unit 113.

[0067] The acquisition unit 111 acquires the first video stream. The acquisition unit 111 may acquire the first video stream from, for example, a broadcast wave. The acquisition unit 111 may further acquire an audio stream corresponding to the first video stream. The acquisition unit 111 may acquire the audio stream corresponding to the first video stream from, for example, a broadcast wave. The acquisition unit 111 is realized by, for example, the controller 101, the tuner 104, the flash memory 102, and the buffer memory 103. Note that the acquisition unit 111 may acquire the first video stream from the Internet, a recording medium, or the like.

[0068] The control unit 112 encodes the first video stream at the first bit rate so that the first video stream is at the second bit rate, thereby generating a second video stream. That is, the control unit 112 generates a second video stream at the second bit rate by encoding the first video stream at the first bit rate. The second bit rate is a bit rate equal to or lower than the first bit rate. Specifically, the control unit 112 may encode the first video stream at the second bit rate by reducing the resolution of each frame of the first video stream, that is, by performing a process of compressing each frame. The control unit 112 may also encode the first video stream at the second bit rate by reducing the frame rate of the first video stream. The control unit 112 may encode the first video stream at the second bit rate by performing a process of compressing each frame and a process of reducing the frame rate on the first video stream in combination. The control unit 112 is an example of an encoding unit included in the transmission device 100.

[0069] Furthermore, the control unit 112 may control the acquisition unit 111 in response to a control instruction received by the communication unit 113. Specifically, the control unit 112 may change the encoded stream acquired by the acquisition unit 111 by switching the broadcast wave received by the tuner 104 to a channel in response to the control instruction (channel selection instruction). Furthermore, the control unit 112 may change a second bit rate, which is a target when encoding and converting the first video stream into a second video stream, in response to the control instruction.

[0070] The control unit 112 is realized by, for example, the controller 101, the flash memory 102, the buffer memory 103, and the encoder 105.

[0071] The communication unit 113 performs wireless communication with the display device 200 to transmit and receive data. Specifically, the communication unit 113 divides the second video stream generated by the control unit 112 into a plurality of transmission packets, and transmits the plurality of packets including the plurality of transmission packets to the display device 200 by wireless communication. Specifically, the communication unit 113 divides the second video stream into a plurality of data units, and generates a plurality of transmission packets by packetizing the plurality of data units. The communication unit 113 transmits a plurality of packets including the plurality of transmission packets one by one sequentially to the display device 200 by wireless communication. Each of the plurality of transmission packets may be assigned with identification information such as a packet sequence number. In other words, the plurality of transmission packets may be indicated with information indicating the order in which they are transmitted. The communication unit 113 is an example of a transmission unit included in the transmission device 100.

[0072] Furthermore, the communication unit 113 may receive a control instruction from the display device 200. The communication unit 113 outputs the received control instruction to the control unit 112.

[0073] The communication unit 113 is realized by, for example, the controller 101, the flash memory 102, the buffer memory 103, and the network IF 106.

[0074] <Functional configuration of the display device> The display device 200 includes, as its functional components, a communication unit 211, a decoding unit 212, a display unit 213, a determination unit 214, a reception unit 215, and a control unit 300.

[0075] The communication unit 211 performs wireless communication with the transmission device 100, and transmits and receives data. Specifically, the communication unit 211 receives a plurality of packets including a plurality of transmission packets. The communication unit 211 is an example of a receiving unit included in the display device 200.

[0076] Furthermore, the communication unit 211 may transmit to the transmission device 100 a control instruction corresponding to the input received by the reception unit 215. The input received by the reception unit 215 is, for example, an input indicating that the channel of the broadcast wave received by the tuner 104 is to be switched to a specified channel. The control instruction in this case is an instruction for switching the channel of the broadcast wave received by the tuner 104 to the specified channel. The communication unit 211 may transmit to the transmission device 100 a control instruction output from the control unit 300. The control instruction in this case will be described in the description of the control unit 300.

[0077] The communication unit 211 is realized by, for example, the controller 201, the flash memory 202, the buffer memory 203, and the network IF 206.

[0078] The decoding unit 212 generates a second video stream using a plurality of transmission packets included in the plurality of packets received by the communication unit 211. Then, the decoding unit 212 decodes a display video from the generated second video stream. The decoding unit 212 outputs the obtained display video to the display unit 213. The decoding unit 212 is realized by, for example, the controller 201, the flash memory 202, the buffer memory 203, and the like.

[0079] The display unit 213 displays the display video obtained by the decoding unit 212. The display unit 213 is realized by the display device 204, for example.

