On Sat, Nov 03, 2007 at 02:21:27PM +0000, Stuart Henderson wrote:
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> On 2007/11/03 13:40, Karel Kulhavy wrote:
> > On Wed, Oct 31, 2007 at 05:48:20PM +0100, Alexandre Ratchov wrote:
> > > no; character devices (such as /dev/audio) keep per-unit state
> > > (encoding, rate, ...). To mix multiple audio streams per-stream
> > > state must be kept. That's why arts/esd/jack/... exist.
> > 
> > You don't need arts/esd/jack because of this. This can be solved in kernel.
> 
> so, the kernel would mix multiple sound sources coming at
> different rates?
> 
> but, /dev/audio uses a character device. like ratchov@ (new audio
> developer) wrote, these keep per-unit state, not per-stream state.
> 
> even ignoring whether it's actually desirable to have the kernel
> do resampling (a quick perusal of the list archives should reveal

Without resampling the illusion of having the soundcard just for you would
be gone.

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> what developers think about that), with a character device you
> *can't track the state of each stream* e.g. which bitrate to use.

The opener actually does some kind of ioctl on the device. So if one opener
does ioctl that he wants 32 kHz and another that he wants 22.05kHz then you
know which bitrate to use for each of them. Why do you think you cannot track
the state of each of them?

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> 
> > mplayer has to do this stuff all the time so it's full of this code.  It does it
> > not only to accomodate for various sample rates, but also when you slow down or
> > speed up your video.  Maybe the code could be taken from mplayer.
> 
> no, it couldn't.
> 
> from your other mail:
> > For example if I have music playing in the background, Audacity cannot open
> > the soundcard for recording. Can you imagine an operating system where if
> > Firefox was writing a webpage to the disk, your e-mail client couldn't read
> > a mail folder from the disk?
> 
> can you imagine an operating system where if Firefox was printing a
> web page, your e-mail client could print an email on the same printer
> at the same time?

Yes every Unix has it. The lpr and lpd - if Firefox and e-mail clients are
printing at the same time, they get assigned different print jobs and
everything prints all right.

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> 
> just because some software which can mix audio sucks, doesn't mean
> that all software which can mix audio has to suck.

What do you mean with the term "suck"?  No matter how good app you write it
always breaks the basic principle - that hw virtualization should be done by
the kernel and not some kind of userland app.

CL<