Set up buffers for individual channels?

Set up buffers for individual channels?

[knuarv]

After browsing through the ASIO SDK I see that one can enable individual 
channels of a card, and only enabled channels will have a buffer set up for 
them. Is there a similar way to specify the exact channels one wants to access 
using Alsa (instead of simply number of channels)? 


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Re: Set up buffers for individual channels?

[Takashi Iwai]

At Mon,  7 Apr 2003 23:49:06 +0200,
knuarv@nith.no wrote:
> 
> After browsing through the ASIO SDK I see that one can enable individual 
> channels of a card, and only enabled channels will have a buffer set up for 
> them. Is there a similar way to specify the exact channels one wants to access 
> using Alsa (instead of simply number of channels)? 

how about accessing via non-interleaved mode?


Takashi


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Re: Set up buffers for individual channels?

[knuarv]

Quoting Takashi Iwai <tiwai@suse.de>:

> At Mon,  7 Apr 2003 23:49:06 +0200,
> knuarv@nith.no wrote:
> > 
> > After browsing through the ASIO SDK I see that one can enable individual 
> > channels of a card, and only enabled channels will have a buffer set up for
> 
> > them. Is there a similar way to specify the exact channels one wants to
> access 
> > using Alsa (instead of simply number of channels)? 
> 
> how about accessing via non-interleaved mode?
>
I'm experimenting with non-interleaved mmap now, but I can't say I understand 
the workings of Alsa yet. From what I can see Alsa sets up memory areas for the 
requested amount of channels (from 0 to 9 for instance), so I can choose myself 
which buffers to actually use? I was thinking I could perhaps specify _which_ 
channels I want to use, and get handed buffers for only those channels. No 
biggie, just need to get to know the interface a bit more.

A




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Re: Set up buffers for individual channels?

[Takashi Iwai]

At Tue,  8 Apr 2003 20:38:16 +0200,
knuarv@nith.no wrote:
> 
> Quoting Takashi Iwai <tiwai@suse.de>:
> 
> > At Mon,  7 Apr 2003 23:49:06 +0200,
> > knuarv@nith.no wrote:
> > > 
> > > After browsing through the ASIO SDK I see that one can enable individual 
> > > channels of a card, and only enabled channels will have a buffer set up for
> > 
> > > them. Is there a similar way to specify the exact channels one wants to
> > access 
> > > using Alsa (instead of simply number of channels)? 
> > 
> > how about accessing via non-interleaved mode?
> >
> I'm experimenting with non-interleaved mmap now, but I can't say I understand 
> the workings of Alsa yet. From what I can see Alsa sets up memory areas for the 
> requested amount of channels (from 0 to 9 for instance), so I can choose myself 
> which buffers to actually use?

basically, you cannot give the buffer pointers from your side.
the buffer pointer will be given by the driver.

> I was thinking I could perhaps specify _which_ 
> channels I want to use, and get handed buffers for only those
> channels.

yes, in the case of non-interleaved mode, a single buffer will be
split for each channel.  so you can access them apparently as if they
are different buffers.

you can check aplay.c for the non-interleaved playback/recording
case.


ciao,

Takashi


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