Occasional metallic sound when recording (cs46xx)

Occasional metallic sound when recording (cs46xx)

[Eloy A. Paris]

Hello,

I am trying to troubleshoot a very annoying problem I have with a Santa
Cruz Turtle Beach (cs46xx). Sometimes, when recording, the recorded
sound is very metallic. If when I get the metallic sound I run alsamixer
and toggle the capture facility of the ADC on and off, sound is fixed
and back to normal.

This problem happens randomly but is very annoying, specially if I
program my PVR (MythTV) to automatically record a show - the show can
get recorded with metallic sound, which makes it very hard to understand
during playback.

This is not MythTV-specific since I have been able to reproduce the
problem using other applications, like the Gnome sound recorder. It is
unrelated to full-duplex operation since when recording a show MythTV
doesn't open /dev/dsp for writing.

I really have no idea about how to troubleshoot this. I don't think
the problem is hardware, but is driver-related instead.

Any suggestions? Are there any debug switches I can enable to get more
information about the problem? I can recompile the drivers and try
anything. I really want to see this fixed, so if anyone has any ideas
to try just let me know.

Thanks,

Eloy.-


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Re: Occasional metallic sound when recording (cs46xx)

[Paul Davis]

>This problem happens randomly but is very annoying, specially if I
>program my PVR (MythTV) to automatically record a show - the show can
>get recorded with metallic sound, which makes it very hard to understand
>during playback.
>
>This is not MythTV-specific since I have been able to reproduce the
>problem using other applications, like the Gnome sound recorder. It is
>unrelated to full-duplex operation since when recording a show MythTV
>doesn't open /dev/dsp for writing.
>
>I really have no idea about how to troubleshoot this. I don't think
>the problem is hardware, but is driver-related instead.

its almost certainly a software problem in mythTV and gnome sound
recorder. i've written code that does this several times - every time
it takes me ages to figure out why, and then i can never remember when
i do it the next time. its related to off-by-1 errors in processing
incoming audio.

not necessarily, of course, just a point of view.



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Re: Occasional metallic sound when recording (cs46xx)

[Eloy A. Paris]

Hello,

Paul Davis <paul@linuxaudiosystems.com> writes:

> its almost certainly a software problem in mythTV and gnome sound
> recorder. i've written code that does this several times - every time
> it takes me ages to figure out why, and then i can never remember when
> i do it the next time. its related to off-by-1 errors in processing
> incoming audio.
>
> not necessarily, of course, just a point of view.

Hhhmmmm, but wouldn't a problem like this cause the metallic sound
everytime? In my case it works fine must of the time, but every now and
then I get the darn metallic noise. Also, I can fix it by running the
alsamixer and toggling on and off the capture setting of the ADC
channel.

I forgot to mention that when I am hearing the metallic sound, if I
increase the volume of the "line in" channel in the mixer, I hear the
audio from the TV tuner just fine (this is the bypass, from line-in
directly to the speakers). This confirms that the input signal is fine,
I think.

What I'll try next is to connect the audio output from the TV tuner card
to my sound card's microphone input, instead of the line-in input just
to see if there are any differences, although I doubt it.

Other suggestions?

Thanks,

Eloy.-


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Re: Occasional metallic sound when recording (cs46xx)

[Wilfried Weissmann]

Paul Davis wrote:
>>This problem happens randomly but is very annoying, specially if I
>>program my PVR (MythTV) to automatically record a show - the show can
>>get recorded with metallic sound, which makes it very hard to understand
>>during playback.
>>
>>This is not MythTV-specific since I have been able to reproduce the
>>problem using other applications, like the Gnome sound recorder. It is
>>unrelated to full-duplex operation since when recording a show MythTV
>>doesn't open /dev/dsp for writing.
>>
>>I really have no idea about how to troubleshoot this. I don't think
>>the problem is hardware, but is driver-related instead.
> 
> 
> its almost certainly a software problem in mythTV and gnome sound
> recorder. i've written code that does this several times - every time
> it takes me ages to figure out why, and then i can never remember when
> i do it the next time. its related to off-by-1 errors in processing
> incoming audio.

i also have the same problem with speakfreely with my cs46xx. it does 
not look like the metallic sound is triggered by any specific event 
(load, I/O,...). out of the sudden somethings goes wrong. i think i also 
experienced it with the kde sound recorder. but i have not updated the 
alsa driver for a while (still 0.9.5 or so). toggleing the ADC sounds 
like a good idea. i have not tried that yet but reloading the modules 
works too.

