[alsa-devel] [PATCH] Fix buffer position for ATI SB4x0
Mauro Carvalho Chehab
mchehab at infradead.org
Fri Jun 6 20:31:45 CEST 2008
On Fri, 06 Jun 2008 18:49:28 +0200
Takashi Iwai <tiwai at suse.de> wrote:
> At Fri, 6 Jun 2008 11:52:32 -0300,
> Mauro Carvalho Chehab wrote:
> > On Thu, 29 May 2008 16:20:21 +0200
> > Takashi Iwai <tiwai at suse.de> wrote:
> > > At Thu, 29 May 2008 11:10:22 -0300,
> > > Mauro Carvalho Chehab wrote:
> > > >
> > > > ATI SB4x0 doesn't need any fix at position.
> > >
> > > It's not about the position fixing but whether to use the
> > > position-buffer. The devices on the blacklist are the ones that have
> > > no position buffer. So, it would fall into LPIB mode, and this list
> > > avoids it from the beginning.
> > >
> > > > This patch solves the issue of receiving several clicks during capture on those
> > > > devices.
> > > >
> > > > Tested with a Gateway Notebook MX-6453.
> > >
> > > The click noise is often a different problem. Did you already try
> > > the patch below?
> > The click seems associated to some residual samples inside the buffer. Here it
> > is a sample of the king of click noise I'm hearing here (captured from CD input entry):
> > http://linuxtv.org/~mchehab/snd.ogg
> (I didn't check the ogg file yet, and just a wild guess)
> Is it with dsnoop plugin? With "default" PCM, ALSA uses dsnoop for
> capture to allow multiplexing for HD-audio. Does it happen with "hw"
> or "plughw" PCM?
Results with the cdplay:
With "default" PCM (both with and without mmap):
several clicks per second, very high clicks;
(like a very risky analog disk)
With "hw" or "plughw" (no mmap):
less clicks (something like two clicks or three per second), with less volume.
both hw and plughw produces the same effect.
With "hw" or "plughw" and mmap (-M):
high quality. no noticeable clicks.
So, it seems that there are two different issues: one with dsnoop and another
with non-mmapped captures.
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