On Sun, 29 Feb 2004, Russell King wrote:
> On Sun, Feb 29, 2004 at 01:31:01PM +0100, Jaroslav Kysela wrote:
> > On Sun, 29 Feb 2004, Russell King wrote:
> > > Could someone enlighten me about the way alsa-lib / alsa-driver are
> > > supposed to work when using mmap mode please? I'm looking at the 1.0.2
> > > code, along with madplay and Linux 2.6.4-rc1.
> > >
> > > madplay sets the start_threshold to the size of the buffer, and min_avail
> > > to one period size - in much the same way as the alsa-lib test/pcm.c
> > > program.
> >
> > We know about this problem. The start_threshold must be equal or less than
> > (buffer_size / avail_min) * avail_min in this case.
>
> I think it's a little more complex than that. In my case,
> buffer_size = 16384, avail_min = 256, so:
>
> (buffer_size / avail_min) * avail_min = 16384
>
> which is what was being programmed anyway. However,
>
> (int(buffer_size / avail_min) - 1) * avail_min = 16128
>
> would make more sense. Do you agree?
No, this combination should work. In your first mail, the avail_min was
2047 bytes and buffer_size 16384 bytes. Note that xfer_align must pass
same expression:
start_threshold = (buffer_size / xfer_align) * xfer_align
But xfer_align is usually 1 or avail_min anyway.
Jaroslav
-----
Jaroslav Kysela <[EMAIL PROTECTED]>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs
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