Acoustic echo cancellation disable how to#
By seeing how their filters work and reading up a great deal on filters on DSP Tutor, I managed to gain some control over how much noise gets removed and how to remove high frequencies, etc. The JNI route is probably still a better way to go, but I like sticking to pure Java if at all possible. In case anyone is interested, I managed to build a fair, working echo canceller by basically converting the Acoustic Echo Cancellation method mentioned by Paul R that uses a Normalised Least Means Square algorithm and a few filters from C into Java. M_ayEchoFreeSignal = (byte) (m_ayEchoSignal - m_ayTransposeOfSpeakerSignal * m_adWeights) M_ayEchoFreeSignal = new byte įor (int i = 0 i < m_ayEchoFreeSignal.length ++i) M_adWeights = byte applyFilter(byte ayAudioBytes) M_ayTransposeOfSpeakerSignal = ayTransposeOfSpeakerSignal Public cNormalisedLeastMeansSquareFilter(byte ayEchoSignal, byte ayTransposeOfSpeakerSignal, double adWeights) * The transpose and the weights need to be updated before applying the filter Private byte m_ayTransposeOfSpeakerSignal // X' Public class cNormalisedLeastMeansSquareFilter X' is the transpose of the loudspeaker signal. d represents the actual microphone signal * Echo cancellation occurs with the following formula: * This filter performs a pre-whitening Normalised Least Means Square on an It's been ages! Hope this is even the right class, but there you go: /**
Acoustic echo cancellation disable code#
Most sample code for the above are in C and C++ and they don't translate well into Java.ĭoes anyone have advice on how to implement them in Java? Any other ideas would also be greatly appreciated. Specifically, a Least Mean Squares filter. I've read that adaptive filters are the way to go. If (m_iDelayIndex = m_awDelayBuffer.length) Short wNewSample = (short) (wOldSample - fDecay * m_awDelayBuffer) Short wOldSample = getSample(aySamples, i) ("Sample length:\t" + aySamples.length) įor (int i = 0 i < aySamples.length i += 2) Manual echo canceller public static byte removeEcho(int iDelaySamples, float fDecay, byte aySamples) I've managed one echo canceller that does work, however it requires a lot of interactive user input and I'd like to have an automatic echo canceller. It also means I have access to as much audio data as I need for any fancy DSP operations before I play the audio data to the speaker line. This is to cater for dodgy connections and to allow for different packet sizes. public synchronized void addAudioData(byte ayAudioData)Īs you can see the audio data arrives and is enqueued in a buffer. Essentially, I'd like to perform some digital signal processing on audio data before I write it to the speaker for output. The nuts and bolts of the VOIP application is just the plain datalines of Java's media framework. There is an echo problem that occurs when users do not use headsets (mostly on laptops with built-in microphones). I'm implementing a VOIP application that uses pure Java.