[FFmpeg-user] Increased latency from filter_complex

Paul B Mahol onemda at gmail.com
Fri Jul 30 00:55:05 EEST 2021

On Thu, Jul 29, 2021 at 7:13 PM <technik+ffmpeg at vistream.online> wrote:

> Hi Paul,
> thanks again for answering.
> > Please show how you use sidechaincompress filter.
> Basically we did what is mentioned here:
> https://superuser.com/questions/1093607/ffmpeg-sidechaincompress-give-more-importance-to-the-sidechain
> We too found no audible difference between ratio 1 and ratio 20.
> But this all doesn't touch the initial question I contacted the mailing
> list for.
> We found that applying any ducking increased latency. by ~8 seconds and
> for every additional audio track it added 8 seconds on top.

Is sidechaincompress adding 8 seconds of latency too?

ratio in processing is used with other options in parallel, especially

Copying random commands with little or no understanding how filter is
working will get you nowhere.

Please read documentation of sidechaincompress filter, and experiment with
command provided in documentation.
Probably need to use amix filter instead of amerge as last filter in

> So it seems like the analyzing of the the audio tracks happens sequentially
> at least for the filters we used.
> What I wanted to know is, if there are ways to write those differently to
> mitigate this problem.
> In case of the sidechain filter, if this is handled sequentially too, the
> problem would still be there, even if a sidechain might be less workload.
> @all Anybody else knows how to do this in parallel instead?

Latency of loudnorm and dynaudnorm filters are extremely high compared to
sidechaincompress, always couple of seconds.

And keeping using those filters you will never expect less latency.

You can control latency in some cases with asetnsamples filter as first
filter in filtergraph.

Also if you willing to provide input demo files I may look more into this,
to help you get correct filtergraph.

Also note that encoder may add additional latency.

> Thanks
> Philipp
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