[FFmpeg-user] Dissecting a transport stream (.ts) temporally

grmat grmat at sub.red
Sun Mar 1 15:40:40 EET 2020


> Can you describe these track changes? Not sure what is changing within the same channel, like a new program?

I hope this example makes it more clear:

The TV channel broadcasted news at 20:00 and started with a movie at ~20:15. The recorded .ts file starts at ~20:05 so the beginning isn't missed.
During the news, audio channel #0:3 is stereo, when the movie starts it switches to 5.1.

When I play the file in mpv with the corresponding channel selected and skip to just before the movie starts, audio is silent for a split second and mpv prints "Invalid audio PTS: 514.912589 -> 515.065922" to the terminal. Therefore, I assume that the 5.1 audio starts at ~515 (seconds) and it would be cool to be able to get this timestamp with ffmpeg so I wouldn't have to manually seek the recorded video with a player beforehand.

>> so that's detected correctly. Any ideas of extracting the actual timesttamps from those track changes?
> There’s literally no information about any timestamp or stream discontinuities in that example… As for the audio it's probably both? (5.1 matrixes into stereo) Just has the lowest common denominator flags for any compatibility issues.

The example was meant to prove that cutting a part out of the movie (or whatever it is), actually shows that we have a 5.1 channel stream here. My intention is to find out when exactly this stream changes from stereo to 5.1 to make a cut there with ffmpeg, if possible.


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