[opendtv] Re: Video compression artifacts and MPEG noise reduction

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Sun, 22 Jun 2008 19:05:20 -0400

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?

You can UNSUBSCRIBE from the OpenDTV list in two ways:

- Using the UNSUBSCRIBE command in your user configuration settings at 

- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word 
unsubscribe in the subject line.

Other related posts: