[mythtv] Mythtv mpeg frame counting - patch?

Daniel Kristjansson danielk at cuymedia.net
Fri Jun 15 13:45:19 UTC 2007

On Fri, 2007-06-15 at 09:00 -0400, Bill wrote:
> Ok now I'm confused. I decided to look at the frame counting on the playback 
> side first, since the decode is already been done, its a little easier to 
> get started and familar with the code.  But it looks it me like the frame 
> counting is ok on playback; its incremented only after a successful decode 
> and anyway, av_read_frame performs some partial parsing and is suppose to 
> return only complete video frames.

The frame counting on the frontend is basically ok, the only
time it is off is when the video resolution or aspect ratio
changes, but this doesn't effect seeking. This is why one of
the suggestions for fixing #799 is to use ffmpeg to do a
partial decode for frame counting on the backend.

> What am I missing for this problem?  I checked the repeat_pic field in 
> AVFrame (I think it is); this is not the problem.  It is almost as if the 
> actual frame rate is 24, or the frame rate is not constant or for DVB 
> broadcast they are playing some other tricks to save bandwidth. 

Frame rate is not always constant for DVB broadcasts. Sometimes
the commercials are at a different rate than the program. Also,
if MythTV catches a little bit of the previous or later program,
these may be at different frame rates. Telecining is not a
problem, ffmpeg sends us all the frames, and leaves it up to
us to do any inverse telecine filtering.

-- Daniel

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