[gstreamer-bugs] [Bug 571610] [pulsesink] Allow setting a log volume, instead of a linear one

[GStreamer (bugzilla.gnome.org)]

http://bugzilla.gnome.org/show_bug.cgi?id=571610


Lennart Poettering <lennart> changed:

           What    |Removed                     |Added
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                 CC|                            |lennart at poettering.net


--- Comment #10 from Lennart Poettering <lennart at poettering.net> 2009-09-04 02:33:14 UTC ---
PA actually uses "opaque" scales wherever possible, i.e. in an unspecified
unit. This is needed because some hardware does not provide any dB information,
so we really have no clue at all what the hardware volumes mean.

However, under some specially flagged conditions volumes are marked as
"software" volumes in which case (and only in this case) they can be converted
to dB or to linear via some utility functions that are part of the PA API.

The mapping between those "opaque" volumes and the linear factor has changed in
the past. The "opaque" volume used to be logarithmic (i.e. basically a linear
function of the dB scale), but nowadays is cubic in its mapping from the linear
factors.

Confusing? Yes, a bit I guess.

The volume property Gst uses, which unit does it actually have? Is it a linear
factor? If so, then it should be easy to fix the whole thing by simply
converting the opaque volume to linear volumes. This should be safe in this
since one of the conditions where this conversion is safe is if the volume is
of a stream and not a device. Which is the case here.

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