Pitch shift in multi channel mode using soundtouch-js

Question

I am using https://github.com/jakubfiala/soundtouch-js soundtouch library to do some pitch shifting on audio files. the lib works fine with pitch shifting but I don't know how to control the audio file's channels to switch them on/off.

I am following this pen https://codepen.io/ezzatly/pen/LLqOgJ?editors=1010

var source = {
        extract: function (target, numFrames, position) {
            $("#current-time").html(minsSecs(position / (context.sampleRate)));
            console.log('width: ', 100 * position / (bufferDuration * context.sampleRate));
            $("#progress").width(100 * position / (bufferDuration * context.sampleRate) + "%");
            if (Math.round(100 * position / (bufferDuration * context.sampleRate)) == 100 && is_playing) {
                //stop recorder
                recorder && recorder.stop();
                __log('Recording complete.');

                // create WAV download link using audio data blob
                createDownloadLink();

                if (typeof recorder != "undefined") {
                    recorder.clear();
                }
                is_playing = false;
            }
            var l = buffer.getChannelData(0);
            if (buffer.numberofChannels > 1) {
                var r = buffer.getChannelData(1);
            } else {
                var r = buffer.getChannelData(0);
            }
            for (var i = 0; i < numFrames; i++) {
                target[i * 2] = l[i + position];
                target[i * 2 + 1] = r[i + position];
            }
            return Math.min(numFrames, l.length - position);
        }
    };






node.onaudioprocess = function (e) {
        if (buffer.getChannelData) {
            pos += BUFFER_SIZE / context.sampleRate;
            console.log('position: ', pos);
            var l = e.outputBuffer.getChannelData(0);
            var r = e.outputBuffer.getChannelData(1);
            var framesExtracted = f.extract(samples, BUFFER_SIZE);
            if (framesExtracted == 0) {
                node.disconnect();
            }
            for (var i = 0; i < framesExtracted; i++) {
                l[i] = samples[i * 2];
                r[i] = samples[i * 2 + 1];
            }

            leftchannel.push(new Float32Array(l));
            rightchannel.push(new Float32Array(r));
            recordingLength += BUFFER_SIZE;
        }
    };

any help?

score 3 · Answer 1 · answered Aug 16 '19 at 12:26

3

First, I have a slightly more modernized version of SoundTouchJs in my GitHub. Might make it slightly easier to hack around.

Second, you probably want to attach a ChannelSplitterNode to your connected audio context. I haven't played with this, but I would think that's what you would need to independently control the gain on each channel. Again, I'm guessing, but hopefully that'll push you in the right direction.

answered Aug 16 '19 at 12:26

Steve -Cutter- Blades

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thank you for your reply, I changed the lib a little bit to support multi channel instead of dual channel – Ahmed ezzat Jun 03 '20 at 12:39
@Ahmedezzat that is great. You should submit a PR. – Steve -Cutter- Blades Jun 03 '20 at 18:32
It there any way to get the stretched audioBuffer from the shifter? – arpo Oct 12 '21 at 09:01

Pitch shift in multi channel mode using soundtouch-js

1 Answers1