[vlc-devel] [RFC v2 2/2] audio: let VLC decode more than 9 audio channels

Tue Oct 13 17:48:34 CEST 2015

2015-10-12 18:16 GMT+02:00 Jean-Baptiste Kempf <jb at videolan.org>:
> On 12 Oct, Emeric Grange wrote :
>> ---
>>  include/vlc_aout.h                    | 14 +++++++++++++-
>>  include/vlc_es.h                      | 17 +++++++++++++++--
>>  modules/codec/araw.c                  |  3 +++
>>  modules/demux/windows_audio_commons.h | 17 +++++++++++++++--
>>  4 files changed, 46 insertions(+), 5 deletions(-)
>>
>> diff --git a/include/vlc_aout.h b/include/vlc_aout.h
>> index 630be72..df16254 100644
>> --- a/include/vlc_aout.h
>> +++ b/include/vlc_aout.h
>> @@ -177,7 +177,19 @@ static const uint32_t pi_vlc_chan_order_wg4[] =
>>      AOUT_CHAN_LEFT, AOUT_CHAN_RIGHT,
>>      AOUT_CHAN_MIDDLELEFT, AOUT_CHAN_MIDDLERIGHT,
>>      AOUT_CHAN_REARLEFT, AOUT_CHAN_REARRIGHT, AOUT_CHAN_REARCENTER,
>> -    AOUT_CHAN_CENTER, AOUT_CHAN_LFE, 0
>> +    AOUT_CHAN_CENTER, AOUT_CHAN_LFE,
>> +
>> +    AOUT_CHAN_SIDE_LEFT,
>> +    AOUT_CHAN_SIDE_RIGHT,
>> +    AOUT_CHAN_TOP_CENTER,
>> +    AOUT_CHAN_TOP_FRONT_CENTER,
>> +    AOUT_CHAN_TOP_FRONT_LEFT,
>> +    AOUT_CHAN_TOP_FRONT_RIGHT,
>> +    AOUT_CHAN_TOP_REAR_CENTER,
>> +    AOUT_CHAN_TOP_REAR_LEFT,
>> +    AOUT_CHAN_TOP_REAR_RIGHT,
>
> Are you sure this is the correct wg4 order?
>
>> diff --git a/include/vlc_es.h b/include/vlc_es.h
>> index 97cdb78..1ce8b7e 100644
>> --- a/include/vlc_es.h
>> +++ b/include/vlc_es.h
>> @@ -108,12 +108,24 @@ struct audio_format_t
>>  #define AOUT_CHAN_REARRIGHT         0x40
>>  #define AOUT_CHAN_MIDDLELEFT        0x100
>>  #define AOUT_CHAN_MIDDLERIGHT       0x200
>> +#define AOUT_CHAN_SIDE_LEFT         0x400
>> +#define AOUT_CHAN_SIDE_RIGHT        0x800
>
> I still don't understand what this AOUT_CHAN_SIDE_RIGHT and
> AOUT_CHAN_SIDE_LEFT are.
>
> AOUT_CHAN_MIDDLE* corresponds to SPEAKER_SIDE_LEFT and
> SPEAKER_SIDE_RIGHT, since AOUT_CHANS_7_1 should correspond to
> KSAUDIO_SPEAKER_7POINT1_SURROUND

Ok I've been reading a bit about speakers. Now I'm lost too.
What seems to be the "reference" when naming speakers is the listing
from WAVE_FORMAT_EX
(https://msdn.microsoft.com/en-us/library/windows/hardware/dn653308(v=vs.85).aspx)
So the way you are using 7.1 it does indeed seems that MIDDLE
correspond to SIDE. So yeah, I'll change SIDE_* to FRONTLEFTOF*.

