[FFmpeg-devel] [PATCH] 8 channel layout fix for Vorbis decoder

[Justin Ruggles]

Michael Niedermayer wrote:

> On Tue, Nov 03, 2009 at 07:39:51PM -0500, Jason Tackaberry wrote:
>> Hi,
>>
>> The attached patch implements sane channel layout behaviour for 7 and 8
>> channel Vorbis files.
>>
>> The Vorbis specification [1] says that the layout for greater than six
>> channels is left up to the application.  I think the most sensible and
>> consistent layout for 7 and 8 channels is their 5 and 6 channel
>> counterparts with back left/right channels appended.
> 
> ahh, xiph-alzheimer design again
> from all options they succeed in selecting the one that is most different
> from everyone else no matter how broken the option is even on its own
> 
> 
> so what are our options
> 1. leave channels as they are ordered
>    -> requires each application to have a special case for vorbis because
>       this order is never what one expects
> 2. do a best effort reordering 
>    -> someone will complain that its not correct for his file (that he just
>       created)
>       and his application could magically do better if only the evil
>       ffmpeg didnt reorder channels
> 
> solution:
> add a value to request_channel_layout that specifies raw channel order and
> layout without any changes and then do the reorder as you do in your patch
> if this is not requested.
> comments? suggestions? flames?

I like it.  So value to use?

0x80000000 already means "all layouts supported" since we're using
Microsoft's dwChannelMask values (for the low 32 bits at least).  So
maybe 0x100000000LL or 0x8000000000000000LL?

-Justin