> 
> not necessarily, of course, just a point of view.

hmm, what makes something sound metallic anyway? echo?

bye,
wilfried




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Re: Occasional metallic sound when recording (cs46xx)

[Eloy A. Paris]

Hello,

Wilfried Weissmann <Wilfried.Weissmann@gmx.at> writes:

> i also have the same problem with speakfreely with my cs46xx.

I'm sorry for you but am happy at the same time that I am not the only
one experiencing this.

> it does not look like the metallic sound is triggered by any specific
> event (load, I/O,...). out of the sudden somethings goes wrong.

Yes, I agree, doesn't seem related to anything in particular.

> also experienced it with the kde sound recorder. but i have not
> updated the alsa driver for a while (still 0.9.5 or so).

I am running version 0.9.8 of the alsa-driver, and the problem is still
there.

> toggleing the ADC sounds like a good idea. i have not tried that yet
> but reloading the modules works too.

Well, try doing the ADC thing and let me know if it works for you. This
has the advantage that you don't have to shut down the application you
are using.

> hmm, what makes something sound metallic anyway? echo?

Good question, I wish I knew. I guess I'll try enabling debugging output
in the cs46xx driver. I am particulary interested in knowing what
happens when you toggle capture of the ADC channel in alsamixer.

Cheers,

Eloy.-


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Re: Occasional metallic sound when recording (cs46xx)

[Joe]

I have the same problem with my Turtle Beach Santa Cruz card (cs46xx). 
I haven't used the capture device yet, but the metallic sound happens in
playback, also randomly.  For example, in gaim, incoming IM sounds will
be normal, and then all of a sudden, switch to that metallic sound (the
source sound file is the same, but the playback is extremely
different).  It seems to be a problem that is triggered only when
opening the device, because it happens in XMMS as well, when playing a
song file -- if this anomaly is triggered when the song is started, it
remains throughout he entire song, unless stopped and restarted, or
going to the next track.  

I hope this helps someone understand the problem, but I'm afraid I can't
tell what is the actual trigger for it.

-Joe

On Thu, 2003-10-23 at 14:01, Eloy A. Paris wrote:
> Hello,
> 
> Wilfried Weissmann <Wilfried.Weissmann@gmx.at> writes:
> 
> > i also have the same problem with speakfreely with my cs46xx.
> 
> I'm sorry for you but am happy at the same time that I am not the only
> one experiencing this.
> 
> > it does not look like the metallic sound is triggered by any specific
> > event (load, I/O,...). out of the sudden somethings goes wrong.
> 
> Yes, I agree, doesn't seem related to anything in particular.
> 
> > also experienced it with the kde sound recorder. but i have not
> > updated the alsa driver for a while (still 0.9.5 or so).
> 
> I am running version 0.9.8 of the alsa-driver, and the problem is still
> there.
> 
> > toggleing the ADC sounds like a good idea. i have not tried that yet
> > but reloading the modules works too.
> 
> Well, try doing the ADC thing and let me know if it works for you. This
> has the advantage that you don't have to shut down the application you
> are using.
> 
> > hmm, what makes something sound metallic anyway? echo?
> 
> Good question, I wish I knew. I guess I'll try enabling debugging output
> in the cs46xx driver. I am particulary interested in knowing what
> happens when you toggle capture of the ADC channel in alsamixer.
> 
> Cheers,
> 
> Eloy.-
> 
> 
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Re: Occasional metallic sound when recording (cs46xx)

[Ray Heasman]

On Wed, 2003-10-22 at 09:22, Eloy A. Paris wrote:
> Hello,
> 
> I am trying to troubleshoot a very annoying problem I have with a Santa
> Cruz Turtle Beach (cs46xx). Sometimes, when recording, the recorded
> sound is very metallic. If when I get the metallic sound I run alsamixer
> and toggle the capture facility of the ADC on and off, sound is fixed
> and back to normal.
> 

My personal experience (not with ALSA, but other things) is that you can
get a horrid metallic sound when a signal is mixed with itself with a
small (a few samples) delay. So, this could be some sort of out by one
error causing the signal to get mixed with a delayed version of itself.

