What is your operating system?
Ubuntu Linux 18.04 (Kubuntu flavor) AMD64
What is your Shotcut version (see Help > About Shotcut)? Is it 32-bit?
Can you repeat the problem? If so, what are the steps?
This either three problems with some relationship to one another, or one problem manifesting itself in three similar yet different symptoms.
When editing MTS files (preliminary editing to create edit-friendly MP4 files for production edits) the preview screen will freeze on the first frame; the audio continues. (rare, sporadic, cannot be reliably repeated)
When editing MTS files (as above) the preview screen will go “white” (actually various tints of very pale pastels). this can sometimes be cured, temporarily, by changing from External Monitor to None, and back again. Usually changing to the small embedded preview fixes it until changing back to External. All editing and exporting functions work correctly (flying blind), except for Problem 3, below.
This white-screen problem also happens sometimes on PNG files inserted into a track.
When exporting from a MTS-file:MLT-file combination which is showing occasional or persistent white screens, the output MP4 file will have from one to ten “white” frames at the beginning. This will occur even when it is in the transient mood to show the preview screen correctly.
These all appear to be related to a library which has recently changed, possibly a library that was incorporated with the latest automatic upgrade of Shotcut (21.1.29).
Even if the library change was done by Ubuntu (Note: It seems to also be happening to some Windows 10 users), Shotcut is not handling it gracefully.
The reason I believe it to be a library is that it seems to be something both new, and shared by all versions of Shotcut on a given system, However, if this is the case, Shotcut 21.1.29 handles the problem with less grace than Shotcut 18.11.18.
– MLT saved sessions using saved original MTS files from a month ago, which showed no symptoms during extensive editing a month ago, show all the symptoms this week.
–The same MLT referencing the same MTS file and PNG file, when opened in Shotcut 18.11.18, will now sometimes show the white-screen symptom. This never happened in 18.11.18 before this week.
When the problem appears in Shotcut 18.11.18, it is easily curable by changing to embedded monitor and then back to the external monitor/ This is rarely reliably achieved in 21.1.29.
–When the same MLT Exports the same MTS to MP4 in Shotcut 18.11.18, the leading white-frames never appear; the output file is perfect.
–The leading white frames problem occurs in 21.1.29 with both nvenc-x264 using the GPU, and libx264 using only the cpu.
This appears to be the same problem described in Video changes to white screen when splitting at playhead