1235044 - AudioParam.setValueAtTime does not make value visible with param.value

Status: RESOLVED DUPLICATE of bug 893020

(Core :: Web Audio, defect)

Description

[jbo]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:45.0) Gecko/20100101 Firefox/45.0
Build ID: 20151223004004

Steps to reproduce:

Create an `AudioBufferSourceNode`, let's call it `node` and start playing some audio on it.

At some point, call `node.playbackRate.setValueAtTime(2, time)` where time is some time in the future and wait until `context.currentTime > time`.


Actual results:

`node.playbackRate.value === 1`. However, the new playback rate is effective in the audio engine and can be heard, but it is not visible to JavaScript.


Expected results:

It is expected that `node.playbackRate.value === 2` at that point. This is the result I am getting on WebKit and Blink based browsers.

This can be tested also on this web app: http://kostspielig.github.io/zbeats/. When moving the BPM slider up and down, the visualization of the loop progress goes out of sync. This has been debugged and confirmed that this bug happens because the code relies on the values reported by `node.playbackRate.value` being accurate to whatever the audio engine is using at a specific `context.currentTime`. The web app behaves correctly in Chromium and Gnome Web.

Comment 1

[Maire Reavy [:mreavy]]

Karl -- do you know the bug # of the dup for this?  Thanks.