[FFmpeg-devel] [PATCH] Dolby Digital dynamic range compression (drc_scale) is now 0 by default

Wiebe Cazemier wiebe at halfgaar.net
Mon Mar 30 11:37:10 CEST 2015

----- Original Message -----
> From: "Kieran Kunhya" <kierank at obe.tv>
> To: "Wiebe Cazemier" <wiebe at halfgaar.net>
> Sent: Monday, 30 March, 2015 10:47:49 AM
> Subject: Re: [FFmpeg-devel] [PATCH] Dolby Digital dynamic range compression (drc_scale) is now 0 by default
> >>
> >> It is not an option and I quote ETSI 102 366:
> >>
> >> "Therefore, the AC-3 decoder shall, by default, implement the
> >> compression characteristic indicated by the dynrng values in the data
> >> stream. AC-3 decoders may optionally allow listener control over the
> >> use of the dynrng values, so that the listener may select full or
> >> partial dynamic range reproduction."
> >>
> >> If an application doesn't want to expose drc settings then that's
> >> their problem. FFmpeg does the right thing and lets you turn it off if
> >> you wish.
> >>
> >> Kieran
> >>
> >
> > (can you reply-all, so that your reply goes to the list?)
> >
> > If you say "it's not an option", that's putting it harder than the spec
> > say. Dolby engineers never meant AC3 audio to be played compressed
> > everywhere, and that's what we're seeing happening.
> >
> > Also, I feel that the word 'decoder' in your quote is written in a time
> > where it had a different context and that quote has to be interpreted that
> > way. Open source software libraries weren't available at that point, and a
> > decoder was a piece of hardware, or a chip embedded in something. Sure,
> > you don't have to allow the user to control it when you embed an AC3
> > decoder in your budget TV so ATSC demanding that you do would be silly
> > here, but all high end receivers I know, do allow you to set the option.
> > Now that we do have a library that people can use, an honest mistake to
> > forget to implement it turns into something that they probably didn't
> > intend. As proven by the Kodi developer denying that they applied DRC.
> >
> > I think we have to consider user experience, and it's great when they can
> > control it, but we're getting the situation where everybody gets it (yet
> > only for AC3), whether they want to or not. That automatically crosses off
> > Kodi and VLC (for example) for use in high quality sound reproduction. And
> > the bad thing is, they may not even know it...
> It's the complete opposite - most people are watching on laptop
> speakers without the dynamic range you have in your setup. FFmpeg lets
> you turn it off and it's the fault of the player for not exposing
> that.

What about those people playing AAC, which is the majority currently.

In any case, I made my point. How do we proceed? I have no idea who is in charge of what, and how the decision making process goes in ffmpeg development.

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