[0080] The determination unit 214 determines whether or not a packet loss has occurred based on a plurality of packets received by the communication unit 211. Specifically, the determination unit 214 checks the information indicating the order of transmission given to each of the plurality of packets, and determines whether or not a packet with a missing number exists. If a packet with a missing number exists, the determination unit 214 determines that a packet loss has occurred, and if a packet with a missing number does not exist, that is, if the information indicating the order of transmission is continuous for a plurality of packets, the determination unit 214 determines that a packet loss has not occurred. For example, each time the communication unit 211 receives a plurality of packets one by one, the determination unit 214 may determine whether or not the information indicating the order of transmission given to the packet is continuous with the information indicating the order of transmission given to the previously received packet, and may determine that a packet loss has occurred if the information is not continuous. Also, for example, the determination unit 214 may check the order of transmission given to each of the plurality of packets received by the communication unit 211 during a predetermined period, and may determine that a packet loss has occurred if the confirmed order is not continuous and a missing number exists. In this case, the determination unit 214 determines whether or not a packet loss has occurred for each of the multiple predetermined periods. The multiple predetermined periods may have overlapping periods as long as there is no period during which no determination is made, or may be continuous with adjacent predetermined periods without overlapping periods. In this way, the determination unit 214 periodically determines whether or not a packet loss has occurred.

[0081] The reception unit 215 receives an input from a user. The reception unit 215 transmits a control instruction corresponding to the received input to the transmission device 100 via the communication unit 211. As described above, the input received by the reception unit 215 is, for example, an input indicating that the channel of the broadcast wave received by the tuner 104 is to be switched to a specified channel. The control instruction in this case is an instruction to switch the channel of the broadcast wave received by the tuner 104 to the specified channel.

[0082] <<Control Unit>> Fig. 4 is a diagram showing the relationship between the communication state of wireless communication and the control of the encoding rate Fig. 5 is a diagram for explaining the control of the encoding rate by the control unit.

[0083] As shown in FIG. 4, the control unit 300 is a device for preventing the video stream transmitted to the display device 200 from being interrupted by controlling the encoding rate (i.e., the second bit rate of the second video stream) in response to a change in the communication state in the wireless communication between the transmission device 100 and the display device 200. The control unit 300 controls the encoding in the transmission device 100 in real time in response to the determination result by the determination unit 214. For example, as shown in FIG. 5, when the determination result by the determination unit 214 indicates that a packet loss has occurred, the control unit 300 determines that the wireless communication state has changed and the wireless communication effective rate has decreased. When the control unit 300 determines that the wireless communication effective rate has decreased, the control unit 300 decreases the encoding rate by decreasing the second bit rate, which is a target value for encoding in the control unit 112 of the transmission device 100. The control unit 300 decreases the second bit rate by a constant width. For this reason, the control unit 300 repeats the process of decreasing the second bit rate by a constant width until no packet loss is detected. It should be noted that instead of reducing the second bit rate by a fixed amount, the second bit rate may be reduced by a transmission rate that is a fixed ratio relative to the transmission rate of the video stream so as not to cause congestion on the network.

[0084] On the other hand, as shown in FIG. 5, when the determination result by the determination unit 214 indicates that no packet loss has occurred for a predetermined period of time, the control unit 300 determines that the wireless communication is being performed stably. When the control unit 300 determines that the wireless communication is being performed stably, the control unit 300 causes the transmitting device 100 to transmit dummy packets in addition to the second video stream currently being transmitted at the second bit rate, and determines whether or not a packet loss will occur. In this way, the control unit 300 determines whether or not the transmitting device 100 can stably transmit data at a bit rate corresponding to the dummy packets added to the second video stream to the display device 200. When the control unit 300 determines that the data at a bit rate corresponding to the dummy packets added to the second video stream can be stably transmitted to the display device 200, the control unit 300 increases the second bit rate, which is a target value for encoding in the control unit 112 of the transmitting device 100, thereby increasing the encoding rate.

[0085] In this way, the control unit 300 detects a change in the wireless communication state by determining whether or not a packet loss has occurred, and controls the encoding rate in the transmission device 100 in real time according to the detected change. This allows the transmission device 100 to transmit the second video stream so that the video stream displayed on the display device 200 is not interrupted, and allows the display device 200 to display a display video of the highest possible quality according to the wireless communication state.

[0086] Note that the control unit 300 generates a control instruction for controlling the encoding of the control unit 112 of the transmitting device 100, and transmits the generated control instruction to the transmitting device 100 via the communication unit 211. As a result, the control unit 300 controls the encoding in the transmitting device 100 according to the determination result by the determination unit 214. Note that hereinafter, the determination result by the determination unit 214 may be referred to as the "determination result".

[0087] The RTP packets in FIG. 5 are an example of transmission packets.

[0088] The specific processing in the control unit 300 will now be described.

