[alsa-devel] [PATCH] ASoC: rockchip: i2s: Support mono capture

[Mark Brown]

On Mon, Jan 08, 2018 at 04:01:15PM -0800, Matthias Kaehlcke wrote:

> Due to different issues in our audio recording path I couldn't test
> this properly, and only looked at the .wav data in audacity, which
> appeared to look ok. After putting some of the missing pieces
> together and I noticed that mono capture doesn't work as intended,
> the recorded audio is slowed down. I think this is because the I2S
> controller keeps generating a two-channel stream, however the sound
> system interprets it as a monophonic stream because of the channel
> configuration.

That seems odd - I'd expect underruns somewhere?

> Not sure if there is a clean solution for this if we can't tell the
> hardware to generate a single-channel stream. Any suggestions or do
> we have to revert the patch?

It sounds like a very standard problem with I2S devices, it's a
fundamentally stereo format after all.  If you can't get it to discard
the second channel there's probably not much doing.
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