CN102647616A

CN102647616A - Audio-video multiplexing device

Info

Publication number: CN102647616A
Application number: CN2012101156253A
Authority: CN
Inventors: 贾惠柱; 肖华; 吉祥虎; 解晓东; 高文
Original assignee: Peking University
Current assignee: Peking University
Priority date: 2012-04-18
Filing date: 2012-04-18
Publication date: 2012-08-22
Anticipated expiration: 2032-04-18
Also published as: CN102647616B

Abstract

The invention discloses an audio-video multiplexing device. The multiplexed video ES (Elementary Stream) and audio PES (Packetized Elementary Stream) both are obtained from an external memory, the video ES is generated by a video encoder in an encoding manner, and an audio PES packet is formed by an audio encoder in a manner of encoding and packaging; a CPU (Central Processing Unit) part packages the program specific information (PSI) and the program clock reference (PCR) into a TS (Transmission Stream) packet according to the syntax rules of the transmission stream (TS) in the standard, and simultaneously generates a video PES head and the configuration information needed for other multiplexer hardware accelerators; and the multiplexer hardware accelerator part selects to multiplex the TS packet and a padding packet into the transmission stream with constant output rate according to a multiplexing strategy, wherein the TS packet is formed by packaging of the PSI, the PCR and the audio-video PES. The invention provides an audio-video multiplexing device, which can process high-definition video in real time, and is high in flexibility, simple in hardware structure, small in delay, constant in multiplexing rate and small in PCR jitter.

Description

The device that a kind of audio frequency and video are multiplexing

Technical field

The present invention relates to the digital video decoding technical field, relate in particular to the multiplexing device of a kind of audio frequency and video.

Background technology

Digitlization audio frequency and video industry is the important industry of national economy and social development, is one of information industry three big parts.

Amount of information after the digitlization is very huge, in order effectively to improve channel utilization, on the one hand, information source is carried out compressed encoding, makes it in transmission course, take minimum bandwidth; On the other hand, consider how in individual channel, to send multiple programs, the multiplexing technique that produces therefrom is very practical.This paper research object is a multiplexing technique, and this multiplex technique is different from traditional time division multiplexing, frequency division multiplexing, and it is a kind of statistic multiplexing based on Bandwidth Dynamic Allocation.

Fig. 1 is an audio/video coding multiplex system block diagram in the prior art, and at present, most multiplexer is not to realize being exactly to realize with software fully with pure hardware, and the traditional hardware multiplexer costs an arm and a leg, portability is poor, do not possess upgradability; The multiplexer that software is realized is then a lot of for the system resource that the requirement that reaches high-definition real-time output takies, and multiplexing equipment has mostly adopted the DSP real-time processing technique, has increased multiplexing cost.

Thereby, how to design a kind of novel audio frequency and video multiplexer to overcome above-mentioned defective, become the technical barrier that those skilled in the art wait to solve.

Summary of the invention

The technical problem that the present invention solves is how to improve portability, reduces cost.

In order to overcome the above problems, the invention discloses a kind of audio frequency and video multiplexer, comprising: CPU part, hardware accelerator part, two parts communicate and transfer of data through bus; CPU has partly comprised PSI and PCR maker, video PES is first-born grows up to be a useful person and the hardware requests responsor, links bus respectively; Hardware accelerator partly comprises parameter acquiring device, request of data device, multiplexing outlet selector, STC, output buffer and RAM, VPES memory, video information memory, VES memory, APES memory, the MPTS debugging output storage that is connected to bus; External memory storage is used for through the ES stream of bus store video and audio frequency PES stream; DMA is used for through bus the transfer of data of external memory storage VES memory and the APES memory in the hardware accelerator part.

Further; As a kind of preferred; The information that PSI and PCR maker provide according to operator generates the TS bag that comprises PSI and is divided into three kinds of PAT, PMT, SDT, and the PCR bag of generation has been reserved the PCR field, all stores into respectively among the RAM in the hardware accelerator part through bus after these four bags generate; The first-born information generation PES head that needs from coding side acquisition generation PES of growing up to be a useful person of video PES stores into VPES the memory.

Further, as a kind of preferred, the parameter acquiring device is used to obtain the configuration information of CPU part to hardware; The enabling signal of hardware accelerator part also is that the mode through parameter acquiring obtains, and the multiplexer outlet selector is according to the output frequency that obtains PSI, PCR and audio frequency and video from the parameter acquiring device, and the priority orders of pressing PCR＞PSI＞audio frequency＞video; Select above-mentioned several kinds of bags output; When the satisfied output of above-mentioned several kinds of bags required, the empty bag filling of output guaranteed that output continuously; When needs VPES data, VPES head output that earlier will be current from the data output of resuming studies out of VES memory relaying, guarantees to form VPES head and the correct VPES of VES composition again.

