[alsa-devel] What about symmetric_channels and symmetric_samplebits?

Nicolin Chen b42378 at freescale.com
Mon Nov 4 12:02:51 CET 2013

Hi all,

As far as I know, some SoCs can only work in mono or stereo mode at
one time. So if we let them capture a mono stream while playing a
stereo stream, there might be a problem occur to one of these two
streams: double-paced or slowed down.

I just want to ask: Is there any existing solution for the case?

In soc-pcm.c, we have soc_pcm_apply_symmetry() to solve unmatched
sample rates situation for simultaneous playback and capture. But
we don't have one for channels. Is that reasonable to add a similar
one for it?

Likewise, we can treat symmetric_rate as a solution for those SoCs
or CODECs which can not handle asymmetrical LRCLK. But it's also
impossible for them to handle asymmetrical BCLK. And accodring to
BCLK = LRCLK * channel number * slot size(fixed or sample bits),
sample bits might also be a problem if they are not using a fixed
slot size.

Thank you,
Nicolin Chen

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