From alsa-devel-owner@alsa.jcu.cz  Mon Nov 30 17:41:36 1998
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	Mon, 30 Nov 1998 17:39:44 +0100
Date: Mon, 30 Nov 1998 17:39:44 +0100 (CET)
From: Jaroslav Kysela <perex@jcu.cz>
To: meme <meme@interzone.org>
cc: alsa-devel@jcu.cz
Subject: Re: Virtual array of audio devices. Filters etc. ?
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On Fri, 27 Nov 1998, meme wrote:

> First off, thanks for the response.  Don't spend too much time thinking
> about this since I believe I'm still some way off from figuring out the
> details.  All I'm trying to do is show the possibilities...  So no worries
> or hurries, please.

OK.

> On Fri, 27 Nov 1998, Jaroslav Kysela wrote:
> > ABU interface (digital professional audio connection between components):

Here is typo from me. I mean AES/EBU interface, of course.

> > 
> >   ALSA already supports:
> > 	- rate up to 96kHz
> > 	- 16-bit samples
> >   ALSA doesn't support at this time (but interface should be easy extend):
> > 	- above 16-bit wide samples (up to 24-bit)
> 
> Ok, that's good.  From what I know of  digital professional recording, the
> current high end is 24bit/96 Khz, but that is technically still lacking.
> (This all depends on hardware which supports this, of course).  Recording
> at 24bit/96Khz and playing it back is good enough to fool the human ear
> into thinking that it is listening to analog.
> 
> In the professional recording world, there are effects and filters which
> need to be applied of course.  Theoretically, applying these causes some
> degredation of quality, which in turn yields less than analog fooling
> abilities of 24/96.  The ideas being discussed are 32/96 recording.  It is
> redundant for just recording, but it allows the application of 24-32 bit
> effects to a sample, and once it has been processed, it will still be good
> enough to go to 24/96 undamaged.  I'm not sure I'm making myself clear.
> The extra bits are there only to be skewed by the effects, thus leaving a
> more than clean 24 bit sample to come out the other end.

I need only info about sample wide which is greater that 16.. I need know
complete list for currently used values, I know about:

	18-bit
	20-bit
	24-bit
	32-bit (optional, but we can be ready for future)

Is something between? Is used another format than Signed Little Endian?
I want extend PCM interface in ALSA driver 0.3.0.

> >   I don't know:
> > 	- maximum channels which should be over this interface transferred?
> > 	- maybe this isn't very important - ALSA have 32-bit variable for
> >           channel count
> 
> Again, this limitation will start with the hardware.  Ensoniq PARIS (6
> ESP-2 DSP's per PCI card) allows for 16 24/48 channels (in or out) per PCI
> card.

OK. ALSA is ready for this. Do you know limit of AES/ABU interface? I mean
maximum number of PCM channels which should be transferred together over
this digital interface.

> I hope I make at least a little bit of sense.  And again, this isn't high
> priority by any means, but perhaps a few of our heads can work out a
> brilliant architecture.

If you will need any info from me - I'm open..

							Jaroslav

-----
Jaroslav Kysela <perex@jcu.cz>
Academic Computer Centre, University of South Bohemia
Branisovska 31, C. Budejovice, CZ-370 05 Czech Republic



