Bug 429920

Summary:	Rendering video with Freeze effect on frame while using Parallel Processing corrupts the frame
Product:	[Applications] kdenlive	Reporter:	h.k.ghost
Component:	Video Effects & Transitions	Assignee:	Vincent PINON <vpinon>
Status:	RESOLVED FIXED
Severity:	normal	CC:	jb, julius.kuenzel
Priority:	NOR
Version First Reported In:	20.08.2
Target Milestone:	---
Platform:	Ubuntu
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	Correct Result (Parallel Processing Disabled) Corrupted Result (Parallel Processing Enabled)

Description h.k.ghost 2020-12-02 11:42:58 UTC

SUMMARY

When I render videos that have a freeze frame effect on a clip's frame the frozen frame ends up corrupted in the rendered video, but only when rendering is done with the "Parallel processing" box enabled/checked.

STEPS TO REPRODUCE
1. Add clip to timeline
2. Grab one frame from the clip (preferably with movement before and after)
3. Add the "Freeze" effect to it
4. Render the project *with* Parallel Processing checkbox checked

OBSERVED RESULT

The frozen frame is corrupted (e.g. white, green, and/or otherwise visually distorted). Audio appears to be fine.

EXPECTED RESULT

The frame looks correct, just like it did prior to rendering.

SOFTWARE/OS VERSIONS

Operating System: Kubuntu 20.10
KDE Plasma Version: 5.19.5
KDE Frameworks Version: 5.74.0
Qt Version: 5.14.2
Kernel Version: 5.8.0-31-generic
OS Type: 64-bit
Processors: 24 × AMD Ryzen 9 3900X 12-Core Processor
Memory: 31.3 GiB of RAM
Graphics Processor: GeForce RTX 2070 SUPER/PCIe/SSE2

ADDITIONAL INFORMATION

I tested several settings (e.g. lower encoder speed slider, lower thread count), but it made no difference. Only unchecking/disabling the "Parallel Processing" checkbox produced the correct result.

I've seen this issue across several projects, with different sources/videos. This is simply the first time I manage to narrow it down to something that seems reproducible.

Comment 1 h.k.ghost 2020-12-02 11:44:10 UTC

Created attachment 133804 [details]
Correct Result (Parallel Processing Disabled)

This is what the rendered result looks like when rendered with parallel processing disabled.

Comment 2 h.k.ghost 2020-12-02 11:44:56 UTC

Created attachment 133805 [details]
Corrupted Result (Parallel Processing Enabled)

This is what the same frame looks like when rendered with the parallel processing option enabled.

Comment 3 h.k.ghost 2020-12-02 11:47:37 UTC

Note that this problem is never visible in the project monitor's preview. The issue appears to be internal to Kdenlive. It doesn't seem like there's anything you can do in a project to work around this issue except rendering with a single thread... (or at least nothing "obvious" and/or "intuitive").

Comment 4 Jean-Baptiste Mardelle 2020-12-02 14:35:28 UTC

This issue was supposedly fixed in MLT on the 3rd of october. Could you try with the 20.08.3 AppImage that contains a recent git version of MLT ?
https://download.kde.org/stable/kdenlive/20.08/linux/kdenlive-20.08.3b-x86_64.appimage.mirrorlist

Thanks for reporting back

Comment 5 h.k.ghost 2020-12-03 02:50:22 UTC

I used version 20.08.3 to render these sections and did not observe the issue. I tested on two different sections of the project, both with freeze effects on a clip's frame.

On a potentially unrelated note: I tried rendering a test using .webm instead of .mp4, and the .webm never show the video content, i.e. only a black screen shows up even though the audio comes across clearly and works. Is this a known issue?

Comment 6 Julius Künzel 2021-03-31 20:00:08 UTC

Thanks for your feedback. I am closing this now.

Concerning your other bug: please test with the latest version (20.12.3 at the moment, https://kdenlive.org/en/download/) and open a new report if you still face it.