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Date:      Tue, 20 Jun 2000 08:46:24 +0100
From:      Roger Hardiman <roger@cs.strath.ac.uk>
To:        Martin Cracauer <cracauer@cons.org>
Cc:        Cameron Grant <cg@FreeBSD.org>, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject:   Re: cvs commit: src/sys/dev/sound/pcm mixer.c
Message-ID:  <394F2150.BFF37294@cs.strath.ac.uk>
References:  <200006192031.NAA41747@freefall.freebsd.org> <20000620090702.A52629@cons.org>

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Martin
> 
> >     sys/dev/sound/pcm    mixer.c
> >   Log:
> >   make mixer reads return the value written instead of the value set
> >
> >   people seem to want this even though it breaks oss spec compliance
> 
> I think that's not an acceptable attitude.  It breaks Linux binaries
> and binaries compiled on older FreeBSD's (commercial stuff).


Can you give an example of what it would break please.
I'm in favour of this commit, but I'd like to know what we are
breaking.

The problem as far as I understood it was this....
 Suppose your mixer has 8 volume levels and
 OSS gives us a scale of 0->100

1) set the volume to 80:80 in the mixer

The mixer can only store volumes in multples of 14.2,
eg 0   1     2     3     4     5     6     7
eg 0, 14.2, 24.8, 42.6, 56.8, 71.0, 85.2, 100.0

 2) read the volume level back in the mixer
 OSS says you read back 85:85 or maybe 71:71

 With Cameron's latest commit we read back 80:80
 which is what I would expect.


The problem was discussed on the multimedia mailing
recently.

Roger


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