[MEncoder-users] B-frames and GOP with MPEG-2 for DVD

[Justin Randall]

On 6/7/07, Nico Sabbi <nicola_sabbi at fastwebnet.it> wrote:
> Nicolas Hesler wrote:
> > Nico Sabbi wrote:
> >
> >>Nicolas Hesler wrote:
> >>
> >>
> >>
> >>>Really??? Good to know.
> >>>
> >>>So, get rid of the vb_strategy thing too? This doesn't affect the GOP on
> >>>2pass without B frames right?
> >>>
> >>>
> >>
> >>vb_strategy affects only the placement of b-frames, and it's damn slow too
> >>_______________________________________________
> >>
> >
> > So why have a b frames option in the first place, if it only degrades
> > the quality?  For smaller encodes?
>
> supposedly for encodes targeting a low bitrate, but even in cases like
> that I've only seen overall image degradation with b-frames, both with
> lavc and with xvid, at any bitrate
>
> > So as a rule, never use B-Frames unless you're concerned with space?
>
> I never use b-frames _at_all_ , although with x264 b-frames maybe
> aren't so harmful (or maybe they are even beneficial, but I never
> tested the encoder extensively to say for sure)

Why would you never use B-frames in your encodes?  Isn't that the
whole point of encoding to MPEG-4?  To save space without sacrificing
quality?? I understand why you don't use B-frames on MEncoder because
support is b0rked as far as I know (has this changed?) but for x264
MPEG-4 AVC etc. B-frames are great!  If you're encoding for Quicktime
with x264 I know it supports up to 2 B-frames, and generally I encode
with 3 B-frames.  It's great for compression and does not sacrifice
quality at all (I can't speak for XviD or ASP compression, but I know
from experience that B-frames on x264 and AVC compression is awesome).