gstreamer playback decklink - delay audio

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Roland Horak

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  • Joined: Tue Aug 28, 2012 8:36 am

gstreamer playback decklink - delay audio

PostFri Oct 21, 2022 2:52 pm

Dear blackmagic developer community,
I am running gstreamer (1.20.3) on ubuntu 22.04 LTS with decklinkdrivers (12.4)
After building (and playing around with gstreamer, watching tutorials etc) the following pipeline I am able to decode a high quality HD SRT Stream (udp streaming) and am outputting it to SDI (in 1080i50), works very well.

gst-launch-1.0 -v srtsrc uri=srt://x.x.x.x:xxxx latency=200 ! tsdemux name=demux demux. ! h264parse ! video/x-h264 ! avdec_h264 ! queue ! videoconvert ! video/x-raw,format=UYVY ! decklinkvideosink mode=1080i50 sync=false demux. ! avdec_aac ! queue ! audioconvert ! audio/x-raw, format=S32LE, channels=2 ! decklinkaudiosink

Audio to Videosync is stable to each other for hours (didn't test for days), but after testing the encoder to decoder end to end on my gstreamer pipeline audio comes a little too early (about 60ms early).

I tried to only change buffersize in audiopart of the pipeline to correct the timing on the audiosite e.g. queue max-size-buffers=0 max-size-time=0 max-size-bytes=0 min-threshold-time=60000000

but audio to video offset didn't change here trying several different min-threshold-times.

for the decklinkaudiosink there is no ts-offset cap to change the timing here and also changing the buffer-time property here didn't change anything.

Can anybody please help me here how to correct the audio timing or audio latency to accurate videodecoding on my pipeline!?
Thanks!

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