[0037] The technical scheme of the present invention is as follows: First, multiple video data streams are received and processed at the same time to obtain multiple program multiplexed streams. Then, all data segments are numbered cyclically. After error correction and marking for each channel. Finally, according to the size of each channel of video program code stream, adaptive grouping and interleaving are then sent in the form of multiple channels of program data, that is, multiple channels of program data streams are simultaneously received and sent. In this way, the transmission and distribution of multi-channel video program data in the wireless WiFi system can be easily realized, and the simultaneous access of multi-programs and general multi-users can be realized.
[0038] Specifically, a wireless WiFi multimedia broadcasting system distribution method, such as figure 1 As shown, including the following steps:
[0039] Step A: Multi-channel video program multiplexing stream collection.
[0040] The data collection form here includes multiplexed streams of multiple video programs, and multiplexed TS (transition stream, TS) streams mainly exist in the form of multiple program streams. However, each channel of video program has its own port number to easily distinguish each channel of program streams. For example, port numbers 8001 to 800N are used to distinguish N channels of program streams. Therefore, although it is a form of multiplexing multiple program streams, each video program stream can be easily separated and processed separately. In addition, the source form of the program can adopt remote multi-channel (multi-channel program) multi-signal source collection. For example: satellite signal, cable TV, terrestrial digital TV, narrowband OFDM transparent transmission with remote program source and IPTV (interactive personality TV, IPTV).
[0041] In detail, assume that the data received in the WiFi coverage system is a multi-channel program stream. The variable R defined here is the multi-program data stream received in the WiFi coverage system, then
[0042]
[0043] Where N is the total number of data stream programs, s i Is the i-th data stream, κ i Is the scale factor. Equation (1) indicates that the video data in the live broadcast system is composed of multiple program streams. We can regard the received multiple channels of video program data as multiplexed TS streams, and each channel of program stream TS stream can be regarded as composed of TS packets. Each TS stream has a different PID (packetidentifier, PID) number to mark TS packets, such as figure 2 Schematic diagram of the TS packet structure in.
[0044] Step B: The multiplexed stream of the multi-channel video program is converted into the multi-program IP stream processing.
[0045] According to the video data stream collected in step A, the data stream receiving and processing form in the distribution processor can be divided into three formats: 1) The received multiple single-channel program IP streams are processed into single-channel multi-program IP streams 2) Multi-program TS multiplexed stream, after demultiplexing the data stream, each single-program TS stream is obtained and transcoded into a multi-channel multi-program IP stream; 3) Multi-program TS multiplexed stream is converted into a single-channel multi-program after conversion IP flow. We are mainly based on the third multi-program TS multiplexed stream for distribution processing.
[0046] In order to increase the video data transmission rate and bandwidth of the wireless WiFi system and reduce the computational load of the distribution processor, we convert the multiplexed stream of multiple video programs into a video stream in the form of multiple-program multiplexed IP packets. The video stream converted into multiplexed IP packets allows the wireless WiFi system to transmit data in the form of IP packets, and broadcast the video data. Among them, one data frame of the WiFi system carries one multi-program IP packet, and one multi-program IP packet is all or part of the information of one frame in an audio and video program.
[0047] In detail, according to the multi-program TS stream format, we divide each video data stream s i According to the program stream rate, multiplexed into the form of IP packet, it can be expressed as
[0048]
[0049] Here there are 7 TS packets of the same or different programs in an IP packet (a TS packet length is 188 bytes), such as figure 2 Shown. In particular, here a multi-program IP packet data is adaptively allocated according to the program stream rate, so that the bandwidth space can be allocated reasonably according to the quality of the communication environment, and the bandwidth utilization rate of the system is improved.
[0050] Step C: Marking, grouping and interleaving of the video stream.
[0051] According to the data stream in the form of the multi-program IP packet obtained in step B, sequential label processing is performed on each multi-program IP packet.
[0052] In the video transmission process, the stream rate of each program is different, and the stream rate of the same program changes at different moments. Therefore, in order to adaptively determine the size of the transmitted data according to different program stream rates during the process of transmitting video data, thereby improving the channel utilization and data transmission efficiency, we group the video data IP packets, and the length of the data group It changes adaptively according to the propagation conditions. However, in the case of selecting a length, the number of multi-program IP packets in each data group remains the same. The number of multi-program IP packets for each program stream is adaptively changed with the size of the stream and the communication status, such as figure 2 Shown.
[0053] After grouping multiple channels of video program data IP streams, the multiplexed multiple program IP streams are obtained. Then, the multi-program IP stream uses a small 2Mbps buffer and is encapsulated into an MPTS (Multi-program transport stream, MPTS) over UDP, such as image 3 Shown. And MSTP has its own data segment number, so you can use MSTP to number each data segment cyclically from 0 to 65535. Among them, the data after the MPTS number is used to convert the UDP port number of each video program. Then, according to the communication status, the multi-program IP data group is adaptively interleaved to improve the anti-interference performance of the wireless WiFi system.
[0054] Step D, distribution processing.
