[snd-intel8x0] distortion on PCM volume >> 50%

[snd-intel8x0] distortion on PCM volume >> 50%

[Eduard Bloch]

Hello,

I have some problems with a ac97 based sound card (Notebook built-in)
where the kernel driver works fine (except of not beeing able to
resample on-the-fly).

When I set the PCM mixer volume to more then 50%, I hear few sound
fragments. If I go over 75% I hear them all the time and on 100% PCM,
the sound is full of scratching fragments. You can get an example
catched with microphone on
http://sites.inka.de/W1752/alsa-distortion.ogg and the original is on
www.vorbis.com/music/Mists_of_Time-4T.ogg . First I suspected a speaker
problem since it sounds very similar to overloud speaker setting, but it
is not!

Another problem is more complicated to describe. With programs that use
the native ALSA device access, I hear very quiet but annoying
crackling/ticking sound every 2-5 seconds. Only hearable with low volume
music. When I use programs that work over snd-pcm-oss emulation, the
repeating cracling is not there, but it comes every 3-5 minutes in
another form: I hear many sound ticks passing in 2-3 seconds, followed
by changed sound frequency for 3-5 seconds, then the out normalises
again.

The hardware part is claimed to be manufactured by Yamaha (AC-XG) but
lspci identifies it as:

00:1f.5 Multimedia audio controller: Intel Corp. 82801CA/CAM AC'97 Audio Controller (rev 02)

Sharing the IRQ with other onboard components:

 11:    3489538          XT-PIC  usb-uhci, usb-uhci, eth0, Toshiba America Info Systems ToPIC95 PCI to Cardbus Bridge with ZV Support, Toshiba America Info Systems ToPIC95 PCI to Cardbus Bridge with ZV Support (#2), ohci1394, Intel 82801CA-ICH3

The described problem appears with every ALSA version I can remember (>= 0.9).

MfG,
Eduard.
-- 
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Für blöde Sprüche brauch ich kein Programm.
		-- Anita Frieda Reimann


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Re: [snd-intel8x0] distortion on PCM volume >> 50%

[Jaroslav Kysela]

On Sun, 30 Nov 2003, Eduard Bloch wrote:

> Hello,
> 
> I have some problems with a ac97 based sound card (Notebook built-in)
> where the kernel driver works fine (except of not beeing able to
> resample on-the-fly).
> 
> When I set the PCM mixer volume to more then 50%, I hear few sound
> fragments. If I go over 75% I hear them all the time and on 100% PCM,
> the sound is full of scratching fragments. You can get an example
> catched with microphone on
> http://sites.inka.de/W1752/alsa-distortion.ogg and the original is on
> www.vorbis.com/music/Mists_of_Time-4T.ogg . First I suspected a speaker
> problem since it sounds very similar to overloud speaker setting, but it
> is not!

Are you sure that you don't have enable any other analog input? My 
notebook has very noisy build-in microphone for example.

Also note that if you have value over 70% with most of AC'97 controls, the 
analog gain is applied to the signal (thus you can really overdrive the 
output or input).

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs


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Re: [snd-intel8x0] distortion on PCM volume >> 50%

[Eduard Bloch]

Moin Jaroslav!
Jaroslav Kysela schrieb am Sunday, den 30. November 2003:

> > I have some problems with a ac97 based sound card (Notebook built-in)
> > where the kernel driver works fine (except of not beeing able to
> > resample on-the-fly).
> > 
> > When I set the PCM mixer volume to more then 50%, I hear few sound
> > fragments. If I go over 75% I hear them all the time and on 100% PCM,
> > the sound is full of scratching fragments. You can get an example
> > catched with microphone on
> > http://sites.inka.de/W1752/alsa-distortion.ogg and the original is on
> > www.vorbis.com/music/Mists_of_Time-4T.ogg . First I suspected a speaker
> > problem since it sounds very similar to overloud speaker setting, but it
> > is not!
> 
> Are you sure that you don't have enable any other analog input? My 
> notebook has very noisy build-in microphone for example.

No, my microphone is not built-in and not attached, the mixer is set to 0.

> Also note that if you have value over 70% with most of AC'97 controls, the 
> analog gain is applied to the signal (thus you can really overdrive the 
> output or input).

After almost an hour playing different stuff with different settings
with the ALSA, Linux-Kernel and Windows driver, I have the following
assumption: both, Kernel driver and Windows driver are cheating! They do
not present the Bass/Treble boost controls and the PCM volume at 75% in
ALSA  is quite comparable with 100% PCM volume with other drivers,
having quite comparable quality when Bass/Treble boost were set to 0.

So what I wish for the future version of ALSA drivers: a module option
to set the real mixer scale for PCM (or other sources) between 0 and X
percent while the visible scale is between 0 and 100 percent and
recalculated internaly to 0..X%.

But back to the second problem, I created a live example on
http://sites.inka.de/W1752/b.ogg - you can hear the fragments on time
points 0:35 and 1:31.

MfG,
Eduard.
-- 
Wer gar zu viel bedenkt, wird wenig leisten.


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Re: [snd-intel8x0] distortion on PCM volume >> 50%

[Jaroslav Kysela]

On Sun, 30 Nov 2003, Eduard Bloch wrote:

> Moin Jaroslav!
> Jaroslav Kysela schrieb am Sunday, den 30. November 2003:
> 
> > > I have some problems with a ac97 based sound card (Notebook built-in)
> > > where the kernel driver works fine (except of not beeing able to
> > > resample on-the-fly).
> > > 
> > > When I set the PCM mixer volume to more then 50%, I hear few sound
> > > fragments. If I go over 75% I hear them all the time and on 100% PCM,
> > > the sound is full of scratching fragments. You can get an example
> > > catched with microphone on
> > > http://sites.inka.de/W1752/alsa-distortion.ogg and the original is on
> > > www.vorbis.com/music/Mists_of_Time-4T.ogg . First I suspected a speaker
> > > problem since it sounds very similar to overloud speaker setting, but it
> > > is not!
> > 
> > Are you sure that you don't have enable any other analog input? My 
> > notebook has very noisy build-in microphone for example.
> 
> No, my microphone is not built-in and not attached, the mixer is set to 0.
> 
> > Also note that if you have value over 70% with most of AC'97 controls, the 
> > analog gain is applied to the signal (thus you can really overdrive the 
> > output or input).
> 
> After almost an hour playing different stuff with different settings
> with the ALSA, Linux-Kernel and Windows driver, I have the following
> assumption: both, Kernel driver and Windows driver are cheating! They do
> not present the Bass/Treble boost controls and the PCM volume at 75% in
> ALSA  is quite comparable with 100% PCM volume with other drivers,
> having quite comparable quality when Bass/Treble boost were set to 0.
> 
> So what I wish for the future version of ALSA drivers: a module option
> to set the real mixer scale for PCM (or other sources) between 0 and X
> percent while the visible scale is between 0 and 100 percent and
> recalculated internaly to 0..X%.

Yes, maybe we can do this in highter layers (our library - alsa-lib) in 
future, but it's not our goal for the driver where hardware should be 
described in most accurate way.

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs


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