[FFmpeg-user] Increased latency from filter_complex

[Paul B Mahol]

On Tue, Jul 27, 2021 at 12:36 PM <technik+ffmpeg at vistream.online> wrote:

> Hi everyone,
>
> we are using ffmpeg to create hls streams in multiple resolutions and also
> languages from incoming rtmp streams.
> When encoding without the filter_complex for ducking we get a minimal
> latency of
> around 8 seconds, but the moment we add the autoducking we jump up to
> around 15
> seconds. Also it seems that for every additional audio stream we add, it
> adds
> another 8 seconds of latency.
> The filter_complex is the folowing:
> ```
> -filter_complex
> "format=nv12,hwupload,scale_vaapi=w=1280:h=720,split=2[720p][480];[480]scale_vaapi=w=854:h=480,split=2[480p][240];[240]scale_vaapi=w=426:h=240[240p];
> \
>         [0:a:0] loudnorm=i=-16.0:lra=12.0:tp=-3.0, asplit=2 [normalize]
> [out]; \
>         [normalize] volume=0.1, asplit=2 [bg1] [bg2]; \
>         [1:a:0] agate, adelay=2900:all=1 [tmp1]; \
>         [bg1][tmp1] amix, dynaudnorm=b=1:p=0.35:r=1:f=150,
> loudnorm=i=-16.0:lra=12.0:tp=-3.0 [out1]; \
>         [2:a:0] agate, adelay=8000:all=1 [tmp2]; \
>         [bg2][tmp2] amix, dynaudnorm=b=1:p=0.35:r=1:f=150,
> loudnorm=i=-16.0:lra=12.0:tp=-3.0 [out2]"
> ´´´
> To us it looks like the audio streams get processed sequentially. Each
> process
> needs to check the secondary audio levels for a few seconds, to be able to
> duck the main audio accordingly, resulting in the increased overall
> latency.
>
> Is this correct and if so, is there a way to achieve this in parallel?
>
> Or is there any other way to get the autoducking, that doesnt introduce
> additional latency?
>

3 loudnorm calls and 2 dynaudnorm calls?

for ducking there is sidechaincompress filter


>
> Thank you!
>
> Philipp
>
> PS: Full ffmpeg call in the appended textfile.
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