[0055] According to the self-adaptively interleaved multi-program IP stream in step C, and because each video program has its own port number, each video program data stream can be distributed to multiple ports. In this way, the receiving efficiency and performance of the user terminal are improved, and the multi-channel video program transmission and smooth playback in general mobile users are guaranteed.
[0056] Here, each port has its own unique and independent number, using p j Indicates the number of the jth port.
[0057]
[0058] Here i j (·) represents the function that the program stream is distributed to the jth port, N j Represents the number of program streams distributed to the jth port, and M represents the number of ports.
[0059] Each program stream corresponds to a port number. This allows the client terminal to conveniently receive each program stream and play it. Use multiple ports to send multiple program streams simultaneously in the form of live transmission in a time-division manner. Mainly as figure 2 In order to send the multi-program IP packets one by one, so that multiple receiving terminals can play videos conveniently, simply and smoothly. The following formula can be used to mathematically model the multi-program stream distribution method
[0060] R k =f(p j ),j=1,2,...,M,k=1,2,...,K (4)
[0061] Here R k Represents the receiving end of the wireless WiFi system, K represents the number of receiving ends, and f(·) represents the transmission function. In order to divide the received data into multiple channels of data, multiple channels of program streams are simultaneously sent. In this process, 8 or more Ethernet channels can be received simultaneously.
[0062] Step E: Data retransmission mechanism.
[0063] Send data according to step D. In order to overcome random interference and burst interference, each data group is sent twice. In the data transmission process, in order to reduce the error rate and data loss, a reasonable data retransmission mechanism needs to be used. Here, according to different communication environments, we provide two data retransmission mechanisms. Method 1: Each receiving terminal has a feedback mechanism. When the receiving terminal detects a data error, it sends an instruction to request the group of data packets to be retransmitted again. Moreover, in order to improve the feedback speed, this feedback mechanism must rely on the first receiving terminal to send feedback to the media synthesis controller by broadcasting. In other cases, the data packet will not be retransmitted. Method 2: Use an adaptive public feedback mechanism, that is, determine the error condition based on the public feedback and initiate a retransmission.
[0064] The present invention will be further described in detail below in conjunction with the drawings:
[0065] A wireless WiFi multimedia broadcasting system, such as Figure 4 As shown, it includes a server, a distributor, and a user (ie, receiving terminal). The distributor receives the data sent by the server, processes the data and sends it to the user through the transmission network. The distributor of the above wireless WiFi multimedia broadcasting system, such as Figure 5 As shown, it includes a collection encoder, a multiplexing module, an error correction module, a grouping module, an encapsulation module, an interleaving module, a sending module, and a retransmission feedback module. Among them, the acquisition encoder, multiplexing module, error correction module, grouping module, encapsulation module, interleaving module and sending module are connected in sequence. The input end of the retransmission feedback module is connected to the receiving terminal, and the output end of the retransmission feedback module is connected to the sending module.
[0066] Capture encoder to capture multiplexed streams of multiple video programs;
[0067] The multiplexing module converts the multiplexed stream of the multi-channel video program output by the acquisition encoder into a data stream in the form of a multi-program multiplexed IP packet;
[0068] The error correction module performs error correction processing on each multi-program IP packet in the data stream in the form of the multi-program multiplexed IP packet output by the multiplexing module;
[0069] The grouping module adaptively adjusts the length of the data group according to the propagation conditions and the program code stream rate, and groups the error-corrected data streams output by the error correction module to obtain a multiplexed multi-program IP stream;
[0070] The encapsulation module encapsulates the multiplexed multi-program IP stream output by the packet module into an MPTS to realize the cyclic numbering of each packet data segment of the multiplexed multi-program IP stream, and convert each channel of video program with the data after the MPTS cyclic numbering UDP port number.
[0071] The interleaving module, according to the communication status, performs adaptive interleaving processing on the cyclically numbered multi-program IP stream group output by the encapsulation module;
[0072] The sending module, according to the respective UDP port number of each video program, distributes each video program data stream of the adaptively interleaved multi-program IP stream output by the interleaving module to the corresponding UDP port;
[0073] The retransmission feedback module determines whether the data group sent by the sending module needs to be retransmitted according to the feedback of the receiving terminal.
[0074] The above modules are programmed in C language to realize productization on the ARM embedded system. Using our products to conduct experimental tests, we found that when the distribution technology is adopted, the packet loss rate of the WiFi-based digital TV broadcasting system can be reduced to 2.87e-4. This makes the system performance has been greatly improved.
[0075] The invention can transmit and send multimedia information such as digital TV in a limited range wireless WiFi coverage system to realize simultaneous access of ordinary multiple users and multi-program playback in the wireless WiFi system, and to improve the data transmission speed and stability of the digital TV system.
[0076] The above-mentioned implementation cases are only specific examples for further describing the objectives, technical solutions, and beneficial effects of the present invention; the present invention is not limited thereto. Any modification, equivalent replacement, improvement, etc. made within the scope of the disclosure of the present invention are all included in the protection scope of the present invention.
