Groups > comp.sys.acorn.programmer > #1320

Re: Sound hardware access for RO

From	Jim Lesurf <jcgl@audiomisc.co.uk>
Subject	Re: Sound hardware access for RO
Newsgroups	comp.sys.acorn.programmer
Date	2012-01-15 17:30 +0000
Message-ID	<52520a9bf5jcgl@audiomisc.co.uk> (permalink)
References	(2 earlier) <5250524405jcgl@audiomisc.co.uk> <jesosq$m25$1@dont-email.me> <4f1253d9$0$5678$ba4acef3@reader.news.orange.fr> <jeugt8$gh9$1@dont-email.me> <almarsoft.7324079975835647142@news.orange.fr>
Organization	None

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In article <almarsoft.7324079975835647142@news.orange.fr>, Rick Murray
<heyrickmail-usenet@yahoo.co.uk> wrote:
> On Sun, 15 Jan 2012 12:30:31 +0000, druck <news@druck.org.uk> wrote:

> > Note the use of the DSP chip.

> Indeed, but what do you think pulls the data from SD/USB, part decodes,
> and pushes into place ready for the DSP to do its magic? If the ARM can
> keep up with 128k + 2500k + file overheads, I maintain that 96k/24
> shouldn't kill it. 

> If, and maybe I'm wrong here, we assume the data rate is 8 bit samples,
> then 24 is three 8s, so 96x3 gives us a data rate of 288kbit which
> ought to be uncompressed so require little further processing (hence no
> DSP requirement).

FWIW The asynch/iso USB systems I've checked (e.g. Halide Bridge and Arcam
r-DAC) expect S24_3LE format. i.e. each 24 bit sample value sent as a 24
bit signed integer. (So packed with a byte of zeros.)

That comes out as a raw data rate of

96000 x 8 bytes per sec = 768,000 bytes/sec

if I've pushed the right buttons on my calculator.

(The '8' is for stereo of course.)

Now that is a lot of data, but I'm surprised if the USB wasn't able to cope
in *any* RO hardware.

Also, the iso/async DACs do the control. They ask the host machine to send
another batch of data as their buffer become empty enough to get another
batch, and so the transfer itself can be in moderately irregular bursts
with no effect on the actual output. The computer doesn't have to worry
about precise timing. And the USB is isolated in many DACs to break any
ground loops or rf crap.

So far as I know, no 'DSP' is needed - unless what was meant was some byte
shuffling from the file format into S24_3LE and then running out via the
USB buffering, etc.

