Clarifies fallback strategy and editorial clean-up #4
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Editorial clean-up
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| <p class="note">The <code>gAMA</code> and embedded ICC profile are provided solely for compatibility with processors that do | ||
| not conform to this specification.</p> | ||
| <p class="note">The <code>gAMA</code> chunk, <code>cHRM</code> chunk, and embedded ICC profile specified in the table above are | ||
| not necessarily accurate, and, even if accurate, their processing is not required to reproduce the image as intended by the |
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Not necessarily? They are known to be inaccurate.
Suggest "... in the table above are inaccurate, due to limitations in ICC V4 with HDR images. However, their processing is not required ..."
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@svgeesus Yes, at this point, all are inaccurate. I used not necessarily to keep the door open for some of these parameters to be accurate if/when more rows are added to the table in the future.
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I prefer to clearly state that the current ones are known to be very inaccurate.
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Ok. cHRM is in fact accurate (it reflects Rec 2020 primaries), so I plan to revise the note to state that ICC and gamma are inaccurate.
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| not conform to this specification.</p> | ||
| <p class="note">The <code>gAMA</code> chunk, <code>cHRM</code> chunk, and embedded ICC profile specified in the table above are | ||
| not necessarily accurate, and, even if accurate, their processing is not required to reproduce the image as intended by the | ||
| author. They are provided for graceful fallback for implementations that do not recognize the semantics associated with a |
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Positioning these as fallback is good. I don't know if it is graceful however. You end up with an SDR image with a peak luminance of 80 cd/m^2,, right? So the whole thing looks super dim?
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(That isn't a change request btw, just that I would like to understand the fallback better.)
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You end up with an SDR image with a peak luminance of 80 cd/m^2,, right?
Well SDR systems typically scale peak sRGB luminance to their peak luminance, so I would expect the same to apply here.
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I meant in the case where a system with HDR capability uses the fallback, because it does not follow this spec..
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I meant in the case where a system with HDR capability uses the fallback, because it does not follow this spec..
I do not think it is possible to predict exactly what HDR systems will do when processing an ICC profile that was not designed for HDR systems... some might map the 80 nits of the ICC profile to what peak SDR luminance would be in SDR mode, others might map it to 80 nits and others might map it to peak HDR luminance.
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| not necessarily accurate, and, even if accurate, their processing is not required to reproduce the image as intended by the | ||
| author. They are provided for graceful fallback for implementations that do not recognize the semantics associated with a | ||
| <code>iCCP</code> Chunk Profile Names defined by this specification. Future versions of this specification might include | ||
| additional ICC profiles, e.g. to reflect improvements in ICC profile capabilities.</p> |
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Like that part, it allows a V5 profile to be added later which actually describes the image.
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@svgeesus See update text. |
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r=me good to go |
Closes #3