[gstreamer-bugs] [Bug 494499] New: replaygain analysis slowdown on low volume (denormals)

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gst-plugins-bad | Ver: HEAD CVS
           Summary: replaygain analysis slowdown on low volume (denormals)
           Product: GStreamer
           Version: HEAD CVS
          Platform: Other
        OS/Version: Windows
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-bad
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: bouvigne at mp3-tech.org
         QAContact: gstreamer-bugs at lists.sourceforge.net
     GNOME version: Unspecified
   GNOME milestone: Unspecified


The RG analysis is awfully slowing down on low volume content.
Usual case: "hidden" tracks on CDs with content after a few minutes of
near-silent.

This is caused by denormal handling on x86 cpu.

Different easy fixes are possible:

#1: always add a small value to the computation, small enough to not
significantly change the overall result.

This is, as an example, done in MPC and LAME:
http://svn.musepack.net/libreplaygain/src/gain_analysis.c
http://lame.cvs.sourceforge.net/lame/lame/libmp3lame/gain_analysis.c?view=markup

#2: if values are small, clear result to 0.

This is done in WavPack:
http://svn.slomosnail.de/wavpack/trunk/cli/wvgain.c

(in every source code linked, search for "denormals")


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