Protocol conversion circuit and protocol conversion method

Abstract

The invention relates to a protocol conversion circuit and a protocol conversion method. The invention discloses a protocol conversion circuit and a protocol conversion method. The protocol conversion circuit comprises a DP signal receiver, a control analysis circuit, a downstream transmitter and a picture buffer. The DP signal receiver analyzes the DP signal to obtain video data and packet information. The control analysis circuit judges that the packet information indicates to start a live broadcast (Live) function or a Panel Replay (PR) function, and controls the picture buffer to store the received current video data and transmit the received current video data to a downstream transmitter when judging that the live broadcast function is started; and when it is judged that the PR function is started, controlling the picture buffer to abandon the received current video data, or updating previous video data stored in the picture buffer in a specified range in the current video data, and transmitting the latest video data to the downstream transmitter so as to output the target signal to the second electronic device.

Description

Technical Field

[0001] The present invention relates to a circuit and a method, and in particular to a protocol conversion circuit and a protocol conversion method. Background Art

[0002] The existing DisplayPort (DP) standard declares a function called Panel Replay, which allows the DP sink display to operate in two different modes. One is the Live mode that plays the video data provided by the current video source in real time, and the other is the Panel Replay (PR) mode that plays the video data stored in the internal buffer.

[0003] Although this technology can achieve effective power saving in specific situations, it is limited to the DP-related product ecosystem. Products of other specifications cannot enjoy the advantages provided by this function. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a protocol conversion circuit and a protocol conversion method to address the deficiencies of the prior art, which can extend the Panel Replay function to products beyond the DP specification.

[0005] In order to solve the above-mentioned technical problems, one of the technical solutions adopted by the present invention is to provide a protocol conversion circuit, including a display port (DisplayPort, DP) signal receiver, a control analysis circuit, a downstream transmitter and a picture buffer. The DP signal receiver receives a DP signal from a first electronic device, and is configured to parse the DP signal to obtain video data and packet information. The control analysis circuit is configured to determine whether the packet information indicates the activation of a live broadcast (Live) function or a panel replay (Panel Replay, PR) function. The downstream transmitter is connected to a second electronic device. The picture buffer receives video data. In response to determining that the live broadcast function is activated, the control analysis circuit executes a preset live broadcast program to control the picture buffer to store the received current video data and transmit the current video data to the downstream transmitter. In response to determining that the PR function is activated, the control analysis circuit is configured to execute a preset PR program, including: controlling the picture buffer to discard the received current video data, or to update the previous video data stored in the picture buffer with the content within a specified range of the current video data; and controlling the picture buffer to transmit the latest stored video data to the downstream transmitter. When the live broadcast function is activated, the downstream transmitter converts the current video data from the picture buffer into a target signal in a target format and outputs it to the second electronic device, and when the PR function is activated, the downstream transmitter converts the latest video data from the picture buffer into a target signal in a target format and outputs it to the second electronic device.

[0006] In order to solve the above-mentioned technical problems, another technical solution adopted by the present invention is to provide a protocol conversion method, including: configuring a DP signal receiver to receive a DP signal from a first electronic device, and parsing the DP signal to obtain video data and packet information; configuring a frame buffer to receive video data; configuring a control analysis circuit to perform the following steps: determining whether the packet information indicates starting a live broadcast function or a PR function; in response to determining that the live broadcast function is started, executing a preset live broadcast program to control the frame buffer to store the current video data received, and at the same time transmit the current video data to a downstream transmitter; in response to determining that the PR function is started, executing a preset PR program, including: controlling the frame buffer to discard the current video data received, or to update the previous video data stored in the frame buffer with the content within a specified range of the current video data; and controlling the frame buffer to transmit the latest stored video data to a downstream transmitter; configuring the downstream transmitter to convert the current video data into a target signal in a target format and output it to a second electronic device when the live broadcast function is turned on, and to convert the latest video data from the frame buffer into a target signal in a target format and output it to the second electronic device when the PR function is turned on.

[0007] To further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are only for reference and description and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 The figure is a functional block diagram of a protocol conversion circuit according to an embodiment of the present invention.

[0009] Figure 2 The figure is a flow chart of a control process of a control analysis circuit according to an embodiment of the present invention.

