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

[Justin Randall]

On 6/8/07, Nico Sabbi <nsabbi at email.it> wrote:
> Nicolas Hesler wrote:
>
> >Nico Sabbi wrote:
> >
> >
> >>Nicolas Hesler wrote:
> >>
> >>
> >>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>Thanks again for your prompt help.    Why do you say magically?  What
> >>>is controversial with those options?
> >>>
> >>>
> >>>
> >>>
> >>>
> >>as I wrote, -mc 0 -noskip disables mencoder's mechanism to keep synchrony
> >>
> >>
> >>
> >
> >I guess what I meant to ask was :  so mencoder's mechanism for keeping
> >synchrony doesn't always work and disabling sometimes keeps sync?
> >
> >
> yes
>
> >So even if I get 1 duplicate frame (which seems to be case, in all my
> >videos), it could still be in absolute sync?
> >
> >
> yes
>
> >How is it that the A-V sync info is not always an indicator of sync?
> >
> >
>
> sometimes, with some crazy containers used in horrible manners
> (think of mpeg*, H264 of avi, packed mpeg4 in avi and other amenities)
> mencoder doesn't even know the correct timestamps of the original streams,
> thus you can't expect it to do a good job in the output stream

I was under the impression that using -harddup at the end of the
filter chain will preserve A-V sync thoughout the steam, so for
example if I pulled out my h.264 video and aac audio from the avi
container and remux into .mp4 container the A-V sync is preserved.
Otherwise it is likely that you will have sync issues because of the
way MEncoder handles duplicate frames in the avi container (just puts
a marker there instead of actually duplicating the frame).  Can
somebody correct me if I'm wrong about this?  Thanks.