[Vorbis-dev] Channels ordering bug

Nicolas George nicolas.george at normalesup.org
Sat May 31 10:44:20 PDT 2008


Hi.

I think that vorbis-tools use a wrong order for channels when dealing with
5.1 surround WAV files.

More precisely, I find in the Vorbis specification that the output order is:

0: front left
1: front center
2: front right
3: rear left
4: rear right
5: LFE

(source: http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#id342556 )

At the same time, the order of channels in WAV files seems to be:

0: front left
1: front right
2: front center
3: LFE
4: rear left
5: rear right

(source: http://www.microsoft.com/whdc/device/audio/multichaud.mspx#E4C )

Now, in oggenc/audio.c, I see that the permutation array is used that way in
wav_ieee_read:

            buffer[j][i] = buf[i*f->channels + f->channel_permute[j]];

To accommodate the specified orders, the permutation array should therefore
be:

	0, 2, 1, 4, 5, 3

But wav_permute_matrix defines it as "0,2,1,5,3,4".

The same incorrect array is also present in oggdec.c.

I hope this problem can be fixed.

Regards,

-- 
  Nicolas George
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