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Version: v3

Watch recorded opus audio file format conversion

Watch Recorded Opus Audio File Parameters​

  • Sampling rate: 16000
  • Channel: 1
  • PCM encoding: 16-bit little endian sequence

Option 1: Node.js script​

Refer to the following Node.js script.

// npm i opusscript wav
const OpusScript = require("opusscript");
const fs = require("node:fs");
const wav = require("wav");
function opus2wav(input, output, rate = 16000, channels = 1) {
  const encoder = new OpusScript(rate, channels, OpusScript.Application.AUDIO);
  const data = fs.readFileSync(input);
  const out = [];
  for (let pos = 0; pos < data.byteLength;) {
    const len = data.readUint32BE(pos);
    const payload = data.subarray(pos + 8, pos + 8 + len);
    out.push(encoder.decode(payload));
    pos += 8 + len;
  }
  const pcm = Buffer.concat(out);
  const writer = new wav.FileWriter(output, {
    channels: channels,
    sampleRate: rate,
    bitDepth: 16
  });
  writer.write(pcm);
  writer.end();
}

opus2wav("userContent.opus", "userContent.wav");

The wav library can be replaced with ffmpeg's WASM implementation to enable conversions to more formats such as wav, aac, mp3, etc.

Option 2: opus_demo and ffmpeg command line tools​

The following tools are required​

  1. Opus official demo library and tools https://gitlab.xiph.org/xiph/opus

Refer to the readme document compile of the Opus official tool library to generate opus_demo tool.

  1. FFmpeg https://www.ffmpeg.org/

Steps​

  1. Convert Opus files to pcm raw format using opus_demo tool
# opus_demo -d <sampling rate (Hz)> <channels (1/2)> <input> <output>
./opus_demo -d 16000 1 userContent.opus userContent.pcm

Successful output

img

  1. Use ffmpeg to convert PCM files to WAV or other formats

Data format: s16le signed, integer, little endian

# ffmpeg -f <format> -ar <sampling rate> -ac <channels> -i <input> <output>
ffmpeg -f s16le -ar 16000 -ac 1 -i userContent.pcm userContent.wav

Successful output

img