[0089] When the determination result indicates that a packet loss has occurred, the control unit 300 generates a control instruction to reduce the second bit rate, which is a target value for encoding by the control unit 112 in the transmitting device 100, and transmits the generated control instruction to the transmitting device 100. In other words, when the determination result indicates that a packet loss has occurred, the control unit 300 generates a control instruction to set a bit rate smaller than the current second bit rate as a target value for encoding, and transmits the generated control instruction to the transmitting device 100. The transmitting device 100 that has received this control instruction converts (encodes) the first video stream into the second video stream so that the bit rate becomes smaller than the current second bit rate in accordance with the received control instruction. In this way, when the determination result by the determination unit 214 indicates that a packet loss has occurred, the control unit 300 controls the encoding by the control unit 112 to reduce the second bit rate.

[0090] Furthermore, when the determination result indicates that no packet loss has occurred for a predetermined time (e.g., 10 seconds), the control unit 300 generates a control instruction to cause the communication unit 113 of the transmitting device 100 to transmit a plurality of dummy packets to the display device 200 via wireless communication together with the plurality of transmission packets, and transmits the generated control instruction to the transmitting device 100. The transmitting device 100, which has received this control instruction, causes the communication unit 113 of the transmitting device 100 to transmit a plurality of dummy packets to the display device 200 via wireless communication together with the plurality of transmission packets in response to the received control instruction. In this way, when the determination result indicates that no packet loss has occurred for a predetermined time, the control unit 300 causes the communication unit 113 of the transmitting device 100 to transmit a plurality of dummy packets to the display device 200 via wireless communication together with the plurality of transmission packets.

[0091] Furthermore, when the determination result indicates that no packet loss has occurred for a predetermined period of time, the control unit 300 may control the encoding by the control unit 112 so as not to change the second bit rate. Specifically, the control unit 300 may not generate a control instruction to change the second bit rate, or may generate a control instruction to set the same bit rate as the current second bit rate as the target value for encoding, and transmit the generated control instruction to the transmitting device 100.

[0092] However, if packet loss occurs when communication unit 113 of transmitting device 100 transmits a plurality of dummy packets and determines whether data at a bit rate corresponding to the addition of the dummy packets to the second video stream can be stably transmitted to display device 200, there is a risk of loss in packets of the video stream (transmission packets) as shown in Fig. 6. Fig. 6 is a diagram for explaining a case in which packet loss occurs in packets of the video stream.

[0093] For this reason, when the communication unit 113 of the transmitting device 100 transmits a plurality of dummy packets together with a plurality of transmission packets, the communication unit 113 may transmit the plurality of transmission packets with priority over the dummy packets. This makes it possible to suppress packet loss of video packets when the amount of data to be transmitted is increased by transmitting dummy packets, as shown in Fig. 7. Fig. 7 is a diagram for explaining control for transmitting packets of a video stream with priority over dummy packets.

[0094] The communication unit 113 of the transmitting device 100 transmits a plurality of transmission packets with priority over dummy packets, for example, by using a mechanism of Quality of Service (QoS). Specifically, as shown in Fig. 8, the transmitting device 100 may set the DSCP (Differentiated Services Code Point) values ​​of the packet headers (IP headers) of a plurality of packets including a video packet and a dummy packet so that the DSCP value of the video packet is greater than the DSCP value of the dummy packet, so that the plurality of transmission packets are transmitted with priority over the dummy packets. For example, the DSCP value of the video packet may be set to 40, and the DSCP value of the dummy packet may be set to 0. Note that Fig. 8 is a diagram showing an example of the configuration of an IP header.

[0095] FIG. 9 is a diagram showing the transition of the number of packet losses when a plurality of transmission packets are transmitted with priority over dummy packets.

[0096] As shown in FIG. 9, by giving priority to transmitting a plurality of transmission packets over dummy packets, it is possible to make the packet loss of dummy packets greater than the packet loss of transmission packets.

[0097] Furthermore, when the communication unit 113 of the transmitting device 100 transmits a plurality of dummy packets and the determination result indicates that no packet loss has occurred for a predetermined period of time, the control unit 300 generates a control instruction to increase the second bit rate, which is the target value of encoding, and transmits the generated control instruction to the transmitting device 100. In other words, when the communication unit 113 of the transmitting device 100 transmits a plurality of dummy packets and the determination result indicates that no packet loss has occurred for a predetermined period of time, the control unit 300 generates a control instruction to set a bit rate higher than the current second bit rate as the target value of encoding, and transmits the generated control instruction to the transmitting device 100. The transmitting device 100, which has received this control instruction, converts (encodes) the first video stream into the second video stream so that the bit rate becomes higher than the current second bit rate in response to the received control instruction. In this way, when the communication unit 113 transmits a plurality of dummy packets and the determination result indicates that no packet loss has occurred for a predetermined period of time, the control unit 300 controls the encoding by the control unit 112 to increase the second bit rate. When the control unit 300 controls the encoding by the control unit 112 so as to increase the second bit rate, the control unit 300 increases the second bit rate by the transmission rate of the multiple dummy packets.

