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As bit-rate reduction has become pervasive in emission, contribution, and distribution of video content,multiple compression and decompression (codec) cycles are required. Concatenation of codecs may beneeded for production, post-production, transcoding, or format conversion. Any time video transformations toor from the coefficient domain of macroblock-based algorithms are performed, care must be exercised inalignment of the video both horizontally and vertically as it is coded from the raster format or decoded andplaced in the raster format.
Over multiple compression and decompression cycles, it is highly desirable to maintain the original positioningof the video signal within the raster. Less obvious, but just as important, is the need for macroblock alignmentto reduce artifacts among encoders and decoders from various equipment vendors. If concatenated encodersdo not share common macroblock boundaries, then additional quantization noise, motion-estimation errors,and poor mode decisions may result. Likewise, encoding decisions that may be carried through theproduction and post-production process with recoding data present will rely upon macroblock alignment.Conforming to this practice will minimize artifacts in multiple generations of compression (bit-rate reduction)encoding and decoding by optimizing macroblock alignment.
Product Details
- Published:
- 04/18/2008
- Number of Pages:
- 7
- File Size:
- 1 file , 97 KB