[0010] Figure 3 FIG. 4 is another flow chart of the control process of the control analysis circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0011] The following is an explanation of the implementation methods of the "protocol conversion circuit and protocol conversion method" disclosed in the present invention through specific specific embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and the details in this specification can also be modified and changed in various ways based on different viewpoints and applications without departing from the concept of the present invention. In addition, the drawings of the present invention are only simple schematic illustrations and are not depicted according to actual dimensions. It is stated in advance. The following implementation methods will further explain the relevant technical contents of the present invention in detail, but the disclosed contents are not intended to limit the scope of protection of the present invention. In addition, the term "or" used in this article may include any one or more combinations of the associated listed items depending on the actual situation.

[0012] Figure 1 FIG. 1 is a functional block diagram of a protocol conversion circuit according to an embodiment of the present invention. Figure 1 As shown, an embodiment of the present invention provides a protocol conversion circuit 100, which may include a display port (DisplayPort, DP) signal receiver 1, a control analysis circuit 2, a picture buffer 3, a downstream transmitter 4 and a stall pattern generator 5, and each of which can be implemented by a processing circuit including a processor and a memory. The protocol conversion circuit 100 is electrically connected between a first electronic device 200 and a second electronic device 300. The first electronic device 200 may be, for example, a general-purpose computer supporting DP specifications, and the second electronic device 300 may be, for example, a display that does not support DP specifications, for example, a display that only supports HDMI / VGA specifications, so the protocol conversion circuit 100 is required to convert the signal format.

[0013] The DP signal receiver 1 can receive the DP signal S1 from the first electronic device 200, and is configured to parse the DP signal S1 to obtain video data and packet information. In detail, the first electronic device 200 is a source device, and the DP signal receiver 1 can be used to receive the DP signal S1 transmitted from the first electronic device 200. In some embodiments, the DP signal receiver 1 may include an 8 / 10b decoder that complies with the DP1.4 specification and a 128 / 132b decoder that complies with the DP2.0 specification. In addition, in addition to the single video stream transmission (Single Stream Transport, SST) mode supported by the general DP source device, the DP signal receiver 1 can also support the application of multi-stream transmission (Multi Stream Transport, MST).

[0014] Through the above decoder, the DP signal receiver 1 can parse the received DP signal S1 to obtain video data and packet information, and the video data will be transmitted to the picture buffer 3, and the packet information will be transmitted to the control analysis circuit 2 for performing subsequent logic judgment processing. The packet information can be, for example, a video stream configuration secondary data packet (VSC SDP) located in the Blanking area of ​​the DP signal S1, but the present invention is not limited thereto.

[0015] It should be noted that the packet information can be used to indicate whether the first electronic device 200 is to work in the live mode or the panel replay (PR) mode. For example, the source device (such as the first electronic device 200) can indicate it through the PR_STATE and Update_RFB fields of the VSC SDP.

[0016] According to the DP specification, in live broadcast mode, the sink device will not only play the video data sent by the source device through the panel, but also store the video data of each screen in the buffer (which can be determined by the source device), so that the video data previously stored in the buffer can be played when the source device switches to PR mode.

[0017] In more detail, the PR mode can be divided into two replay modes: Entire Frame Replay and Selective Update. The former means that the destination device will perform panel replay for all the images. The latter means that the source device instructs the destination device to broadcast live within a specified range in the image, while the remaining range continues to play the existing images stored in the buffer. The benefits of partial update are achieved. In addition, in selective update, the specified range to be updated in each image is not limited to only a single area. For example, the image buffer 3 can receive video data from multiple areas specified by the source device for selective update, and dynamically update and push each image accordingly.

[0018] More specifically, during the selective update, the DP signal receiver 1 will synchronously update the video data received in the specified range to the corresponding range in the buffer, and the content finally displayed in the range can be, for example, the picture directly transmitted by the source device. To this end, a main purpose of the present invention is to extend the above-mentioned live broadcast function and the two panel replay functions to non-DP specification products.

[0019] It should be noted that in order to let the source device know that the protocol conversion circuit 1 can support Panel Replay related functions, when the DP signal receiver 1 is electrically connected to the first electronic device 200, the DP signal receiver 1 and the first electronic device 200 will perform a first handshake procedure to inform the first electronic device 200 that the protocol conversion circuit 100 supports the PR function under the DP specification. When the first electronic device 200 knows that the protocol conversion circuit 100 supports the PR function, it will include a packet indicating the activation of the live broadcast function or the PR function in the DP signal S1.

