snd-powermac produces only low quality dirty sound

snd-powermac produces only low quality dirty sound

[Olaf Hering]

All 2.6 versions I tried so far produce only "dirty" low quality sound
when playing mp3 with xmms with either the alsa or oss plugin.
But it works as expected when I use dmasound_pmac and the liboss plugin.

Any ideas how to debug it?
I "see" it on an ibook 600MHz, but also on a G4 and a 400MHz Powerbook.



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RE: snd-powermac produces only low quality dirty so

[Giuliano Pochini]

[-- Attachment #1: Type: text/plain, Size: 488 bytes --]


On 14-Dec-2004 Olaf Hering wrote:

> All 2.6 versions I tried so far produce only "dirty" low quality sound
> when playing mp3 with xmms with either the alsa or oss plugin.
> But it works as expected when I use dmasound_pmac and the liboss plugin.
>
> Any ideas how to debug it?

It seems that the chip is not happy with some period/buffer sizes.
Someone was trying to find the right constraints to set for those
parameters. Maybe the attached patch fixes it (untested).



--
Giuliano.

[-- Attachment #2: pmac.patch --]
[-- Type: text/plain, Size: 551 bytes --]

--- alsa-kernel/ppc/pmac.c__	Wed Dec 15 10:15:37 2004
+++ alsa-kernel/ppc/pmac.c	Wed Dec 15 10:37:15 2004
@@ -538,6 +538,11 @@
 	runtime->private_data = rec;
 	rec->substream = subs;
 
+	if ((i = snd_pcm_hw_constraint_pow2(runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_SIZE
)) < 0)
+		return i;
+	if ((i = snd_pcm_hw_constraint_pow2(runtime, 0, SNDRV_PCM_HW_PARAM_BUFFER_SIZE
)) < 0)
+		return i;
+
 #if 0 /* FIXME: still under development.. */
 	snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_RATE,
 			    snd_pmac_hw_rule_rate, chip, rec->stream, -1);

Re: snd-powermac produces only low quality dirty sound

[Giuliano Pochini]

On Wed, 15 Dec 2004 11:10:02 +0100 (CET)
Giuliano Pochini <pochini@shiny.it> wrote:

> > All 2.6 versions I tried so far produce only "dirty" low quality sound
> > when playing mp3 with xmms with either the alsa or oss plugin.
> > But it works as expected when I use dmasound_pmac and the liboss plugin.
> >
> > Any ideas how to debug it?
>
> It seems that the chip is not happy with some period/buffer sizes.
> Someone was trying to find the right constraints to set for those
> parameters. Maybe the attached patch fixes it (untested).


Uffff, that stupid program wrapped long lines.


--- alsa-kernel/ppc/pmac.c__	Wed Dec 15 10:15:37 2004
+++ alsa-kernel/ppc/pmac.c	Wed Dec 15 10:37:15 2004
@@ -538,6 +538,11 @@
 	runtime->private_data = rec;
 	rec->substream = subs;
 
+	if ((i = snd_pcm_hw_constraint_pow2(runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_SIZE)) < 0)
+		return i;
+	if ((i = snd_pcm_hw_constraint_pow2(runtime, 0, SNDRV_PCM_HW_PARAM_BUFFER_SIZE)) < 0)
+		return i;
+
 #if 0 /* FIXME: still under development.. */
 	snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_RATE,
 			    snd_pmac_hw_rule_rate, chip, rec->stream, -1);




-- 
Giuliano.


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Re: snd-powermac produces only low quality dirty so

[Olaf Hering]

 On Wed, Dec 15, Giuliano Pochini wrote:

> 
> On 14-Dec-2004 Olaf Hering wrote:
> 
> > All 2.6 versions I tried so far produce only "dirty" low quality sound
> > when playing mp3 with xmms with either the alsa or oss plugin.
> > But it works as expected when I use dmasound_pmac and the liboss plugin.
> >
> > Any ideas how to debug it?
> 
> It seems that the chip is not happy with some period/buffer sizes.
> Someone was trying to find the right constraints to set for those
> parameters. Maybe the attached patch fixes it (untested).

This patch does not help.


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RE: snd-powermac produces only low quality dirty so

[danny]

On Wed, 15 Dec 2004, Giuliano Pochini wrote:

> 
> On 14-Dec-2004 Olaf Hering wrote:
> 
> > All 2.6 versions I tried so far produce only "dirty" low quality sound
> > when playing mp3 with xmms with either the alsa or oss plugin.
> > But it works as expected when I use dmasound_pmac and the liboss plugin.
> >
> > Any ideas how to debug it?
> 
> It seems that the chip is not happy with some period/buffer sizes.
> Someone was trying to find the right constraints to set for those
> parameters. Maybe the attached patch fixes it (untested).
> 
O yes, I forgot to send it. Will do later tonight. It doesn't have to be a 
power of 2 though, at least not on my Snapper.
However, the problem never occured with oss emulation, so I doubt above 
problem is the same. Low quality sound was happening a few versions ago, 
but latest ALSA produces very reasonable sound, only distortion when 
I turn up PCM too much (and DRC Range is set high).

So:
-what version (libs+driver)
-what is "dirty" low quality?

d.

 



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Re: snd-powermac produces only low quality dirty so

[Olaf Hering]

 On Wed, Dec 15, danny@mailmij.org wrote:

> -what version (libs+driver)

its alsa-1.0.3 with kernel 2.6.10, but happens also with 2.6.5.

> -what is "dirty" low quality?

I guess you have to hear it. Sounds like a mp3 with a very low sampling
rate, or a broken LP (vinyl, gramophone record however you name it).


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Re: snd-powermac produces only low quality dirty so

[Olaf Hering]

 On Wed, Dec 15, danny@mailmij.org wrote:

> On Wed, 15 Dec 2004, Giuliano Pochini wrote:
> 
> > 
> > On 14-Dec-2004 Olaf Hering wrote:
> > 
> > > All 2.6 versions I tried so far produce only "dirty" low quality sound
> > > when playing mp3 with xmms with either the alsa or oss plugin.
> > > But it works as expected when I use dmasound_pmac and the liboss plugin.
> > >
> > > Any ideas how to debug it?
> > 
> > It seems that the chip is not happy with some period/buffer sizes.
> > Someone was trying to find the right constraints to set for those
> > parameters. Maybe the attached patch fixes it (untested).
> > 
> O yes, I forgot to send it. Will do later tonight. It doesn't have to be a 
> power of 2 though, at least not on my Snapper.
> However, the problem never occured with oss emulation, so I doubt above 
> problem is the same. Low quality sound was happening a few versions ago, 
> but latest ALSA produces very reasonable sound, only distortion when 
> I turn up PCM too much (and DRC Range is set high).

You are right, reducing the volume to 80% in xmms fixes it and the mp3
sounds ok.


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