Re: questions about card detection

[Takashi Iwai <tiwai@suse.de>]

At Fri, 29 Aug 2003 11:31:35 +0100,
holborn wrote:
> 
> On Viernes, 29 de Agosto de 2003 10:37, Takashi Iwai wrote:
> 
> Hi!
> 
> 
> > "sub-device" is the lowest level of PCM abstration.
> > an actual PCM stream is always assigned to a sub-stream.
> >
> > the sub-device is introduced to represent the cases like
> > multi-playback function.  for example, SB Live can play 32 stereo
> > streams at the same time.  in the ALSA, the driver assigns 32
> > sub-devices (sub-streams) to a playback device.
> 
> Are this sub-devices used by the internal SB Live synthesizer?  

well, not directly.
on emu10k1, PCM streams and WaveTable synth voices are identical.
(so, indeed, you can even change the pitch, apply LFO, lowpass filter,
 etc. to PCM streams in real-time (in theory :) )

WaveTable synth allocates the voices dynamically.  it looks for an
empty (hardware) stream and assigns it for the MIDI voice.  after the
voice is released (i.e. tone is finished), the stream is released
again for free.

usually, PCM looks for the empty pair of stereo slots to assign the
PCM substream automatically.  thus, using WaveTable at the same time
would influence on the substream number to be assigned at the open
time. 

note that the WaveTable has lower priority than PCM.  if all hardware
streams are in use, PCM tries to stop WaveTable voices until a pair of
stereo streams becomes available.


> Or if that is not true, anyway to assign the sound of the different Midi 
> Channels to that sub-devices in a way to apply LADSPA effects?

no.  the MIDI wavetable is hardware only.  there is no feedback to
apply effects on the fly.


Takashi


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