[alsa-devel] PulseAudio and SNDRV_PCM_INFO_BATCH

[Raymond Yau]

> Hmm...I was trying to understand this power save argument. I tried to
figure out a "typical" URB size by just plugging my headset in, and I saw
wMaxPacketSize being 96 and/or 192 bytes.
> Then, MAX_PACKS is set to either 6 (or 48 for USB 2.0 devices, but this
is just a headset).
>
> Can this be correct? Does it mean that we are getting interrupts every
192 * 6 bytes (i e, every 6 ms for a 48kHz/stereo/16bit stream)?
>
>

Do this mean that the driver report exact one period only when period size
is multiple of wMaxPackerSize ?

Using other period size give bad result , the driver use variable  period
size

hw_ptr does not always at period boundary , seem more like DSP_CAP_BATCH

>From the result , minimum and maximum time difference bewteen hw_ptr change
can varies from 20% to 400%