Stereo sound files play back at half speed about audioio.jl HOT 3 CLOSED

From libsndfile's FAQ it appears that it doesn't actually do any interleaving/deinterleaving automatically. So my guess is that the problem has to do with the implementation of Base.read for AudioFiles. This currently returns arr[1:nread]. Now for stereo files this is a 2 x n_frames array. Since Julia reads through arrays in column-major order, every sample from the stereo file is 'repeated', which results in stereo files playing back at half speed (or something along those lines).

Returning arr[:, 1:nread] instead should solve this. I have implemented this in #20. I've tested a stereo file and it was mixed down properly into a single channel playing at regular speed. Since playing files was broken for me I wasn't able to check the behavior you describe here.

A point for discussion is given that Julia uses column-major order, should AudioIO perhaps use this to its advantage by representing audio data in n_frames x n_channels arrays instead of in n_channel x n_frames. The upside is that this would (theoretically) improve performance when working in Julia. The downside being that the latter is the convention for most C libraries AudioIO interfaces with, so any function interfacing with those should take care of proper conversion.

from audioio.jl.

Looking a bit more into the code. I think most of AudioIO already expects audio data to be in this format when dealing with stereo audio. So I've added a commit to #20 that makes sure audio data is read from a file as n_frames x n_channels.

from audioio.jl.

#20 fixes this, thanks!

from audioio.jl.