[Bug 673970] New: rgvolume does'nt apply gain using fallback-gain (without Track and Album tags)

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=673970
  GStreamer | gst-plugins-good | git

           Summary: rgvolume does'nt apply gain using fallback-gain
                    (without Track and Album tags)
    Classification: Platform
           Product: GStreamer
           Version: git
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-good
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: anthony.violo at ubicast.eu
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


Created an attachment (id=211909)
 View: https://bugzilla.gnome.org/attachment.cgi?id=211909
 Review: https://bugzilla.gnome.org/review?bug=673970&attachment=211909

rgvolume does'nt apply gain using fallback-gain (without Track and Album tags)

When trying to apply the advised gain (that is the result of rganalysis) by
using the fallback-gain property (no ReplayGain tags), the result gain is
always near 0 and no normalization is being applied.

The reason is that in this case, the plugin assumes a peak value of 1.0, which
makes the clipping prevention mecanism prevent any normalization (because gain
+ linear_to_db(peak) is always > headroom, in fact in our case here,
linear_to_db(1.0) is 0 every time), so as long as the gain is positive, the
result gain will always be reduced.

To sum up, the anti-clipping mecanism is counter-productive when the media has
no ReplayGain tags: assuming a peak of 1.0 means that the track has full
volume, therefore normalization cannot be safely applied (according to the
anti-clipping feature).

I propose a patch to change peak value from 1.0 to 0.000001
(linear_to_db(0.000001) = -120, which equals to the maximum appliable gain,
i.e. pre-amp + fallback-gain), so that in the case of using fallback-gain, the
gain will always be applied.

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