Having Color/Contrast/W. Balance Issues When Reversing Clips

Hello,

I am having repeated issues when reversing clips in my project timeline. It is happening with multiple projects all using different source material, so it’s not one isolated incident with a single wonky file.

I take a small clip in my timeline and copy/paste it next to itself. I then want to reverse the copied clip, so that when they’re both played together it creates a “back and forth loop.” That part I have no problems with. The reversed copy, however is always different in appearance; shifts in white balance, contrast, color and skin tones. Obviously when played together with its counterpart, there is a sudden and jarring shift in overall appearance.

I ran a controlled experiment of sorts to try and figure this out on my own. The source video is 2160p 25fps and the default info in “Properties” when I load it into Shotcut are:

  • Codec: H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
  • Format: yuv420p
  • Color Space: ITU-R BT.709
  • Color Transfer: NA
  • Color Range: Broadcast Limited (MPEG)

I added the video to my timeline, then cut out a 10-second clip and made five copies of it to try the following. All reverse conversions were done using the “Best” method.

  • Clip 1: Original clip

  • Clip 2: Reversed, Convert to BT.709 OFF

  • Clip 3: Reversed, Convert to BT.709 ON

  • Clip 4: Color Range changed to “Full (JPG)”

  • Clip 5: Reversed, Convert to BT.709 OFF

  • Clip 6: Reversed, Convert to BT.709 ON

Results were that clips 2-6 all had the same appearance, which was different than Clip 1. The most noticeable change was a shift toward cooler blue in overall color tone. The histogram for clip 1 fluctuated between 0 and 6 for a minimum. Clips 2-6 all bounced around between 16 and 22.

Version 25.01.25
Mac OS 15.2 Sequoia

Thanks for the detailed report. I am not able to recreate this with my test clips.

As a work around, I think you could try this:

  1. One the original clip, choose “Convert”. Choose a conversion quality and click OK
  2. After the conversion job completes, Shotcut will replace the clip with the converted clip
  3. Now, copy the converted clip, and choose “Reverse”.

I would expect the color to match between the two clips.

If you want to help to get to the root of the problem, would you be willing to share a short example clip so I can reproduce the problem?

Hi Brian,

Converting the full clip initially and working on that copy worked out fine and I am happy with that.

One more thing I just noticed: all of the converted clips I talked about in my initial post, the ones that looked wrong, ended up being converted to ITU-R BT.601. Does that tell you anything?