CN100574452C - A Method for Improving Receiving Performance of Mobile Multimedia Broadcasting Terminal - Google Patents

Abstract

The invention discloses a method for improving the receiving performance of a mobile multimedia broadcasting terminal, aiming at extracting each video/audio unit data when the CRC check error of the video/audio section header in the multiplexing subframe. The main point is to use the length of the video/audio segment header obtained by the latest correct analysis to locate the video/audio segment header position in the target multiplexing subframe; according to the relative The playing time is to obtain the starting playing time of each video/audio unit of the target multiplexing subframe. The method of the invention makes full use of the next frame parameter and the length information of the multiplexed frame header in the multiplexed frame received and analyzed correctly last time, and avoids the terminal discarding the entire multiplexed frame data due to the CRC check error of the multiplexed frame header.

Description

A Method for Improving Receiving Performance of Mobile Multimedia Broadcasting Terminal

technical field

The invention relates to a method for improving the receiving performance of a terminal, in particular to a method for improving the receiving performance of a mobile multimedia broadcasting terminal.

Background technique

In recent years, digital mobile multimedia broadcasting technology and standards have developed rapidly, such as DVB-H (Digital Video Broadcast Handheld, digital video broadcasting handheld reception) in Europe, MediaFLO (Media Forward Link Only, media single forward link) in the United States and China's CMMB (China Mobile Multimedia Broadcasting, Mobile Multimedia Broadcasting), etc., provide its end users with many services, such as advertisements, weather forecasts, news, sports programs, variety shows, multimedia radio dramas, movies and other programs. Users can choose the service programs of mobile multimedia broadcasting according to their own preferences.

In China's CMMB standard, mobile multimedia broadcasting uses a time-division method to send multimedia broadcasting services. A broadcast channel frame has a duration of 1 second and consists of 40 time slots of 25 milliseconds. One or more time slots can carry data encapsulated in a multiplexing frame (Multiplexing Frame, MF for short). In the multiplexing frame structure of mobile multimedia broadcasting, the multiplexing frame is divided into three parts: the multiplexing frame header, the multiplexing frame payload and the padding, as shown in FIG. 1 .

FIG. 2 shows the relationship between multiplexed frames and multiplexed subframes. A broadcast channel frame, such as broadcast channel frame k in FIG. 2 , transmits information content divided into control information and service data. The control information is transmitted in the multiplexed frame 0, and the service data is transmitted in the multiplexed frame 1, the multiplexed frame 2, . . . , the multiplexed frame n, where n is less than 40. The multiplexed frame payload of each service data multiplexed frame consists of one or more multiplexed subframes, as shown in the figure, multiplexed subframe 1, multiplexed subframe 2, ..., multiplexed subframe p, but can only include 15 multiplexed subframes at most, that is, p is less than or equal to 15. Each multiplexing subframe carries a multimedia service.

The structure of the multiplexing frame header is shown in Figure 3, which includes parameters such as the length of the multiplexing subframe. The "next frame parameter indication" field indicates whether the key parameter of the next multiplexed frame with the same multiplexed frame identifier MF_ID is included in the multiplexed frame header, '0' means no, '1' means yes. If the value of the "Next Frame Parameter Indication" field is '1', the "Next Frame Parameter" includes the multiplexing frame header length, multiplexing subframe 1 ( The length of the first multiplex subframe) and the header length of multiplex subframe 1. The multiplexing frame header adopts 32-bit CRC (Cyclic Redundancy Check, Cyclic Redundancy Check) for checking.

The structure of the multiplexed subframe is shown in Figure 4, which consists of a subframe header, a video segment, an audio segment and a data segment. Wherein the subframe header includes the header length (occupies 8 bits), start playing time, video segment length, audio segment length, data segment length, extension area parameters, etc., and also adopts 32-bit CRC check.

The video segment of the multiplexed sub-frame is composed of a video segment header and a plurality of video units, as shown in FIG. 5 . The video segment header describes the parameters of each video unit, and also adopts 32-bit CRC check.

The audio segment of the multiplexed subframe is composed of an audio segment header and multiple audio units, as shown in FIG. 6 . The audio segment header describes the parameters of each audio unit, and also adopts 32-bit CRC check.

