yuv: Use more accurate BT.601 coefficients #12
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Nope, this doesn't work, sorry. |
torokati44
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Okay, I did end up making this work after all! Sorry for the spam... :| |
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This also matches exactly what the SWF specification says about the YUV to RGB conversion, for at least VP6 video. |
kmeisthax
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Sep 24, 2021
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I merged in the other PR about nightly warnings, but we don't have the CI fixes from Ruffle itself in here, so I'm still going to need this to get rebased so the CI can pass. |
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Rebased, hopefully it'll pass. |
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In the spirit of preferring bite-sized PRs instead of comprehensive rewrites, I split this out of #9, as it is a relatively independent change.
Quoting #9 (comment) as explanation:
While adding tests, I also discovered some off-by-one errors in the results. These were caused by rounding more than necessary.
So I switched to a more precise formula to precompute the linear functions, with coefficients taken exactly from the BT.601 standard. (I'm much happier with these, instead of those 5 float literals just copied from a random piece of code somewhere.)
Now that all of this goes into a lookup table anyway, the cost of all of these additional computations shouldn't matter that much. (They are only done once, and only on the 256 values of a
u8.)