Bug 361163

With reference to an earlier feature request to add opacity control for the exisiting transition blend modes https://bugs.kde.org/show_bug.cgi?id=358052

The requested feature was implemented and made available in KDenLive 16.07.70 from the developmental branch ppa:kdenlive/kdenlive-master
 
On testing the feature however it has been observed that a number of the blend modes are producing abnormal results with chroma aberrations

Reproducible: Always

Steps to Reproduce:
1. Test system - KdenLive 16.07.70 on Kubuntu 15.10 
2. Test video clip - a 1080/29.97p.mts clip from a Canon HF-G10 AVCHD camcorder transcoded to Matroska.mkv (HuffYUV). Project profile set accordingly. 
3. Loaded the clip on the timeline and aligned to the track (Video 1) head.
4. Duplicated and co-aligned the clip on track Video 2
5. Applied Cairo Blend transition between the two tracks, spanning the full length of the clip.
6. Selected the desired blend mode and adjusted the opacity using the slider. 
7. Observed the result at the set opacity and took a screen shot of the frame off the Project Monitor view.
8. Compared the results with those obtained with scripted AVISynth function that applies the same blend mode operations. 

Actual Results:  
The results are demonstrated in full in this post on the KDenLive forum:
https://forum.kde.org/viewtopic.php?f=270&t=116876#p354253

In summary: The Overlay, Hardlight, Softlight, Screen and Color Dodge blend modes produced a similar pattern of chroma aberrations which appeared when the opacity was set to 50% or more and increased in severity up to 100% opacity. With the Add blend mode these aberrations progressively increased in severity over the entire 0 - 100% opacity range.  


Expected Results:  
It was expected that the blend mode operations would produce the intended effect, without these chroma aberrations.