webkitAudioContext Playback of base64 WAV

Question

I have a wav file which with: ffmpeg -i my.wav

Gives the output:

output:   Duration: 00:00:12.63, bitrate: 352 kb/s
    Stream #0.0: Audio: pcm_s16le, 22050 Hz, 1 channels, s16, 352 kb/s

This is stored as a base64 string in JavaScript loaded in memory as base64 variable listed below.

Here is the code:

byte_str = Base64.decode(base64)
buffer = new ArrayBuffer(byte_str.length*2)
buffer_view = new Uint16Array(buffer)
/* this is coffeescript */
for i in [0..byte_str.length]
   buffer_view[i] = byte_str.charCodeAt(i)
console.log(byte_str.length)
console.log(buffer_view)
console.log(buffer_view.buffer)
context = new webkitAudioContext()
context.decodeAudioData(buffer,function (buffer) {
    /* never gets hit */
    source = @context.createBufferSource()
    source.buffer = buffer
    source.connect(@context.destination)
    source.noteOn(0)
});

Output:

108185
[82, 73, 70, 70, 36, 128, 87, 65, 86, 69, 102, 109, 116, 32, 16, 0, 0, 0, 1, 0, 1, 0, 34, 86, 0, 0, 68, 49152, 2, 0, 16, 0, 100, 97, 116, 97, 0, 128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,....]
ArrayBuffer {byteLength: 216370} 

If you look in this presentation it has a WAV header: http://html5-demos.appspot.com/static/html5-whats-new/template/index.html#29

var header = new Uint8Array([
    0x52,0x49,0x46,0x46, // "RIFF"
    0, 0, 0, 0,          // put total size here
    0x57,0x41,0x56,0x45,
    ...
]);

Which is identical to mine if you convert the first values to hex, yet on mine the callback never fires for decodeAudioData. Any ideas?

Answer 1

It turns out it was an encoding issue using this library: http://www.webtoolkit.info/javascript-base64.html I removed the _utf8_decode step and it worked great!