[opus] Meaning of mapping[]

Brendan Bolles brendan at fnordware.com
Mon Jan 6 12:36:00 PST 2014

On Jan 6, 2014, at 11:54 AM, Ralph Giles wrote:

> The first entry, mapping[0],
> describes front left and contains the value '0', so that speaker is the
> left channel of the first coupled stream. mapping[1] is '4', so the
> front centre speaker is given the first mono stream. mapping[2] is '1'
> so the front right speaker gets the right channel of the first coupled
> stream, and so on.

Ahh, I see.  Thanks for the explanation.

It's sort of the opposite of what I'd expect.  I'd expect mapping[stream_index] = vorbis_index, but it's actually mapping[vorbis_index] = stream_index.

And so I guess that means that the interleaved audio samples you pass into opus_multistream_encode_float() should always be in Vorbis order, and mapping[] just tells the encoder how to package them in the streams?


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