The other option that occurs to me is that perhaps there is a routing
problem with the signals - ie... an audio output is being "monitored"
and mixed back into the input. I have found it very easy to do this with
some applications with the ALSA drivers - they unintentionally produce
an output which gets mixed back into the input. The solution is to mute
all the stuff you don't want using alsamixer.

A good thing to try would be to set up GnomeMeeting on your alsa card.
It has a test mode that makes it easy to tell if you are getting an
unintentional loopback.

Hope this helps,
Ray




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Re: Occasional metallic sound when recording (cs46xx)

[Manuel Jander]

Hello,

> > hmm, what makes something sound metallic anyway? echo?
> 
> Good question, I wish I knew. I guess I'll try enabling debugging output
> in the cs46xx driver. I am particulary interested in knowing what
> happens when you toggle capture of the ADC channel in alsamixer.

It could be a stereo demultiplexer problem. I had such kind of problems
on the Aureal driver while reverse engineering the Audio routing. If you
mess the order of the samples, you can end up with the MSB in place of
the LSB on such things, one piece of one channel swapped into the
other... very weird things, and interesting special effects :D.

I would suggest trying with other formats, say 8 bit mono, since if the
problem appears in such a format, where byte stream misalignment doesn't
care (one frame = one byte), then maybe the problem is related to
somewhat else, like DAC Antialiasing filter being setup wrong, or left
unprogrammed.

Once you have the pattern, of which formats are affected and which don't
its much easier to figure out where the problem lies.

Best Regards




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Re: Occasional metallic sound when recording (cs46xx)

[Takashi Iwai]

At Thu, 23 Oct 2003 15:01:50 -0400,
Eloy A. Paris wrote:
> 
> Hello,
> 
> Wilfried Weissmann <Wilfried.Weissmann@gmx.at> writes:
> 
> > i also have the same problem with speakfreely with my cs46xx.
> 
> I'm sorry for you but am happy at the same time that I am not the only
> one experiencing this.

then it sounds like the specific problem for cs46xx driver.
i guess some drift occured during the sample rate conversion or so.
please check whether the same symptom happens on 48000Hz ?


Takashi


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Re: Occasional metallic sound when recording (cs46xx)

[Eloy A. Paris]

Hi Takashi,

This is from a thread about two weeks old. Didn't respond before because
was trying the suggestion you provided (see below.)

Takashi Iwai <tiwai@suse.de> writes:

> then it sounds like the specific problem for cs46xx driver.

That's a possibility, although I don't have another card to test the
theory.

> i guess some drift occured during the sample rate conversion or so.
> please check whether the same symptom happens on 48000Hz ?

I set the sample rate to 48 KHz, and while the problem still happens
sporadically it happens a *lot* less than when the rate was 32 KHz.

Does this offer any clues? Do you have any debugging suggestions to try
to pinpoint the problem, like printk's in some places, etc.?

Cheers,

Eloy.-


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Re: Occasional metallic sound when recording (cs46xx)

[Florian Schmidt]

On Wed, 05 Nov 2003 10:08:33 -0500
peloy@chapus.net (Eloy A. Paris) wrote:

> Hi Takashi,
> 
> This is from a thread about two weeks old. Didn't respond before
> because was trying the suggestion you provided (see below.)
> 
> Takashi Iwai <tiwai@suse.de> writes:
> 
> > then it sounds like the specific problem for cs46xx driver.


i don't know if i answered back then but i have the same problem with my
terratec dmx xfire 1024 [cs46xx]. Occasionally the sound is metallic and
distorted and a bit quiter than normal. Turning the Capture on the ADC
device Off and On again usualy remedies the situation.

