[gstreamer-bugs] [Bug 556756] New: audioresample does not low-pass filter ("antialias") when down-sampling

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gst-plugins-base | Ver: HEAD CVS
           Summary: audioresample does not low-pass filter ("antialias")
                    when down-sampling
           Product: GStreamer
           Version: HEAD CVS
          Platform: Other
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-base
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: kcannon at ligo.caltech.edu
         QAContact: gstreamer-bugs at lists.sourceforge.net
     GNOME version: Unspecified
   GNOME milestone: Unspecified


When down-sampling an audio time series to a lower sample rate, one must first
remove frequency components above the Nyquist frequency of the new time series.
 This is accomplished by low-pass filtering the data before resampling, a
process sometimes referred to as "anti-aliasing".  Failure to anti-alias the
time series results in high-frequency components being "aliased" down to lower
frequencies, corrupting the audio.

The audioresample element does not anti-alias the time series when
down-sampling.  In a pipeline, one can work-around this bug by preceding the
audioresample element with a low-pass filter element like audiowsinclimit, but
audioresample, like any element, should Just Work (tm).


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