Further, as a kind of preferred, the request of data device is judged the memory space residue size of VES memory and APES memory, when remaining space is lower than threshold value, just partly sends request signal to CPU; The request configuration DMA of hardware requests responsor real-time response request of data device, DMA from external memory storage, obtains audio frequency PES and video ES stores in the corresponding memory.

Wherein: PSI: program Proprietary Information, PCR: program clock reference, STC: system sequence clock, DMA: direct memory access (DMA) module, PAT: Program Association Table, PMT: program information table, SDT: service describing table, VPES: video PES.

In terms of existing technologies, the present invention has following advantage: 1) adopt the software-hardware synergism design, can strengthen multiplexing flexibility, reduced the complexity of hardware again simultaneously, most important real-time also can be guaranteed.2) the PCR counter has adopted the hardware realization, and PCR renewal when final output, guarantees to have reduced the PCR shake.3) valid data of audio frequency and video evenly distribute in whole code stream, have reduced decoding end is received the buffer zone size.

Description of drawings

When combining accompanying drawing to consider; Through with reference to following detailed, can more completely understand the present invention better and learn wherein many attendant advantages easily, but accompanying drawing described herein is used to provide further understanding of the present invention; Constitute a part of the present invention; Illustrative examples of the present invention and explanation thereof are used to explain the present invention, do not constitute to improper qualification of the present invention, wherein:

Fig. 1, audio/video coding multiplex system figure in the prior art;

Fig. 2, audio frequency and video multiplexer figure of the present invention;

Fig. 3, STC structure chart of the present invention.

Embodiment

For make above-mentioned purpose, feature and advantage can be more obviously understandable, below describe with reference to Fig. 2-3 pair embodiments of the invention.

The present invention has mainly designed a kind of audio frequency and video multiplexer, and its structure such as Fig. 2 mainly comprise like lower unit:

CPU part 1 comprises:

PSI and PCR maker 11, the data that provide according to operator generate the TS bag that comprises PSI and PCR;

Video PES is first-born to grow up to be a useful person 12, generates video PES head, and video is that a PES divides into groups with the data of a frame;

Hardware requests responsor 13, the request of data that real-time response hardware sends also disposes DMA, comprises the Voice & Video request of data;

Hardware accelerator part 2 comprises:

Parameter acquiring device 21 obtains parameter from configuration register;

RAM22, storage PSI and PCR bag;

VPES memory 23, video information memory 24, VES memory 25, APES memory 26, MPTS are debugged output storage 28, and several memory are stored corresponding data respectively;

Multiplexing outlet selector 29 is selected suitable bag output from PSI, PCR, audio frequency and video and empty bag;

Output buffer 31, the TS stream of interim storage output guarantees that output is continuously;

STC30, the system reference clock generates PCR_Base and PCR_Ext.

The information that multiplexer PSI and PCR maker 11 provide according to operator generates the TS bag that comprises PSI and is divided into three kinds of PAT (Program Association Table), PMT (program information table), SDT (service describing table); The PCR bag that generates has been reserved the PCR field, all stores into respectively among the RAM 22 in the multiplexer hardware accelerator part 2 through bus 5 after these four bags generate; 12 information that obtain to generate PES and need from coding side of growing up to be a useful person that video PES is first-born generate the PES head store into multiplexer hardware accelerator part 23.

Configuration register in the hardware accelerator part 2 of multiplexer CPU part 1 configure multiplexer; The parameter acquiring device is resolved configuration register; And start the enabling signal of multiplexer hardware accelerator part 2, the operation of two aspects below after multiplexer obtains enabling signal, mainly carrying out according to front end coded data preparation configuration:

On the one hand, multiplexer request of data device 27 is judged the memory space residue size of VES memory 25 and APES memory 26, when remaining space is lower than threshold value, just sends request signal to multiplexer CPU part 1; The request configuration DMA4 of hardware requests responsor 13 real-time response request of data devices 27, DMA4 from external memory storage 3, obtains audio frequency PES and video ES stores in the corresponding memory.

On the other hand; Multiplexer outlet selector 29 is according to the output frequency that obtains PSI, PCR and audio frequency and video from the parameter acquiring device, and the priority orders of PCR＞PSI＞audio frequency＞video, selects above-mentioned several kinds of bags output; When also exporting by the suitable bag of selection from the bag of PSI, PCR, audio frequency and video and this several types of filling bag; When the satisfied output of above-mentioned several kinds of bags required, the empty bag filling of output guaranteed that output continuously; When needs VPES (video PES) data, VPES head output that earlier will be current is exported from the VES memory relaying data of resuming studies out again.Guarantee to form VPES head and the correct VPES of VES composition.

