Research On H.264 Rate Control Algorithm And Implementation Of The Encoder Based On DM642

As the newest generation of video coding standard, H.264 inherits merits from contemporary video coding standards as well as brings up many new ideas to achieve a better compression performance. However, the performance improvement is at the expense of computational complexity increment.Compared with some traditional standard like MPEG-4, complexity of the encoder and the decoder of h.264 are increase sharply, therefore, maintaining the high compression ratio and reducing the computational complexity at the same time is the hotspot in the research of h.264.In this paper, our work focus on two parts, one is the research and improvement of H.264 rate control algorithm; the other is the implementation and optimization of H.264 soft codec on DM642.The main object of video coding is to minimize the distortion subject to a constraint bit rate, rate control play a important role in video coding and communication systems, it has been widely studied in kinds of video coding standards. In H.264, the quantization parameters are used in both rate control algorithm and rate distortion optimization, which resulted in the following chicken and egg dilemma: to perform RDO for macroblocks in the current frame, a quantization parameter should be first determined for each MB by using the mean absolute difference of current frame or MB. However, the MAD of current frame or MB is only available after the RDO. In this paper, based on JVT-G012 and JVT-O016, perform a improvement to rate control algorithm of JM8.6, approved a new weight predict model instead of traditional linear pridict model MAD, meanwhile, macroblocks level rate control scheme is added in, the encoder which adopts the new rate control algorithm get a better reconstructed image quality. TMS320DM642 is one high performance digital media processor recommended by TI. Its two-level cache structure could help to operate the high-complexity video coding algorithm efficiently. In this paper, achieving the communication between the DSP and PC through JTAG simunations, H.264 software codec was obtained in CCS, and it was emulated on DM642 EVM, the optimizations of the DSP code are carried out according to the features of DM642 at three levels gradually: project level, algorithm level and structure level, which reduce the length of the code obviously, improve the compression ratio, decrease the encoding time and delay efficiently.The experiments show that, compared with video encoder based on PC, our design has better performance and efficiency, achieves well image compression ratio(20~30 times)and high quality of the reconstructed video image(PSNR about 40dB), could meet the requirement of the real-time application in video compression and transmission.