Chroma is lossier than luma in most common video codecs. AVC is 4:2:0 on YouTube. 4:2:0, quite confusingly, means that chroma is halved in both dimensions compa

Chroma is lossier than luma in most common video codecs. AVC is 4:2:0 on YouTube. 4:2:0, quite confusingly, means that chroma is halved in both dimensions compared to luma (so one chroma pixel is congruent with four luma pixels). As well, most decoders will apply filtering on the chroma to upsample it to match the luma, meaning that your color boundaries are going to be indistinct at best, and you might even lose the original chroma values entirely in the process. You'd have to use multiple chroma pixels as one metapixel in order to increase resilience, which would diminish the capacity. With modern codecs, a monochrome signal seems better to use for actual data, although I could see it being useful to use chroma for metadata.