2. 5 bpc (often called Thousands of Colors or High Color)
ÆThe 5‐bpc color mode was used for some very early video‐compression codecs. Today, it is mainly used for screen recording applications where it may provide better compression and performance than 8‐bpc color without any obvious degradation.
4.8 bpc (also called Millions or True Color) Sometimes called 24‐bit or 32‐bit mode. Æ The 32‐bit mode still uses 8 bits per channel but with an added alpha channel.
5.10 bpc
ÆThis mode is used in high‐end Y’CbCr authoring systems (such as Digital Betacam andD1) and some analog capture cards.
ÆIt provides 1024 gradations instead of 256, which reduces banding (uneven transitions in gradated colors), especially with multiple generations of effects.
ÆIt isn’t used in any delivery formats, although some authoring codecs support it. Æ provides 4X more accuracy per channel than 8‐bpc color when converting to or from 16‐bit‐per‐channel RGB in After Effects.
6. 16 and 32 bpc
ÆSome high‐end applications use 16‐bpc or 32‐bpc colour to preserve more colour detail.
Æespecially useful when you have a multi‐step authoring process, need to apply visual effects to your images, or when you convert from and then back to Y’CbCr.
COLOUR SAMPLING
‐Color sampling records fewer pixels of chroma (color) information than luma (intensity) information.
‐The terminology for color sampling uses an X:Y:Z format. X = number of luma samples that are described. Y = number of chroma samples perluma sample on the first, third, fifth, and succeeding odd lines. Z = number of chroma samples per luma sample on the second, fourth, sixth, and succeeding even lines. If this number is zero, the chroma sample from the first line is used.
• 4:4:4 ‐ Chroma is sampled every pixel with no subsampling.
ÆY’CbCr delivery codecs don’t use this format because it uses a lot of bits and doesn’t provide any additional apparent quality. RGB is always 4:4:4.