[0098] When the communication unit 113 of the transmitting device 100 transmits a plurality of dummy packets, if the determination result indicates that a packet loss has occurred, the control unit 300 controls the encoding by the control unit 112 so as not to change the second bit rate. The control not to change the second bit rate is the same as described above.

[0099] In this case, the control unit 300 further generates a control instruction to cause the communication unit 113 to transmit a plurality of packets not including a dummy packet to the display device 200 by wireless communication, and transmits the generated control instruction to the transmission device 100. The transmission device 100, which has received this control instruction, causes the communication unit 113 to transmit a plurality of packets not including a dummy packet to the display device 200 in response to the received control instruction. In this way, when the communication unit 113 of the transmission device 100 transmits a plurality of dummy packets and the determination result indicates that a packet loss has occurred, the control unit 300 causes the communication unit 113 to transmit a plurality of packets not including a dummy packet to the display device 200 by wireless communication. In addition, when the communication unit 113 of the transmission device 100 transmits a plurality of dummy packets and the determination result indicates that a packet loss has occurred, the control unit 300 controls the encoding by the control unit 112 so as not to change the second bit rate.

[0100] When transmitting a plurality of dummy packets, the communication unit 113 of the transmitting device 100 may transmit the plurality of dummy packets at a fixed transmission rate (for example, 1 Mbps).

[0101] [1-2. Operation] The operation of the video transmission system 1 configured as above will now be described.

[0102] FIG. 10 is a flowchart showing an example of viewing control in the display device.

[0103] When the display device 200 receives a channel selection instruction from a user, the display device 200 transmits a channel selection instruction command indicating the channel selection instruction to the transmission device 100 (S11). The process of step S11 is a process performed by the reception unit 215 of the display device 200.

[0104] Next, the display device 200 starts adaptive rate control of the display device 200 (S12). The adaptive rate control of the display device 200 will be described in detail later with reference to FIG.

[0105] Next, the display device 200 receives the video stream by receiving the multiple packets transmitted from the transmission device 100 (S13). The process of step S13 is a process performed by the communication unit 211 of the display device 200.

[0106] Next, the display device 200 performs a process of detecting lost packets (S14). The detection results of this process are accumulated and stored in the flash memory 202.

[0107] Next, the display device 200 determines whether or not there is a lost packet, that is, whether or not a packet loss has occurred (S15). The processes of steps S14 and S15 are processes performed by the determination unit 214 of the display device 200.

[0108] When it is determined that a packet loss has occurred (Yes in S15), the display device 200 requests the transmitting device 100 to retransmit the packet that has been lost (S16), and receives the retransmitted packet (S17). The process of step S17 is performed by the communication unit 211 of the display device 200.

[0109] If the display device 200 determines that no packet loss has occurred (No in S15), or after step S17, it uses the multiple received packets to decrypt (decrypt) the video stream (encoded stream) encrypted by DTCP (Digital Transmission Content Protection) to generate a video stream (S18), and further decrypts the video to be displayed from the video stream (S19).

[0110] The processes in steps S18 and S19 are performed by the decoding unit 212 of the display device 200.

[0111] When step S19 is completed, the process returns to step S13.

[0112] FIG. 11 is a flowchart showing an example of adaptive rate control in the display device.

[0113] The display device 200 checks the packet loss state by referring to the packet loss detection results stored in the flash memory 202 (S21). The process of step S21 is a process performed by the determination unit 214.

[0114] Next, the display device 200 determines whether the counter T recorded in the flash memory 202 is less than 10 (S22).

[0115] When the display device 200 determines that the counter T is equal to or greater than 10 (No in S22), it resets the counter T to 0 (S23). The processes of steps S22 and S23 are performed by the control unit 300.

[0116] Next, the display device 200 determines whether or not a packet loss has occurred (S24). The process of step S24 is performed by the determination unit 214.

[0117] When the display device 200 determines that a packet loss has occurred (Yes in S24), it determines whether or not the transmitting device 100 is transmitting a dummy packet (S25). Specifically, the display device 200 may determine that the transmitting device 100 is transmitting a dummy packet when the display device 200 is receiving a dummy packet, and may determine that the transmitting device 100 is not transmitting a dummy packet when the display device 200 is not receiving a dummy packet. The process of step S25 is performed by the communication unit 211 of the display device 200.

[0118] If the display device 200 determines that the transmitting device 100 is transmitting dummy packets (Yes in S25), it transmits a dummy packet stop command (control instruction) to the transmitting device 100 to stop transmitting the dummy packets (S26).

