1214250 - [Web Audio] Zippering when changing gain or pan

Status: RESOLVED INVALID

(Core :: Web Audio, defect)

Description

[jyk2048]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36

Steps to reproduce:

JSFiddle:

https://jsfiddle.net/s_c_g/ta88zzwa/

JSFiddle source (for reference):

var context = new (window.AudioContext || window.webkitAudioContext)();
var source = context.createOscillator();
var gain = context.createGain();
source.connect(gain);
gain.connect(context.destination);
source.start(0);

window.requestAnimationFrame(function loop() {
  window.requestAnimationFrame(loop);
  gain.gain.value = (Date.now() / 1000) % 1;
});

Tested using 41.0.1 and 42.0b5, including with a new profile. Steps to reproduce are to open Firefox, paste the JSFiddle URL into the URL bar, and press enter.


Actual results:

Modifying gain (or pan) in a fast loop (requestAnimationFrame is used in the example) introduces glitches and zippering artifacts.


Expected results:

It may be that this isn't a bug. I decided to report it though because the Web Audio spec seems to indicate that de-zippering should be applied in this case, and because the other browsers I tested on don't exhibit the zippering behavior.

Comment 1

[Maire Reavy [:mreavy]]

To the reporter (@[e-mail]):  Can you try this with Nightly (Firefox 44)?  We've made a number of improvements since Fx41/42.

Adding Paul (who is at TPAC this week but can probably take a look at this next week if the problem still exists in Fx44).

Comment 2

[Karl Tomlinson (:karlt)]

This is now specified behavior since
https://github.com/WebAudio/web-audio-api/issues/76#issuecomment-107679878

We should check though that our automation methods actually support smooth transitions from the value at the time when the automation event is received.
That is we need option 2 for https://github.com/WebAudio/web-audio-api/issues/573#issuecomment-149401915

https://github.com/WebAudio/web-audio-api/issues/344#issuecomment-151315580 seems to be claiming that it is not possible to spec automation methods to give smooth results, but I don't believe that.  I think we can make them work in a way that is useful.

Comment 3

[jyk2048]

In response to the above request I tried the example JSFiddle with the Firefox 44 nightly. As far as I can tell the behavior is the same as or similar to the behavior of 41/42 (that is, the zippering is still present).

That said, as noted above it appears that maybe the zippering provision has been or will be removed from the spec (it appears to be absent in the most recent editor's draft).

Comment 4

[Paul Adenot (:padenot)]

Yes, de-zippering has been removed from the spec in https://github.com/WebAudio/web-audio-api/issues/76, so this can be closed. Thanks !