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Brett, I’m using the oggdropxpd you suggested. I am dropping 5.1 wav files generated from Adobe Audition. I noticed that although FMOD plays the wav file channels correctly, it mixes up the ogg channels.

The Wav 5.1 channel ordering is L, C, R, LFE, RL, RR
The Ogg 5.1 channel ordering is L, R, C, RL, RR, LFE

What I get from FMOD is that it appears to map the Ogg channels into the Wav channels. So R goes to C, RL goes to LFE, etc…

Some players like FooBar Beta 0.9 play the Ogg 5.1 mapping correctly but WinAmp does not.

Of course it could be Audition or oggdropxpd, but I wanted to get your opinion.

I posted the 6-channel wav in another thread. If you run it through the oggdropxpd util, you will hear what I mean.

Thanks!
Jason

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I tried three different versions including the linked one and they all have the same mapping. I’ll add an optional speaker mix fix for 5.1 ogg files.

Thanks!
Jason

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According to the Vorbis spec:
http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html

Section 4.3.9:

4.3.9.?output channel order
Vorbis I specifies only a channel mapping type 0. In mapping type 0, channel mapping is implicitly defined as follows for standard audio applications:

one channel
the stream is monophonic
two channels
the stream is stereo. channel order: left, right
three channels
the stream is a 1d-surround encoding. channel order: left, center, right
four channels
the stream is quadraphonic surround. channel order: front left, front right, rear left, rear right
five channels
the stream is five-channel surround. channel order: front left, front center, front right, rear left, rear right
six channels
the stream is 5.1 surround. channel order: front left, front center, front right, rear left, rear right, LFE
greater than six channels
channel use and order is defined by the application

Applications using Vorbis for dedicated purposes may define channel mapping as seen fit. Future channel mappings (such as three and four channel Ambisonics) will make use of channel mappings other than mapping 0.

So, it may be that the oggdropxpd and others are operating exactly as the Vorbis spec dictates (and different than the wav standard). I also understand that there is no mapping info stored in the ogg format so you would have to assume that they followed the Vorbis spec.

In this case, would it make more sense to modify FMOD to use the Vorbis spec mapping or to use a SpeakerMix override? I guess the question comes down to how much FMOD code is invested in 5.1 ogg playback (assuming it had been worked around already)?

Thanks,
Jason

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http://www.hydrogenaudio.org/forums/ind … opic=38611

Sounds like John doesn’t plan to change the ordering now that it matches the Vorbis spec.

Since my wavs include the WAVE_FORMAT_EXTENSIBLE header oggdropxpd codes it to the vorbis channel map.

To verify his comments, I went in with a hex editor and removed the WAVE_FORMAT_EXTENSIBLE structure and replaced it with a PCM_WAVE_FORMAT structure. When I re-encoded the wav into an ogg, it left the channel mapping as is and, of course, it played back correctly in FMOD.

So, unless the Vorbis spec is changed, it seems to have been resolved (i.e. go with the original spec and expect everyone to follow suit).

Jason

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