avoid decoding not-linked streams
Submitted by Thiago Sousa Santos
Since the 0.10 -> 1.0 move, the feature that was used to make not-linked streams skip decoding until linked again is gone.
It was done by input-selector returning not-linked on pad-allocs and the decoder would drop that buffer and return not-linked. Nothing has replaced this behavior in 1.0 (yet).
This can be easily demonstrated with the following scenario:
Create a test clip with multiple videos:
gst-launch-1.0 videotestsrc num-buffers=500 pattern=0 ! x264enc ! qtmux name=m ! filesink location=3video.mov videotestsrc num-buffers=500 pattern=1 ! x264enc ! m. videotestsrc num-buffers=500 pattern=18 ! x264enc ! m.
Play the clip and look at the debug logs for the video decoders:
GST_DEBUG=videodec:9,avdec:9 gst-launch-1.0 playbin uri=file:///path/to/3video.mov
A similar scenario is solved in dash/mss demuxers using the not-linked return and reconfigure events to stop/reactivate those streams. The use case is a bit different but I guess the mechanism can work the same.
- Is this a behavior break?
- How to avoid dropping buffers that are ahead of the current play position? It would be better if the decoder would only drop a buffer to avoid decoding when it knew that this buffer is too late to be used.
- How does this interfere with the buffer pools and allocation queries?