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GStreamer Good Plugins 0.10 Plugins Reference Manual | |
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| Top | Description | Object Hierarchy | Properties | ||||
GObject
+----GstObject
+----GstElement
+----GstBaseTransform
+----GstAudioFilter
+----GstAudioFXBaseIIRFilter
+----GstAudioChebLimit
"cutoff" gfloat : Read / Write "mode" GstAudioChebLimitMode : Read / Write "poles" gint : Read / Write "ripple" gfloat : Read / Write "type" gint : Read / Write
Attenuates all frequencies above the cutoff frequency (low-pass) or all frequencies below the cutoff frequency (high-pass). The number of poles and the ripple parameter control the rolloff.
This element has the advantage over the windowed sinc lowpass and highpass filter that it is much faster and produces almost as good results. It's only disadvantages are the highly non-linear phase and the slower rolloff compared to a windowed sinc filter with a large kernel.
For type 1 the ripple parameter specifies how much ripple in dB is allowed in the passband, i.e. some frequencies in the passband will be amplified by that value. A higher ripple value will allow a faster rolloff.
For type 2 the ripple parameter specifies the stopband attenuation. In the stopband the gain will be at most this value. A lower ripple value will allow a faster rolloff.
As a special case, a Chebyshev type 1 filter with no ripple is a Butterworth filter.
Be warned that a too large number of poles can produce noise. The most poles are possible with a cutoff frequency at a quarter of the sampling rate.
gst-launch audiotestsrc freq=1500 ! audioconvert ! audiocheblimit mode=low-pass cutoff=1000 poles=4 ! audioconvert ! alsasink gst-launch filesrc location="melo1.ogg" ! oggdemux ! vorbisdec ! audioconvert ! audiocheblimit mode=high-pass cutoff=400 ripple=0.2 ! audioconvert ! alsasink gst-launch audiotestsrc wave=white-noise ! audioconvert ! audiocheblimit mode=low-pass cutoff=800 type=2 ! audioconvert ! alsasink
"cutoff" property "cutoff" gfloat : Read / Write
Cut off frequency (Hz).
Allowed values: [0,100000]
Default value: 0
"mode" property "mode" GstAudioChebLimitMode : Read / Write
Low pass or high pass mode.
Default value: Low pass (default)
"poles" property "poles" gint : Read / Write
Number of poles to use, will be rounded up to the next even number.
Allowed values: [2,32]
Default value: 4
"ripple" property "ripple" gfloat : Read / Write
Amount of ripple (dB).
Allowed values: [0,200]
Default value: 0.25