Divx resolution ?

[PoH]

I have tried to understand this but...
When I have ripped a DVD I look at the video
resolution and it says:720*576 pix
But when I am saving the output video file (DIVX) I can't understand what resolution I should use. When I crop the outout file to remove the black borders at the top and bottom, how can I calculate the resolution ??
If i don't have to crop the file, what resolution should I use then ??

thanks

//PoH

[mats.hogberg]

You're free to choose. Most DivX's Ive seen are 640 wide, the height set proportionally. But "anything goes" - lower resolution requires lower bitrate, which leads to smaller AVI file.

/Mats

[Gazorgan]

Not quite anything goes. DivX (and XviD) needs to be in multiples. Depending on what you read where, vertical and hotizontal resolution should be in multiples of 8. I have much better luck (less macroblocking) with multiples of 16. Combine this with 4:3 and 16:9 aspect ratios and suddenly you know why certain resolutions are always seen.

[EddyH]

Assuming you're making it for a 4:3 screen, i.e. a computer monitor...

Crop the picture. Resize it to 640, 512, or 400 wide (as a general guide..) depending what rez you think you'll be viewing it in. 512 will look good on a 1024x768 screen which is currently quite popular, whilst 640 has just that tiny little edge in sharpness (and can be viewed on a 640x480 display - and so with most TV out cards - or at 1280x1024 for sublime progressive-scan/HD like quality).

The next bit is trickier and im having trouble thinking of an easy explanation

Simpest: Work out what % of the full frame the cropped pic takes across. Then find out what 480 or 576 is times that percent. Divvy your cropped height by that, then multiply again by 480*, 384 or 300, then snap to the nearest multiple of 8; or of 16 if it can be managed without obvious stretching. That should work OK most of the time...

* ie if you're converting from an NTSC DVD to 640 wide, you can pretty much keep the cropped vertical height the same, just remember to round to the nearest 8 as oddly many dvds aren't right on the block boundaries. Similar for PAL at 640, but simply make it 5/6ths of raw crop height (480/576) and modulo-8..

[EddyH]

Example: Current conversion of a PAL DVD that's letterboxed & sidebordered to the equivelent of something slightly wider than a full 16:9 screen (though it's a 4:3 frame )

First go, aimed it at 640x352 (after deinterlacing* and that 5/6 size decrease), as that was the best mathed fit and a fairly common resolution. Looked a tiny bit squashed in tests (car wheels looked a bit bent, etc) so increased it just a touch to an even better fit, but a little less optimal/common, 640x368.

However had a hell of a time making that look good inside of 710mb with decent sound, so shrunk it down to 512 wide (a better fit for my screen, too). This reduces the height, at best/optimal fit, to a nice 288, an easily legal height as it's used in PAL VCDs
Looking good so far, doublesizing on an XVGA screen. Also has the advantage that it could be very simply horizontally squooshed down, to make a fullscreen 16:9 VCD, if ever needed.. very slight aspect error perhaps, both one way for PC and the other on VCD, but shouldn't be noticable.
(Or equally simply resized to 480x576 for SVCD/512x576 in a 528/544 wide frame with KVCD - yeah, upsampling is blasphemy i know)
(has kwag made any 528x288 templates yet? )

Blaaaa

Just some example sizes for you.


* usually you wouldnt need to deinterlace a PAL movie, but this disc was special. Like it used to get on a different school bus..