Output buffer 31 comprises the memory space of two TS bags, and the data that multiplexing outlet selector can be exported TS bag when residual memory space wraps greater than a TS are in buffering area; When output buffer is exported, need to judge output bag type, when the output-pcr bag, need PCR_Base and the PCR_Ext of STC be updated in the PCR respective field in this bag; Multiplexer CPU part 1 configurable outgoing route, one is to form MPTS through PSI output, other one is to output to transmit stream debugging output storage 28, outputs to convenient debugging in the external memory storage 3 through bus 5 again.

As shown in Figure 3 is STC30 structure chart of the present invention, mainly comprises following components:

Mux clock 11, the reference clock of PCR is 27MHz, but the clock frequency of multiplexer of the present invention operation might not be 27MHz, could obtain PCR value accurately so need carry out frequency division to system clock in use;

Frequency divider 12, be for the clock that obtains 27MHz as the reference clock that obtains the PCR_Ext counter;

Frequency divider 13, the clock that the mux clock frequency division is obtained 90KHz is counted reference clock as PCR_Base;

Counter 14, bit wide are 9, with the 27MHz clock count, generation be PCR_Ext;

Counter 15, bit wide are 33, with the 90KHz clock count, generation be PCR_Base.

Whole STC30 generates PCR value accurately, upgrades the value of PCR during TS output.Reduce the PCR shake.

As stated, embodiments of the invention have been carried out explanation at length, but as long as not breaking away from inventive point of the present invention and effect in fact can have a lot of distortion, this will be readily apparent to persons skilled in the art.Therefore, such variation also all is included within protection scope of the present invention.

Claims

1. an audio frequency and video multiplexer is characterized in that, comprising: CPU part (1), hardware accelerator part (2), and two parts communicate and transfer of data through bus (5); CPU part (1) has comprised PSI and PCR maker (11), video PES is first-born grows up to be a useful person (12) and hardware requests responsor (13), links bus (5) respectively; Hardware accelerator part (2) comprises parameter acquiring device (21), request of data device (27), multiplexing outlet selector (29), STC (30), output buffer (31) and RAM (22), VPES memory (23), video information memory (24), VES memory (25), APES memory (26), the MPTS debugging output storage (28) that is connected to bus (5); External memory storage (3) is used for through the ES stream of bus (5) store video and audio frequency PES stream; DMA (4) is used for through bus (5) the transfer of data of external memory storage VES memory (25) and the APES memory (26) in the hardware accelerator part (2).

2. audio frequency and video multiplexer according to claim 1; It is characterized in that; The information that PSI and PCR maker (11) provide according to operator generates the TS bag that comprises PSI and is divided into three kinds of PAT, PMT, SDT; The PCR bag that generates has been reserved the PCR field, all passes through bus (5) after these four bags generate and stores into respectively among the RAM (22) in the hardware accelerator part (2); Video PES is first-born, and grow up to be a useful person information that (12) to generate PES and need from coding side generates the PES head and stores into VPES the memory (23).

3. audio frequency and video multiplexer according to claim 1; It is characterized in that; Request of data device (27) is judged the memory space residue size of VES memory (25) and APES memory (26), when remaining space is lower than threshold value, just sends request signal to CPU part (1); The request configuration DMA (4) of hardware requests responsor (13) real-time response request of data device (27), DMA (4) from external memory storage (3), obtains audio frequency PES and video ES stores in the corresponding memory.

4. audio frequency and video multiplexer according to claim 1; It is characterized in that parameter acquiring device (21) is used to obtain the configuration information of CPU part (1) to hardware, the enabling signal of hardware accelerator part (2) also is that the mode through parameter acquiring obtains; Multiplexer outlet selector (29) obtains the output frequency of PSI, PCR and audio frequency and video from parameter acquiring device (21); And the priority orders of pressing PCR＞PSI＞audio frequency＞video, select above-mentioned several kinds of bags output, when the satisfied output of above-mentioned several kinds of bags requires; The empty bag of output is filled, and guarantees that output continuously; When needs VPES data, earlier with current VPES head output, with the output of VES stream, assurance forms the VPES head and VES forms correct VPES again.

5. audio frequency and video multiplexer according to claim 1; It is characterized in that; Output buffer (31) adopts the PING-PANG structure, comprises the memory space of two TS bags, and the data that multiplexing outlet selector (29) can be exported TS bag when residual memory space wraps greater than a TS are in buffering area; When TS bag when output buffer export, need to judge that output wraps type, when the output-pcr bag, need PCR Base and the PCR Ext of STC be updated in the PCR respective field in this bag; The configurable outgoing route of CPU part, one is to form MPTS through PSI output, other one is to output to transmit stream debugging output storage (28), outputs in the external memory storage (3) through bus (5) again.