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ProRes422 codec 4:4:4 chroma filtering
There is an option to enable 4:4:4 chroma filtering, what does it do?? Generally will it brings better results ?
Thank you.
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5 Replies
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Hi Esky,
When you digitize video to a “Chroma Downsampled’ format (420,411,..) basically you make blocks of four pixels and you record the Luminance information of each pixel. But the Chroma is averaged so you keep only one value for the four pixels.
When you play or render the movie, this chroma is combined with the Luminance value of each pixels. This is what produce the “Blockiness” typical of the DV footage. The Chroma is applied in lineal fashion to all the four pixels.
But if you apply a “Chroma Filtering” the Chroma is not applied in the same way to the four pixels. “Chroma Filtering” try to re-build the original Chroma as it was before down-sampling.
It makes the DV footage looks definitively much better.
When working with 422 footage you have two chroma samples for each four pixels block. You don’t have the blockiness of the DV so really no the same need for Chroma Filtering,
When I work with ProRess, by default I let it OFF but is something that I still have to consider.
Rafael -
Thanks Rafael for the response and Esky to bring this up. I found this post very useful myself.
Carlo
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Are there any stats on if this:
1. Increases encoding time significantly
2. Increases filesize -
Hi Elijah,
I don’t think that affects the compression time. I think that just add a kind of flag to force the Chroma Filtering on playing.
But that is just my theory. I have no info at all about how that really works.
Rafael -
Hi Elijah,
Having a second look, I’m think I was wrong.
The text has changed in the Prores compressor panel.
I think before was “Enable 444 chroma filtering”.
Now writes “Enable chroma filtering for 444 sources”.
This must affects how the 444 stuff is down-sampled to 422.
I think I wouldn’t check this button.
Rafael
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