As shown in Figure 7, after the mobile multimedia broadcasting terminal in the CMMB system receives the multiplexing frame, it needs to perform the following steps of demultiplexing processing:

Step 701: Analyze the multiplexed frame header to obtain the length of the multiplexed frame header, the update sequence number of various control information tables and the length of each multiplexed subframe;

Step 702: According to the length of the multiplexing frame header and the length of each multiplexing subframe, the required multiplexing subframe is parsed from the payload of the multiplexing frame, which is called the target multiplexing subframe;

Step 703: Parsing out the video segment, audio segment and data segment from the target multiplexing subframe;

Step 704: Parse the payloads of the video unit, audio unit and data unit from the video segment, audio segment and data segment respectively, and send them to an upper-layer application (such as a player) for processing.

The CMMB system broadcasts multimedia through air channels. Because the wireless environment is very complex, even if channel coding with excellent performance is adopted during broadcasting, channel bit errors cannot be avoided. When the mobile multimedia broadcasting terminal performs demultiplexing processing on the received data, it involves the CRC check of the video segment header and the audio segment header. The current general practice is to discard all data in the multiplexed subframe if a CRC error is detected when the CRC of the video segment header and the audio segment header is checked.

Fig. 8 shows the detailed process steps of the demultiplexing processing embodiment in the prior art, including:

Step 801: when the terminal processes the multiplexed frame, obtains the length of the multiplexed frame header and the data of the multiplexed frame header, and performs a CRC_32 check on the multiplexed frame header;

Step 802: Perform operations such as updating and saving the data information in the multiplexing frame header respectively, specifically including processing the update sequence number of the control information table, such as emergency broadcast instructions, and saving the length of the multiplexing frame header, if there is a next frame parameter Then cache the parameter; and obtain the length of each multiplexed subframe in the multiplexed frame;

Step 803: In bytes, under the offset value of the length of the multiplexing frame header, the 4-byte CRC_32 code and the sum of the lengths of the subframes before the target multiplexing subframe, obtain the starting position of the target multiplexing subframe and length, that is, according to the sequence number of the target multiplexing subframe and the length of each multiplexing subframe in the multiplexing frame, the starting position and length of the target multiplexing subframe are obtained; and then the length of the target multiplexing subframe header is obtained Multiplex the data in the subframe header with the target;

Step 804: Obtain the length and start time of the video segment, audio segment and data segment in the target multiplexing sub-frame header;

Step 805: Obtain the header length of video segment, audio segment and data segment, and carry out CRC_32 check to the header of video segment and audio segment, if the CRC_32 check is correct, then turn to step 806, otherwise turn to step 807;

Step 806: Process the video unit and audio unit in the target multiplexing subframe;

Step 807: Discard the received multiplexed frame data.

Since multiplexed frames are multiplexed for services in units of one second, when a CRC error is detected, the terminal directly discards the operation of the entire multiplexed data, which is equivalent to all video data and audio transmitted within one second All the data is discarded, which directly causes serious interruptions in the picture and sound of the terminal. Such a processing process makes the reception of the terminal very sensitive to the bit error rate of the channel, and the resistance to the bit error rate is poor, which seriously reduces the efficiency of data reception and affects the smoothness of the user's audio and video experience.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for improving the receiving performance of the mobile multimedia broadcasting terminal, which is applied to extracting each video/audio unit when the CRC check error of the video/audio header in the multiplexed subframe received by the terminal data.

In order to solve the above-mentioned technical problems, the present invention provides a method for improving the receiving performance of a mobile multimedia broadcast terminal, comprising the following steps:

(1) The terminal parses the received multiplexing frame, and parses the target multiplexing subframe from the multiplexing frame payload, and after obtaining the length of the video segment header and the audio segment header length in the target multiplexing subframe, Carry out cyclic redundancy check to the segment header of described video segment and audio segment, if check is correct then go to step (2), otherwise go to step (3);

(2) process the video unit and the audio unit in the multiplexing subframe of the target, obtain the relative playback time of the video segment header length and the audio segment header length and the last video unit and the last audio unit, and save;

(3) Utilize the length of the video/audio segment header that is correctly analyzed last time to locate the video/audio segment header position in the target multiplexing subframe;

(4) Locate the video/audio unit of the target multiplexed subframe, and obtain the start of each video/audio unit of the target multiplexed subframe according to the relative play time of the last video/audio unit obtained from the latest correct analysis playback start time.

