ALSA Programming Examples

ALSA Programming Examples

[Philipp Vollmer]

Hello to all ALSA Devolpers,

I am actually starting to program with the ALSA library.
My Problem:

When I try to compile the examples of the HOWTO exactly discriped in the 
README of this directory.
So I get a message as if there was a mistake in the code. There isn't I think.
I searched for the source and I found the "open" ( for the sound device ) 
codeline where constants seemed to me inexistant.

Where is the problem?
Is there a mistake in the example or in the HOWTO.

With best regards 

Philipp Vollmer

PS: post to do1ypv@darc.de


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Re: ALSA Programming Examples

[Philipp Vollmer]

Hello dear Mr Davis,

My library version is 0.5.10b and the driver version is 0.5.12a.

The author of the HOWTO is Matthias Nagorni.

Best regards

Philipp Vollmer

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Re: ALSA Programming Examples

[Paul Davis]

>Hello to all ALSA Devolpers,
>
>I am actually starting to program with the ALSA library.

Please tell us which version of ALSA you are using.

I also suggest you use Matthias Nagorni's examples that are linked to
from the website. My own are there also but they have not been
completed and are incorrect right now.

--p

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Re: ALSA Programming Examples

[Paul Davis]

>My library version is 0.5.10b and the driver version is 0.5.12a.

0.5 is no longer really supported. You should be using 0.9.X. The web
  site says on the front page:

 *** N.B. The 0.5.x series is considered deprecated and is no longer
     supported by ALSA developers ***

>The author of the HOWTO is Matthias Nagorni.

AFAIK, his HOWTO is for 0.9 ...

--p

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Alsa Programming Examples

[Philipp Vollmer]

Hello to all ALSA developers!

I had compiled the examples of the Programming HOWTO succesfully!!!
I saw many programming mistakes in these files. I don't think ANSI C supports 
polymorphism! So I had to take parts out of other running code and put it 
into the example.
But now, after a few changes I could run the program which starts to send 
Random PCM Data to the interface.

Now I have following problem:
Although the program compiled succesfully I get following output:

how1: pcm_params.c:2136: snd_pcm_hw_refine: Assertion && params failed.
Canceled

What is the problem?
( My conditions:
CMI8738
ALSA 0.90 driver and library
)

Yours Philipp Vollmer



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Re: Alsa Programming Examples

[Tim Goetze]

Philipp Vollmer wrote:

>Hello to all ALSA developers!
>
>I had compiled the examples of the Programming HOWTO succesfully!!!
>I saw many programming mistakes in these files. I don't think ANSI C supports 
>polymorphism! So I had to take parts out of other running code and put it 
>into the example.
>But now, after a few changes I could run the program which starts to send 
>Random PCM Data to the interface.
>
>Now I have following problem:
>Although the program compiled succesfully I get following output:
>
>how1: pcm_params.c:2136: snd_pcm_hw_refine: Assertion && params failed.
>Canceled
>
>What is the problem?

$ man assert

it seems params == 0 when you're calling snd_pcm_hw_refine.

tim


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Re: Alsa Programming Examples

[Philipp Vollmer]

[-- Attachment #1: Type: text/plain, Size: 251 bytes --]

> it seems params == 0 when you're calling snd_pcm_hw_refine.
Hello,

Sorry but there is no codeline like snd_pcm_hw_refine in the example.
I will send you the file as an attachment.

Best regards 

Philipp Vollmer
vollmer.philipp@t-online.de

[-- Attachment #2: how1.c --]
[-- Type: text/x-csrc, Size: 1503 bytes --]

      #include <stdlib.h>
      #include <alsa/asoundlib.h>
      
      main (int argc, char *argv[])
      {
           int i;
           char buf[4096];
           snd_pcm_t *playback_handle;
           snd_pcm_hw_params_t *hw_params;

           if ((playback_handle = snd_pcm_open (&playback_handle, "default", SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
                 fprintf (stderr, "cannot open audio device %s\n", argv[1]);
                 exit (1);
           }
	   // snd_pcm_open (&playback_handle, pcm_name, SND_PCM_STREAM_PLAYBACK, 0)
           
           snd_pcm_hw_params_malloc (&hw_params);
           snd_pcm_hw_params_any (playback_handle, hw_params);
           snd_pcm_hw_params_set_access (playback_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);
           snd_pcm_hw_params_set_format (playback_handle, hw_params, SND_PCM_FORMAT_S16_LE);
           snd_pcm_hw_params_set_rate_near (playback_handle, hw_params, 44100, 0);
	 //snd_pcm_hw_params_set_rate_near(playback_handle, hw_params, 44100, 0);
           snd_pcm_hw_params_set_channels (playback_handle, hw_params, 2);
           snd_pcm_hw_params (playback_handle, hw_params);
           snd_pcm_hw_params_free (hw_params);

           snd_pcm_prepare (playback_handle);

           for (i = 0; i < 10; ++i) {
                   snd_pcm_writei (playback_handle, buf, sizeof (buf));
		  //snd_pcm_writei (playback_handle, buf, nframes);
           }

           snd_pcm_close (playback_handle);
           exit (0);
     }

Re: Alsa Programming Examples

[Tim Goetze]

Philipp Vollmer wrote:

>> it seems params == 0 when you're calling snd_pcm_hw_refine.
>Hello,
>
>Sorry but there is no codeline like snd_pcm_hw_refine in the example.
>I will send you the file as an attachment.

