[alsa-devel] ALSA DMIX support without MMAP ?

ANISH KUMAR anish.singh at samsung.com
Thu Jan 14 11:30:59 CET 2010

>mmap is supported by the Samsung drivers.

Thanks for this information which i overlooked.
>This looks like the dmix data rates are getting out of sync with what
>the hardware is doing.  Enabling CONFIG_SND_PCM_XRUN_DEBUG will produce
>more diagnostic information from the driver side
I got the problem and after doing the changes DMIX plugin is working very fine.
As you know XRUN was happening and this happening in snd_pcm_update_hw_ptr_post function.
This happened because stop_threshold is increased suddenly(Is it done by dmix? If yes then why ?) ??????
 In normal condtions this would have been fine but in my code i was multiplying it by some amount causing it to wrap around(stop_threshold=0 );Causing XRUN.So i just removed this multiplying factor.
One more Rate conversion query:
./alsa_aplay -v -D"plug:'dmix:RATE=44100'" bond.wav
Playing WAVE 'bond.wav' : Unsigned 8 bit, Rate 11025 Hz, Mono
Plug PCM: Rate conversion PCM (44100, sformat=U8)
As you can see bond.wav is sampled at 11025k but when i am playing with Plug PCM there is some noise in the song why????Is rate conversion algoritm not able to resample it properly?
If i play with ./alsa_aplay -v -D"plug:'dmix:RATE=11025'" bond.wav then no noise.Probably because no resampling happening?
Mark Brown Heartfelt Thanks for your time.

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