[alsa-devel] dmix produces garbled sound on ARM

[Ihar Filipau]

Hi All!

When using the dmix on ARM, the sound comes out garbled, with as if
overlapping, increasing-in-number echoes. That happens even with a
single aplay instance.

In a forum discussion, it was suggested that ARM lacks optimized dmix
implementation. But that implies that the generic dmix code is broken,
since it is what is used on ARM/etc, but not on i386/amd64. (The forum
discussion about my particular issue:
http://unix.stackexchange.com/questions/288451/sound-corruption-echo-when-trying-to-use-alsa-dmix
)

Does anybody has any suggestions how to fix/avoid the dmix issue on ARM?

Thanks.

P.S. Versions: Linux v3.18.24, alsa-lib/-utils v1.0.29. The hardware:
FreeScale i.MX35 (ARM1136) with SGTL5000 sound chip (used in 48KHz
mode).

P.P.S. The generic code has outdated functions for the "concurrent"
implementation with cmpxchg. The code probably could be updated, and
revised to use the C11's stdatomic.h when available.