Slainte,

Jim

-- 
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html

Thread

Sound hardware access for RO Jim Lesurf <jcgl@audiomisc.co.uk> - 2012-01-11 12:18 +0000
  Re: Sound hardware access for RO Alan Wrigley <spamhater@keepyourfilthyspamtoyourself.co.uk> - 2012-01-11 12:30 +0000
    Re: Sound hardware access for RO Jim Lesurf <jcgl@audiomisc.co.uk> - 2012-01-11 13:43 +0000
      Re: Sound hardware access for RO Jeremy Nicoll - news posts <jn.nntp.scrap007@wingsandbeaks.org.uk> - 2012-01-11 22:35 +0000
        Re: Sound hardware access for RO Jim Lesurf <jcgl@audiomisc.co.uk> - 2012-01-12 10:08 +0000
          Re: Sound hardware access for RO Alan Wrigley <spamhater@keepyourfilthyspamtoyourself.co.uk> - 2012-01-12 17:57 +0000
            Re: Sound hardware access for RO Jim Lesurf <jcgl@audiomisc.co.uk> - 2012-01-13 12:05 +0000
      Re: Sound hardware access for RO Roger Darlington <rogerarm@freeuk.com> - 2012-04-03 09:03 +0100
        Re: Sound hardware access for RO Jim Lesurf <jcgl@audiomisc.co.uk> - 2012-04-03 09:53 +0100
  Re: Sound hardware access for RO John Kortink <kortink@inter.nl.net> - 2012-01-11 14:10 +0100
    Re: Sound hardware access for RO Jim Lesurf <jcgl@audiomisc.co.uk> - 2012-01-11 15:13 +0000
      Re: Sound hardware access for RO Theo Markettos <theom+news@chiark.greenend.org.uk> - 2012-01-11 17:04 +0000
      Re: Sound hardware access for RO John Kortink <kortink@inter.nl.net> - 2012-01-11 19:58 +0100
    Re: Sound hardware access for RO "Ste (news)" <steve@revi11.plus.com> - 2012-01-15 17:14 +0000
      Re: Sound hardware access for RO Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-01-17 07:11 +0100
  Re: Sound hardware access for RO druck <news@druck.org.uk> - 2012-01-11 20:52 +0000
    Re: Sound hardware access for RO Jim Lesurf <jcgl@audiomisc.co.uk> - 2012-01-12 09:21 +0000
      Re: Sound hardware access for RO druck <news@druck.org.uk> - 2012-01-14 20:34 +0000
        Re: Sound hardware access for RO Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-01-15 05:19 +0100
          Re: Sound hardware access for RO druck <news@druck.org.uk> - 2012-01-15 12:30 +0000
            Re: Sound hardware access for RO Jim Lesurf <jcgl@audiomisc.co.uk> - 2012-01-15 13:38 +0000
              Re: Sound hardware access for RO druck <news@druck.org.uk> - 2012-01-17 23:38 +0000
                Re: Sound hardware access for RO Jim Lesurf <jcgl@audiomisc.co.uk> - 2012-01-18 09:37 +0000
                Re: Sound hardware access for RO Jeremy Nicoll - news posts <jn.nntp.scrap007@wingsandbeaks.org.uk> - 2012-01-27 02:05 +0000
                Re: Sound hardware access for RO Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-01-27 05:19 +0100
            Re: Sound hardware access for RO Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-01-15 15:57 +0100
              Re: Sound hardware access for RO Jim Lesurf <jcgl@audiomisc.co.uk> - 2012-01-15 17:30 +0000
                Re: Sound hardware access for RO Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-01-17 07:22 +0100
                Re: Sound hardware access for RO Jim Lesurf <jcgl@audiomisc.co.uk> - 2012-01-17 09:28 +0000
                Re: Sound hardware access for RO Theo Markettos <theom+news@chiark.greenend.org.uk> - 2012-01-17 11:31 +0000
                Re: Sound hardware access for RO Jim Lesurf <jcgl@audiomisc.co.uk> - 2012-01-17 12:34 +0000
            Re: Sound hardware access for RO Dave Higton <davehigton@dsl.pipex.com> - 2012-01-16 21:19 +0000
          Re: Sound hardware access for RO Jim Lesurf <jcgl@audiomisc.co.uk> - 2012-01-15 10:18 +0000
            Re: Sound hardware access for RO Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-01-15 16:18 +0100
              Re: Sound hardware access for RO Jim Lesurf <jcgl@audiomisc.co.uk> - 2012-01-15 17:39 +0000
        Re: Sound hardware access for RO Jim Lesurf <jcgl@audiomisc.co.uk> - 2012-01-15 10:01 +0000
  Re: Sound hardware access for RO Dave Higton <davehigton@dsl.pipex.com> - 2012-01-16 21:28 +0000
    Re: Sound hardware access for RO Jim Lesurf <jcgl@audiomisc.co.uk> - 2012-01-17 09:35 +0000
    Re: Sound hardware access for RO Theo Markettos <theom+news@chiark.greenend.org.uk> - 2012-01-17 11:37 +0000
      Re: Sound hardware access for RO davehigton <davehigton14@googlemail.com> - 2012-01-17 05:07 -0800
        Re: Sound hardware access for RO Theo Markettos <theom+news@chiark.greenend.org.uk> - 2012-01-17 16:46 +0000
          Re: Sound hardware access for RO Ron <beeb@woosh.co.nz> - 2012-01-18 11:22 +1300
            Re: Sound hardware access for RO Theo Markettos <theom+news@chiark.greenend.org.uk> - 2012-01-17 23:42 +0000
              Re: Sound hardware access for RO Ron <beeb@woosh.co.nz> - 2012-01-18 13:47 +1300
      Re: Sound hardware access for RO Jim Lesurf <jcgl@audiomisc.co.uk> - 2012-01-17 12:36 +0000

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