897895 - MediaRecorder - The recorded sound is incorrect when recording the mediaStream generated from AudioContext

Status: VERIFIED FIXED

(Core :: Audio/Video: Recording, defect)

Description

[Randy Lin [:rlin] - Be Mozillian on 2015/01/26]

I found the recording sound is incorrect when use the AudioContext to generate an 1k tone. 
The audio sounds like zzzzzz, not like the original one.
Test page is http://people.mozilla.com/~rlin/MediaRecorder.html
1. click getAudioContext, you will hear 1k tone from speaker. 
2. start
3. stop
4. playbackfromMemoery, the sound is incorrect.

Comment 1

[Shelly Lin [:shelly]]

Attachment: Correct the pcm offset

In the process of interleaving raw data to pcm buffer, the calculation of pcm buffer's offset is previously wrong. It just happened to be correct with audio source that has only one channel.

This fix should correct the calculation.

Comment 2

[Shelly Lin [:shelly]]

Observe that AudioContext generates an audio source with two channels and sampling rate at 48K.

Comment 4

[Shelly Lin [:shelly]]

Try server result:
https://tbpl.mozilla.org/?tree=Try&rev=8b6f972eb359

Comment 5

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/integration/b2g-inbound/rev/e55aa63b06ac

Comment 6

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/e55aa63b06ac

Comment 7

[Jason Smith [:jsmith]]

Marking verified per the dupe's testing.

Comment 8

[Bogdan Maris, Desktop Test Engineering]

Verified on Aurora 26.0a2 (buildID: 20131011004001).