[FFmpeg-user] Need info on ATSC3 stream capture going wrong

Deron deron at pagestream.org
Thu Apr 18 19:25:52 EEST 2019

> Hello, this is a really strange one for me that is way outside my 
> understanding. I've been using ffmpeg to stream tv shows and I've run 
> across a TV station I can not capture! The symptoms are after 12:55 or 
> so minutes the audio goes silent in the output, and shortly after that 
> ffmpeg quits. This works with some 40 other tv channels!

I've managed to narrow down my problem to -async. Put simply, these 
commands work:

    ffmpeg -i "/dev/dvb/adapter5/dvr0" -y out.ts

    ffmpeg -i "/dev/dvb/adapter5/dvr0" -async 1 -y out.ts

and this does not:

    ffmpeg -i "/dev/dvb/adapter5/dvr0" -async 2000 -y out.ts

And I get similar output from my previous report:

[graph_1_aresample_in_0_0 @ 0x563ce00fa0c0] [SWR @ 0x563ce063a8c0] 
compensating audio timestamp drift:-0.001021 compensation:-49 in:48000
[graph_1_aresample_in_0_0 @ 0x563ce00fa0c0] [SWR @ 0x563ce063a8c0] Using 
fltp internally between filters
[graph_1_aresample_in_0_0 @ 0x563ce00fa0c0] [SWR @ 0x563ce063a8c0] 
adding 16384 audio samples of silence
[graph_1_aresample_in_0_0 @ 0x563ce00fa0c0] [SWR @ 0x563ce063a8c0] 
adding 15312 audio samples of silence
/dev/dvb/adapter5/dvr0: Value too large for defined data type
[out_0_1 @ 0x563ce00f9d40] EOF on sink link out_0_1:default.
/dev/dvb/adapter5/dvr0: Value too large for defined data type
[out_0_0 @ 0x563ce05928c0] EOF on sink link out_0_0:default.
No more output streams to write to, finishing.

Looking for some ideas on the nature of my problem. The log output that 
talks about "compensating audio timestamp drift" clearly gets it -49 
value as number of samples needed to compensate for the drift (-.001021 
seconds * 48000 samples/second = -49 samples). So why does it try to add 
16384 + 15312 samples? Is that it can only compensate in a positive 
direction (it should be dropping 49 samples not inserting 49)?

Thanks for any help,


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