[0020] That is, before transmitting the DP signal S1 containing valid information such as video and audio data, the source device (first electronic device 200) can access the DisplayPort configuration data (DPConfiguration Data, DPCD) of the DP signal receiver 1 through, for example, the AUX pin to perform message exchange before transmitting the signal. This message exchange may include a handshake procedure and a DP link training procedure related to the PanelReplay function, and is basically in accordance with the DP specification, so it is not repeated here.

[0021] Please refer to Figure 1 The control and analysis circuit 2 can be electrically connected to the DP signal receiver 1 , the frame buffer 3 and the downstream transmitter 4 .

[0022] In order to smoothly expand the PR function, a picture buffer 3 is set on the transmission path of the video data, which can store or update the entire picture or a specific range in the picture of the input video data. The picture buffer 3 can be implemented by any memory or storage unit, such as DDR, SRAM and other memories. The behavior of the picture buffer 3 is controlled by the control analysis circuit 2 to determine the content to be output to the downstream transmitter 4, or to determine whether to update the video data stored therein to the received video data.

[0023] For the sake of clarity, the following will first describe the downstream transmitter 4. The downstream transmitter 4 is connected to the second electronic device 300 and is mainly used to transmit the video signals of various output interfaces (e.g., HDMI, VGA, etc. interfaces) and the packet information containing audio data and other auxiliary information to the downstream device (i.e., the second electronic device 300). The downstream transmitter 4 will obtain the video data to be transmitted from the frame buffer 3 or the stall pattern generator mentioned below. It should be noted that although Figure 1 Only one downstream transmitter 4 is shown, but the number of downstream transmitters 4 may be determined according to the number of downstream devices to which the protocol conversion circuit 100 is designed to be connected. Therefore, the number of output ports of the protocol conversion circuit 100 may be one or more, and the number of downstream transmitters 4 corresponds to the number of output ports, which may also be one or more.

[0024] When the downstream transmitter 4 is connected to the second electronic device 300 , the downstream transmitter 4 and the second electronic device 300 perform a second handshake procedure to obtain device information related to the second electronic device 300 , such as device type, manufacturer, supported resolution, and supported capability.

[0025] For example, the downstream transmitter 4 further includes a PR capability analyzer 40, which is configured to obtain the extended display identification data (EDID) and status and control data channel (SCDC) data of the second electronic device 300 in the second handshake procedure.

[0026] Therefore, the packet information (e.g., VSC SDP information) parsed by the DP signal receiver 1 and the device information analyzed by the PR capability analyzer 40 are further input into the control analysis circuit 2 for analysis to determine the arbitration instruction corresponding to the live broadcast function or the RP function. The arbitration instruction can be used to control the frame buffer 3 and the stall pattern generator 5 mentioned below.

[0027] It should be noted that the present invention also provides a protocol conversion method, which can be applied to the protocol conversion circuit 100 mentioned in the above embodiment. For the sake of clarity, the details described above are not repeated here, and the following will focus on the process in which the control analysis circuit 2 participates in the protocol conversion method. Figure 2 Flow chart of the control process of the control analysis circuit 2 according to the embodiment of the present invention.

[0028] like Figure 2 As shown, the control process includes configuring the control analysis circuit 2 to perform the following steps:

[0029] Step S20: Determine whether the packet information indicates starting a live broadcast function or a panel replay (PR) function.

[0030] In response to determining that the live broadcast function is activated in step S20, the control flow enters step S21: executing a preset live broadcast program to control the frame buffer to store the received current video data and transmit the current video data to the downstream transmitter. The stored current video data will be transformed into previous video data over time, so that the previous picture can be provided for the replay mechanism of the PR function.

[0031] In response to determining in step S20 that the PR function is activated, the control flow enters step S22: executing a preset PR program.

[0032] like Figure 2 As shown, the preset PR procedure includes the following steps:

[0033] Step S220: Determine whether the activated PR function is full-screen replay or selective update.

[0034] In response to determining that the activated PR function is full-screen replay, the process proceeds to step S221: controlling the frame buffer to discard the received current video data.

