Is there any way to save mulaw audio stream from twilio in a file

I am using Twilio voice stream feature and i don't want to use Twilio record functionality. When Twilio starts sending voice stream to my server i want to store it into disk as an audio file in realtime.

I was running into the same issue today and figured a way to generate a WAVE Header for the mu-law header:

If you're following Twilio's blog post, that's the code I ended implementing:

    wss.on('connection', (socket) => {
      socket.on('message', (msg) => {
        const { event, ...message } = JSON.parse(msg);
        switch (event) {
          case 'start':
            let streamSid = message.start.streamSid;
            socket.wstream = fs.createWriteStream(__dirname + `/${Date.now()}.wav`, { encoding: 'binary' });
            // This is a mu-law header for a WAV-file compatible with twilio format
            socket.wstream.write(Buffer.from([
              0x52,0x49,0x46,0x46,0x62,0xb8,0x00,0x00,0x57,0x41,0x56,0x45,0x66,0x6d,0x74,0x20,
              0x12,0x00,0x00,0x00,0x07,0x00,0x01,0x00,0x40,0x1f,0x00,0x00,0x80,0x3e,0x00,0x00,
              0x02,0x00,0x04,0x00,0x00,0x00,0x66,0x61,0x63,0x74,0x04,0x00,0x00,0x00,0xc5,0x5b,
              0x00,0x00,0x64,0x61,0x74,0x61,0x00,0x00,0x00,0x00, // Those last 4 bytes are the data length
            ]));
            break;
          case 'media':
            // decode the base64-encoded data and write to stream
            socket.wstream.write(Buffer.from(message.media.payload, 'base64'));
            break;
          case 'stop':
            // Now the only thing missing is to write the number of data bytes in the header
            socket.wstream.write("", () => {
              let fd = fs.openSync(socket.wstream.path, 'r+'); // `r+` mode is needed in order to write to arbitrary position
              let count = socket.wstream.bytesWritten;
              count -= 58; // The header itself is 58 bytes long and we only want the data byte length
              console.log(count)
              fs.writeSync(
                fd,
                Buffer.from([
                  count % 256,
                  (count >> 8) % 256,
                  (count >> 16) % 256,
                  (count >> 24) % 256,
                ]),
                0,
                4, // Write 4 bytes
                54, // starts writing at byte 54 in the file
              );
            });
            break;
        }
      });
    });