[Vorbis-dev] Help understand decoding of stereo vorbis data

[Adam Bradley]

Hi,

I'm trying to implement a vorbis decoder, and am having some trouble getting it to work with stereo vorbis data.

It's giving me some PCM output which is roughly right, but it has artefacts.

I think it's most likely something to do with my handling of floor decode/curve synthesis. My first thoughts are that I'm handling the submap number/floor mapping incorrectly;

I'm interested in finding out about this from the documentation;
(4.3.2. floor curve decode)
[submap_number] = element [i] of vector [vorbis_mapping_mux]
What happens if during mapping decoding vorbis_mapping_mux is empty because vorbis_mapping_submaps was 1? Do both channels use the single submap in this case?

Also, I'm noticing that in this same situation, I'm getting a vorbis_floor_count of 2. What's the purpose of the second floor in this case, if both channels are referencing the first floor?

Thanks,

Adam Bradley
Audio Systems Developer
Jagex Games Studio


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