From justin.fletcher@ntlworld.com Fri Jul 13 10:34:07 2001
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From: Justin Fletcher <justin.fletcher@ntlworld.com>
Newsgroups: comp.sys.acorn.programmer
Subject: Re: CD_
Message-ID: <f9ea26994a.Justin@gerph.movspclr.co.uk>
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 <8820df984a.Geoff@solutionsweb.co.uk>
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In message <8820df984a.Geoff@solutionsweb.co.uk>
          Geoff Youngs <geoff@solutionsweb.co.uk> wrote:

> In message <3b4d5ae1.259491509@news.salford.ac.uk>
>           paulf.johnson@ukonline.co.uk (Paul Johnson) wrote:
>
> > On Thu, 12 Jul 2001 02:56:19 +0200, John Tytgat <John.Tytgat@aaug.net>
> > wrote:
>
> > > > Any ideas what I am doing wrong and if CD_PlayTrack and CD_StopDisc are
> > > > available on all the versions of the CD drivers?
>
> > > What's wrong with OSCLI("Play <track> <driver>") ?
>
> > Nothing, except that if I do something like
>
> > Sys "CD_PlayTrack",1,255,,,,,,cd_block%
>
> > I can play from the very start of the CD with the likes of
>
> > Sys "CD_StopDisc" and Sys "CD_AudioPause" should do what they say on
> > the box.
>
>  <blatant-plug>
>    Try the code in http://www.iconbar.com/comms/intro/cgicdusrc.txt (or
>    http://www.iconbar.com/comms/intro/cgicd.bas for a compressed tokenised
>    version).
>  </blatant-plug>
>
> Which works here (obviously :)
>
> It's probably worth checking that you're doing obvious things, like setting
> up the control block correctly, etc.
>
> Does anyone have any documentation on controlling the CD volume? I know
> applications like Leo White's CDPlay do it (without altering the volume of
> the entire computer), but I can't find any documentation on it either in
> Acorn's old AppNotes or in any of the SH manuals.

This always amuses me.

CD_AudioLevel *isn't* what you want. Well, it might be, and CD_Supported
will return bit 5 set if it is, but I've yet to find a single CD driver that
actually /does/ support this. Or the register set they use.

Amusing, huh ?

CD_SetAudioParms /is/ what you want.

=> R0 = 0 (volume)
   R1 = pointer to block :
         +0 left volume, 0-&FFFF
         +4 right volume, 0-&FFFF

CD_GetAudioParms is similar.

=> R0 = 0 (volume)
   R1 = pointer to block
<= block at R1 updated

Note also (oh, yes, it gets better) that some drivers don't have this call
implemented. With such drivers you should be able to call CD_Supported
and check that bit 15 is set, and if not they don't support those calls.

Fun, huh ?

-- 
Gerph {djf0-.3w6e2w2.226,6q6w2q2,2.3,2m4}
URL: http://www.movspclr.co.uk/
... Eyes to the heavens, screaming at the sky;
    Trying to send you messages, but choking on goodbye.