1603729 - MSE VP8 Video with low frame rate freezes, video time keeps going

Status: NEW

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

Description

[Holger Rasmussen]

Attachment: debug.json

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36

Steps to reproduce:

We have noticed, that our dash videos sometimes stops displaying video frames in Firefox. Audio continues playing normally, the video time also keeps going. We have created the following test case, which lets us reproduce the issue on our devices consistently. After two seconds, the frames are not updated anymore. The video has silent audio.

In Chrome, the video plays as expected.

Test case: https://cdn.ubivent.com/web/test/firefox/framerate/index.html

Our theory is, that the issue occurs when the frame rate is below a certain threshold. On average the video has 10 fps.

When combining the segments into a single webm, the video plays correctly in Firefox:
https://cdn.ubivent.com/web/test/firefox/framerate/index-full.html

Actual results:

The video frames are not updated anymore after two seconds

Expected results:

The video frames should continue being displayed.

Comment 1

[BugBot [:suhaib / :marco]]

Bugbug thinks this bug should belong to this component, but please revert this change in case of error.

Comment 2

[Holger Rasmussen]

Correction: On average the video has 1.33 fps (174 frames / 131 seconds )

Comment 3

[Michael Froman [:mjf]]

Bryce, any thoughts here?

Comment 4

[Bryce Seager van Dyk [:bryce] (he/him) - Not reading bugmail]

:kinetik, would you be able to look at the file and check if there's anything unexpected happening with the demuxing?

Comment 5

[Matthew Gregan [:kinetik]]

(In reply to Bryce Seager van Dyk (:bryce) from comment #4)

:kinetik, would you be able to look at the file and check if there's anything unexpected happening with the demuxing?

Checked the files, but I didn't notice any obvious issues. Video rate is ~1.3 fps as mentioned, audio is continuous but silent (all 1 byte blocks).

If I had to guess, I'd say there's something odd with the key frame skipping/recovery logic. Looking at the media element's VideoPlaybackQuality stats, once a frame drops we seem to continue dropping a sequence and generally don't recover.

Comment 6

[BugBot [:suhaib / :marco]]

The priority flag is not set for this bug.
:bryce, could you have a look please?

For more information, please visit auto_nag documentation.

Comment 7

[Bryce Seager van Dyk [:bryce] (he/him) - Not reading bugmail]

(In reply to Matthew Gregan [:kinetik] from comment #5)

(In reply to Bryce Seager van Dyk (:bryce) from comment #4)

:kinetik, would you be able to look at the file and check if there's anything unexpected happening with the demuxing?

Checked the files, but I didn't notice any obvious issues. Video rate is ~1.3 fps as mentioned, audio is continuous but silent (all 1 byte blocks).

If I had to guess, I'd say there's something odd with the key frame skipping/recovery logic. Looking at the media element's VideoPlaybackQuality stats, once a frame drops we seem to continue dropping a sequence and generally don't recover.

Thanks.

:jya, based on the above, do you have insight into what could cause this in our MSE machinery?