This is the correspondence between VLC naming and WAVE_FORMAT_EX:

/* Values available for audio channels */
#define AOUT_CHAN_CENTER            0x1       // front center
#define AOUT_CHAN_LEFT              0x2       // front left
#define AOUT_CHAN_RIGHT             0x4       // front right
#define AOUT_CHAN_REARCENTER        0x10      // back center
#define AOUT_CHAN_REARLEFT          0x20      // back left (also
called surround left "B" when there is no side left/right in the
speaker configuration)
#define AOUT_CHAN_REARRIGHT         0x40      // back right (also
called surround right "B")
#define AOUT_CHAN_MIDDLELEFT        0x100     // side left (also
called surround left "A" most of the time)
#define AOUT_CHAN_MIDDLERIGHT       0x200     // side right (also
called surround right "A" most of the time)
#define AOUT_CHAN_FRONT_LEFT_of_CENTER 0x400   // previously what I
called side left
#define AOUT_CHAN_FRONT_RIGHT_of_CENTER 0x800  // previously what I
called side right
#define AOUT_CHAN_LFE               0x1000
#define AOUT_CHAN_TOP_CENTER        0x2000            // front "height" center
#define AOUT_CHAN_TOP_FRONT_CENTER  0x4000    // etc...
#define AOUT_CHAN_TOP_FRONT_LEFT    0x8000
#define AOUT_CHAN_TOP_FRONT_RIGHT   0x100000
#define AOUT_CHAN_TOP_REAR_CENTER   0x200000
#define AOUT_CHAN_TOP_REAR_LEFT     0x400000
#define AOUT_CHAN_TOP_REAR_RIGHT    0x800000

Your profiles could also use a bit of documentation, so I came up with
that after reading this page
(https://en.wikipedia.org/wiki/Surround_sound#Standard_speaker_channels)
:

#define AOUT_CHANS_3_0    (AOUT_CHANS_FRONT | AOUT_CHAN_CENTER)     //
3.0 stereo
#define AOUT_CHANS_3_1    (AOUT_CHANS_3_0   | AOUT_CHAN_LFE)
#define AOUT_CHANS_4_0    (AOUT_CHANS_FRONT | AOUT_CHANS_REAR)      //
4.0 quadraphonic (dolby, but using rear left/right as surround
left/right)
#define AOUT_CHANS_4_1    (AOUT_CHANS_4_0   | AOUT_CHAN_LFE)
#define AOUT_CHANS_5_0    (AOUT_CHANS_4_0   | AOUT_CHAN_CENTER)     //
5.0 surround (dolby)
#define AOUT_CHANS_5_1    (AOUT_CHANS_5_0   | AOUT_CHAN_LFE)
#define AOUT_CHANS_6_0    (AOUT_CHANS_4_0   | AOUT_CHANS_MIDDLE)    //
what is this one? seems like 6.0 side (4.0 surround + side left/right)
but using 4.0 quadriphonic instead
#define AOUT_CHANS_7_0    (AOUT_CHANS_6_0   | AOUT_CHAN_CENTER)     //
what is this one?
#define AOUT_CHANS_7_1    (AOUT_CHANS_5_1   | AOUT_CHANS_MIDDLE)    //
7.1 surround (dolby)
#define AOUT_CHANS_8_1    (AOUT_CHANS_7_1   | AOUT_CHAN_REARCENTER) //
seems ok but I can't find any resources about it

I think these one could be added:
#define AOUT_CHANS_9_1    (AOUT_CHANS_7_1   | AOUT_CHANS_TOP_FRONT) //
9.1 surround (dolby)
#define AOUT_CHANS_11_1   (AOUT_CHANS_9_1   |
AOUT_CHAN_FRONT_LEFT_of_CENTER | AOUT_CHAN_FRONT_RIGHT_of_CENTER) //
11.1 surround (dolby)

And finally this one (I don't know anything about the other "special" profiles:
#define AOUT_CHANS_4_CENTER_REAR (AOUT_CHANS_FRONT |
AOUT_CHANS_CENTER)  // 4.0 surround

> With my kindest regards,
>
> --
> Jean-Baptiste Kempf
> http://www.jbkempf.com/ - +33 672 704 734
> Sent from my Electronic Device
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