1500238 - StereoPanner does not handle a pan value of zero for mono signals

Status: RESOLVED FIXED

(Core :: Web Audio, defect, P2)

Description

[chrisguttandin]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.67 Safari/537.36

Steps to reproduce:

const offlineAudioContext = new OfflineAudioContext(1, 1, 44100);
const constantSourceNode = new ConstantSourceNode(offlineAudioContext, { channelCount: 1, offset: 1 });
const stereoPanner = new StereoPannerNode(offlineAudioContext, { channelCount: 1 });

constantSourceNode.start();

constantSourceNode
    .connect(stereoPanner)
    .connect(offlineAudioContext.destination);

offlineAudioContext
    .startRendering()
    .then((buffer) => {
        const channelData = buffer.getChannelData(0);

        console.log(channelData[0]);
    });


Actual results:

The output of the snippet above is 1. The code sends a constant signal through a StereoPanner. In this case it is a mono signal that gets fed into the StereoPanner. After the rendering is done the first value of the rendered buffer gets printed to the console.


Expected results:

The output should be close to 0.707 as the algorithm for the StereoPanner requires the signal to be modified when the channelCount is 1 and the value of pan is 0.

https://webaudio.github.io/web-audio-api/#stereopanner-algorithm

Please let me know if I should provide more detailed information. Many thanks.

Comment 1

[Nils Ohlmeier [:drno]]

Paul can you please help me triage this?

Comment 2

[Karl Tomlinson (:karlt)]

Thank you for filing.  This is a discontinuity we don't want, and is reasonably easy to fix.

Comment 3

[Karl Tomlinson (:karlt)]

Attachment: Bug 1500238 correct expected result for monoPanningNoop tests r?padenot

Comment 4

[Karl Tomlinson (:karlt)]

Attachment: Bug 1500238 output null from StereoPannerNode when input is null r?padenot

This is necessary for efficient processing of silence, and is consistent with
behavior of other nodes.

A null block current has a single channel of silence, which isn't aligned with
the current spec, but is consistent with the direction of
https://github.com/WebAudio/web-audio-api/issues/1471#issuecomment-405668690

Depends on D9210

Comment 5

[Karl Tomlinson (:karlt)]

Attachment: Bug 1500238 correct mono-to-stereo panning at centre position r?padenot

and re-use input buffer instead of copying.

Depends on D9211

Comment 6

[Karl Tomlinson (:karlt)]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=43d108aa12060e3cc23014adc3af64e29bfcd725

Comment 7

[Karl Tomlinson (:karlt)]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=1701a31031ccedb91c7b83b2d423561bbb9b7f8e

Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/cc7ddb5861a8
correct expected result for monoPanningNoop tests r=padenot
https://hg.mozilla.org/integration/autoland/rev/17f777b16189
output null from StereoPannerNode when input is null r=padenot
https://hg.mozilla.org/integration/autoland/rev/01b1f806550b
correct mono-to-stereo panning at centre position r=padenot

Comment 9

[Daniel Varga [:dvarga]]

https://hg.mozilla.org/mozilla-central/rev/cc7ddb5861a8
https://hg.mozilla.org/mozilla-central/rev/17f777b16189
https://hg.mozilla.org/mozilla-central/rev/01b1f806550b