A few misc question

[chet]

firstly sorry if this is in the wrong forum, but I thought this would be the most appropriate.

Right - I've just got myself a 5g (video) iPod, and am converting divx videos to mp4 (the stupid thing doesn't support / play divx). Doing this has just made me more curious about the topic. I have a few questions:

(a) If the video I have is encoded at say (for example) 624 x 352, is there any point in re-encoding it at a resolution higher than this? (this is a bit of a funny resolution, no?)

(b) If the video I have is encoded at say (for example) 1Mbps, is there any point in re-encoding it at a bitrate higher than this?

(c) tell me about bitrates... and the difference between CBR and VBR? I'm encoding @ 768kbps (and 640 x 360 for 16:9 material) with pretty good results.

(d) I've been told that the product of resolution must be less than 230400 ("bandwidth") (H x W < 230400), and that (H x W)/256 < 900). I'm confused.

cheers for any help.

[nurbs]

a) Upscaling to a higher resolution would be a bad idea sice the iPod only supports resolutions up to 480*480 at 30fps according to the posts in the MeGUI profiles thread.

Can't help you with the other questions, sorry.

[Richard Berg]

First of all, the iPod DOES support MPEG4-ASP codecs like Divx. Whether your existing files will work depends on what Divx settings you used.

(a) No. The iPod screen is only like 320x240, so even if you spent lots of CPU power on really fine upscaling, it would be worthless.
(b) No. Maybe if (again) you spent a lot of CPU time cleaning up artifacts in the original encode, but the iPod can't handle high bitrate encodes anyway.
(c) CBR is pretty dumb if efficiency matters. No video distribution codec is CBR by default.
(d) What's confusing? 230400 / 256 = 900.

[bond]

firstly sorry if this is in the wrong forum, but I thought this would be the most appropriate.moved to where general asp belongs