If it is any help i can try making a recording of the sound..

FLorian Schmidt


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Re: Occasional metallic sound when recording (cs46xx)

[Takashi Iwai]

At Thu, 06 Nov 2003 23:11:21 +0100,
Benny Sjostrand wrote:
> 
> >
> >
> >then it sounds like the specific problem for cs46xx driver.
> >i guess some drift occured during the sample rate conversion or so.
> >please check whether the same symptom happens on 48000Hz ?
> >
> >  
> >
> Sorry that I've been lost from the list from a long time ...
> 
> Your right this sympton may be specific for the cs46xx, I've
> been experiencing this sympton with JACK and Ardour several
> times.
> 
> The sample rate should not matter.
> My guess is that internal buffers occasionally get unsynchronized inside 
> the DSP,  
> may happen on playback too.
> 
> The only I've found to get around the problem when it happens is to
> restart the playback or capturing process.

does changing ADC volume (or so, sorry, i forgot the detail) fix?
IIRC, one post mentioned that.

anyway, it'd be helpful for debugging if someone can reproduce this
certainly under a fixed condition...


Takashi


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Re: Occasional metallic sound when recording (cs46xx)

[Eloy A. Paris]

Hi Takashi,

Takashi Iwai <tiwai@suse.de> writes:

>> Your right this sympton may be specific for the cs46xx, I've
>> been experiencing this sympton with JACK and Ardour several
>> times.
>> 
>> The sample rate should not matter.  My guess is that internal buffers
>> occasionally get unsynchronized inside the DSP, may happen on
>> playback too.
>> 
>> The only I've found to get around the problem when it happens is to
>> restart the playback or capturing process.
>
> does changing ADC volume (or so, sorry, i forgot the detail) fix?
> IIRC, one post mentioned that.

Yes, when you start recording and get the darn metallic noise, if you
run alsamixer and toggle off and back on the capturing facility of the
ADC (hitting the space bar twice), sound comes back without the metallic
noise. There is no need to restart the playback or capturing process, at
least that's what I've found. Of course, this is less than ideal since
most of the times I am not around when my MythTV PVR starts to record a
show :-)

> anyway, it'd be helpful for debugging if someone can reproduce this
> certainly under a fixed condition...

Well, about 3 times out of 7 I get the problem, so it's not hard to
reproduce at all. What I'd have to know is where to place the debugging
printk()'s or something like that :(

Cheers,

Eloy.-


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Re: Occasional metallic sound when recording (cs46xx)

[Paul Davis]

>> anyway, it'd be helpful for debugging if someone can reproduce this
>> certainly under a fixed condition...
>
>Well, about 3 times out of 7 I get the problem, so it's not hard to
>reproduce at all. What I'd have to know is where to place the debugging
>printk()'s or something like that :(

just wanted to mention that i mis-remembered the situation under which
this used to happen with the rme9652 driver. it was an error in the
*driver*, not the application, and it was related to the logic for
figuring out the hardware buffer pointer being incorrect. i forget the
error, and its probably something a bit different anyway (because of
the ASIO-style design of the rme9652), but i just wanted to mention it
in case it provides any help.

once i fixed the driver to get this right, i could never (and have
never) heard the problem again.

--p



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Re: Occasional metallic sound when recording (cs46xx)

[Christian Esken]

On Friday 24 October 2003 15:18, Takashi Iwai wrote:
> At Thu, 23 Oct 2003 15:01:50 -0400,
>
> Eloy A. Paris wrote:
> > Hello,
> >
> > Wilfried Weissmann <Wilfried.Weissmann@gmx.at> writes:
> > > i also have the same problem with speakfreely with my cs46xx.
> >
> > I'm sorry for you but am happy at the same time that I am not the only
> > one experiencing this.

You are not alone. It happens on my CS46xx as well (Hercules 
GameTheaterXP7.1).

> then it sounds like the specific problem for cs46xx driver.

Sounds like it.

Chris


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