mmaped play in multichannel mode (fwd)

mmaped play in multichannel mode (fwd)

[barat]

hi,
i have written some code for mmaped-play. it works so far for up to 2 
channels, but in multichannel-mode i get some mismatch about available 
buffersize or exactly a snd_pcm_mmap_commit error.
the essential part is the following:

  snd_pcm_mmap_begin(alsa_handler, &area, &offset, &frames_transmit);

  /* this is specific to interleaved streams (or non-interleaved
   * streams with only one channel) */
  outbuffer = ((char *) area->addr + (area->first + area->step * offset) / 
8);

  //write data
  memcpy(outbuffer, data, (frames_transmit * bytes_per_sample));
 
  commitres = snd_pcm_mmap_commit(alsa_handler, offset, frames_transmit);

i guess that outbuffer has a wrong size. does somebody have any idea about 
this outbuffer calculation?


thanx and regards

joy

________________________________________
do interactive tv on www.remote-tv.de


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Re: mmaped play in multichannel mode (fwd)

[Paul Davis]

>i have written some code for mmaped-play. it works so far for up to 2 
>channels, but in multichannel-mode i get some mismatch about available 
>buffersize or exactly a snd_pcm_mmap_commit error.
>the essential part is the following:
>
>  snd_pcm_mmap_begin(alsa_handler, &area, &offset, &frames_transmit);
>
>  /* this is specific to interleaved streams (or non-interleaved
>   * streams with only one channel) */
>  outbuffer = ((char *) area->addr + (area->first + area->step * offset) / 
>8);
>
>  //write data
>  memcpy(outbuffer, data, (frames_transmit * bytes_per_sample));
> 
>  commitres = snd_pcm_mmap_commit(alsa_handler, offset, frames_transmit);
>
>i guess that outbuffer has a wrong size. does somebody have any idea about 
>this outbuffer calculation?

i don't know exactly why you're spending time doing this. whether you
decide to use it or not, JACK (http://jackit.sf.net/) has full,
working code that shows how to do this. but i'd personally recommend
that you consider using it instead of reinventing the wheel, etc.

--p


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Could someone have a look at a my driver code please.

[Dan Mills]

Hi all,
I have written a  *very*  crude driver for the waveterminal 192L (mostly 
my guesswork as to how the thing is hooked up). It is based on the ice1724 
code but is really an engineering prototype (worked for the first time 20 
minutes ago) and not ready for prime time.
 
In particular it ignores the eeprom except for a check that its contents 
match that of the one on my card. It works for output pair 1, and may work 
for the others but that is uncertain at this point. It probably also has 
locking issues at present. 

Would someone be willing to take a look and give some pointers as to how 
to make this thing into a fully correct alsa driver? 

Undocumented hardware and a driver architecture with which you are not 
familiar make development fun!

My code will go up on the web once I have shaken a few more bugs out
(The mixer does nothing very useful at present & I am fairly sure that
playing with the GPIO pins some will get the phantom power and mic pre 
working.....). 

Regards, Dan.


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Re: mmaped play in multichannel mode (fwd)

[barat]

On Wed, 30 Jul 2003, Paul Davis wrote:

> >i guess that outbuffer has a wrong size. does somebody have any idea about 
> >this outbuffer calculation?
> 
> i don't know exactly why you're spending time doing this. whether you
> decide to use it or not, JACK (http://jackit.sf.net/) has full,
> working code that shows how to do this. but i'd personally recommend
> that you consider using it instead of reinventing the wheel, etc.
> 

im indeed working on using jack as another audio-out, but at first i 
wanted to improve the existing alsa-out. but thanks anyway.

joy


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