# audiochebband

Attenuates all frequencies outside (bandpass) or inside (bandreject) of a frequency band. The number of poles and the ripple parameter control the rolloff.

This element has the advantage over the windowed sinc bandpass and bandreject 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.

## Example launch line

     gst-launch-1.0 audiotestsrc freq=1500 ! audioconvert ! audiochebband mode=band-pass lower-frequency=1000 upper-frequency=6000 poles=4 ! audioconvert ! alsasink
     gst-launch-1.0 filesrc location="melo1.ogg" ! oggdemux ! vorbisdec ! audioconvert ! audiochebband mode=band-reject lower-frequency=1000 upper-frequency=4000 ripple=0.2 ! audioconvert ! alsasink
     gst-launch-1.0 audiotestsrc wave=white-noise ! audioconvert ! audiochebband mode=band-pass lower-frequency=1000 upper-frequency=4000 type=2 ! audioconvert ! alsasink

## Hierarchy

    GObject
        ╰──GInitiallyUnowned
            ╰──GstObject
                ╰──GstElement
                    ╰──GstBaseTransform
                        ╰──GstAudioFilter
                            ╰──GstAudioFXBaseIIRFilter
                                ╰──audiochebband

## Factory details

Authors: – Sebastian Dröge

Classification: – `Filter/Effect/Audio`

Rank – none

Plugin – audiofx

Package – GStreamer Good Plug-ins

## Pad Templates

### `sink`

    audio/x-raw:
             format: { F32LE, F64LE }
               rate: [ 1, 2147483647 ]
           channels: [ 1, 2147483647 ]
             layout: interleaved

Presence – always

Direction – sink

Object type – GstPad

### `src`

    audio/x-raw:
             format: { F32LE, F64LE }
               rate: [ 1, 2147483647 ]
           channels: [ 1, 2147483647 ]
             layout: interleaved

Presence – always

Direction – src

Object type – GstPad

## Properties

### lower-frequency

    “lower-frequency” gfloat

Start frequency of the band (Hz)

Flags : Read / Write

Default value : 0

### mode

    “mode” Audio-cheb-band-mode *

Low pass or high pass mode

Flags : Read / Write

Default value : band-pass (0)

### poles

    “poles” gint

Number of poles to use, will be rounded up to the next multiply of four

Flags : Read / Write

Default value : 4

### ripple

    “ripple” gfloat

Amount of ripple (dB)

Flags : Read / Write

Default value : 0.25

### type

    “type” gint

Type of the chebychev filter

Flags : Read / Write

Default value : 1

### upper-frequency

    “upper-frequency” gfloat

Stop frequency of the band (Hz)

Flags : Read / Write

Default value : 0

## Named constants

### Audio-cheb-band-mode

#### Members

`band-pass` (0) – Band pass (default)
`band-reject` (1) – Band reject

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