[FFmpeg-devel] Default dynamic range compression on AC3

Zach Swena zach.swena at gmail.com
Thu Mar 26 18:48:27 CET 2015

I guess my understanding of where DRC should be set is based on some
assumptions on how it is implemented.  Your explanation sounds reasonable.
I will have to do some research myself to see if I can use this metadata
feature to reduce how much we need to compress our signal.


On Mar 26, 2015 7:51 AM, "Wiebe Cazemier" <wiebe at halfgaar.net> wrote:
> ----- Original Message -----
> > From: "Zach Swena" <zcybercomputing at gmail.com>
> > To: "FFmpeg development discussions and patches" <
ffmpeg-devel at ffmpeg.org>
> > Sent: Thursday, 26 March, 2015 3:34:22 PM
> > Subject: Re: [FFmpeg-devel] Default dynamic range compression on AC3
> >
> > Something to keep in mind, AC3 is a broadcast format, so it makes sense
> > have range compression built in because many listeners are viewing on TV
> > sets with limited range capabilities.  I wasn't aware of this option,
> > will probably end up using it for a program I am making.  I don't care
> > about the default value, as long as I can change it and the feature and
> > default value get proper documentation.  That is just a bit of
> > on why the AC3 spec has this feature.  Theoretically it should be turned
> > off at the decoder if connected to proper speakers though.
> This was brought up in the Kodi discussion as well. I haven't answered
there (yet), but it has been my experience that TV networks already apply a
whole bunch of compression on the stream itself, outside of the meta data.
Disabling DRC doesn't help in preventing horrible compressed sound quality.
> In any case, the use of AC3 for broadcasting shouldn't mean that DRC is
on by default. Settop etc boxes that want this should turn it on
themselves, not rely on a library that performs it with the developer using
ffmpeg not even knowing about the existence of it. And the developers that
do know, will simply set drc_scale.
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