Recorded videos from Firefox play at the wrong speed

[flotwig]

Current behavior:

• Firefox records videos as a WEBM with variable framerate.
• When Cypress streams these chunks to ffmpeg, the variable framerate is incorrectly interpreted at a constant 15fps.
• This results in the output video appearing to run more quickly and more slowly at times, as the CPU load of other processes go up and down and affect the output framerate.
• A related issue occurs when a navigation of the runner occurs, which causes the timestamps of the WEBM to reset to 0.

Desired behavior:

• Use the correct ffmpeg options so that the timestamp and framerates are accurately represented in the final captured mp4.
  • https://github.com/stoyanovgeorge/ffmpeg/wiki/Variable-Frame-Rate recommended .outputOption('-vsync=0').videoFilter('setpts=N/FRAME_RATE/TB')
  • framerate video filter may help: https://www.ffmpeg.org/ffmpeg-all.html#framerate
  • fps video filter may help: https://www.ffmpeg.org/ffmpeg-all.html#fps-1

Versions

• Cypress 4.0.0
• Firefox, any version

Possibly caused by https://bugzilla.mozilla.org/show_bug.cgi?id=1717868

[flotwig]

Seems to be much more evident with FF 80 now that we're not pausing so much...

[jennifer-shehane]

With the provided video from #9566, the Test Runner shows 13 seconds of runtime, but the video has already spread through it in 1 second of video time - then the frames are frozen for the rest of the 17 secs of video. https://github.com/cypress-io/cypress/files/5660042/actions.spec.js.mp4.zip

I was able to easily reproduce this on my Mac, running Firefox 81. The video speeds up very quickly (showing 30 seconds of tests in 1 sec) and then is frozen for the duration of the video. This makes the videos recorded from Firefox completely unusable.

[jpita]

I'm also having this issue on circleCI with firefox 83, so it seems platform independent

[oembe]

Same issue on Azure DevOps

Versions:
Cypress 6.2.1
Firefox 84.0.2

[flotwig]

This seems to be a bug with the mediaSource: 'browser' API used in video-recorder.ts to record videos in FF. Filed a bug on Mozilla's end: https://bugzilla.mozilla.org/show_bug.cgi?id=1717868

[cypress-app-bot]

This issue has not had any activity in 180 days. Cypress evolves quickly and the reported behavior should be tested on the latest version of Cypress to verify the behavior is still occurring. It will be closed in 14 days if no updates are provided.

[cypress-app-bot]

This issue has been closed due to inactivity.

[jennifer-shehane]

This issue still exists. Reopening for tracking purposes.

[cypress-app-bot]

This issue has not had any activity in 180 days. Cypress evolves quickly and the reported behavior should be tested on the latest version of Cypress to verify the behavior is still occurring. It will be closed in 14 days if no updates are provided.

[cypress-app-bot]

This issue has been closed due to inactivity.