[FFmpeg-devel] Stream selection algorithm crossing program boundaries

Gyan Doshi gyandoshi at gmail.com
Fri May 18 17:24:07 EEST 2018

On 5/18/2018 6:50 PM, Devin Heitmueller wrote:

> Is this something anyone is actively looking into?  If not, I'll dig into it and see about respecting program membership in ffmpeg's selection algorithm.  My larger concern is that with MPEG-TS streams, the commonly accepted heuristic is to play the first audio/video streams in the first PMT entry (this is what VLC does for example), rather than trying to pick the "best quality" streams, and it's not clear whether such a change in the selection algorithm would be accepted upstream (since it would make selection of audio/video in MPEG-TS streams behave differently than other formats).
> Thoughts?

If nb_input_files is 1, coupling the stream selection seems to me an 
improvement. But in the scenario of multiple inputs and no -map options, 
users usually intend to want a stream from all the sources, so in that 
case, using one of the streams as a 'key' for the other streams will 
break expectations. Unless the other inputs are meant for filtering, 
like a watermark, or background music.

Your query has come at an inopportune time, since I intended to rewrite 
the Stream Selection chapter this weekend, since there are some quirks 
and nuances not covered or made plain, at present. But if you intend to 
proceed, of course, I'll wait.


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