On 11/20/2017 3:19 PM, Dave Rice wrote:
> TN2162 requires a colr atom for uncompressed yuv (including v210, v308, v408, 
> etc) in mov, so I'd prefer to write it in this case. Note that the colr atom 
> provides an option for unspecified for each of the color values, so there's a 
> method to write a colr atom which basically says ¯\_(ツ)_/¯.


> I disagree. I'd prefer to follow the specification and write a colr atom (in 
> the case of uncompressed yuv in mov) that say the colr is unspecified rather 
> than to write no colr atom at all and create an invalid file. See 
> https://developer.apple.com/library/content/technotes/tn2162/_index.html#//apple_ref/doc/uid/DTS40013070-CH1-TNTAG9.
> I do agree that guesswork should be avoided or provided under an option that 
> users could opt into. I suppose my preference order from support to oppose 
> for writing uncompressed yuv in mov would be:
> 1: write a colr atom in all cases (if unknown, use unspecified values in colr 
> atom)
> 2: write a colr atom if color data the known (no colr atom if unknown)
> 3: write a colr atom in all cases (if unknown, just make stuff up, #yolo)

My opinion falls somewhere in between, to something like this (in pseudo-code):

    if (colors_known) {
    } else if (uncompressed_yuv) {
        if (guesswork_user_option) {
        } else {
    } else if (guesswork_user_option) {
    } else {
        // Don't write a colr atom because it adds no value, to write 
unspecified in it
        // and no spec requires it for compressed streams.

Does this make sense?

- Derek
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