why do most people record divx at 640(w) or less and not 720

[zenhack]

Is playback performance the only reason someone would downsample a 720*480(720*304 for widescreen) source (like a dvd) to 640*480 or less?

[Gazorgan]

Yes.

Look, if you take a 5 GB MPEG2 DVD, and convert it to DivX, with the AC5.1 audio track, and you leave it 720x480; it will be 2 GB when you done with no artifacts.

Most people don't want a 3 CDR DivX movie. So, they turn the compression up and the resolution down. This drives the bitrates down to the 2 CDR level. 1 CDR DivX are strictly VCD resolution only. 2 CDR movies are usually 'good enough' for most people, especially if it's 2-pass VBR.

Also, most people confuse Resolution with Aspect Ratio. A 640x480 DivX is truly 4:3. Since a computers pixels are square and a TV's are rectangles, aspect ratio and resoltuion can be different. 720x480 is 4:3 on a TV, but not on a computer.

[zenhack]

gazorgan,

So let me ask you this, if i were to take a 2 hour movie, and convert it to 720*306 w/ 384 kps ac3, do you think 1.46GB (1/2 of a dvdr) would be enough to maintain (in general) high quality?


Also, since you brought it up, a question of aspect, i'm making some divx movies with intention of watching them primarily on a tv. To this end i will use a tv out video card or the XCard from sigma. I think my tv out card can support NTSC resolution(720*480), but i'm not sure how the XCard handles resolution ratios. I'm just trying to decide on the optimal resolution for divx to most faithfully reproduce the original NTSC source, i don't care about the bitrate as long as i can get 2-3 movies on 1 dvdr.

what do you advise?

[zenhack]

err meant 1.46gb (1/3 of a dvdr)