Fission
October 23rd, 2003, 05:43 PM
Enlightenment....lol...I didn't know what else to slam in there :p
Anyway, the post a few days ago grabbed my interest about film aspect ratios that was posted here and I wanted to respond, but thought it would be more suiting for just a new topic.
Anyway I thought I would mention this just in case anyone ever thought why the hell do I see some NTSC pixel ratios at 720 x 486 and some at 720 x 480. From what I know this is what's up and just wanted to share it: (This is beginner's talk so hopefully it may help someone)
NTSC CCIR-601 (broadcast) is 720 x 486
NTSC DV is 720 x 480
Modern digital video applications such as DV, DVD and digital television often use MPEG-1 or MPEG-2 formats (or their derivatives) which are all based on 16×16 pixel macroblocks. Having the height and width of the image readily divisible by 16 makes it easier and more efficient for an MPEG encoder to compress video.
The guys out here that use 3D apps and paint textures will know this because its the same deal. We (for most artists) make our texture maps that are easily divisible dimensions....256x256, 512x512, 1024x1024 etc. and the computer can make more efficient and faster calculations when rendering.
So modern DV equipment will usually crop 6 lines off to make it 480 which is easily divisible by 16....
486 / 16 = 30.375
480 / 16 = exactly 30
Almost done......the most important thing to know here is that NTSC pixels are also not square, they are slightly taller than they are wide (thus the 0.9 value). Computer pixels are square. (If you ever design a DVD interface you'll run into this and there are certain format sizes you have to be aware of to avoid crazy strectching of your images)
I really hope this is correct and helps somebody out at sometime. If you have something to add please do, and if I made an error please let me know so I don't mislead anyone here. Thanks.
If anyone out here has a chart handy comparing NTSC, PAL, HDTV and film formats it would be cool if you could post it. Just as a reference for us artists that want to start a project in a certain format but are not sure of what pixel ratio, aspect ratio's, etc to start with. I think that would be a cool contribution here.
Cheers
Anyway, the post a few days ago grabbed my interest about film aspect ratios that was posted here and I wanted to respond, but thought it would be more suiting for just a new topic.
Anyway I thought I would mention this just in case anyone ever thought why the hell do I see some NTSC pixel ratios at 720 x 486 and some at 720 x 480. From what I know this is what's up and just wanted to share it: (This is beginner's talk so hopefully it may help someone)
NTSC CCIR-601 (broadcast) is 720 x 486
NTSC DV is 720 x 480
Modern digital video applications such as DV, DVD and digital television often use MPEG-1 or MPEG-2 formats (or their derivatives) which are all based on 16×16 pixel macroblocks. Having the height and width of the image readily divisible by 16 makes it easier and more efficient for an MPEG encoder to compress video.
The guys out here that use 3D apps and paint textures will know this because its the same deal. We (for most artists) make our texture maps that are easily divisible dimensions....256x256, 512x512, 1024x1024 etc. and the computer can make more efficient and faster calculations when rendering.
So modern DV equipment will usually crop 6 lines off to make it 480 which is easily divisible by 16....
486 / 16 = 30.375
480 / 16 = exactly 30
Almost done......the most important thing to know here is that NTSC pixels are also not square, they are slightly taller than they are wide (thus the 0.9 value). Computer pixels are square. (If you ever design a DVD interface you'll run into this and there are certain format sizes you have to be aware of to avoid crazy strectching of your images)
I really hope this is correct and helps somebody out at sometime. If you have something to add please do, and if I made an error please let me know so I don't mislead anyone here. Thanks.
If anyone out here has a chart handy comparing NTSC, PAL, HDTV and film formats it would be cool if you could post it. Just as a reference for us artists that want to start a project in a certain format but are not sure of what pixel ratio, aspect ratio's, etc to start with. I think that would be a cool contribution here.
Cheers