playbin3 hang when one of video/audio/text track failed to setup in decodebin3

[Edward Hervey]

Hi,

  This is indeed a regression, playbin3 should carry on playing back the other
tracks even though there is a missing decoder.

  I opened an issue to track this :
https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/1662

  BR,

    Edward

On Wed, 2022-12-14 at 06:40 +0000, Jared Hu wrote:
> Hi
>  
> We found when use playbin3 as playback pipeline, it will hang at startup when
> one of video/audio/text track setup fail.
>  
> After some analysis, eg, when video track setup fail, the hang happens like
> below:
>  
> Parsebin post stream collection message to parent bin when it expose all src
> pad (video audio & text)
> Playbin3 will handle stream collection message and do stream selection.
> Playbin3 will continue request sink pad for selected stream, eg, video and
> audio pad.
> But when setup video track in decodebin3, it failed (missing decoder) and
> didn’t release playsink video pad.
> Playsink will block sink pads until all pads receive something but video pad
> will never receive data.
>  
> Can we request playsink pads when decodebin emit no_more_pad signal, in this
> way, playsink only request the needed pads just like playbin2 do?
>  
> Attachment is my debug log, here I paste some key log:
> Decoder selection fail:
> 0:00:00.196080488   785 0xffff7c06ee40 DEBUG             decodebin3
> gstdecodebin3.c:2232:reconfigure_output_stream:<decodebin3-0> Reconfiguring
> output 0xffff74002490 to slot 0xffff80035f10, needs_decoder:1
> 0:00:00.200613128   785 0xffff7c06ee40 DEBUG             decodebin3
> gstdecodebin3.c:2323:reconfigure_output_stream: Could not find an element for
> caps video/x-pn-realvideo, width=(int)1920, height=(int)1080,
> framerate=(fraction)785645/32768,
> codec_data=(buffer)000000225649444f5256343007800438000c000000000017f9da0148102
> 040008000
> 0:00:00.200686688   785 0xffff7c06ee40 LOG               decodebin3
> gstdecodebin3.c:2329:reconfigure_output_stream:<decodebin3-0> selection
> unlocking from thread 0xffff7c06ee40
> 0:00:00.200935928   785 0xffff7c06ee40 LOG               decodebin3
> gstdecodebin3.c:2336:reconfigure_output_stream:<decodebin3-0> selection
> locking from thread 0xffff7c06ee40
> 0:00:00.200967608   785 0xffff7c06ee40 LOG               decodebin3
> gstdecodebin3.c:2336:reconfigure_output_stream:<decodebin3-0> selection locked
> from thread 0xffff7c06ee40
> 0:00:00.200994968   785 0xffff7c06ee40 DEBUG             decodebin3
> gstdecodebin3.c:2426:reconfigure_output_stream:<decodebin3-0> Cleanup
>  
> Audio pad is blocked, but video pad cannot been block, playsink only un block
> all pad when they are all blocked.
> 0:00:00.268118651   785 0xffff7c06eea0 LOG                 playsink
> gstplaysink.c:4425:sinkpad_blocked_cb:<playsink> locking from thread
> 0xffff7c06eea0
> 0:00:00.268144571   785 0xffff7c06eea0 LOG                 playsink
> gstplaysink.c:4425:sinkpad_blocked_cb:<playsink> locked from thread
> 0xffff7c06eea0
> 0:00:00.268166531   785 0xffff7c06eea0 DEBUG               playsink
> gstplaysink.c:4433:sinkpad_blocked_cb:<playsink:audio_sink> Audio pad blocked
> 0:00:00.268189451   785 0xffff7c06eea0 LOG                 playsink
> gstplaysink.c:4451:sinkpad_blocked_cb:<playsink> unlocking from thread
> 0xffff7c06eea0
>  
> Playsink: sinkpad_blocked_cb:
>   if (gst_play_sink_ready_to_reconfigure_locked (playsink)) {
>     GST_DEBUG_OBJECT (playsink, "All pads blocked -- reconfiguring");
>  
>     gst_play_sink_do_reconfigure (playsink);
>  
>     video_set_blocked (playsink, FALSE);
>     audio_set_blocked (playsink, FALSE);
>     text_set_blocked (playsink, FALSE);
>   }
>  
> Best regards
> Jared Hu