In the above-mentioned method for improving the receiving performance of a mobile multimedia broadcasting terminal, before the terminal in step (1) obtains the target multiplexing subframe, it may further include, for the multiplexing received before the target multiplexing subframe Use the cyclic redundancy check in the subframe to correct the video segment/audio segment header, save the cyclic redundancy check correct video segment header length and audio segment header length, and the relative value of the last video unit and the last audio unit play time.

The above-mentioned method for improving the receiving performance of a mobile multimedia broadcasting terminal, the step (3) includes, at the end position of the subframe header of the target multiplexed subframe, skipping the video/audio segment header that was correctly parsed last time length plus the length of the cyclic redundancy check code to locate the video/audio segment header position in the target multiplexing subframe.

The above-mentioned method for improving the receiving performance of a mobile multimedia broadcasting terminal, its step (4) may include, through the video unit start code identifier in the target multiplexing subframe, locating the video unit of the target multiplexing subframe ; Locate the audio unit of the target multiplexing subframe by using the audio unit start code identifier in the target multiplexing subframe.

The above-mentioned method for improving the receiving performance of a mobile multimedia broadcasting terminal, its step (4) may also include, the relative play time of the last video unit obtained by the latest correct analysis, plus the play time of each video unit , to obtain the initial playback time of each video unit; the relative playback time of the last audio unit obtained by the latest correct analysis, plus the playback time of each audio unit, to obtain the initial playback time of each audio unit play time.

The method of the present invention makes full use of the next frame parameter and the length information of the multiplexed frame header in the multiplexed frame received and correctly parsed last time when the CRC check error of the target video segment header and the audio segment header is obtained from the target multiplexed frame. Video data and audio data of the target multiplexing subframe are extracted. Compared with the existing technology, it prevents the terminal from discarding the entire multiplexed frame data due to the CRC check error of the multiplexed frame header, significantly improves the receiving performance of the terminal under the condition of bit error, and improves the serious discontinuity of the picture and sound of the terminal Case.

Description of drawings

FIG. 1 is a schematic structural diagram of an embodiment of a multiplexing frame in the prior art;

FIG. 2 is a schematic structural diagram of an embodiment of a multiplexing frame and a multiplexing subframe in the prior art;

Fig. 3 is a schematic structural diagram of an embodiment of a multiplexing frame header in the prior art;

FIG. 4 is a schematic structural diagram of an embodiment of multiplexing subframes in the prior art;

Fig. 5 is a schematic structural diagram of an embodiment of a video segment in the prior art;

FIG. 6 is a schematic structural diagram of an embodiment of an audio segment in the prior art;

Fig. 7 is a schematic flow diagram of an embodiment of multiplexing frame receiving processing in the prior art;

FIG. 8 is a schematic flow diagram of an application embodiment of multiplexing frame receiving and processing in the prior art;

Fig. 9 is a schematic flow chart of a method embodiment of the present invention;

Fig. 10 is a schematic flow chart of an application example of the method of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Analyzing the structure of multiplexed subframes, we can find the following characteristics:

(A) For a multiplexed frame, besides obtaining the length of each multiplexed subframe in the multiplexed frame from the multiplexed frame header, there is another way to obtain it: when the subframe of the multiplexed subframe When the header is parsed correctly, in bytes, the length of the multiplexed subframe=the length of the subframe header+the CRC_32 code of 4 bytes+the length of each information segment;

(B) The relative playback time of multiple video/audio units contained in the video/audio segment header, except that when the multiplexed subframe header CRC is correct, the relative playback time in the multiplexed subframe header is used as a reference to offset, and There is another method, which does not rely on the starting playback time in the multiplexing subframe header, but uses the relative playback time obtained from the latest correct analysis as a reference to offset, and the latter is also a more general method.

