Mixing Two Audio Buffers, Put One On Background Of Another By Using Web Audio Api
I want to mix two audio sources by put one song as background of another into single source. for example, i have input :
Solution 1:
Two approach originally posted at Is it possible to mix multiple audio files on top of each other preferably with javascript, adjusted to process File objects at change event of <input type="file"> element.
The first approach utilizes OfflineAudioContext(), AudioContext.createBufferSource(), AudioContext.createMediaStreamDestination(), Promise constructor, Promise.all(), MediaRecorder() to mix audio tracks, then offer mixed audio file for download.
var div = document.querySelector("div");
function handleFilesSelect(input) {
div.innerHTML = "loading audio tracks.. please wait";
var files = Array.from(input.files);
var duration = 60000;
var chunks = [];
var audio = new AudioContext();
var mixedAudio = audio.createMediaStreamDestination();
var player = new Audio();
var context;
var recorder;
var description = "";
player.controls = "controls";
function get(file) {
description += file.name.replace(/\..*|\s+/g, "");
return new Promise(function(resolve, reject) {
var reader = new FileReader;
reader.readAsArrayBuffer(file);
reader.onload = function() {
resolve(reader.result)
}
})
}
function stopMix(duration, ...media) {
setTimeout(function(media) {
media.forEach(function(node) {
node.stop()
})
}, duration, media)
}
Promise.all(files.map(get)).then(function(data) {
var len = Math.max.apply(Math, data.map(function(buffer) {
return buffer.byteLength
}));
context = new OfflineAudioContext(2, len, 44100);
return Promise.all(data.map(function(buffer) {
return audio.decodeAudioData(buffer)
.then(function(bufferSource) {
var source = context.createBufferSource();
source.buffer = bufferSource;
source.connect(context.destination);
return source.start()
})
}))
.then(function() {
return context.startRendering()
})
.then(function(renderedBuffer) {
return new Promise(function(resolve) {
var mix = audio.createBufferSource();
mix.buffer = renderedBuffer;
mix.connect(audio.destination);
mix.connect(mixedAudio);
recorder = new MediaRecorder(mixedAudio.stream);
recorder.start(0);
mix.start(0);
div.innerHTML = "playing and recording tracks..";
// stop playback and recorder in 60 seconds
stopMix(duration, mix, recorder)
recorder.ondataavailable = function(event) {
chunks.push(event.data);
};
recorder.onstop = function(event) {
var blob = new Blob(chunks, {
"type": "audio/ogg; codecs=opus"
});
console.log("recording complete");
resolve(blob)
};
})
})
.then(function(blob) {
console.log(blob);
div.innerHTML = "mixed audio tracks ready for download..";
var audioDownload = URL.createObjectURL(blob);
var a = document.createElement("a");
a.download = description + "." + blob.type.replace(/.+\/|;.+/g, "");
a.href = audioDownload;
a.innerHTML = a.download;
document.body.appendChild(a);
a.insertAdjacentHTML("afterend", "<br>");
player.src = audioDownload;
document.body.appendChild(player);
})
})
.catch(function(e) {
console.log(e)
});
}<!DOCTYPE html>
<html>
<head>
</head>
<body>
<input id="files"
type="file"
name="files[]"
accept="audio/*"
multiple
onchange="handleFilesSelect(this)" />
<div></div>
</body>
</html>The second approach uses AudioContext.createChannelMerger(), AudioContext.createChannelSplitter()
var div = document.querySelector("div");
function handleFilesSelect(input) {
div.innerHTML = "loading audio tracks.. please wait";
var files = Array.from(input.files);
var chunks = [];
var channels = [
[0, 1],
[1, 0]
];
var audio = new AudioContext();
var player = new Audio();
var merger = audio.createChannelMerger(2);
var splitter = audio.createChannelSplitter(2);
var mixedAudio = audio.createMediaStreamDestination();
var duration = 60000;
var context;
var recorder;
var audioDownload;
var description = "";
player.controls = "controls";
function get(file) {
description += file.name.replace(/\..*|\s+/g, "");
console.log(description);
return new Promise(function(resolve, reject) {
var reader = new FileReader;
reader.readAsArrayBuffer(file);
reader.onload = function() {
resolve(reader.result)
}
})
}
function stopMix(duration, ...media) {
setTimeout(function(media) {
