Bug 229611 – MediaRecorder with canvas captureStream() produces blank video

• Component: WebRTC
• Status: RESOLVED DUPLICATE

[Ashley Gullen]

Using MediaRecorder to record a MediaStream from the canvas captureStream() method appears to only produce a blank video in Safari 15 / TP 130 on macOS 12 beta (21A5304g).

Demo URL: https://downloads.scirra.com/labs/screenrecording/

Steps to reproduce:

1. Click 'Record canvas'
2. Wait a few seconds
3. Click 'Stop recording'

A video file will then be downloaded.

Observed result:
The video has the expected duration, but just displays all black.

Expected result:
Video to show canvas content that was recorded.

Other notes:
This appears to work correctly on iOS 14, so may be unique to macOS. Also note we have reports that a flickery video is recorded on Safari 14 on macOS, but we can't easily test that right now. Finally the 'Record screen' option - using getDisplayMedia() - appears to work correctly, so this looks like an issue specific to using MediaRecorder with canvas captureStream().

[Radar WebKit Bug Importer]

<rdar://problem/82724497>

[Alexander Khovansky]

We ran into the same problem (except with a bit more erratic behavior) when using a canvas for realtime video modification.
It looks like it's not MediaRecorder specific but rather captureStream producing a bad stream.

Here's a codepen that demonstrates the issue:
https://codepen.io/alx-khovansky/pen/KKqgeNw

It has a video source that is rendered to a canvas, which is then rendered to a different video element using captureStream. Works in Safari 14 but not in TP.

[David Halls]

I'm also seeing this. It's captureStream generating blank video.

One example is https://experiments.withgoogle.com/webcam-displacement

This works on Safari 14.1.2 but not on TP 131 (both Big Sur).

[youenn fablet]

> It looks like it's not MediaRecorder specific but rather captureStream
> producing a bad stream.

Right, this is also my understanding.

[David Halls]

Broken on Safari 15 now :(

[jerry]

How do we get the devs to at least confirm this?

This happens to the latest TP 133.

[Kongpheng]

Issue still reproducible on Safari version 15.1 (15612.2.9.1.30, 15612).

Another way to reproduce:
* Open https://webrtc.github.io/samples/src/content/capture/canvas-video/
* Using mouse, move teapot on the left side around, by holding down left-click and dragging your mouse around
* Notice that teapot on the right doesn't mirror the left teapot's movement

I wonder if issue is due to auto-play constraint violation.  Console logs follows.

MediaElementSession::clientWillBeginAutoplaying(74E6F415461C6466) state = Autoplaying
HTMLMediaElement::setShouldDelayLoadEvent(74E6F415461C6466) true
MediaElementSession::removeBehaviorRestriction(74E6F415461C6466) removed RequirePageConsentToLoadMedia
MediaElementSession::autoplayPermitted(74E6F415461C6466) Returning FALSE because element is not visible in the viewport
MediaElementSession::beginInterruption(74E6F415461C6466) state = Autoplaying, interruption type = InvisibleAutoplay, interruption count = 0

Adding on here that this is affecting capture for Flipgrid in Safari 15. We can fall back to a standard video element -> MediaRecorder capture, but that removes our ability to provide all of the canvas enabled effects. For a quick fix for this bug, we are just disabling capture on Safari 15.

@youenn - anything else I can help provide to diagnose?

[Jon Lee]

*** This bug has been marked as a duplicate of bug 230613 ***

[Ashley Gullen]

This issue was marked a duplicate of 230613 which was apparently fixed in 2022. I'm not an Apple developer, but if there are still issues you should file a new issue, I doubt anyone from Apple is going to track comments on an old and apparently already fixed issue.