[alsa-devel] safe support for rewind in ALSA
superquad.vortex2 at gmail.com
Thu Feb 11 07:52:52 CET 2010
2010/2/10 Clemens Ladisch <clemens at ladisch.de>
> Raymond Yau wrote:
> > ...
> > The rest of those sound cards which have period_mins = 1 are regarded as
> > broken by PA developer (e.g. intel8x0 ,emu10k1 , ens1371 , ... ) and
> > did not work with one period per buffer too.
> > what is the hardware requirement for the driver to support one period per
> > buffer ?
> That the hardware can be programmed to generate only one interrupt per
> > if none of the those driver can be fixed
> > why don't we change the period_min of all those broken drivers from 1 to
> > ?
> Because period_min has nothing to do with the brokenness. PA wants to
> use as few periods as possible because it does not use period interrupts
> but the DMA pointer, and it's the latter that is broken.
Are the one period per buffer designed for specific purpose such as
playing/looping the pre-loaded soundfont ?
Other than pulseaudio , are there any application use this mode properly
without glitch ?
Do you mean that PA only wake up once when configure sound card to use two
periods per buffer ?
if sound card only support non-interleaved mode and exactly two periods ,
even if you limit the rewind of application pointer to the period boundary
is not 100% safe if the sound card pre-fetch audio using DMA
Most sound cards hardware register only provide the number of sample
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