mirror of https://bitbucket.org/ausocean/av.git
97 lines
3.1 KiB
JavaScript
97 lines
3.1 KiB
JavaScript
/*
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NAME
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pcm-to-wav.js
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AUTHOR
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Trek Hopton <trek@ausocean.org>
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LICENSE
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This file is Copyright (C) 2018 the Australian Ocean Lab (AusOcean)
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It is free software: you can redistribute it and/or modify them
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under the terms of the GNU General Public License as published by the
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Free Software Foundation, either version 3 of the License, or (at your
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option) any later version.
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It is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License in gpl.txt.
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If not, see [GNU licenses](http://www.gnu.org/licenses).
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*/
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// pcmToWav takes raw pcm data along with the sample rate, number of channels and bit-depth,
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// and adds a WAV header to it so that it can be read and played by common players.
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// Input should be a Uint16Array containing 16 bit PCM samples, output will be a Uint8Array representing the bytes of the wav file.
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// WAV spec.: http://soundfile.sapp.org/doc/WaveFormat/
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function pcmToWav(data, rate, channels, bitdepth) {
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let subChunk2ID = [100, 97, 116, 97]; // "data".
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let subChunk2Size = int32ToBytes(data.length);
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let subChunk1ID = [102, 109, 116, 32]; // "fmt ".
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let subChunk1Size = int32ToBytes(16);
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let audioFmt = int16ToBytes(1); // 1 = PCM.
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let numChannels = int16ToBytes(channels);
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let sampleRate = int32ToBytes(rate);
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let byteRate = int32ToBytes(rate * channels * bitdepth / 8);
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let blockAlign = int16ToBytes(channels * bitdepth / 8);
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let bitsPerSample = int16ToBytes(bitdepth)
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let chunkID = [82, 73, 70, 70]; // "RIFF".
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let chunkSize = int32ToBytes(36 + data.length);
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let format = [87, 65, 86, 69]; // "WAVE".
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let result = new Uint8Array((data.length*2) + 44);
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let off = 0;
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result.set(chunkID, off);
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off += 4;
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result.set(chunkSize, off);
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off += 4;
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result.set(format, off);
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off += 4;
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result.set(subChunk1ID, off);
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off += 4;
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result.set(subChunk1Size, off);
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off += 4;
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result.set(audioFmt, off);
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off += 2;
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result.set(numChannels, off);
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off += 2;
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result.set(sampleRate, off);
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off += 4;
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result.set(byteRate, off);
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off += 4;
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result.set(blockAlign, off);
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off += 2;
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result.set(bitsPerSample, off);
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off += 2;
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result.set(subChunk2ID, off);
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off += 4;
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result.set(subChunk2Size, off);
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off += 4;
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result.set(data, off);
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return result;
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}
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// int32ToBytes takes a number assumed to be an int 32 and converts it to an array containing bytes (Little Endian).
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function int32ToBytes(num) {
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let b = new Uint8Array(4);
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b[0] = (num & 0x000000ff);
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b[1] = (num & 0x0000ff00) >> 8;
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b[2] = (num & 0x00ff0000) >> 16;
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b[3] = (num & 0xff000000) >> 24;
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return b;
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}
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// int16ToBytes takes a number assumed to be an int 16 and converts it to an array containing bytes (Little Endian).
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function int16ToBytes(num) {
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let b = new Uint8Array(2);
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b[0] = (num & 0x00ff);
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b[1] = (num & 0xff00) >> 8;
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return b;
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} |