Use log2_{v,h}_chroma_subsample #94
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ffv1.md
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| PDF:`h_chroma_subsample` indicates the subsample factor between luma and chroma width ($chroma\_width=2^{-log2\_h\_chroma\_subsample}luma\_width$). | ||
| RFC:`h_chroma_subsample` indicates the subsample factor between luma and chroma width (`chroma_width = 2^(-log2_h_chroma_subsample) * luma_width`). | ||
| PDF:`log2_h_chroma_subsample` indicates the subsample factor, stored in powers to which the number 2 must be raised, between luma and chroma width ($chroma\_width=2^{-log2\_h\_chroma\_subsample}luma\_width$). |
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I suggest avoiding lowercase must to not confuse with RFC2119 meaning. Also stored in powers to which the number 2 must be raised seems passive wording. Could you say the base-two logarithm of the subsample factor...?
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same comment applies 3x below
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PR updated with the suggested wording.
ffv1.md
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| `plane_pixel_width[ p ]` is the width in pixels of plane p of the slice. | |||
| `plane_pixel_width[ 0 ]` and `plane_pixel_width[ 1 + ( chroma_planes ? 2 : 0 ) ]` value is `slice_pixel_width`. | |||
| PDF:If `chroma_planes` is set to 1, `plane_pixel_width[ 1 ]` and `plane_pixel_width[ 2 ]` value is $\lceil slice\_pixel\_width / v\_chroma\_subsample \rceil$. | |||
| RFC:If `chroma_planes` is set to 1, `plane_pixel_width[ 1 ]` and `plane_pixel_width[ 2 ]` value is `ceil(slice_pixel_width / v_chroma_subsample)`. | |||
| PDF:If `chroma_planes` is set to 1, `plane_pixel_width[ 1 ]` and `plane_pixel_width[ 2 ]` value is $\lceil slice\_pixel\_width / ( 1 << log2\_h\_chroma\_subsample) \rceil$. | |||
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oops, glad to see this fixed (v->h), though unclear why there's now a bitshift
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Bitshift is due to the use of log2 version of the value, and means "2 power x" (see Derek comment on CELLAR)
JeromeMartinez
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"log2_v_chroma_subsample` indicates the subsample factor, stored in powers to which the number 2 must be raised between luma and chroma height" This sounds very odd, is this correct english ? |
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Should have been changed after Dave comment, something went wrong, I force update tomorrow. |
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@michaelni I check the current version of the PR, the text you are looking at is from a former version of the PR, now you should have |
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73e6f51 introduces a typo: (,) |
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Fixed + rebased. |
Use log2_{v,h}_chroma_subsample everywhere instead of using log2_{v,h}_chroma_subsample and {v,h}_chroma_subsample depending of the context.
Issue reported by @dwbuiten
& a small typo making the spec wrong.