http://www.perlmonks.org?node_id=52132

PipTigger has asked for the wisdom of the Perl Monks concerning the following question:

Hello, oh ye who possess magical wisdom,
I'm trying to manipulate sound volume (both main && pcm) from a script. Right now I've got aumix installed so just doing system("aumix -v$NewVolum") werks for me but is not a good solution. I've STFC (Serched The Fscking CPAN) && only found a wrapper for mixing .wav files together. How can I cleanly manipulate /dev/mixer in order to change volumes && stuff? The source to aumix doesn't give me a good clue of how I might mimic in Perl. Thanks muchly for any assistance you might be able to provide. TTFN.

-PipTigger
p.s. Initiate Nail Removal Immediately!

Replies are listed 'Best First'.
Re: Changing volume in Linux with Perl?
by eg (Friar) on Jan 16, 2001 at 06:47 UTC
[reply]
      Actually I have in fact read almost everything at that linq before too... the problem is that the method described there is basically what the aumix C-code I already have does. Is there an equivalent to 'sys/ioctl.h' in Perl? Is there a way to manipulate /dev/mixer properly without compiling C? If not, aumix will suffice but it'd be nice to do it right in Perl if possible. Maybe it'd make a great CPAN module too. We'll see. Thanks. TTFN.

      -PipTigger
      p.s. I don't need your authority!
[reply]
        Have a look at ioctl for a way to roll your own in perl. I agree that this would make a handy CPAN module when you get it working. Good luck!

[reply]
Re: Changing volume in Linux with Perl?
by PipTigger (Hermit) on Jan 16, 2001 at 16:15 UTC
    I've tried hard to get ioctl && all the other .ph files to werk. I had to run h2ph on like 7 different .h files to fulfill all the embedded require's but I've tried tons of stuff for the past hour to tweak my new /usr/local/lib/site_perl/i386-linux/linux/soundcard.ph file so that it'd let my little script run to no avail. My little test is: 
    #!/usr/bin/perl -w

require 'ioctl.ph';
require 'linux/soundcard.ph';

my $data = 0;

open MIXR, "</dev/mixer" || die "Can't open mixer!\n";
ioctl(MIXR, &MIXER_READ(0), $data) || die "Can't ioctl!\n";
close MIXR;
print "data: $data\n";

    [download]
    This results in:

    Use of uninitialized value at (eval 621) line 1.
    Can't ioctl!

    && the eval ending on that line looks like another normal one: 
    eval 'sub SEQ_PITCHBEND {
    local($dev, $voice, $value) = @_;
        eval q( &SEQ_V2_X_CONTROL($dev, $voice,  &CTRL_PITCH_BENDER, $
+value) );
}' unless defined(&SEQ_PITCHBEND);

    [download]
    If you can possibly point me in a better direction, I'd really appreciate it. I've been pounding my head against this for a long time && can't seem to go anywhere with this. I'm feeling really surprised at how difficult this seems to be in Perl! Maybe it's appropriate since it's one of the "hard/possible" things but it seemed like it should be "easy/easy". Anyways, I'm probably just gonna cave in && use C if I can't get Perl to do it within the next day or so. I really wanted to be competent enough to get this to werk on my own but I'm left to conclude that I'm really not experienced enough with Perl || Linux to do this alone yet. Thanks for any help or encouragement you can offer. I'm feeling kinda down (I thinq the caffeine is wearing off). TTFN.

    -PipTigger
    p.s. Mr., would you please help my pony?
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