Example for using Kali in real time that produce reasonably good audio

[Willena]

Hi !
I am currently trying to use your project in a realtime project. Audio should be processed and pushed to speakers without the latency of processing the whole track.

I am using the scriptPrecessorNode witch is feeding the Kali instance with the buffer given by the scriptProcessor.
Actualy it is working but the sound is very bad. You can listen the audio sample to understand a bit more what it sound like.

Here the code I use :

this.kali = new Kali(2);
this.setup(audioContext.sampleRate, 0.5);
input = audioContext.createScriptProcessor(4096, 1, 1);
that = this;
input.onaudioprocess = function (audioProcessingEvent) {
      var inputBuffer = audioProcessingEvent.inputBuffer;
      var outputBuffer = audioProcessingEvent.outputBuffer;

      var inputData = inputBuffer.getChannelData(0);

      var numInputFrames = inputData.length;
      var numChannels = 1;
      var stretchFactor = 1;

      var completed = new Float32Array(numInputFrames * numChannels + 1);

      that.kali.input(dataToInput);
      that.kali.process();
      that.kali.output(complete)
      that.kali.flush();

    outputBuffer.copyToChannel(completed, 0, 0);

  };

Any ideas of what I am doing wrong ?

[saste]

You should not flush data if not after you finish to consume the input data, otherwise you will drop audio data and produce signal discontinuities.

[Willena]

Thanks, I removed the kali.flush(), but still the same problem. the only thing I think is that I drop some part of the audio between two AudioBuffers.

Edit : It seems to be good with only one channel

[saste]

@Willena: from my experiments kali+real time streaming is fine, at least if you correctly manage the AudioBuffer. For example in my case I have something like this for each processed chunk of input data:

        var kaliOutputData = new Float32Array(Math.round(chunkSize / TEMPO_RATIO));
        kali.input(chunk);
        kali.process();
        
        var kaliOutputSize = kali.output(kaliOutputData);
        console.log("kali in:" + chunk.length + " out:" + kaliOutputSize + " time:" + timeOff);

        if (kaliOutputSize === 0) {
            continue;
        }

        // fill channel with interleaved data
        source = audioCtx.createBufferSource(channels);
        outputBuffer = audioCtx.createBuffer(channels, kaliOutputSize / channels, audioCtx.sampleRate);
        for (var i = 0; i < kaliOutputSize / channels; i++) {
            for (var j = 0; j < channels; j++) {
                outputBuffer.getChannelData(j)[i] = kaliOutputData[i * channels + j];
            }
        }
        
        source.buffer = outputBuffer;
        source.connect(audioCtx.destination);
        source.start(timeOff, 0, outputBuffer.duration);

The issue you noticed might be due to #6 in case it depends on the number of channels.
HTH

[Willena]

Yes I've seen #6 and I will have a look at your code.
Thank for the help !