[0035] In response to determining that the activated PR function is a selective update, step S222 is entered: the frame buffer is controlled to update the previous video data stored in the frame buffer with the content within the specified range of the current video data. In the selective update, the source device (the first electronic device 200) can, for example, frame a specific live broadcast range and replay range from the picture through the coordinate indication field in the VSC SDP.

[0036] After executing step S221 or step S222, the control flow enters step S223: controlling the frame buffer to transmit the latest video data stored therein to the downstream transmitter.

[0037] That is, if the PR function is full-screen replay, the previous video data (or its corresponding previous frame) stored in the frame buffer 3 is used as the latest video data stored, and if the PR function is selective update, the video data of the live broadcast area that has been updated is used as the latest video data stored. In addition, in this case, the frame buffer 3 will discard the current video data received.

[0038] Therefore, when the live broadcast function is turned on, the downstream transmitter 4 can convert the current video data from the picture buffer 3 into a target signal S2 in a target format and output it to the second electronic device 300. When the PR function is turned on, the downstream transmitter 4 converts the latest video data from the picture buffer 3 into a target signal S2 in a target format and outputs it to the second electronic device 300.

[0039] Therefore, by executing the control process, the PR function can be extended to the second electronic device 300 that is not DP-compliant. In other words, when the source device (first electronic device 200) of DP-compliant is connected to the second electronic device 300 that is not DP-compliant through the protocol conversion circuit 100 of the present invention, the PR function can still be used to achieve the advantages of power saving or flexible use.

[0040] On the other hand, in the protocol conversion circuit 100 of the present invention, different signal transmission mechanisms are also designed for specific types of devices. For example, the downstream transmitter 4 can determine whether the second electronic device 300 is a specific type of device based on the device information from the second electronic device 300. More precisely, the PR capability analyzer 40 can be configured to determine whether the second electronic device 300 is a specific type of device based on EDID and / or SCDC data in the second handshake procedure.

[0041] In response to the PR capability analyzer 40 determining that the second electronic device 300 is not a specific type of device, the configuration control analysis circuit 2 executes Figure 2 control flow.

[0042] Please refer to Figure 3 , Figure 3 FIG. 2 is another flow chart of the control process of the control analysis circuit 2 according to an embodiment of the present invention. In response to the PR capability analyzer 40 determining that the second electronic device 300 is a specific type of device, the control analysis circuit 2 is configured to execute Figure 3 It should be noted that when the second electronic device 300 is a specific type of device, it is a non-DP specification electronic device and has another built-in picture buffer that can be used to implement the PR function.

[0043] Figure 3 The control flow includes the following steps:

[0044] Step S30: Determine whether the packet information indicates starting the live broadcast function or the PR function.

[0045] In response to determining in step S30 that the live broadcast function is activated, the control flow enters step S31: executing a specific live broadcast program to control the frame buffer to directly transmit the received current video data to the downstream transmitter. Different from the previous embodiment, in this step, the frame buffer 4 may not store the current video data, that is, it does not need to provide the previous frame for the replay mechanism of the PR function.

[0046] In response to determining in step S20 that the PR function is activated, the control flow enters step S32: executing a specific PR program.

[0047] Please refer to Figure 1 The protocol conversion circuit 100 further includes a stall pattern generator 5. The stall pattern generator 5 generates stall video data with a stall pattern according to the horizontal information and vertical information of the resolution provided by the DP source device (the first electronic device 200) and transmits the stall pattern to the downstream transmitter 4. Whether to output the stall pattern depends on the arbitration result generated by the control analysis circuit 2.

[0048] like Figure 3 As shown, the specific PR procedure includes the following steps:

[0049] Step S320: Determine whether the activated PR function is full-screen replay or selective update.

[0050] In response to determining in step S320 that the activated PR function is full-screen replay, step S321 is entered: the picture buffer is controlled to discard the current video data received, the freeze pattern generator 5 is controlled to generate freeze video data with a freeze pattern, and the downstream transmitter 4 is controlled to generate a custom packet instructing the second electronic device 300 to enter the full-screen replay mode.

