[alsa-devel] Noise using pulseaudio with ymf724f

Raymond Yau superquad.vortex2 at gmail.com
Fri Sep 16 03:10:15 CEST 2011

2011/9/14 Clemens Ladisch <clemens at ladisch.de>:
> Raymond Yau wrote:
>> Is 256 frames/period in s16 stereo since the card support mono ,
>> stereo , U8 and S16 ,
> The hardware uses S16 stereo at 48 kHz internally; everything else is
> converted and resampled to that.

using ubuntu 11.04 Live CD

After select "Mono Duplex" profile in gnome sound preference  , gnome
speaker-test crash

>> What is the meaning of SNDRV_PCM_INFO_BLOCK_TRANSFER
> That the card transfers samples in blocks.
>> since the rewind_safeguard of PA server is 256 bytes ?
> A block in the native format has 1024 bytes.

Do you mean hardware pointer is only updated every 5.333ms ?

similar to usb audio using 5 urbs

and this is why the driver force the application to use 3 periods per buffer

>> help since minimum period time of snd_ymfpci is 5.333ms but
>> alsa-pulse plugin announce a lower value 128 bytes (period_bytes_min)
>> to the alsa application ?
> Doesn't PA assume that the hardware has accurate pointer positions?
> Without this, smaller periods do not make sense unless PA can
> interpolate from the period interrupts.

PA server use the value from snd_pcm_available() to determine the sleep time ,
You have to ask PA developer whether PA can interpolate from the
period interrupts

e.g. hda , emu10k1 and au88x0 use the values from hardware register as
the playback position in pointer callback

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