[opendtv] Re: Comparison of H.264 with MPEG-2
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Mon, 26 Sep 2005 19:59:07 -0400
Craig Birkmaier wrote:
> Gary Sullivan wrote:
> >
> > This notion that the gain in compression effectiveness
> > for using the new standard instead of MPEG-2 has
> > something to do with stretching out the GOP length is
> > annoying. That is definitely *NOT* what is going on,
> > and it is *NOT* how we estimate compression benefits in
> > codec design.
>
> Thanks Gary. It's good to see that you are listening, and
> willing to take the time to help educate the OpenDTV
> community.
Indeed it was good of Gary to explain the impact of the
reduced size of the separate types of pictures (I, P, B).
The results according to
http://www.chiariglione.org/mpeg/working_documents/mpeg-04/avc/avc_vt.zi
p
show that if you limit your comparisons to those scenarios
that apply to SDTV or HDTV, improvements of 2x or better
were not the majority of cases. For SD examples, 2x or
better was achieved in 14 out of 40 tests. For HD, 2x or
better was achieved in 10 out of 32 tests.
So even though the GOP length did not change when making
these comparisons, GOP length *would* be a factor if you
want to show off consistently large imporvements. And
that is evidently why GOP length was an issue at IBC, Craig.
Which is what Gary Hughes pointed out. I don't think either
Gary has said "GOP has nothing to do with it."
Bert
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