Aliasing in audio in->out patch

[DIY DSP]

After updating and building this evening (git commit dfafbedbba293145e8308e3576767a02c9cf7677), I tried the guitar multi-fx patch and heard aliasing.  So I modified it to patch in (left channel) directly to out and heard the same aliasing.  I made a short recording which I can upload later.

[Johannes Taelman]

Hmmm probably a timing issue with the ADC and DAC DMA buffers, resulting in a ADC buffer getting used while it is still being filled.

Both ADC and DAC use a double-buffer DMA setup, but their buffer-swap is not linked.

I had this happening in development, but thought I solved it, and haven't noticed it since, so I'm a bit surprised you get this. Maybe a small variation in timing caused by a different version of gcc or something.
firmware/codec_ADAU1961_SAI.c is the relevant file to look at.

On Wed, Apr 15, 2015 at 4:22 AM, 'DIY DSP' via axoloti-dev <axolo...@googlegroups.com> wrote:

After updating and building this evening (git commit dfafbedbba293145e8308e3576767a02c9cf7677), I tried the guitar multi-fx patch and heard aliasing.  So I modified it to patch in (left channel) directly to out and heard the same aliasing.  I made a short recording which I can upload later.

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