[0119] When the display device 200 determines that the transmission device 100 is not transmitting a dummy packet (No in S25), it transmits a command (control instruction) to the transmission device 100 to change the encoding rate to a lower value (S27).

[0120] When it is determined that no packet loss has occurred (No in S24), the display device 200 determines whether or not the transmission device 100 is transmitting a dummy packet (S28). The process of step S28 is the same as the process of step S25.

[0121] When the display device 200 determines that the transmission device 100 is transmitting a dummy packet (Yes in S28), it transmits a command (control instruction) to the transmission device 100 to greatly change the encoding rate (S29).

[0122] If the display device 200 determines that the transmitting device 100 is not currently transmitting dummy packets (No in S25), it transmits a dummy packet start command (control instruction) to the transmitting device 100 to cause the transmitting device 100 to start transmitting dummy packets (S30).

[0123] After steps S26, S27, S29, and S30, the display device 200 sleeps (stands by) for one second, increments the value of the counter T by 1, and stores the incremented counter T in the flash memory 202 (S31).

[0124] The process of steps S25 to S31 is performed by the control unit 300.

[0125] When step S31 is completed, the process returns to step S21.

[0126] FIG. 12 is a flowchart showing an example of transmission control in the transmitting device.

[0127] The transmission device 100 receives a channel selection instruction command from the display device 200 (S41). The process of step S41 is a process performed by the communication unit 113 of the transmission device 100.

[0128] Next, the transmitting device 100 starts adaptive rate control of the transmitting device 100 (S42). Details of the adaptive rate control of the transmitting device 100 will be described later with reference to FIG.

[0129] Next, the transmission device 100 performs channel selection control to switch to the channel indicated by the received channel selection instruction command (S43). The process of step S43 is performed by the control unit 112.

[0130] Next, the transmitting device 100 encodes the first video stream to the initial rate, and generates a second video stream (S44).

[0131] Next, the transmitting device 100 waits to see whether encoding of the video stream in a predetermined section is completed (S45). The predetermined section is, for example, a random access section, or a GOP (Group Of Picture) section.

[0132] Next, the transmitting device 100 generates a video stream (encoded stream) encrypted by DTCP (Digital Transmission Content Protection) (S46). The processes of steps S44 to S46 are performed by the control unit 112.

[0133] Next, the transmission device 100 packetizes the generated encoded stream and transmits it to the display device 200 (S47). The process of step S47 is a process performed by the communication unit 113.

[0134] When step S47 is completed, the process returns to step S45.

[0135] FIG. 13 is a flowchart showing an example of adaptive rate control in the transmitting device.

[0136] The transmitting device 100 waits for reception of a command (control instruction) (S51). The process of step S51 is a process performed by the communication unit 113.

[0137] The transmitting device 100 determines whether the received command is a command to change the encoding rate, a command to start transmitting dummy packets, or a command to stop transmitting dummy packets (S52).

[0138] If the received command is a command to change the encoding rate ("change encoding rate" in S52), the transmitting device 100 changes the encoding rate to the encoding rate indicated by the command (S53).

[0139] If the received command is a command to start transmitting dummy packets ("START DUMMY" in S52), the transmitting device 100 starts transmitting dummy packets (S54).

[0140] If the received command is a command to stop the transmission of dummy packets ("Dummy Stop" in S52), the transmitting device 100 stops the transmission of dummy packets (S55). The processing of steps S53 to S55 is performed by the control unit 112.

[0141] When steps S53 to S55 are completed, the process returns to step S51.

[0142] [1-3. Effects, etc.] As described above, the video transmission system 1 according to the present embodiment includes the transmission device 100 that transmits a video stream, the display device 200 that receives the video stream and displays a video represented by the video stream and is separate from the transmission device 100, and the control unit 300. The transmission device 100 includes a control unit 112 and a communication unit 113. The control unit 112 encodes the first video stream so that the first video stream having a first bit rate becomes a second bit rate that is equal to or lower than the first bit rate, thereby generating a second video stream. The communication unit 113 divides the second video stream into a plurality of transmission packets, and transmits the plurality of packets including the plurality of transmission packets to the display device 200 by wireless communication. The display device 200 includes a communication unit 211, a decoding unit 212, a display unit 213, and a determination unit 214. The communication unit 211 receives the plurality of packets. The decoding unit 212 generates a second video stream using the plurality of transmission packets, and decodes a display image from the second video stream. The display unit 213 displays the display image. The determination unit 214 determines whether or not a packet loss has occurred based on the multiple packets received by the communication unit 211. When the determination result by the determination unit 214 indicates that a packet loss has occurred, the control unit 300 controls the encoding by the control unit 112 to reduce the second bit rate. When the determination result indicates that no packet loss has occurred for a predetermined continuous period of time, the control unit 300 causes the communication unit 113 to transmit multiple dummy packets together with the multiple transmission packets to the display device 200 via wireless communication.

