Open Bug 1942609 Opened 20 days ago Updated 12 days ago

Video playbackRate not working when silent video is connected to AudioContext

Categories

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

Firefox 134
x86_64
All
defect

Tracking

()

UNCONFIRMED

People

(Reporter: gismya, Unassigned)

References

Details

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/132.0.0.0 Safari/537.36

Steps to reproduce:

  1. Load a video file without audio tracks
  2. Create an AudioContext and connect the video element using createMediaElementSource
  3. Attempt to change the video's playbackRate

Minimal reproduction page: https://gismya.github.io/firefox-playbackrate-bug-report/

Github repo for the repro: https://github.com/gismya/firefox-playbackrate-bug-report/

Actual results:

  • When a silent video is connected to an AudioContext via createMediaElementSource, the playbackRate property is ignored
  • The video plays at 1x speed regardless of the playbackRate value
  • The video.playbackRate property reports the correct set value, but the actual playback speed remains unchanged

Expected results:

  • The video should play at the speed specified by the playbackRate property
  • Changing playbackRate should affect the video playback speed, regardless of whether the video has audio or is connected to an AudioContext

Issue reported from multiple end users with, but I think all of them (Including me) is using it on MacOS. Unknown if the issue is in other operating systems.

Component: Untriaged → Audio/Video: Playback
OS: Unspecified → macOS
Product: Firefox → Core
Hardware: Unspecified → x86_64

Confirmed that it's an issue at least as far back as the ESR (v.128) and in the latest nightly (136.0a1 (2025-01-19))

Karl, would you mind taking a look here? Something related to audio context.

Flags: needinfo?(karlt)

Thank you for the nice testcase. Reproduces on Linux too.

Given this works in the other combinations of with sound and/or not connected to an AudioContext, I expect this shouldn't be hard to fix once the clock source choice for the no sound and connected to AudioContext case is identified.

Connecting a no sound video to an AudioContext is a combination that I wouldn't expect to be common.

Severity: -- → S3
Flags: needinfo?(karlt)
OS: macOS → All
See Also: → 1517199
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