https://bugs.kde.org/show_bug.cgi?id=505578

--- Comment #17 from [email protected] ---
(In reply to Yash Bavadiya from comment #16)
> I had a look at the two backtraces with debug symbols (attachments 183612
> and 183613), and both crash in the same place, inside MLT's avformat
> producer rather than in Kdenlive code.
> 
> Attachment 183613 [details], thread 20303:
> 
> ```
> #0  avformat_find_stream_info () at /app/lib/libavformat.so.61
> #1  get_basic_info (...) at producer_avformat.c:911
> #2  producer_open (..., take_lock=0, test_open=0) at producer_avformat.c:1178
> #3  producer_set_up_video (...) at producer_avformat.c:2988
> ```
> 
> Attachment 183612 [details], thread 1 (the main thread):
> 
> ```
> #0  producer_open (..., take_lock=0, test_open=0) at producer_avformat.c:1241
> ```
> 
> Two things stand out. Both crashes are in `producer_open` reached from the
> lazy reopen path, the "Reopen the file if necessary" branch that runs when
> the format context is null, and in both cases `take_lock=0`, so the producer
> is being opened without taking its own internal lock. The video reopen path
> passes `take_lock=0` and locks `video_mutex` by hand around the call, while
> the audio reopen path passes `take_lock=1`, so the locking is asymmetric
> between the two.
> 
> The other thing is that one crash is on a worker thread and the other is on
> the main thread, and both dumps have 18 threads inside producer_avformat.c
> at the moment of the crash. That fits the "random, happens when I am not
> expecting it" description better than a specific user action does, since
> what varies is the timing rather than the operation. The reported triggers,
> dragging a clip, moving the playhead, zooming, importing, are all things
> that cause producers to be opened or reopened.
> 
> Worth noting the file in 183613 is a .webm and in 183612 a proxy .mov, so it
> does not look format specific.
> 
> I have not reproduced this locally and I am not claiming a specific root
> cause, the line numbers in the trace are from the AppImage's MLT build so
> they do not map exactly onto current MLT sources. But the crash is
> consistently in that reopen path, so that seems like the place to look, and
> it may be worth raising upstream with MLT rather than treating it as a
> Kdenlive bug.
> 
> @antimidia if you hit it again, a backtrace from a debug build would help
> narrow it further, the two attachments above are the only ones in the ticket
> with symbols and they are from 2025.

Yeah, I can do that. I'll start using the flatpak version to be able to provide
more debug logs.

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