Own cam screen flickers during videoconference when Signal window is in certain sizes

[ThiloteE]

• I have searched open and closed issues for duplicates

• I am using Signal-Desktop as provided by the Signal team, not a 3rd-party package.

Bug Description

My own video flickers constantly during videoconference

Steps to Reproduce

1. Create Videoconference with 2 other users of Signal.
2. Maximize the Signal-window
3. Decrease vertical size of window to minimum
4. Decrease or increase horizontal size of window until it flickers

Actual Result:

• My own cam flickers
• My friends cam does not flicker
• When the screen is configured to be in certain sizes, there is a black box / dark shadow

Expected Result:

• no flickering
• no dark shadow / black box

Screenshots

Platform Info

Signal Version:

5.35.0
production

Operating System:

Windows 10

Linked Device Version:

My phone was off, so it should not influence this behaviour, I guess?

[scottnonnenberg-signal]

Can we get a debug log (View -> Debug Log)? it includes metrics about data collected and received for your call, so it would help us track down the cause of the flicker.

[ThiloteE]

Here you go, the: https://debuglogs.org/desktop/5.35.0/6a466bccca158853166875036a10fdf4738f12243e33f6bd77dce63a7cfc4734.gz

Also:

• I found out, the problem can be reproduced with two users in the videoconference as well. It is not required to be three machines. Two are sufficient.

• I am just a normal user, so I am not well versed with coding, but if there is anything else I can provide, just ask :)

[scottnonnenberg-signal]

We did a little bit of research about your webcam - perhaps you could try changing its Flicker Control setting? https://support.creative.com/kb/ShowArticle.aspx?sid=111448&c

[ThiloteE]

Thank you for looking into this. I did a little more research as well.

1. I tried changing my cameras flicker control setting, but the program that would allow me to do that works only with the v2 version of my camp. Unfortunately, I do not have v2, but it was good you mentioned this, because I noticed there was a firmware update for my version of the webcam available. I installed the latest version of this firmware, but unfortunately there was no change to the flickering in Signal.

2. Changed my computer screen (not the cam!) from 74,973Hz to 60Hz and also to 50Hz and tested Signal --> still flickers.

3. I think there is a misunderstanding: My webcam does not flicker constantly, but it only flickers under certain configurations, namely when the Signal window is very small. These black boxes seem to be involved and appear above other Signal objects, rather than behind them or rather than the boxes being made smaller. In short: the flickering seems to be, because these boxes appear and vanish. When I maximize the Signal window, or have it in medium size, there is no flickering and the black boxes do not appear. Signal, so far, has been the only videoconferencing application where I have encountered any type of flickering on this computer using this webcam.

4. I tested with my laptop (Linux Mint) and there is NO flickering: https://debuglogs.org/desktop/5.35.0/63c3c80ba731e580e9b13d6df69b48441d308fb09f096979e11a4c39e4961251.gz

[scottnonnenberg-signal]

We don't know what those black boxes are - we've never seen that before. You can open the Developer Tools and then click the cursor button, then highlight the box, and then tell us what you see in the Elements tab. That would give us a hint of what is creating those boxes.

[ThiloteE]

I managed to find out how to start the Developer Tools after reading about it in another issue here on github 😅

1. An example for black box that I cannot click on via Developer Tools:
   

2. Maybe this footer plays a role? (This is one i can click on)
   

3. More examples of black boxes. They change their location if the Signal windows size is changed. I even saw one that was at the top of the conference screen:

   • When using the Developer Tools, I can make all the buttons disappear, just by moving my mouse randomly. This does not happen during a videoconference without Developer Tools. See here:
     
   • Then there is this one:
     
     Notice how my correspondents video is cut off at the bottom. If you compare it to the other pictures I uploaded, the difference is obvious.

4. There were a lot of issues in the log!
   

[ThiloteE]

2022-03-21.Signal.Desktop.Issue.5820.18-44-24-1.mp4

[scottnonnenberg-signal]

@ThiloteE Thanks for that video; it really gives us a feel for what's going wrong. Can you try starting Signal Desktop with --disable-gpu or --in-process-gpu and see if that helps? It looks like a hardware rendering artifact to me.

[ThiloteE]

OK, I started signal per command line.

• signal --disable-gpu: the flickering stops and the Signal videoconference apparently (from what I have seen!) works perfectly normal. Nice!
• signal --in-process-gpu: still has the flickering. Here the log of my command line, some warnings and an error emerged. Here Signal's internal diagnose protocol.

.

[ThiloteE]

I will install the newest graphic cards driver today. Will report back, if that helped.

[ThiloteE]

Nope, newest nvidia driver (512.15, game ready, win10) for NVIDIA GeForce GTX 1060 did not change anything.

[scottnonnenberg-signal]

Thanks for that additional detail. For now, it looks like --disable-gpu will be a good workaround.