in your file:

  if ((playback_handle = snd_pcm_open (&playback_handle, "default", 
	SND_PCM_STREAM_PLAYBACK, 0)) < 0) {

snd_pcm_open returns 0 on success, *not* the pcm handle. have you
tried reading the docs yet ;) and haven't you wondered why you pass
the address of 'playback_handle' to snd_pcm_open()?

gcc warns you about this:

$ gcc -c how1.c 
how1.c: In function `main':
how1.c:11: warning: assignment makes pointer from integer without a
cast

and if you had endeavoured to read the sources of alsa-lib, you'd 
have discovered that (alsa-lib/src/pcm/pcm.c):

int snd_pcm_hw_params_any(snd_pcm_t *pcm, snd_pcm_hw_params_t *params)
{
  _snd_pcm_hw_params_any(params);
  return snd_pcm_hw_refine(pcm, params);
}

with all respect, i think you could have tried a little harder to find
the error.

tim



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Re: Alsa Programming Examples

[tomasz motylewski]

On Sun, 9 Jun 2002, Tim Goetze wrote:

> with all respect, i think you could have tried a little harder to find
> the error.

There is a prominent link on
http://www.alsa-project.org/documentation.php3#0.9doc

Howto use the ALSA API - Paul Davis has also written a brief explanation. 
http://www.op.net/~pbd/alsa-audio.html#captureex

You will find there:

 if ((capture_handle = snd_pcm_open (argv[1], SND_PCM_STREAM_CAPTURE, 0)) <0) {
         fprintf (stderr, "cannot open audio device %s\n", argv[1]);
                 exit (1);
 }

and many other errors.

While examples are the best for of developers documentation, broken examples
are the worst form of misinformation.

I have written about a week ago to pbd@users.sourceforge.net, no answer yet.

Best regards,
--
Tomasz Motylewski



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Re: Alsa Programming Examples

[Tim Goetze]

tomasz motylewski wrote:

>On Sun, 9 Jun 2002, Tim Goetze wrote:
>
>> with all respect, i think you could have tried a little harder to find
>> the error.
>
>There is a prominent link on
>http://www.alsa-project.org/documentation.php3#0.9doc
>
>Howto use the ALSA API - Paul Davis has also written a brief explanation. 
>http://www.op.net/~pbd/alsa-audio.html#captureex
>
>You will find there:
>
> if ((capture_handle = snd_pcm_open (argv[1], SND_PCM_STREAM_CAPTURE, 0)) <0) {
>         fprintf (stderr, "cannot open audio device %s\n", argv[1]);
>                 exit (1);
> }
>
>and many other errors.
>
>While examples are the best for of developers documentation, broken examples
>are the worst form of misinformation.

i offer my apologies, i had no idea this tutorial fails its purpose so
badly.

tim


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Re: Alsa Programming Examples

[Paul Davis]

>There is a prominent link on
>http://www.alsa-project.org/documentation.php3#0.9doc
>
>Howto use the ALSA API - Paul Davis has also written a brief explanation. 
>http://www.op.net/~pbd/alsa-audio.html#captureex

Right here, on this mailing list, and in private mail to Philipp, and
in mail to LAD, I made it clear that the examples in my document are
incomplete and incorrect.

The link is included because it was felt that the non-code material in
my document was useful. 

>While examples are the best for of developers documentation, broken examples
>are the worst form of misinformation.

agreed. perhaps you can fix them, or produce a version of the document
with them removed so that a better link can be used. If you would like
to pay me to rearrange my time to get the code removed and/or fixed,
thats fine. Otherwise, please accept the limited offering thats linked
to right now.

>I have written about a week ago to pbd@users.sourceforge.net, no answer yet.

thats not my email address, and its not listed as that on the web
site. i get approximately 150 email messages per day connected with
linux audio issues. i do not have time to answer them all.

--p

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Re: Alsa Programming Examples

[Patrick Shirkey]

Paul Davis wrote:

> 
> agreed. perhaps you can fix them, or produce a version of the document
> with them removed so that a better link can be used. If you would like
> to pay me to rearrange my time to get the code removed and/or fixed,
> thats fine. Otherwise, please accept the limited offering thats linked
> to right now.
> 
> 

If people send in a fix to that file I'll add it in and put up the 
revision on ALSA if Paul doesn't mind.


-- 
Patrick Shirkey - Boost Hardware Ltd.
For the discerning hardware connoisseur
Http://www.boosthardware.com
Http://www.boosthardware.com/LAU/guide/
========================================


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Resetting audio device with ALSA

[Jon Webb]

Hello, I'm having trouble with resetting an ALSA audio device (an RME 9652
Hammerfall card) when the audio input buffer overflows. I'm using the
following code:
	rc = snd_pcm_drain(pcmIn);
	rc = snd_pcm_prepare(pcmIn);
	rc = snd_pcm_start(pcmIn);
where pcmIn is a snd_pcm_t* variable that's been initialized by
snd_pcm_open. I don't usually any problems reading from the device using the
same variable, and the return code from the above calls is always zero, but
it appears that once my audio input buffer overflows, I can never get going
again--it just keeps overflowing (snd_pcm_readn returns -EPIPE). Any ideas
what I'm doing wrong?

Jon Webb
pingAUDIO



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