MPEG2 - How many bits per channel?!

[Cunhambebe]

I've got a doubt here. When I render a sequence with my Lightwave to Targa, I can choose for instance Targa 32. After Effects now can work with 32 bits per channel. Combustion 3.0 already worked with 32 bits. I was just wondering how many bits per channel we get when we render to MPEG2 for the final output.
Thanks in advance.

[Abond]

I can be wrong here, but isn't this 32 a RGB32? If so MPEG2 (for DVD) is not RGB at all. AFAIK it has more bits for luminance than for chroma.

[Cunhambebe]

Thanks for replying but.... I don't get it.
Anyone??? Thanks

[Cornucopia]

When a 3D/Animation rendering process talks about "32bits" they mean:

32 total bits per pixel =
8 Red, 8 Green, 8 Blue, + 8 Alpha (transparency level)

This differs from standard 24 bit which doesn't have any Alpha channel, so everything is fully opaque.

"Per channel" is a misnomer here.
If it were to REALLY mean per channel, it would be:
32 Red, 32 Green, 32 Blue = 96 bits per pixel. AFAIK no system uses this much (or really needs to). Even HDR imaging usually only uses 16bits/channel.

MPEG2 8bit 4:2:2 is YUV with 1/2 rez on the U and on the V, so that = 16bits/pixel instead of 24.
DVD is 4:2:0, and DV is 4:1:1, both of which = 12bits/pixel.

SO, you won't use very much of those 32bits in the final viewing, but you shouldn't "miss" them too much either (that shows the weakness of the Human Visual System). However, it really doesn't hurt to have 32bit source files.

Scott

[Cunhambebe]

Thanks for the input, Scott. Thank u very much for the information, really!
C u around,
Mark