Distorted sound on Raspberry Pi 2

[Svatopluk Kraus]

Is it recent problem? If yes, some info about kernel version would be
really nice.



On Fri, Apr 8, 2016 at 5:28 PM, Sylvain Garrigues
<sylvain at sylvaingarrigues.com> wrote:
> Hello,
>
> I have continuous warnings on my Raspberry PI 2 regarding sound when hw.snd.verbose=4:
>
> ...
> pcm0: WARNING: PCMDIR_PLAY DMA completion too fast/slow ! hwptr=120000, old=120000 delta=0 amt=0 ready=8192 free=119808
> pcm0: WARNING: PCMDIR_PLAY DMA completion too fast/slow ! hwptr=124000, old=124000 delta=0 amt=0 ready=8192 free=119808
> pcm0: WARNING: PCMDIR_PLAY DMA completion too fast/slow ! hwptr=0, old=0 delta=0 amt=0 ready=8192 free=119808
> pcm0: WARNING: PCMDIR_PLAY DMA completion too fast/slow ! hwptr=4000, old=4000 delta=0 amt=0 ready=8192 free=119808
> pcm0: WARNING: PCMDIR_PLAY DMA completion too fast/slow ! hwptr=8000, old=8000 delta=0 amt=0 ready=8192 free=119808
> pcm0: WARNING: PCMDIR_PLAY DMA completion too fast/slow ! hwptr=12000, old=12000 delta=0 amt=0 ready=8192 free=119808
> pcm0: WARNING: PCMDIR_PLAY DMA completion too fast/slow ! hwptr=16000, old=16000 delta=0 amt=0 ready=8192 free=119808
> pcm0: WARNING: PCMDIR_PLAY DMA completion too fast/slow ! hwptr=16000, old=16000 delta=0 amt=0 ready=8192 free=119808
> pcm0: WARNING: PCMDIR_PLAY DMA completion too fast/slow ! hwptr=20000, old=20000 delta=0 amt=0 ready=8192 free=119808
> …
>
> The sound is frequently slightly distorted (like every 5s), and I am trying to figure out why.
>
> To reproduce:
> # sysctl dev.pcm.0.dest=1
> # sysctl  hw.snd.verbose=4
> # mpg123 anympegfile
>
> I still get the warnings on the HDMI output (dev.pcm.0.dest=2) but the sound is not distorted.
>
> Any idea?
>
> Best,
> Sylvain.
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