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