Thanks Moritz for the quick response!
Here's my command in its full context:
ffmpeg -hide_banner -f s16le -ac 2 -ar 44100 -channel_layout stereo -f alsa
-i hw:2 -filter:a "volume=1.5" -ab 192k -acodec mp3 -f mp3 - | ffmpeg
-hide_banner -f mp3 -i - -c copy -f mpegts udp://<ip>:1685 -c copy -f mp3
udp://0.0.0.0:1685
Input #0, alsa, from 'hw:2':
Duration: N/A, start: 1726316588.273876, bitrate: 1411 kb/s
Stream #0:0: Audio: pcm_s16le, 44100 Hz, stereo, s16, 1411 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (pcm_s16le (native) -> mp3 (libmp3lame))
Press [q] to stop, [?] for help
Output #0, mp3, to 'pipe:':
Metadata:
TSSE : Lavf58.45.100
Stream #0:0: Audio: mp3 (libmp3lame), 44100 Hz, stereo, fltp, 192 kb/s
Metadata:
encoder : Lavc58.91.100 libmp3lame
Input #0, mp3, from 'pipe:':0.91 bitrate= 197.4kbits/s speed=0.912x
Metadata:
encoder : Lavf58.45.100
Duration: N/A, start: 0.000000, bitrate: 192 kb/s
Stream #0:0: Audio: mp3, 44100 Hz, stereo, fltp, 192 kb/s
Output #0, mpegts, to 'udp://<ip>:1685':
Metadata:
encoder : Lavf58.45.100
Stream #0:0: Audio: mp3, 44100 Hz, stereo, fltp, 192 kb/s
Output #1, mp3, to 'udp://0.0.0.0:1685':
Metadata:
TSSE : Lavf58.45.100
Stream #1:0: Audio: mp3, 44100 Hz, stereo, fltp, 192 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Stream #0:0 -> #1:0 (copy)
size= 1346kB time=00:00:57.39 bitrate= 192.1kbits/s speed=0.999x
No, it doesn't glitch if I stream directly from the first ffmpeg process to
any of the outputs.
Thanks for the tip regarding the complete, uncut console output, which I
didn't study in detail before. I suddenly realized that there are
corresponding entries with "ALSA buffer xrun." in the log for every glitch.
I reckon this may be fixed by setting "-thread_queue_size" for the input in
my second ffmpeg. I will try different values and come back here if I don't
get it right...
Thanks again
Anders
Den lör 14 sep. 2024 kl 13:50 skrev Moritz Barsnick via ffmpeg-user <
ffmpeg-user@ffmpeg.org>:
> Hej Anders,
>
> On Sat, Sep 14, 2024 at 13:32:01 +0200, Anders Bjerkén wrote:
> > ffmpeg -f alsa -i hw:2 -filter:a "volume=1.5" -ab 192k -acodec mp3 -f
> mp3 -
> > | ffmpeg -f mp3 -i - -c copy -f mpegts udp://<external_ip>:1685 -c copy
> -f
> > mp3 udp://0.0.0.0:1685
>
> It's usually expected to also post the complete, uncut console
> output(s) here.
>
> > Conceptually, it works. However, every now and then I get synchronized
> 1-2
> > second long glitches in the outcoming data stream for both outputs.
>
> This sounds like a buffering issue.
>
> What happens if you stream directly from the first ffmpeg process to
> one of the outputs? Does it also glitch?
>
> You could consider using one ffmpeg process and the "tee" muxer. I'm
> not sure it will solve your problem, but could be an alternative and a
> more lightweight command line.
>
> > have used all suggested versions of this command mentioned
> > on https://trac.ffmpeg.org/wiki/Creating%20multiple%20outputs, but with
> the
> > same result in the end.
>
> Ah, I forgot that the "tee" muxer is mentioned there as well.
>
> Moritz
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