AVS Decoding Algorithm Research And Optimized Implementation On DSP

AVS (digital audio and video codec technology),which is taken as source coding standards by our own intellectual property and its video portions’ standards have the properties that contain very high compression coding efficiency and low complexity algorithm, is suitable for development in the embedded platform and widely used in the fields such as digital TV, web camera. With the rapid development of embedded systems, the mobile terminal to transmit video streams, whose use volume is smaller and appearance is more attractive, becomes the mainstream increasingly. Texas Instruments company provides an open Multimedia Application Platform-OMAP3530(Open Multimedia Application Platform), which is a system-on-chip (SoC). It not only has the very small size and power consumption, but also has more efficient processing of multimedia data streaming video. In view of the implements that OMAP3530platform AVS video decoder real-time decoding704*576format video stream, this topic’s main research content, work and achievements are as follows:Firstly, this paper introduces the AVS video standard system structure, gives the overall block diagram of the decoder, analyses the decoder and the related core technologies of AVS video decoder from the two parts of parsing and decoding, researches the core module of the decoder algorithm, highlights the entropy decoding, the intra and inter frame prediction, the filter.Secondly, in view of the characteristics of DSP, the paper adjusts the overall process of AVS video decoder transplanted into the DSP platform, divides the I-frame decoding and PB-frame decoding separately, gives the important flowchart of the decoder module, and analyses the decoder decoding complexity of the main function by the DSP platform testing tools.Finally, the paper implements the C-level optimization and assembly optimization for the core module of the decoder, emphasis AVS entropy decoding variable length code decoding features, improves the look-up table by the different packet reordering of the code word, make it can depredate complexity on the DSP, and adjusts the table storage structure accordingly to reduce the number of look-up table, reduces the complexity of the look-up table through the assembly language. To further enhance the decoding speed and improve the quality of the decoded image, the paper also proposes a new the boundary loop filter mode, reuses the current macro block data at the greatest extent by the assembly code to save loop filter required time.Through the comprehensive test, we can see that using the assembly instructions optimizer not only saves a lot of storage space, but also the code execution cycle is only23.8%of the original decoder and improves the decoding efficiency to reach the goal of real-time decoding requirements under the premise that not changing the image quality.