kern/140453: [sound] No sound inside Virtualbox on 50% volume
Marcin Wisnicki
mwisnicki+freebsd at gmail.com
Wed Dec 16 16:10:02 UTC 2009
The following reply was made to PR kern/140453; it has been noted by GNATS.
From: Marcin Wisnicki <mwisnicki+freebsd at gmail.com>
To: Ariff Abdullah <ariff at freebsd.org>
Cc: bug-followup at freebsd.org
Subject: Re: kern/140453: [sound] No sound inside Virtualbox on 50% volume
Date: Wed, 16 Dec 2009 17:03:12 +0100
On Wed, Dec 16, 2009 at 02:57, Ariff Abdullah <ariff at freebsd.org> wrote:
> Virtualbox (QEMU too) default to 5bit volume resolution, but it
> appears through the volume resolution calibration process as
> 6bit. Clearly, it is a "hardware" bug. Virtualbox doing
> slightly a better job by "clamping" the results (the lower bits
> written as '1') whenever there is a write attempt on 5th (or
> 13th) bit, but _without_ resetting those high bit. As such, it
> appears as a full 6-bit resolution result on the next codec
> read. FreeBSD try to be honest here by doing supposed to be
> correct calibration process and see/measure the result as is.
> Others <insert whatever..> probably have their own static
> mapping (think about vendor specific driver) or depends on
> whatever magic marker, etc.
>
> You have two choices:
>
> 1) Fix virtualbox ac97 codec emulation (probably not for you
> given the fact that your vbox runs on Windows).
>
Good to hear it's a known problem. Is there any reason why this patch
was not submitted to virtualbox (at least I couldn't find a ticket
there) ?
I don't really care about it since workaround is so simple, but it
would be nice to have it working correctly out of the box.
> or
>
> 2) "Fix" FreeBSD ac97 volume resolution calibration by
> accepting certain lower bits magic marker, ignoring the high bit.
>
>
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