[mythtv] GOP_BYFRAME vs. GOP_START and mythcommflag --rebuild

[Boleslaw Ciesielski]

Doug Larrick wrote:
> Is there a reason that avformatdecoder creates positionmaps using
> MARK_GOP_START (using keyframe number, assuming a fixed keyframe
> interval) rather than MARK_GOP_BYFRAME (using frame number) by default?
>  Maybe non-avformatdecoder playback needs the other format?
> 
> When using mythcommflag --rebuild on an ATSC-sourced MPEG2 recording,
> this results in a totally broken positionmap, since ATSC keyframes come
> in at irregular intervals.
> 
> I've "fixed" this in my local tree by hardcoding the affected function
> (AvFormatDecoder::OpenFile) to always use MARK_GOP_BYFRAME but I'm
> wondering if there's a more general way to fix the problem.  Currently
> it chooses BYFRAME for avi files; perhaps it should do so for transport
> streams as well?  Or for everything?

I don't have the answer but there is a ticket for this:

http://svn.mythtv.org/trac/ticket/1088

Bolek