How does the syntax facilitate parallelism?
A. For MPEG-1, slices may consist of an arbitrary number of macroblocks. The coded bitstream must first be mapped into fixed-length elements before true parallelism in a decoder application can be exploited. Further, since macroblocks have coding dependencies on previous macroblocks within the same slice, the data hierarchy must be pre-processed down to the layer of DC DCT coefficients. After this, blocks may be independently inverse transformed and quantized, temporally predicted, and reconstructed to buffer memory. Parallelism is usually more of a concern for encoders. Macroblock motion estimation and some rate control stages can be processed independently. An encoder also has the freedom to choose the slice structure.