[0051] Please refer to Figure 1 In response to determining in step S320 that the activated PR function is a selective update, the process proceeds to step S322: updating the previous video data stored in the frame buffer with the content within the specified range of the current video data, controlling the frame buffer to transmit the latest stored video data to the downstream transmitter, and controlling the stagnation pattern generator to generate stagnation video data with a stagnation pattern corresponding to the specified range to transmit to the downstream transmitter. That is, in Figure 3 In the selective update, the source device (the first electronic device 200) can first frame a specific live broadcast range and replay range from the screen through the coordinate indication field in the VSC SDP. The replay range is filled with a stagnant pattern, and the live broadcast range is updated with the content within the specified range in the current video data.

[0052] After step S322 is completed, the downstream transmitter 4 obtains the video data to be transmitted from the frame buffer 3 and the stall pattern generator 5, and converts it into a target signal S2 in a target format and outputs it to the second electronic device 300. At the same time, the downstream transmitter 4 is also controlled by the control analysis circuit 2 to generate a custom packet indicating that the second electronic device 300 enters the selective update mode. Therefore, when only stalled video data with a stall pattern is transmitted, the overall power consumption of the protocol conversion circuit 100 can be reduced. In some embodiments, the stall pattern can be implemented by means other than transmitting video data. For example, the stall pattern generator 5 can generate a minimum power consumption signal that can maintain a physical channel, which is a digital signal that can maintain a link between a transmitting end and a receiving end. The second electronic device 300 can generate a video signal by itself when receiving this minimum power consumption signal.

[0053] When the second electronic device 300 receives a custom packet for entering a full-screen replay mode, it can output a previous frame stored in another built-in frame buffer. When the second electronic device 300 receives a custom packet for entering a selective update mode, it can update a previous frame stored in another built-in frame buffer with video data in an area outside the stagnant pattern in the target signal S2, and display the updated video data. It should be noted that the above-mentioned custom packet may be, for example, a Sony / Philips Digital Interconnect Format (S / PDIF) or a Vendor Specific InfoFrame (VSIF) packet of HDMI, whereby the downstream transmitter 4 can indicate the operating mode required for a specific type of device, thereby achieving a PR function similar to DP.

[0054] In other embodiments, for a part of a specific type of device with a specific interface, the LFPS mechanism can be used to change the downstream transmitter 4 to directly not transmit the video signal during the time interval of the stagnant video data when the stagnant pattern generator 5 generates the stagnant pattern when the PR function is full-screen replay. Therefore, for a specific type of device, the relevant circuit of its video receiving end can be in a sleep state, and when the downstream transmitter 4 is required to send valid video content (that is, when the source device indicates to start the live broadcast mode or the PR function is switched to selective update), the downstream transmitter 4 can be controlled to send the LFPS wake-up signal in advance to wake up the relevant circuit of the video receiving end of the specific type of device. Therefore, the protocol conversion circuit and the specific type of device can operate in a more power-saving manner.

[0055] [Beneficial Effects of Embodiments]

[0056] One of the beneficial effects of the present invention is that in the protocol conversion circuit and the protocol conversion method provided by the present invention, the PR function can be extended to a second electronic device that is not of DP specification, so that when a source device of DP specification is connected to an electronic device that is not of DP specification through the protocol conversion circuit of the present invention, the PR function can still be used to achieve the advantages of power saving or flexible application.

[0057] Furthermore, the protocol conversion circuit and protocol conversion method provided by the present invention also design different video data transmission processes for specific types of devices. There is no need to store video data in live broadcast mode and full-screen replay mode, and only video data within the live broadcast range is stored in selective update mode. In addition to saving the power required for the overall protocol conversion circuit, it also allows specific types of devices to operate in a more power-saving manner.

[0058] The contents disclosed above are only preferred feasible embodiments of the present invention, and are not intended to limit the scope of the present invention. Therefore, all equivalent technical changes made using the contents of the present invention's specification and drawings are included in the scope of the present invention.

[0059]