[0143] According to this, when packet loss occurs in the display device 200, the control unit 300 determines that the communication bandwidth between the transmitting device 100 and the display device 200 is insufficient for transmitting the video stream, and controls the encoding by the control unit 112 of the transmitting device 100 to reduce the second bit rate. Therefore, the transmitting device 100 can reduce the bit rate of the video stream in accordance with the communication bandwidth, and can transmit the video stream from the transmitting device 100 to the display device 200 without any loss.

[0144] Furthermore, when the determination result indicates that no packet loss has occurred for a predetermined period of time, the control unit 300 determines that the communication bandwidth is sufficient for transmitting the video stream, and causes the transmitting device 100 to transmit a plurality of dummy packets together with a plurality of transmission packets to the display device 200. As a result, the transmitting device 100 transmits data with a bit rate that is higher by the amount of the dummy packets to the display device 200. Therefore, it can be determined that there is more room in the communication bandwidth than before the dummy packets were transmitted.

[0145] Therefore, the bit stream of the video stream to be transmitted can be appropriately adjusted according to the communication band of the wireless communication.

[0146] Furthermore, in the video transmission system 1 according to this embodiment, when the determination result indicates that no packet loss has occurred for a predetermined consecutive period of time, the control unit 300 controls the encoding by the control unit 112 so as not to change the second bit rate.

[0147] As a result, the transmitting device 100 transmits data with a bit rate that is larger by the amount of the dummy packets to the display device 200. Therefore, it is possible to measure that there is more room in the communication band than before the dummy packets were transmitted. In addition, since dummy packets may be lost when the communication band is narrowed and packet loss occurs, it is possible to transmit multiple packets from the transmitting device 100 to the display device 200 without missing any video stream.

[0148] Furthermore, in the video transmission system 1 according to this embodiment, when the communication unit 113 is transmitting multiple dummy packets and the determination result indicates that no packet loss has occurred for a predetermined period of time, the control unit 300 controls the encoding by the control unit 112 to increase the second bit rate.

[0149] As a result, if it is determined that the communication bandwidth is sufficient for transmitting the video stream during dummy packet transmission, the second bit rate is increased, so that the video quality can be improved if there is sufficient communication bandwidth.

[0150] Furthermore, in the video transmission system 1 according to this embodiment, when the control unit 300 controls the encoding by the control unit 112 to increase the second bit rate, the control unit 300 increases the second bit rate by the transmission rate of the multiple dummy packets.

[0151] As a result, if it is determined during transmission of dummy packets that the communication bandwidth is sufficient for transmitting the video stream, the second bit rate is increased by the transmission rate of the multiple dummy packets, thereby improving the video quality when there is sufficient communication bandwidth.

[0152] Furthermore, in the video transmission system 1 according to this embodiment, when the communication unit 113 is transmitting multiple dummy packets and the determination result indicates that packet loss has occurred, the control unit 300 causes the communication unit 113 to transmit multiple packets not including the dummy packets to the display device 200 via wireless communication.

[0153] As a result, if, during transmission of dummy packets, it is determined that the communication bandwidth between the transmitting device 100 and the display device 200 is insufficient for transmitting the video stream, the dummy packets are not transmitted, thereby making it possible to reduce the transmission bit rate without degrading the quality of the video.

[0154] Furthermore, in the video transmission system 1 according to this embodiment, when the communication unit 113 is transmitting multiple dummy packets and the determination result indicates that packet loss has occurred, the control unit 300 further controls the encoding by the control unit 112 so as not to change the second bit rate.

[0155] As a result, if it is determined during transmission of dummy packets that the communication bandwidth between the transmitting device 100 and the display device 200 is insufficient for transmitting the video stream, the second bit rate is not changed and no dummy packets are transmitted, thereby reducing the transmission bit rate without degrading the video quality.

[0156] Furthermore, in the video transmission system 1 according to the present embodiment, when the communication unit 113 transmits a plurality of dummy packets together with a plurality of transmission packets, the communication unit 113 transmits the plurality of transmission packets with priority over the dummy packets.

[0157] Therefore, when the communication band is narrowed and packet loss occurs, dummy packets are preferentially lost, so that the video stream can be transmitted from the transmitting device 100 to the display device 200 without any loss.

[0158] Furthermore, in the video transmission system 1 according to the present embodiment, when the communication unit 113 transmits a plurality of dummy packets, the communication unit 113 transmits the plurality of dummy packets at a fixed transmission rate.

[0159] This makes it possible to adjust the transmission rate at which data is transmitted from transmitting device 100 by transmitting dummy packets or stopping the transmission of dummy packets.

