[vlc-devel] [PATCH 2/2] es: replace i_original_channels with i_stereo_mode

[Thomas Guillem]

On Tue, Jul 11, 2017, at 16:09, Rémi Denis-Courmont wrote:
> On mardi 11 juillet 2017 15:58:08 EEST Thomas Guillem wrote:
> > On Tue, Jul 11, 2017, at 15:29, Rémi Denis-Courmont wrote:
> > > On mardi 11 juillet 2017 10:01:34 EEST Thomas Guillem wrote:
> > > > The i_original_channels value (that is now i_stereo_mode) should not be
> > > > used by aout modules, and shouldn't be set by input if there is no
> > > > special stereo mode.
> > > > 
> > > > If accepeted, this commits will be splitted in the following way:
> > > >  - One commit per module that remove the usage of i_original_channels
> > > >  when
> > > > 
> > > > not needed at all.
> > > > 
> > > >  - One big commit that replace i_original_channels with i_stereo_mode
> > > >  and
> > > > 
> > > > that changes few modules (mpg/a52/dca/dts/filters/core).
> > > 
> > > I have tried to move the original channels to a proper set of flags
> > > already.
> > > But I failed everytime, because I never understood what the channel mask
> > > within original channels was exactly meant to be. As far as I could tell,
> > > it
> > > was simply three flags with the channels identical to the physical mask
> > > 
> > > :(
> > > 
> > > Also, if you want to rationalize this, there is really only one flag that
> > > belongs there (Dolby). Reverse stereo could just as well be fixed by
> > > reordering
> > > in the decoder (easy). And in principles, dual-mono should be two
> > > separate
> > > audio ES's (less easy).
> > 
> > You mean, reodering in the audio_output code, just between the filters
> > and the output ?
> 
> I don't understand the question.
> 
> > I have a branch that allow users to force a stereo-mode even with non
> > stereo input.
> 
> I don't see how forced downmixing relates to my comment at all, nor how
> it 
> relates to the current stereo modes.
> 
> > Some people asked this feature, I guess some content are
> > better downmixed to stereo than rendered on a 5.1 for example.
> 
> Have they? As far as I can tell, there are only requests to:
> - force stereo downmixing to work-around misconfigured physical layouts
> (this 
> does not belong in VLC, as it is not an application-specific setting),
> and
> - force mono downmixing to abuse a stereo headset as a pair of mono
> speakers 
> (likewise more of an system-wide than application matter).

For me, it does belong in VLC, and should be reachable from the audio
menu. Users don't want to change the speaker configuration just when
matching one media, and lot of users don't even know how to do it.

I think, we need to remove the stereo-mode and replace it with a
rendering-mode (or downmix), with these specifics choices:
 - Original
 - 5.1 (if channels is > to 5.1)
 - Stereo
 - Reverse Stereo
 - Mono
 - Headphones (will append the binaural audio-filters or configure the
 ambisonics renderer to use binaural decoders)


> 
> > I can have a look for reverse-stereo, this mode is only asked by the
> > user will never come from the input.
> > I would also like to add the Binauralizer here.
> 
> Those flags are supposed to be format properties, set by the demuxer/
> packetizer/decoder. I don't really see how a somethingizer belongs there.
> 
> 
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