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javascript - 网络音频 Api 输出

转载 作者:搜寻专家 更新时间:2023-10-31 22:32:30 25 4
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我正在开发一个基于社区的网络广播,用户可以在其中录制自己的消息。

我希望我的用户能够为他们的录音添加效果(例如双二阶滤波器、混响等等)

是否可以将最终混音(包括效果)处理为单个 PCM 输出(例如音频标签 src="data:audio/wav;base64")以便我可以发送通过邮寄混音到服务器?

我试过这个:

recorder.locals.filter1.connect(recorder.locals.filter3);
recorder.locals.filter3.connect(recorder.locals.filter2);
recorder.locals.filter2.connect(context.destination);
recorder.locals.source.noteOn(0);
context.oncomplete = function(e) { var buffer = e.renderedBuffer; };
context.startRendering();

但它没有给我任何东西。

最佳答案

我找到了一个解决方案。似乎在使用 startRendering() 时,您必须在创建时向上下文提供 durationsamplerate

(new webkitAudioContext(channels, duration * samplerate, samplerate);

这是我生成预渲染的 audioBuffer 并将其转换为 base64 wav 的解决方案。

var audioBuffer = audio.createBuffer(arrayBuffer, false), /* <- Input Audio */
offlineContext = new webkitAudioContext(1, audioBuffer.duration * 44100, 44100);

offlineContext.oncomplete = function(event) {

var buffer = event.renderedBuffer;
var UintWave = createWaveFileData(buffer);
var base64 = btoa(uint8ToString(UintWave));

document.getElementById("audio").src = "data:audio/wav;base64," + base64;

};

var source = offlineContext.createBufferSource();
source.buffer = audioBuffer;
var gain = offlineContext.createGainNode();
// Effects
var filter1 = offlineContext.createBiquadFilter();
filter1.type = 2;
filter1.frequency.value = 4000;
filter1.Q.value = 0.1;
// Connect
source.connect(filter1);
filter1.connect(gain);
gain.connect(offlineContext.destination);

source.noteOn(0);
offlineContext.startRendering();

function createWaveFileData(audioBuffer) {

var frameLength = audioBuffer.length;
var numberOfChannels = audioBuffer.numberOfChannels;
var sampleRate = audioBuffer.sampleRate;
var bitsPerSample = 16;
var byteRate = sampleRate * numberOfChannels * bitsPerSample/8;
var blockAlign = numberOfChannels * bitsPerSample/8;
var wavDataByteLength = frameLength * numberOfChannels * 2; // 16-bit audio
var headerByteLength = 44;
var totalLength = headerByteLength + wavDataByteLength;

var waveFileData = new Uint8Array(totalLength);

var subChunk1Size = 16; // for linear PCM
var subChunk2Size = wavDataByteLength;
var chunkSize = 4 + (8 + subChunk1Size) + (8 + subChunk2Size);

writeString("RIFF", waveFileData, 0);
writeInt32(chunkSize, waveFileData, 4);
writeString("WAVE", waveFileData, 8);
writeString("fmt ", waveFileData, 12);

writeInt32(subChunk1Size, waveFileData, 16); // SubChunk1Size (4)
writeInt16(1, waveFileData, 20); // AudioFormat (2)
writeInt16(numberOfChannels, waveFileData, 22); // NumChannels (2)
writeInt32(sampleRate, waveFileData, 24); // SampleRate (4)
writeInt32(byteRate, waveFileData, 28); // ByteRate (4)
writeInt16(blockAlign, waveFileData, 32); // BlockAlign (2)
writeInt32(bitsPerSample, waveFileData, 34); // BitsPerSample (4)

writeString("data", waveFileData, 36);
writeInt32(subChunk2Size, waveFileData, 40); // SubChunk2Size (4)

// Write actual audio data starting at offset 44.
writeAudioBuffer(audioBuffer, waveFileData, 44);

return waveFileData;

}

function writeString(s, a, offset) {
for (var i = 0; i < s.length; ++i) {
a[offset + i] = s.charCodeAt(i);
}
}

function writeInt16(n, a, offset) {
n = Math.floor(n);

var b1 = n & 255;
var b2 = (n >> 8) & 255;

a[offset + 0] = b1;
a[offset + 1] = b2;
}

function writeInt32(n, a, offset) {
n = Math.floor(n);
var b1 = n & 255;
var b2 = (n >> 8) & 255;
var b3 = (n >> 16) & 255;
var b4 = (n >> 24) & 255;

a[offset + 0] = b1;
a[offset + 1] = b2;
a[offset + 2] = b3;
a[offset + 3] = b4;
}

function writeAudioBuffer(audioBuffer, a, offset) {
var n = audioBuffer.length;
var channels = audioBuffer.numberOfChannels;

for (var i = 0; i < n; ++i) {
for (var k = 0; k < channels; ++k) {
var buffer = audioBuffer.getChannelData(k);
var sample = buffer[i] * 32768.0;

// Clip samples to the limitations of 16-bit.
// If we don't do this then we'll get nasty wrap-around distortion.
if (sample < -32768)
sample = -32768;
if (sample > 32767)
sample = 32767;

writeInt16(sample, a, offset);
offset += 2;
}
}
}

function uint8ToString(buf) {
var i, length, out = '';
for (i = 0, length = buf.length; i < length; i += 1) {
out += String.fromCharCode(buf[i]);
}
return out;
}

如果有人想出更简单或更短的方法来做到这一点,那就太好了!

关于javascript - 网络音频 Api 输出,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/12822652/

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