[0160] [1-4. Modifications] In the above embodiment, an example in which the control unit 300 is included in the display device 200 has been described, but the present invention is not limited to this. The control unit 300 may be included in the transmission device 100. In this case, the transmission device 100 periodically acquires the determination result by the determination unit 214 of the display device 200 from the display device 200. As a result, the control unit 300 can control the encoding in the transmission device 100 by executing the adaptive rate control described in FIG. 11 according to the determination result of the determination unit 214 and outputting a command to the control unit 112.

[0161] Furthermore, the control unit 300 may be separate from the transmission device 100 and the display device 200. In this case, the control unit 300 periodically acquires the determination result by the determination unit 214 of the display device 200 from the display device 200, and can control the encoding in the transmission device 100 by executing the adaptive rate control described in FIG.

[0162] Although the video transmission system and the like according to the embodiment of the present disclosure have been described above, the present disclosure is not limited to this embodiment.

[0163] Furthermore, each processing unit included in the video transmission system, the transmission device, the display device, etc. according to the above-mentioned embodiments is typically realized as an LSI, which is an integrated circuit. These may be individually implemented as single chips, or some or all of them may be included in a single chip.

[0164] The integrated circuit is not limited to an LSI, but may be realized by a dedicated circuit or a general-purpose processor. A field programmable gate array (FPGA) that can be programmed after the LSI is manufactured, or a reconfigurable processor that can reconfigure the connections and settings of the circuit cells inside the LSI may also be used.

[0165] In each of the above embodiments, each component may be implemented by dedicated hardware or by executing a software program suitable for each component. Each component may be implemented by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0166] The present disclosure may also be realized as a video transmission method, a transmission method, a display method, etc., executed by a video transmission system, a transmission device, a display device, etc.

[0167] In addition, the division of functional blocks in the block diagram is an example, and multiple functional blocks may be realized as one functional block, one functional block may be divided into multiple blocks, or some functions may be transferred to another functional block. Furthermore, the functions of multiple functional blocks having similar functions may be processed in parallel or in a time-sharing manner by a single piece of hardware or software.

[0168] In addition, the order in which each step is performed in the flowchart is merely an example for specifically explaining the present disclosure, and the steps may be performed in an order other than the above. In addition, some of the steps may be performed simultaneously (in parallel) with other steps.

[0169] Although the video transmission system, the transmission device, the display device, etc. according to one or more aspects have been described based on the embodiments, the present disclosure is not limited to these embodiments. As long as it does not deviate from the spirit of the present disclosure, various modifications conceived by a person skilled in the art to the present embodiment and forms constructed by combining components in different embodiments may also be included within the scope of one or more aspects. [Industrial Applicability]

[0170] The present disclosure is applicable to a video transmission system that can appropriately adjust the bit stream of a video stream transmitted according to the communication band of wireless communication. [Explanation of symbols]

[0171] 1. Video transmission system 100 Transmitting device 101, 201 Controller 102, 202 Flash memory 103, 203 Buffer memory 104 Tuner 105 Encoder 106, 206 Network Interface 107, 208 Power supply 111 Acquisition Department 112 Control section 113, 211 Communications Department 200 Display device 204 Display Device 205 Speaker 207 Input IF 212 Decoding section 213 Display section 214 Judgment section 215 Reception 300 Control section

Claims

1. A video transmission system including a transmitting device that transmits a video stream, a display device that receives the video stream and displays a video represented by the video stream and is separate from the transmitting device, and a control unit, The transmitting device an encoding unit that encodes a first video stream having a first bit rate into a second bit rate that is equal to or lower than the first bit rate, to generate a second video stream; a transmission unit that divides the second video stream into a plurality of transmission packets and transmits a plurality of packets including the plurality of transmission packets to the display device via a network, The display device includes: A receiving unit for receiving the plurality of packets; a decoding unit that generates the second video stream using the plurality of transmission packets and decodes a display video from the second video stream; A display unit that displays the display image; a determination unit that determines whether or not a packet loss has occurred based on the plurality of packets received by the receiving unit, The control unit is (i) when a determination result by the determination unit indicates that a packet loss has occurred, the encoding by the encoding unit is controlled so as to reduce the second bit rate by a fixed width or reduce the second bit rate by a fixed ratio of a transmission rate; (ii) when the determination result indicates that no packet loss has occurred for a predetermined period of time, causing the transmitting unit to transmit a plurality of dummy packets together with the plurality of transmission packets to the display device via the network; Video transmission system.

2. The transmitting device further includes an acquisition unit that acquires the first video stream from outside the transmitting device, The encoding is controlled in real time.

2. The video transmission system according to claim 1.

3. The control unit controls the encoding by the encoding unit so as not to change the second bit rate when the determination result indicates that no packet loss has occurred for a predetermined period of time.

