When a video was being played in VLC and I opened a new Firefox window with Ctrl-N partly over the VLC window or close to it (I use FVWM manual placement), garbage (more or less a set of rectangles) appeared in place of the video for a few seconds. This was always reproducible. This issue never occurred when I opened an Xterm window instead of a Firefox window. I wanted to do a recording with recordmydesktop, but each time recordmydesktop was running, the issue no longer appeared. The issue was still occurring after I stopped recordmydesktop. After I stopped the video and played it again, the issue was no longer occurring at all.
I could reproduce the issue again, which is like it occurred for the first time. I have 2 monitors. The video was being played full screen on the left one. In a Firefox window on the right monitor, I typed Ctrl-N and put the new Firefox window entirely in the left screen. And I got garbage around the Firefox window. I could also reproduce the issue when opening an Emacs window. But still not with an Xterm window.
I could eventually reproduce the issue with an xterm. The window does not need to be close to the VLC window. What seems to matter is that I do not position the new window too quickly. Note that until the window is placed, the image cannot be updated (but the sound still goes on).
Control: retitle -1 vlc: When playing a video: garbage for a few seconds after X11 display updates have been blocked for a sufficiently long time Retitling according to this.
Le lauantaina 28. kesäkuuta 2025, 3.18.49 Itä-Euroopan kesäaika Vincent Lefevre a écrit : That sounds like a problem with the WM, or perhaps the compositor or display drivers, especially when you add: It's unlikely that Debian multimedia or upstream VLC devs can do anything.
The WM might make the bug apparent, but it is not responsible for the display. I do not use a compositor. I could try on other machines that have different display drivers. I think that the cause is just that the display is locked. That was frequent in the past with modal dialogs, but I don't know if such dialogs still exist so that I could try.
This is now worse with vlc 3.0.22-1: garbage is now permanent once it occurs. Resizing the window or switching to full screen does not make the garbage disappear. A pause/play sequence does not make it disappear either. But if I go backward or forward by changing the cursor position on the time bar, the garbage disappears. [...] There is no issue with ffplay (from ffmpeg), so no. And this looks more like a stream decoding issue. See attached screenshot.
If I run vlc with VLC_VERBOSE=3, I get warnings such as [00007f4a04c13530] avcodec decoder warning: More than 11 late frames, dropping frame [00007f4a04c13530] avcodec decoder warning: More than 11 late frames, dropping frame [00007f4a04c13530] avcodec decoder warning: More than 11 late frames, dropping frame [00007f4a04c13530] avcodec decoder warning: More than 11 late frames, dropping frame [00007f4a04c13530] avcodec decoder warning: More than 11 late frames, dropping frame [00007f4a04c13530] avcodec decoder warning: More than 11 late frames, dropping frame [00007f4a04c13530] avcodec decoder warning: More than 11 late frames, dropping frame [00007f4a04c13530] avcodec decoder warning: More than 11 late frames, dropping frame [00007f4a04c13530] avcodec decoder warning: More than 11 late frames, dropping frame [00007f4a04c13530] avcodec decoder warning: More than 11 late frames, dropping frame [00007f4a04c13530] avcodec decoder warning: More than 11 late frames, dropping frame [00007f4a04c13530] avcodec decoder warning: More than 11 late frames, dropping frame [00007f4a04c13530] avcodec decoder warning: More than 11 late frames, dropping frame when the problem occcurs. Such warnings are probably expected since the X11 display was blocked. But it seems that something like frame dropping is not handled correctly.