[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



--- Comment #11 from Sebastian Dröge <slomo at circular-chaos.org> 2009-09-04 05:02:14 UTC ---
(In reply to comment #10)
> 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.

Thanks for the explanations :)

> 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.

Yes, the GStreamer volumes are a simple linear factor.

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