2. The video transmission system according to claim 1.

4. When the determination result indicates that no packet loss has occurred for the predetermined period of time while the transmission unit is transmitting the plurality of dummy packets, the control unit controls the encoding by the encoding unit to increase the second bit rate. The video transmission system according to any one of claims 1 to 3.

5. When the control unit controls the encoding by the encoding unit so as to increase the second bit rate, the control unit increases the second bit rate by an amount corresponding to a transmission rate of the plurality of dummy packets.

5. The video transmission system according to claim 4.

6. When the determination result indicates that a packet loss has occurred while the transmission unit is transmitting the plurality of dummy packets, the control unit causes the transmission unit to transmit the plurality of packets not including the dummy packets to the display device via the network. The video transmission system according to any one of claims 1 to 3.

7. When the determination result indicates that a packet loss occurs in a case where the transmission unit is transmitting the plurality of dummy packets, the control unit further controls the encoding by the encoding unit so as not to change the second bit rate.

7. A video transmission system according to claim 6.

8. When transmitting the plurality of dummy packets together with the plurality of transmission packets, the transmission unit transmits the plurality of transmission packets with priority over the dummy packets. The video transmission system according to any one of claims 1 to 3.

9. Each of the plurality of transmission packets and each of the plurality of dummy packets include a priority, The priority included in each of the plurality of transmission packets is set to be higher than the priority included in each of the plurality of dummy packets. The video transmission system according to claim 8.

10. When transmitting the plurality of dummy packets, the transmission unit transmits the plurality of dummy packets at a fixed transmission rate. The video transmission system according to any one of claims 1 to 3.

11. A video transmission system including a transmitting device that transmits a video stream, a display device that receives the video stream and displays a video represented by the video stream and is separate from the transmitting device, and a control unit, the transmitting device comprising: an encoding unit that encodes a first video stream having a first bit rate into a second bit rate that is equal to or lower than the first bit rate, to generate a second video stream; a transmission unit that divides the second video stream into a plurality of transmission packets and transmits a plurality of packets including the plurality of transmission packets to the display device via a network, The control unit is (i) when a determination result as to whether or not a packet loss has occurred in the display device indicates that a packet loss has occurred, the encoding by the encoding unit is controlled so as to reduce the second bit rate by a fixed width or to reduce the second bit rate by a fixed proportion of a transmission rate, and (ii) when the determination result indicates that no packet loss has occurred for a predetermined consecutive period of time, the transmitting unit is caused to transmit a plurality of dummy packets together with the plurality of transmission packets to the display device via the network. Transmitting device.

12. A display device included in a video transmission system including a transmitting device that transmits a video stream, a display device that receives the video stream and displays a video represented by the video stream and is separate from the transmitting device, and a control unit, a receiving unit that receives a plurality of packets including a plurality of transmission packets from the transmitting device via a network; a decoding unit that generates a second video stream using the plurality of transmission packets and decodes a display video from the second video stream; A display unit that displays the display image; a determination unit that determines whether or not a packet loss has occurred based on the plurality of packets received by the receiving unit, the plurality of transmission packets are generated by the transmitting device by dividing a second video stream having a second bit rate equal to or lower than the first bit rate, the second video stream being generated by encoding a first video stream having a first bit rate; The control unit is (i) when the determination result by the determination unit indicates that a packet loss has occurred, the second bit rate is reduced by a fixed amount, or the encoding by the transmission device is controlled so as to reduce the second bit rate by a fixed proportion of the transmission rate; and (ii) when the determination result indicates that no packet loss has occurred for a predetermined consecutive period of time, the transmission device is caused to transmit a plurality of dummy packets together with the plurality of transmission packets to the display device via the network. Display device.

13. A video transmission method for a video transmission system including a transmitting device that transmits a video stream, a display device that receives the video stream and displays a video represented by the video stream and is separate from the transmitting device, and a control unit, comprising: The transmitting device encoding a first video stream having a first bit rate into a second bit rate that is equal to or lower than the first bit rate, thereby generating a second video stream; Dividing the second video stream into a plurality of transmission packets, and transmitting a plurality of packets including the plurality of transmission packets to the display device via a network; The display device includes: receiving the plurality of packets; generating the second video stream using the plurality of transmission packets, and decoding a display image from the second video stream; Displaying the display image; determining whether or not a packet loss has occurred based on the received packets; The control unit is (i) when the determination result by the display device indicates that a packet loss has occurred, controlling the encoding by the transmission device so as to reduce the second bit rate by a fixed width or reduce the second bit rate by a fixed ratio of a transmission rate; (ii) when the determination result indicates that no packet loss has occurred for a predetermined period of time, causing the transmitting device to transmit a plurality of dummy packets together with the plurality of transmission packets to the display device via the network; Video transmission method.

14. A program for causing a computer to execute the video transmission method according to claim 13.

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