Metering on record

Metering on record

[Erik de Castro Lopo]

Hi all,

I was hoping someone might be able to shine some light on the
following issue. I am currently opening an ALSA device for 
record say 44.1 kHz and reading 32k frames of data at a time.

Now with the above setup, if I want to do a meter, I can only
only update the meter every 32k frames or a little more than
once a second which makes for a very poor display.

So, looking at /usr/include/alsa/pcm.h I find some function
definitions which seem like they are meant for metering purposes.
Unfortunalety I can't seem to find any documentation on the ALSA
site nor can I find example code showing how this stuff is 
used.

Am I missing something or does this stuff just not exist? Do
these snd_pcm_meter_* functions work? Anybody have working code
that uses these things?

Thanks,
Erik
-- 
+-----------------------------------------------------------+
  Erik de Castro Lopo  nospam@mega-nerd.com (Yes it's valid)
+-----------------------------------------------------------+
"Anyone who says you can have a lot of widely dispersed people hack
away on a complicated piece of code and avoid total anarchy has never
managed a software project." - Andy Tanenbaum in 1992 on comp.os.minix


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Re: Metering on record

[Jaroslav Kysela]

On Sun, 28 Sep 2003, Erik de Castro Lopo wrote:

> Hi all,
>
> I was hoping someone might be able to shine some light on the
> following issue. I am currently opening an ALSA device for
> record say 44.1 kHz and reading 32k frames of data at a time.
>
> Now with the above setup, if I want to do a meter, I can only
> only update the meter every 32k frames or a little more than
> once a second which makes for a very poor display.
>
> So, looking at /usr/include/alsa/pcm.h I find some function
> definitions which seem like they are meant for metering purposes.
> Unfortunalety I can't seem to find any documentation on the ALSA
> site nor can I find example code showing how this stuff is
> used.
>
> Am I missing something or does this stuff just not exist? Do
> these snd_pcm_meter_* functions work? Anybody have working code
> that uses these things?

The examples are in alsa-lib/src/pcm/scopes directory, but don't expect
a better response times, because the meter plugin is also activated
when an application reads or writes data to device.

						Jaroslav

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


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Re: Metering on record

[Erik de Castro Lopo]

On Mon, 29 Sep 2003 10:37:56 +0200 (CEST)
Jaroslav Kysela <perex@suse.cz> wrote:

> The examples are in alsa-lib/src/pcm/scopes directory, but don't expect
> a better response times, because the meter plugin is also activated
> when an application reads or writes data to device.

Does that mean that the only way to get better meter response is to
read smaller blocks?

Erik
-- 
+-----------------------------------------------------------+
  Erik de Castro Lopo  nospam@mega-nerd.com (Yes it's valid)
+-----------------------------------------------------------+
"The day Microsoft makes something that doesn't suck is probably the
day they start making vacuum cleaners." -- Ernst Jan Plugge


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Re: Metering on record

[Jaroslav Kysela]

On Mon, 29 Sep 2003, Erik de Castro Lopo wrote:

> On Mon, 29 Sep 2003 10:37:56 +0200 (CEST)
> Jaroslav Kysela <perex@suse.cz> wrote:
>
> > The examples are in alsa-lib/src/pcm/scopes directory, but don't expect
> > a better response times, because the meter plugin is also activated
> > when an application reads or writes data to device.
>
> Does that mean that the only way to get better meter response is to
> read smaller blocks?

Not really. The plugins are activated when snd_pcm_avail_update() is
called, so if you write own meter plugin and call snd_pcm_avail_update
more frequently in the read thread, you may get better results. But I
think that it might be better to read small chunks, because samples are
already processed when snd_pcm_avail_update() is called so there is no
point to delay the processing in application. In other words, it's better
to do additional (large) buffering in application to avoid xruns.

						Jaroslav

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


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PDAudio-CF ALSA Driver Intermittent Failure

[Len Moskowitz]

On the Linux Audio User mailing list, Jamie Lutch wrote:

[Begin]

From: Jamie Lutch <jlutch@al...>
 audioio-alsa error
2003-09-23 20:05
 So I have my setup (pdaudiocf card>ecasound) running fine at 24/96, but
 every once in awhile it just stops mid-stream and gives the following
error:

 (audioio-alsa) Unknown Device State!

 it just scrolls this message frantically, I have to reboot to get the card
 to work again.

 any suggestions on where to start troubleshooting? It seems to be random. I
 can sometimes record for hours before it happens, other times it happens
 sooner (like the other night, halfway through the first set of david
grisman
 quintet :( )

 thanks,
 jamie

[End]

Might someone help us with this problem?  What might we do to track down the
cause of this failure?


Len Moskowitz
Core Sound
www.core-sound.com



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