media.forEach(function(node) {
node.stop()
})
}, duration, media)
}
Promise.all(files.map(get)).then(function(data) {
return Promise.all(data.map(function(buffer, index) {
return audio.decodeAudioData(buffer)
.then(function(bufferSource) {
var channel = channels[index];
var source = audio.createBufferSource();
source.buffer = bufferSource;
source.connect(splitter);
splitter.connect(merger, channel[0], channel[1]);
return source
})
}))
.then(function(audionodes) {
merger.connect(mixedAudio);
merger.connect(audio.destination);
recorder = new MediaRecorder(mixedAudio.stream);
recorder.start(0);
audionodes.forEach(function(node, index) {
node.start(0)
});
div.innerHTML = "playing and recording tracks..";
stopMix(duration, ...audionodes, recorder);
recorder.ondataavailable = function(event) {
chunks.push(event.data);
};
recorder.onstop = function(event) {
var blob = new Blob(chunks, {
"type": "audio/ogg; codecs=opus"
});
audioDownload = URL.createObjectURL(blob);
var a = document.createElement("a");
a.download = description + "." + blob.type.replace(/.+\/|;.+/g, "");
a.href = audioDownload;
a.innerHTML = a.download;
player.src = audioDownload;
document.body.appendChild(a);
document.body.appendChild(player);
};
})
})
.catch(function(e) {
console.log(e)
});
}<!DOCTYPE html>
<html>
<head>
</head>
<body>
<input id="files"
type="file"
name="files[]"
accept="audio/*"
multiple onchange="handleFilesSelect(this)" />
<div></div>
</body>
</html>Solution 2:
I just want to complement the excellent answer of guest271314 and post here the solution based on answer of guest271314 for second scenario (the second source is microphone input). Actually is client karaoke. Script:
window.AudioContext = window.AudioContext || window.webkitAudioContext;
var context = new window.AudioContext();
var playbackTrack = null;
function handleFileSelect(event){
var file = event.files[0];
var freader = new FileReader();
freader.onload = function (e) {
context.decodeAudioData(e.target.result, function (buf) {
playbackTrack = context.createBufferSource();
playbackTrack.buffer = buf;
var karaokeButton = document.getElementById("karaoke_start");
karaokeButton.style.display = "inline-block";
karaokeButton.addEventListener("click", function(){
startKaraoke();
});
});
};
freader.readAsArrayBuffer(file);
}
function stopMix(duration, mediaRecorder) {
setTimeout(function(mediaRecorder) {
mediaRecorder.stop();
context.close();
}, duration, mediaRecorder)
}
function startKaraoke(){
navigator.mediaDevices.getUserMedia({audio: true,video: false})
.then(function(stream) {
var mixedAudio = context.createMediaStreamDestination();
var merger = context.createChannelMerger(2);
var splitter = context.createChannelSplitter(2);
var duration = 5000;
var chunks = [];
var channel1 = [0,1];
var channel2 = [1, 0];
var gainNode = context.createGain();
playbackTrack.connect(gainNode);
gainNode.connect(splitter);
gainNode.gain.value = 0.5; // From 0 to 1
splitter.connect(merger, channel1[0], channel1[1]);
var microphone = context.createMediaStreamSource(stream);
microphone.connect(splitter);
splitter.connect(merger, channel2[0], channel2[1]);
merger.connect(mixedAudio);
merger.connect(context.destination);
playbackTrack.start(0);
var mediaRecorder = new MediaRecorder(mixedAudio.stream);
mediaRecorder.start(1);
mediaRecorder.ondataavailable = function (event) {
chunks.push(event.data);
}
mediaRecorder.onstop = function(event) {
var player = new Audio();
player.controls = "controls";
var blob = new Blob(chunks, {
"type": "audio/mp3"
});
audioDownload = URL.createObjectURL(blob);
var a = document.createElement("a");
a.download = "karaokefile." + blob.type.replace(/.+\/|;.+/g, "");
a.href = audioDownload;
a.innerHTML = a.download;
player.src = audioDownload;
document.body.appendChild(a);
document.body.appendChild(player);
};
stopMix(duration, mediaRecorder);
})
.catch(function(error) {
console.log('error: ' + error);
});
}
And Html:
<input id="file"
type="file"
name="file"
accept="audio/*"
onchange="handleFileSelect(this)" />
<span id="karaoke_start" style="display:none;background-color:yellow;cursor:pointer;">start karaoke</span>
Here the working plnkr example: plnkr
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