Bug with "selected zone" render that only affects non-official builds

[Alistair Riddoch]

I have come across a bug which affects rendering a selected zone, but does
not occur when using the Appimages downloaded from kdenlive.org. I am
uncertain whether to file a bug in the tracker, as I'm guessing it is
actually a problem with a dependency. I'll describe it here, and I'm happy
to file it properly, and help resolve if that seems appropriate.

I'm using Fedora 30 and the bug is present in all the binaries I have built
from source since some time during 19.04. I have built from the release
labels, from the 19.08 branch, and from head and seen the same problem in
each case. The bug is also present in the semi-official rpm package from
RPM Fusion. The installed Melt is mlt-6.16.0, and is comon to all recent
affected builds.

The bug is that when I render a "selected zone" of the project, the output
of the render is not the correct length, and doesn't contain the correct
range of the project output. Very frequently the output is only 1 or 2
frames long, and renders almost instantly, despite the selected zone being
much longer.

Repro steps:

   1. Create or load a project with some clips on the timeline.
   2. Define in in-point on the project time line which is _not_ at time
   00:00:00.
   3. Define an out-point on the project time line which is after the
   in-point.
   4. Open the Render dialog.
   5. Select "selected zone".
   6. Format does not appear to matter, but I have only tested with WAV and
   MP4.
   7. Press "Render to File".

Expected Result: The output video is the range of the project selected.
Actual Result: The output video is apparently random in length, and not
obviously directly related to the selected zone.

I attach a project file which is a trivial repro case for the bug, and the
mp4 file I got when I tried to render a 2 second zone from the middle of
this project. The actual output is 2 frames long, and is not correct for
the start of the selected zone.

Please let me know if more information is required, or if I can do anything
else to help fix the bug.

Keep up the good work!

Al
-- 
Alistair Riddoch
alriddoch at googlemail.com
http://alistairriddoch.org/
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.kde.org/pipermail/kdenlive/attachments/20191014/30811d4d/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: untitled.mp4
Type: video/mp4
Size: 2537 bytes
Desc: not available
URL: <http://mail.kde.org/pipermail/kdenlive/attachments/20191014/30811d4d/attachment.mp4>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: region_rendering_bug_repro_1904.kdenlive
Type: application/x-kdenlive
Size: 9957 bytes
Desc: not available
URL: <http://mail.kde.org/pipermail/kdenlive/attachments/20191014/30811d4d/attachment.bin>