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luma/chroma shifts on rendered dissolves in FCP
Hello there
I hope someone might be able to shed light on an annoying problem I’m having.
The problem: When I play a rendered dissolve between two clips in Final Cut Pro, there is a small but noticable jolt in colour (or maybe luma?) at the head and tail of the dissolves.
The setup: HD 1080i quicktimes, encoded from targa sequences using Apple’s uncompressed 8bit codec. Using FCP 5 and AJA Kona 2. Outputting HD from FCP and Kona, downconverting to SD via HD deck.
I’ve tried setting the sequence to render in RGB, YUV or YUV high precision; they make no difference (so I just stick to YUV).
The only workaround I’ve found is to modify the alpha channel of any clips that will need rendering, from the default ‘none/ignore’ to “straight”. This means the whole clips becomes a red-bar render; however, it does solve the problem of the colour/luma jolt. I don’t understand why this works, but it does.
This solution is not very practical though, because it adds a fair chunk of extra rendering time to all my playouts (and I’ve got a lot of them to do!). Also, I seem more likely to get dropped frames on playout when playing rendered material. Currently, with all this rendering, (and with having to restart at least once on each playout attempt due to dropped frames), it is taking me a minimum of one hour to lay down a 10 minute programme.
Any recommendations or ideas very welcome!
thank you
Richard Overall. -
2 Replies
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Richard.
Here is a simple workaround for render times. Use the razor blade to make splices around the dissolves.
Are you seeing these “pops” on the Apple display or the external display?
David
Peace and Love 🙂
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Thanks for your reply.
I’m getting the pops on the external display. If I use the razor blade to cut either side of the dissolve, I still get the pop, because it is the rendering of the dissolve that changes the colour/luminance. So there remains a noticable change at the point that the dissolves start and end. For now I’m just going to keep using the mysterious workaround of changing all dissolve clips to ‘alpha type – straight’, and rendering the whole clip.
regards
Richard.
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