From the above analysis of the multiplexing frame structure, we have come to such a conclusion: when the terminal does not switch services, the terminal obtains the video segment header length and After the length of the audio segment header, when the CRC check error is performed on the video segment header/audio segment header, you can use the video segment header/audio segment header length information obtained from the last correct analysis to obtain the video segment in the target multiplexing subframe Header length/audio segment header length information.

Therefore, the idea of the present invention is: after the terminal obtains the length of the video segment header and the length of the audio segment header in the target multiplexing subframe, if the CRC check error is performed on the video segment header/audio segment header, then by making full use of the last correct Parse the obtained video segment header/audio segment header length information to obtain the video segment header length/audio segment header length information in the target multiplexing subframe, and extract relevant video data from the target multiplexing subframe as much as possible and audio data. This prevents the terminal from discarding the entire multiplexed data due to CRC check error of the video segment header/audio segment header, resulting in severe discontinuity of the terminal screen and sound, which affects the smoothness of the user's audio and video experience.

Referring to Figure 9, the process flow of the method embodiment of the present invention mainly includes the following steps:

Step 901: Before performing CRC check on the video segment/audio segment header in the target multiplexed subframe, the terminal checks the correct video segment header/audio segment header in the previously received multiplexed subframe. After the unit and the audio unit are processed, save the length of the video segment header and the length of the audio segment header, as well as the relative playback time of the last video unit and the last audio unit;

Step 902: After the terminal analyzes the received multiplexed frame and obtains the header length of the video segment and the header length of the audio segment in the target multiplexed subframe, it performs CRC_32 check on the headers of the video segment and the audio segment of the target multiplexed subframe Check, if the check is correct, go to step 903, otherwise go to step 913;

Step 903: Process the video unit and audio unit in the target multiplexing subframe to obtain the length of the video segment header and the length of the audio segment header, the length of each video and audio unit, the relative play time of each video and audio unit, and the length of each video segment and audio unit data information;

Step 904: save the length of the video segment header and the length of the audio segment header, and the relative play time of the last video unit and the last audio unit, and the processing of the video segment and the audio segment ends;

Step 913: Utilize the length of the video/audio segment header saved by the latest correct analysis to locate the video/audio segment header in the target multiplexing subframe;

Step 914: Find the video unit start code identifier/audio unit start code identifier, and locate the video/audio unit of the target multiplexing subframe;

Step 915: Offset according to the relative playback time of the last video/audio unit of the multiplexed subframe in the multiplexed frame obtained by correctly parsing the multiplexed frame last time to obtain each video/audio of the target multiplexed subframe The start playback time of the unit, and complete the processing of the video segment and audio segment.

Referring to Fig. 10, the flow of the method application embodiment of the present invention includes the following steps:

Step T01 to step T04 are the same as steps 801 to 804;

Step T05: Obtain the header lengths of the video segment, audio segment, and data segment, and perform CRC_32 checks on the headers of the video segment and audio segment. If the CRC_32 checks of the video segment and audio segment are correct, then go to step T06. Otherwise go to step T16;

Step T06: Process the video unit and audio unit in the target multiplexing subframe to obtain the video segment header length and audio segment header length, the length and relative playback time of each unit of the video/audio segment, and obtain the data of each unit;

Step T07: save the length of the video segment header and the length of the audio segment header, and the relative play time of the last video unit and the last audio unit; the processing of the video segment and the audio segment ends;

Step T16: Utilize the length of the video/audio segment header obtained from the latest correct analysis to locate the position of the video/audio segment header in the current target multiplexing subframe;

Step T17: Find the video unit identifier/audio unit start code identifier to locate the corresponding video/audio unit, thereby obtaining the data content of each video/audio unit;

Step T18: Offset the relative playback time of the last video unit and the last audio unit of the multiplexed subframe in the multiplexed frame according to the stored last correct analysis of the multiplexed frame, so as to obtain the Start playing time, complete the processing of video segment and audio segment.

In step T16, locate the video/audio segment header in the current target multiplexing subframe according to the length of the video/audio segment header obtained by the latest correct analysis. The specific operation is at the end position of the subframe header of the target multiplexing subframe, Skip the video/audio segment header length obtained by the latest correct analysis plus the length of the 4-byte CRC_32 code, and determine it as the current video/audio segment header position to be parsed.

