The emerging video coding standard, H.264/AVC, exhibits the unprecedented coding performance. Comparing to traditional coders, e.g., MPEG-2 and MEPG-4 ASP, about half bitrate saving is shown in the official verification test. Such outstanding performance makes it become the video compression candidate for the upcoming HD-DVD. As a side effect, it was also blamed that H.264/AVC is much more logically complex and requires more computation power than any of the existing standards. A low-cost and efficient implementation of the international standard hence plays an important role of its success. In this paper, we realize an H.264/AVC baseline decoder by a low-cost DSP processor, i.e., Philips’ TriMedia TM-1300, and illustrate that less computation demand for H.264/AVC decoding becomes feasible by using effective software core. To this end, we first consider different approaches and take advantage of SIMD instruction set to optimize critical time-consuming coding modules, such as the fractional motion compensation, spatial prediction and inverse transform. Next, we also present some other optimization approaches for entropy decoding and in-loop deblocking filtering, even though they cannot get benefits from utilizing SIMD. In our experiments, by exploiting appropriate instruction level parallelism and efficient algorithms, the decoding speed can be improved by a factor of 8~10; a CIF video sequence can be decoded at up to 19.74~28.97 fps on a 166-MHz TriMedia TM-1300 processor compared to 2.40~2.98 fps by the standard reference software.
Finding out the better parameter set (OffsetA and OffsetB) for conducting the de-blocking process of H.264/AVC, is capable of improving visual quality, said eliminating the resultant blocking artifact. Identifying which edges belong to blocking regions relies on the perceptual judging process of human beings. In fact, this subjective assessment may not exactly match existing objective assessing measurements, and the meaning of high PSNR does not always stand for less blocking artifacts. In this paper, we first introduce a new criterion for measuring the block boundary distortion by comparing the source video and the reconstructed video prior to the deblocking process. By jointly optimizing the objective picture quality and the blocky energy, the deblocking parameters decision process can find out a good balance between signal matching and blocky elimination, and therefore, maximize the effect of the built-in deblocking process. In our experiments, the proposed method can efficiently pick a better deblocking parameter set from all 169 possibilities for each coded frame and result in a better visual quality.