1714448 - Crackling sound in the beginning of the audio when seeking with currentTime

Status: RESOLVED INVALID

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

Description

[Ksenia Berezina [:ksenia]]

Attachment: 68847.html

The original problem is with duolingo.com stories where a lot of "stories" have this cracking sound in the beginning and it was reported in https://github.com/webcompat/web-bugs/issues/68847

It seems intermittent for certain audio files, but with the file in the reduced test case it's reproducible consistently.

From mozregression:

 4:06.82 INFO: No more integration revisions, bisection finished.
 4:06.82 INFO: Last good revision: b55828d6e11a0a4de1e0464c6239c64e429049fd
 4:06.82 INFO: First bad revision: 748e0d854d86610243b5a6e85e0c9e0f76f22f50
 4:06.82 INFO: Pushlog:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=b55828d6e11a0a4de1e0464c6239c64e429049fd&tochange=748e0d854d86610243b5a6e85e0c9e0f76f22f50

Comment 1

[Ksenia Berezina [:ksenia]]

FWIW, Duolingo is using Howler.js (https://github.com/goldfire/howler.js) and this is the reduced test case when using the library API https://codepen.io/ksy36/pen/GRWQXKM with two audio files

Comment 2

[Ksenia Berezina [:ksenia]]

Attachment: 68847.html

Comment 3

[Ksenia Berezina [:ksenia]]

Comment on attachment 9225081 [details]
68847.html

(testcase without using howler.js)

Comment 4

[Ksenia Berezina [:ksenia]]

Hi Paul, would you be able to take a look?

Comment 5

[Paul Adenot (:padenot)]

This is something that Duolingo put in place because in the past, Firefox didn't decode mp3 correctly. But I've fixed this somewhat recently in bug 1566389 as you found. Consequently, this is not something we should or even can fix.

Specifically, we used to not trim the very beginning of mp3s, which was incorrect, and here we see Duolingo skipping a very short portion of the file at the beginning, corresponding to this portion of the file. We now do trim this portion of the file (matching the behaviour of Chrome and Edge, which have been correct for a long time), so they should remove their workaround.

Skipping in the middle of a mp3, and landing on a zone where the audio is not silent frequently results in a burst of noise (like the example you gave us, which was very nice to understand what is going on), because it causes a discontinuity in the stream of audio sample, from a sample that is 0 (silent) to a sample that is non-zero (non-silent).

Comment 6

[Ksenia Berezina [:ksenia]]

Thanks for the explanation, I've contacted Duolingo on github