org.openimaj.audio.filters

Class FFTBandPassFilter

java.lang.Object

org.openimaj.audio.Audio

org.openimaj.audio.AudioStream

org.openimaj.audio.processor.AudioProcessor

org.openimaj.audio.filters.FFTBandPassFilter

All Implemented Interfaces:

Iterable<SampleChunk>

public class FFTBandPassFilter
extends AudioProcessor

Naive band pass filter that uses the Fourier transform to filter unwanted frequencies. The high and low pass filter values will be rounded to the nearest bin in the frequency domain, so may not exactly match the specified output. If the high pass filter frequency is greater than the low pass filter frequency, then the class will output empty audio.

If you want to process the samples in the chain, override the processSamples(SampleChunk) method. This method will be called even if the FFT fails and it will be called with the input samples.

The class makes the assumption that all channels have the same length of data.

Note that this class will produce inconsistencies at the frame boundaries, so cannot sensibly be used for filtering audio that is to be replayed.

Also check out the EQFilter which contains high and low pass filter implementations which can also provide band-pass filter functionality.

Version:

$Author$, $Revision$, $Date$

Author:

David Dupplaw (dpd@ecs.soton.ac.uk)

See Also:

EQFilter

Created:

11 Jul 2012

Field Summary

Fields inherited from class org.openimaj.audio.Audio

format

Constructor Summary

Constructors

Constructor and Description
FFTBandPassFilter(AudioStream as, int highPassHz, int lowPassHz) Chainable constructor
FFTBandPassFilter(int highPassHz, int lowPassHz) Default constructor

Method Summary

Modifier and Type	Method and Description
SampleChunk	process(SampleChunk sample) Function that takes a sample chunk and processes the chunk.
SampleChunk	processSamples(SampleChunk sc) Process the band-filtered samples.

Methods inherited from class org.openimaj.audio.processor.AudioProcessor

getLength, getUnderlyingStream, nextSampleChunk, process, processingComplete, reset, setUnderlyingStream

Methods inherited from class org.openimaj.audio.AudioStream

iterator, seek

Methods inherited from class org.openimaj.audio.Audio

getFormat, setFormat

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Constructor Detail

FFTBandPassFilter

public FFTBandPassFilter(AudioStream as,
                         int highPassHz,
                         int lowPassHz)

Chainable constructor

Parameters:

as - The audio stream to process

highPassHz - The frequency of the high pass filter.

lowPassHz - The frequency of the low pass filter.

FFTBandPassFilter

public FFTBandPassFilter(int highPassHz,
                         int lowPassHz)

Default constructor

Parameters:

highPassHz - The frequency of the high pass filter

lowPassHz - The frequency of the low pass filter.

Method Detail

process

public final SampleChunk process(SampleChunk sample)
                          throws Exception

Function that takes a sample chunk and processes the chunk. It should also return a sample chunk containing the processed data. If wished, the chunk may be side-affected and the input chunk returned. It should not be assumed that the input chunk will be side-affected, but it must be noted that it is possible that it could be. This process function may also return null. If null is returned it means that the rest of the audio stream is not required to be processed by this processing function. Whether the rest of the sample chunks are copied or ignored is up to the caller.

Specified by:

process in class AudioProcessor

Parameters:

sample - The sample chunk to process.

Returns:

A sample chunk containing processed data.

Throws:

Exception - If the processing could not take place

See Also:

AudioProcessor.process(org.openimaj.audio.SampleChunk)

processSamples

public SampleChunk processSamples(SampleChunk sc)

Process the band-filtered samples.

Parameters:

sc - The band-filtered samples

Returns:

Processed samples