Ron Economos wrote: > BTW, the 8x8 transform (and variable quantization matrix) > was put back into H.264 High Profile after it was found that > the 4x4 transform looks like shit at HD resolutions. > Basically the 4x4 transform (with it's fixed quantization > matrix) cannot always generate enough coefficients to > provide a sharp image. Today, almost all broadcast HD H.264 > is using High Profile. You mean, just for the motion estimation, I assume. The macroblocks are still 16 X 16. Interesting tradeoff. The idea of gaining motion estimation efficiency with the 4 X 4 fixed block size, because smaller parts of the image could be used for the difference signals, had to be balanced against the loss of high frequency components when doing the integer transform of the motion vector. Resulting from such small blocks. If that turned out to be a bad choice, I wonder if this has anything to do with the actual bit rates required for H.264 HDTV, vs the more optimistic predictions made previously? In other words, maybe this was another reason to keep the GOP smaller than ideal, from a compression point of view? Bert ---------------------------------------------------------------------- You can UNSUBSCRIBE from the OpenDTV list in two ways: - Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word unsubscribe in the subject line.