Bug 411261

Created attachment 122331 [details]
Screenshot of the "Rendering" dialog with "f=mkv" format after restarting kdenlive.

SUMMARY
If a custom render format is created with "f=mkv", then it can be used to render output. However, when kdenlive is restarted, the "Rendering" dialog no longer recognizes the custom format as valid. Editing the format and saving it with no changes restores it to usability. This happens only with "f=mkv" and not with "f=matroska". Both "mkv" and "matroska" are listed as supported formats by "melt -query formats".

STEPS TO REPRODUCE
1. Open the Rendering dialog (Ctrl-Enter).
2. Create a custom render format that specifies "f=mkv", such as:

properties=x264-medium f=mkv vcodec=libx264 acodec=flac g=120 crf=9 global_quality=500 me_method=umh

3. Save this format.
4. Exit kdenlive.
5. Restart kdenlive.
6. Re-open the "Rendering" dialog.

OBSERVED RESULT
The custom format with "f=mkv" is displayed with a glyph of an 'x' in a red circle, and the window contains a panel near the bottom (orange with the Breeze Dark colour scheme) with the text "Unspported video format: mkv". If the custom format is selected, the pencil icon is clicked to edit it, and the "Edit Profile" dialog is closed by clicking "OK" with no changes, then the custom format changes to a recognized format. If there are multiple custom formats with "f=mkv", then they all become recognized simultaneously.

EXPECTED RESULT
The custom format with "f=mkv" should be listed as a valid custom format immediately upon first opening the "Rendering" dialog.

SOFTWARE/OS VERSIONS
Windows: Windows 10 1903
KDE Frameworks Version: 5.61.0
Qt Version: 5.13.0

ADDITIONAL INFORMATION
In bug 384148, it is mentioned that "mkv" isn't a valid format for ffmpeg, and to use "matroska" instead. However, it is my understanding that the render properties for a custom format are passed to MELT not ffmpeg, and MELT lists both "mkv" and "matroska" as valid formats. Either way, there is a consistency problem, because editing and re-saving the custom format clears the error. Either the error shouldn't have been there in the first place, or re-saving the profile shouldn't fix it. I feel like it should be the latter, since I render using "f=mkv" regularly.