The file is one big VOB file. I don't want to rely on any information that
isn't actually included in the file that we are using - the application that
will use this is being designed to work with any MPEG2 video stream like you
would find on a DVD. To keep things independent, I need to determine the
number of frames programmatically, without any user input or foreknowledge
of the stream being analyzed.

I know the framerate information has to be in there somewhere, as the VOB
file that I dump using mplayer is playable, and I can get correct framerate
info out of players like VLC and the various mplayer frontends.

Thanks for all the help,

Sam


sngardner wrote:
> 
> Hey Guys -
> 
> I need to figure out how to do a rough estimation of the number of frames
> in an mpeg file.
> 
> I would just figure out the number of seconds in the file by reading the
> AVFormatContext info, and multiply by 30, but the duration field doesn't
> always seem to be accurate. The file I am attempting to analyze seems,
> based on mplayer's output, to change framerates from something higher to
> the normal NTSC film standard after about 30 seconds. The duration field
> seems to be set using the higher framerate, as, after doing the AVRational
> math, I end up with a movie that the duration field says is one hour long
> but in actuality is about an hour and fifteen minutes.
> 
> The frame count I need doesn't need to be accurate, but this is far enough
> off that it's causing problems.
> 
> Does anyone have any idea how I might more accurately estimate the number
> of frames, and also, how to read the framerate out of the video using
> libav?
> 
> Thanks a lot for the help
> 

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