This is because in actual business, the allocated bandwidth is certain, and the lengths of video segment headers and audio segment headers do not change much. Therefore, the length of video segment headers and audio segment headers in the last second can be used to estimate the video segment in the current subframe. length and audio segment header length.

The relative playing time of the last video/audio unit in step T18 is an estimated value, an empirical value that can be taken according to the coding law of the video/audio unit. The starting playback time of each video unit is equal to the relative playback time point of the last video unit obtained by the latest correct analysis, plus the playback time of each video unit; the starting playback time of each audio unit is equal to the last correct analysis. The relative playback time of the last audio unit in , plus the playback time of each audio unit.

In the present invention, before the header CRC_32 of the video segment and the audio segment is checked incorrectly, the header CRC_32 of the video segment and the audio segment must be checked correctly at least once to ensure that the preservation process carried out in the above-mentioned step T07 is step T16 ~Provide support for the execution of step T18.

In the method of the present invention, when the CRC check error of the video segment header and the audio segment header in the target multiplexing subframe is made full use of the video segment header and audio segment header length information received and correctly parsed last time, the video unit in the target multiplexing subframe is fully utilized. and audio unit for positioning and analysis, and use the video unit start code identifier and audio unit start code identifier to respectively locate the video unit and audio unit, extract the relevant video data and audio data, and also according to the latest received and The playing time obtained by correct analysis is offset to obtain the playing time of the video unit and the audio unit, which prevents the terminal from discarding the entire multiplexed frame data due to the CRC error of the multiplexed frame header and the multiplexed subframe header, and significantly improves the bit error condition Improve the receiving performance of the terminal, and improve the situation that the terminal discards the multiplexed frame data due to the error of the CRC check of the multiplexed frame header, which causes severe intermittent picture and sound.

Certainly, the present invention also can have other multiple embodiments, without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding changes and All deformations should fall within the scope of protection of the appended claims of the present invention.

Claims (5)

1. A method for improving the receiving performance of a mobile multimedia broadcasting terminal, characterized in that, comprising the steps: (1) The terminal parses the received multiplexing frame, and parses the target multiplexing subframe from the multiplexing frame payload, and after obtaining the length of the video segment header and the audio segment header length in the target multiplexing subframe, Carry out cyclic redundancy check to the segment header of described video segment and audio segment, if check is correct then go to step (2), otherwise go to step (3); (2) process the video unit and the audio unit in the multiplexing subframe of the target, obtain the relative playback time of the video segment header length and the audio segment header length and the last video unit and the last audio unit, and save; (3) Utilize the length of the video/audio segment header that is correctly analyzed last time to locate the video/audio segment header position in the target multiplexing subframe; (4) Locate the video/audio unit of the target multiplexed subframe, and obtain the start of each video/audio unit of the target multiplexed subframe according to the relative play time of the last video/audio unit obtained from the latest correct analysis playback start time. 2. The method according to claim 1, wherein in step (1), before obtaining the target multiplexing subframe, the terminal further includes, for the multiplexing received before the target multiplexing subframe Use the cyclic redundancy check in the subframe to correct the video segment/audio segment header, save the cyclic redundancy check correct video segment header length and audio segment header length, and the relative value of the last video unit and the last audio unit play time. 3. The method according to claim 1, wherein step (3) includes, at the end position of the subframe header of the target multiplexing subframe, skipping the length of the video/audio segment header obtained by the latest correct analysis The length of the cyclic redundancy check code is added to locate the video/audio segment header position in the target multiplexing subframe. 4. The method according to claim 1, wherein step (4) comprises, through the video unit start code identifier in the target multiplexing subframe, locating the video unit of the target multiplexing subframe; The audio unit of the target multiplexing subframe is located through the audio unit start code identifier in the target multiplexing subframe. 5. The method according to claim 1, wherein step (4) comprises, adding the relative playing time of the last video unit obtained by the latest correct analysis to the playing time of each video unit, to obtain The starting playing time of each video unit; the relative playing time of the last audio unit obtained by the latest correct analysis, plus the playing time of each audio unit, to obtain the starting playing time of each audio unit .

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