Closed Bug 1780150 Opened 1 year ago Closed 6 months ago

Twitter video clock flashes "-1:0-1:0-1" before looping


(Core :: Audio/Video: Playback, defect, P3)




116 Branch
Tracking Status
firefox-esr91 --- unaffected
firefox-esr102 --- wontfix
firefox102 --- wontfix
firefox103 --- wontfix
firefox104 --- wontfix
firefox110 --- wontfix
firefox114 --- wontfix
firefox115 --- wontfix
firefox116 --- fixed


(Reporter: cpeterson, Assigned: padenot)




(Keywords: regression)


(4 files)

Attached image screenshot.png

@ Paul, this bug is a regression in 102 from muted audio stream bug 1743834. I bisected this regression to this pushlog:

Steps to reproduce

  1. Open
  2. Scroll up to the first tweet. (I linked to a reply tweet because directly linking to the first tweet sometimes causes the video to play without showing a clock.)
  3. Play the video.
  4. Watch the video loop.

Expected result

The video's clock should seamlessly roll over from 0:00 to 0:09.

Actual result

Before rolling over to 0:09, the clock flashes -1:0-1:0-1. See the attached screenshot.

Flags: needinfo?(padenot)

I can reproduce this bug on both Windows and macOS.

OS: Unspecified → All
Hardware: Unspecified → All

By doing a quick check, from the point of the MDSM, I didn't see any problem yet. When the video reaches to the end, its current time and the media time in MDSM are both correct. That video would be seeked from zero as well, not from a negative timestamp. If you hover cursor over the video, Twitter would show another video control interface, which time is correct when looping back to the head.

Maybe we incorrectly dispatch some events or change media element's attribute causing Twitter think the video's duration in unknown?

Severity: -- → S4
Priority: -- → P3

I've observed that the currentTime can be greater than the duration on this page, by doing this in the console:

setInterval(function() { if ($$("video")[0].currentTime > $$("video")[0].duration) { console.log($$("video")[0].currentTime)}})

it has printed: 9.673986, the duration being 9.636281.

I'll get us a fix.

Assignee: nobody → padenot
Flags: needinfo?(padenot)

Set release status flags based on info from the regressing bug 1743834

Pushed by
Cap currentTime to the end time of the last packet when a video with an audio track is muted. r=alwu
Test that a muted media element with an audio track never has currentTime exceeding its duration. r=alwu

Backed out for causing build bustages on AudioSinkWrapper.h

  • Backout link
  • Push with failures
  • Failure Log
  • Failure line: /builds/worker/checkouts/gecko/dom/media/mediasink/AudioSinkWrapper.h:144:9: error: unknown type name 'TimeUnit'; did you mean 'media::TimeUnit'?
Flags: needinfo?(padenot)
Pushed by
Cap currentTime to the end time of the last packet when a video with an audio track is muted. r=alwu
Test that a muted media element with an audio track never has currentTime exceeding its duration. r=alwu
Flags: needinfo?(padenot)
Closed: 1 year ago
Resolution: --- → FIXED
Target Milestone: --- → 105 Branch
Flags: qe-verify+

Reproduced the issue in Nightly 105.0a1 (build id: 20220727214405)
Verified - Fixed in Beta 105.0b4 and the latest Nightly 106.0a1 (2022-08-30) using Windows 10 and macOS 12.

Flags: qe-verify+
Regressions: 1789103

We're backing this out in bug 1789103, and we'll reland a different fix.

Reopening, this has been backed out.

Resolution: FIXED → ---
Target Milestone: 105 Branch → --- might plausibly address this but I wasn't able to reproduce as originally reported, so cannot check.

Depends on: 1829054

I wasn't able to repro either, and I'm absolutely sure I could reproduce 100% of the time before. But considering my fixes about time and duration reporting all over the place in the recent week, Alastor fixes about seamless looping and audio, and your fixes from yesterday, it would be fairly plausible that this cannot happen anymore. All of those are somewhat related, but it's hard to know exactly which one fixed this particular issue (and all patches were needed on their own anyways), see below for the explanation why.

setInterval(function() { if ($$("video")[0].currentTime > $$("video")[0].duration) { console.log($$("video")[0].currentTime)}})

is what I used to characterize the problem, running in the console, previously. Over a couple loops of the video, this would emit a log statement.

But Twitter has seemingly broken their mp4 muxer and the video sometimes has a duration of 1:36 instead of 0:09. Depending on the resolution (apparently) they have incorrect value for BaseMediaDecodeTime in traf boxes for the audio track. But I've tried a number of loops with a current nightly and was lucky to get the non-broken video, and it didn't seem to reproduce. This broken duration happens in the nightly used to report this bug, and also in current Chrome release version.

I'm closing this.

Here's the broken video for posterity, I used to understand the structure easily and compare to what our demuxer is doing. I was afraid that I had broken something subtly because of all my changes in the mp4 demuxer recently.

Closed: 1 year ago6 months ago
Resolution: --- → FIXED
Target Milestone: --- → 116 Branch
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