[linux-audio-user] Re: hardware mixing - what it _actually_ is?

linux-audio-user at music.columbia.edu linux-audio-user at music.columbia.edu
Wed Jan 24 06:51:01 EST 2007


> > > "Hardware mixing" in ALSA terminology refers to the mixing of multiple
> > > sound sources from the PC by the hardware.  For example, mplayer
> > > output and system notification sounds.
> >
> > Yeah. I suspect (and Mark apparently did, too) that the original
> > poster meant to ask about hardware monitoring, which is completely
> > different :-)
> >
> > Explanation here:
> > http://ardour.org/manual/recording/monitoring

well, i asked about hardware _mixing_, since it is pretty obscure thing, unlike hardware _monitoring_ :)

> Is there a commonly understood meaning? I guess I'm uncommonly (or
> commonly for me) in the dark about that.

that's troo :)

> > I stand corrected.  Mark was right - these devices do have hardware
> > mixing, they just implement it in an odd way, probably to keep the
> > interface similar to other OS.
> 
> its not true to say that with ALSA, they support what is commonly
> understood as h/w mixing. you cannot do independent open's of several
> subdevices and get the output of each subdevice mixed down to the
> outputs. 
> 
> yes, they do have a very powerful h/w matrix mixer, but it is not
> accessible via a series of independent subdevices. it also is not
> supported by the ALSA mixer API at this time.


> > > you cannot do independent open's of several
> > > subdevices and get the output of each subdevice mixed down to the
> > > outputs.
> > 
> > This seems a Linux Software Developer centric statement. What does it mean?
> 
> it means that you can have up to N apps all using the same card without
> any s/w mixing going on. each one calls snd_pcm_open() which internally
> calls snd_pcm_open_subdevice() and assuming the subdevices are not all
> busy, it will work. a subdevice is a "stream" that always sends its
> signal to the outputs associated with the PCM device, but can be opened
> and closed independently.

ok. this clarifies things enough.
so, if i use only one app (csound), seems like there's no need to care about this hardware mixing thing.

thanx again.

-- 

sex, pot, open source!!


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