Distorted sound on Raspberry Pi 2

[Sylvain Garrigues]

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.