[alsa-devel] Noise using pulseaudio with ymf724f

[Raymond Yau]

2011/9/12 Clemens Ladisch <clemens at ladisch.de>:
> Raymond Yau wrote:
>> How accurate is the ymfpci timer ?
>
> The period interrupts are not accurate at all.  The ymfpci hardware
> internally uses fixed periods of 256 frames at 48 kHz; the driver
> reports a period interrupt when the next hardware interrupt at or after
> a period boundary occurs.  The current position reported by the hardware
> is the position at the time of the last hardware interrupt.
>
>> my ymf724f seem play quite well with alsa "hw" device but with bad
>> noise with alsa-pulse plugin (e.g. aplay when not using default period
>> times )  and it also occurrs on   benshee on ubuntu 11.4 live cd
>
> It should be possible to increase accuracy by using the hardware period
> parameters (48 kHz _and_ 256 frames/period).
>
> TODO: implement support for the NORESAMPLE flag.
>
>

Is 256 frames/period in s16 stereo since the card support mono ,
stereo , U8 and S16 ,

What is the meaning of SNDRV_PCM_INFO_BLOCK_TRANSFER since the
rewind_safeguard of PA server is 256 bytes ?

Will this 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 ?

PA server has

#define ABSOLUTE_MIN_LATENCY (500)
#define ABSOLUTE_MAX_LATENCY (10*PA_USEC_PER_SEC)