Explanation of symbols

[0060] Protocol conversion circuit: 100

[0061] DP signal receiver: 1

[0062] Control analysis circuit: 2

[0063] Frame Buffer: 3

[0064] Downstream transmitters: 4

[0065] Stasis Pattern Generator: 5

[0066] First electronic device: 200

[0067] Second electronic device: 300DP Signal: S1 Target signal: S2

Claims

1. A protocol conversion circuit, comprising: a display port (DP) signal receiver, receiving a DP signal from a first electronic device, and configured to parse the DP signal to obtain video data and packet information; a control analysis circuit configured to determine whether the packet information indicates starting a live broadcast function or a panel replay (PR) function; a downstream transmitter connected to a second electronic device; and a picture buffer for receiving the video data, wherein, in response to determining that the live broadcast function is activated, the control and analysis circuit executes a preset live broadcast program to control the picture buffer to store the received current video data and transmit the current video data to the downstream transmitter; In response to determining that the PR function is activated, the control and analysis circuit is configured to execute a preset PR program, including: Controlling the frame buffer to discard the received current video data, or to update the previous video data stored in the frame buffer with the content within a specified range of the current video data; and Controlling the frame buffer to transmit the latest video data stored therein to the downstream transmitter; When the live broadcast function is turned on, the downstream transmitter converts the current video data from the screen buffer into a target signal in a target format and outputs it to the second electronic device. When the PR function is turned on, the downstream transmitter converts the latest video data from the screen buffer into the target signal in the target format and outputs it to the second electronic device.

2. The protocol conversion circuit according to claim 1, wherein: When the DP signal receiver is connected to the first electronic device, the DP signal receiver and the first electronic device perform a first handshake procedure to inform the first electronic device that the PR function under the DP specification is supported.

3. The protocol conversion circuit according to claim 1, wherein: When the downstream transmitter is connected to the second electronic device, the downstream transmitter and the second electronic device perform a second handshake procedure to determine whether the second electronic device is a specific type of device according to the device information from the second electronic device.

4. The protocol conversion circuit as claimed in claim 3, wherein: In response to determining that the second electronic device is the specific type of device and determining that the live broadcast function is activated, the control analysis circuit executes a specific live broadcast program to control the frame buffer to directly transmit the current video data to the downstream transmitter without storing the received current video data.

5. The protocol conversion circuit as claimed in claim 3 further comprises a stall pattern generator, wherein: In response to determining that the second electronic device is the specific type of device and determining that the PR function is activated, the control and analysis circuit executes a specific PR program, including: Control the frame buffer to discard the received current video data, and control the freeze pattern generator to generate freeze video data with a freeze pattern; or The previous video data stored in the frame buffer is updated with the content within the specified range of the current video data, the frame buffer is controlled to transmit the latest stored video data to the downstream transmitter, and the stall pattern generator is controlled to generate stall video data with a stall pattern to transmit to the downstream transmitter.

6. The protocol conversion circuit as claimed in claim 5, wherein: The downstream transmitter obtains the video data to be transmitted from one or more of the frame buffer and the stall pattern generator, and converts the target signal into the target format and outputs it to the second electronic device.

7. The protocol conversion circuit according to claim 5, wherein: The stagnation pattern generator also generates the stagnation video data with the stagnation pattern according to the horizontal information and the vertical information provided by the first electronic device, or generates a minimum power consumption signal.

8. The protocol conversion circuit according to claim 3, wherein: In response to determining that the second electronic device is the specific type of device, the downstream transmitter transmits a custom packet to inform the second electronic device that the live broadcast function or the PR function needs to operate when the live broadcast function or the PR function is turned on.

9. The protocol conversion circuit as claimed in claim 3, wherein: The downstream transmitter also includes a PR capability analyzer, which is configured to determine whether the second electronic device is the specific type of device based on the extended display identification data (EDID) and / or status and control data channel (SCDC) data of the second electronic device in the second handshake procedure.

10. A protocol conversion method, comprising: A display port (DP) signal receiver is configured to receive a DP signal from a first electronic device, and parse the DP signal to obtain video data and packet information; configuring a picture buffer to receive the video data; Configure a control analysis circuit to perform the following steps: Determining whether the packet information indicates starting a live broadcast function or a panel replay (PR) function; In response to determining that the live broadcast function is activated, executing a preset live broadcast program to control the frame buffer to store the received current video data and transmit the current video data to the downstream transmitter; and In response to determining that the PR function is activated, executing a preset PR program, including: Controlling the frame buffer to discard the received current video data, or to update the previous video data stored in the frame buffer with the content within a specified range of the current video data; and Controlling the frame buffer to transmit the latest video data stored therein to the downstream transmitter; and The downstream transmitter is configured to convert the current video data into a target signal in a target format and output it to the second electronic device when the live broadcast function is turned on, and to convert the latest video data from the picture buffer into the target signal in the target format and output it to the second electronic device when the PR function is turned on.

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