I have tried to bring this issue to light many times, and your own users have argued it ad finem, but to no avail! I am TIRED of getting terrible alpha blending (and opacity curve) results with GPU acceleration enabled, vs CPU. In fact, it is SO BAD that I NEVER work with GPU acceleration any more.
Here is the issue:
When GPU acceleration is enabled, you simply CANNOT do a smooth fade and/or cross dissolve. It appears to fade down smoothly to about 20% opacity, and then the next frame it will jump right to 0% quite abruptly and disappear. It's almost as if the fade simply gives up and switches off! Regardless of whether you use Cross Dissolve, or Film Dissolve the results are the same. Also, your alpha blending is all messed up, CLEARLY showing a different result when comparing CPU and GPU rendering outputs. Once again, this issue ONLY exists with GPU acceleration ENABLED. Switch off GPU/MPE and the problems disappear. But of course you lose the speed and other benefits GPU acceleration offers, which would be great to have! Especially seeing as I have also heard (from various other resources) that GPU acceleration can improve the quality of rendering out to compressed formats like H264. But we will never know that, will we? Because, every time I enable GPU, my fades and blending looks noticeably bad!
I have seen in various other threads that your response has been along the lines of: "That's just the way it is". But unless your name is Bruce Hornsby, this response is unacceptable! You cannot advertise a "great feature" of your products (in this case, GPU/MPE), yet when people try to use it and see odd results, simply tell us: "oh by the way, yeah, it does not work in a few scenarios, like fading, but otherwise you are good to go!" The way I see it: cross-fades (even fades in general) as well as opacity/blending are some of the most common, if not THE most common techniques used in video projects! Having an anomaly of this nature showing a DISTINCT difference in quality output when one of your fantastic "features" is enabled is just poor form. What is evern poorer is your responses (or lack thereof) related to the issue. Especially seeing as this problem has been present since CS5, and now we are STILL seeing it in CC!
Here is a thread which documents the issue well (even shows examples, and other details someone prepared for you to apparently ignore):
...it was never addressed there.
Another issue which details it going back as far as CS 5.5:
...once again, never resolved.
Now I am using CC, latest version, up-to-date, a fast i7 processor, a CUDA supported card, and all of those go to waste because I have to have GPU and the mercury playback engine disabled to yield decent quality results.
I implore you, not just for myself, but on behalf of everybody here who has already addressed this issue, but has had their pleas fall on deaf ears: PLEASE FIX THIS PROBLEM. Telling us simply that: "This is the way GPU cards choose to render" is NOT ACCEPTABLE. It's just like me saying when I drive my car on the wrong side of the road: "that's just the way I drive!". Doesn't mean it is acceptable!
You may have won people over since Final Cut Pro screwed the pooch with version X... but I can guarantee if this does not get resolved soon, the issue won't just be isolated to the forums here. Expect to read about it in MANY online publications that I am sure your competitors will ENJOY watching!