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Date:      Sat, 6 Sep 1997 05:51:43 +0200 (MET DST)
From:      Luigi Rizzo <luigi@labinfo.iet.unipi.it>
To:        jacob@jblhome.ping.dk (Jacob Bohn Lorensen)
Cc:        multimedia@FreeBSD.ORG
Subject:   Re: snd970904.tgz - can't hear anything while sampling from CD.
Message-ID:  <199709060351.FAA13137@labinfo.iet.unipi.it>
In-Reply-To: <87oh675q0n.fsf@pippin.jblhome.ping.dk> from "Jacob Bohn Lorensen" at Sep 6, 97 00:55:49 am

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> Luigi Rizzo <luigi@labinfo.iet.unipi.it> writes:
> 
> > I have fixed the mixer support for the SoundBlaster16 cards, and also
> 
> This works just fine!
> 
> Now, when I use xmix to set the recording source to "CD", I can hear
> no sound. When recording source is either microphone or line I can
> hear the CD playing just fine.

the problem is the following: in most sound cards, there is a
multiplexer driving the ADC input, and separate volume controls on the
path to the speaker. So if you want to speak and not listen to your
voice (or avoid Larsen, etc), you can set the mic volume to 0 and you
are done. On the SB16, the ADC has a real mixer, but the volume
controls are shared among the two mixers, so you cannot put the volume
to 0 or you wouldn't get anything. In order to remove the feedback, I
decided to disconnect from the output mixer the source(s) currently
being used for record. This explains the behaviour you see.

I could have let the user selectively disable sources to the output
mixer but there is no ioctl() to do that, so I would need a new one,
and applications would not work without recompiling.

> Now for some more serious work: does anybody know if there exists
> programs that can "slow down" a sample. I.e. play it at half it's

not sure on what you want, perhaps you want to keep the shape of
the envelope (e.g.  make it twice as long) but maintain the
istantaneous waveform ? Seems something non trivial. Anyways the
OSS page at www.4front-tech.com has a long listing on applications
working with OSS which should help.

> Oh, by the way, I just tried playing "xboing" with sound - it hangs
> after a while, syslog saying: 
> 
>    Sep  6 00:48:16 pippin /test: dsp sync
>    Sep  6 00:48:18 pippin /test: chan 3 not busy
>    Sep  6 00:48:49 pippin last message repeated 3032 times
>    Sep  6 00:50:42 pippin last message repeated 11221 times

I'll try xboing and see what it does.

	Thanks
	Luigi



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