What resolution do I use for a widescreen video for XVID?

astronoobx · Post by **astronoobx** » Tue May 23, 2006 10:00 pm

Its my first time making a video that isn't 640x480.
What resolution do I make the video if it is in widescreen for encoding with XVID?
Would I use 640 x 360?
Ah... sorry, I don't remember what the rule was but it was something about the resolution having to be multiplied by 4 or something?...
Thanks for the help dudes and dudettes.

Qyot27 · Post by **Qyot27** » Tue May 23, 2006 10:08 pm

16, actually. The filter VDMod Resize for (VirtualDub) can help with this. It allows you to not only specify an aspect ratio, but also force the results for the height and width to be multiples of 16. The filter can be found on VirtualDubMod's Sourceforge page, and a few other places online. To find the corrected size, you'd look at the right-most dimensions it gives in the blue topbar (can never for the life of me remember the technical term for it), but you can't miss it.

For a 16:9 ratio image, the necessary dimensions (at multiples of 16) are 640x368. It could also be 640x352, depending on the circumstances (meaning, it's anamorphic or otherwise widescreen footage upsized to 480 height, and instead of rounding the width down to 848x480, you rounded up to 864x480, which results in the 640x352 image when scaled down to 640 width).

Keeper of Hellfire · Post by **Keeper of Hellfire** » Wed May 24, 2006 9:43 am

Why do you wanna make it that small at all? Why don't you keep at least one dimension in the size of the original footage, like you do it for 4:3? This would result in 720x400 frames, which have nearly the same number of pixels as 640x480 frames, if you're concerned for compression.

My personal preference is 768x432. Unlike the other formats used for 16:9 it is both, exact 16:9 and the dimenisons are multiples of 16. The number of pixels/frame is only 10% larger than for 640x480.

Qyot27 · Post by **Qyot27** » Wed May 24, 2006 12:22 pm

Keeper of Hellfire wrote:Why do you wanna make it that small at all? Why don't you keep at least one dimension in the size of the original footage, like you do it for 4:3? This would result in 720x400 frames, which have nearly the same number of pixels as 640x480 frames, if you're concerned for compression.

Well, it could be that every pixel saved counts toward the final filesize - 640x368(352) is more likely to need less bits than a video at 720 or wider width (and a lot more likely than a video at 848+ width), even if the savings are marginal at best. If you're authoring for NTSC DVD and plan on letterboxing it to 4:3 rather than making it anamorphic, you need to use 640 width to determine the height and calculate the borders, even though in the end you use that height and 720 width.

In the cases of my videos (the new ones anyway), though, I keep them at the resolution I edited at - [common] widescreen could be either 848/864x480 or 720x480 with a 16:9 flag. Of course, I'm also not using XviD anymore to compress them for Local distribution, so I don't have to be nearly as concerned with the filesize meeting the 100MB upload requirement.

Zero1 · Post by **Zero1** » Sat May 27, 2006 4:27 pm

Upscaling video is suboptimal. You are losing quality from resizing it to begin with and you increase the amount of space required.

My take on this would be to resize to 640x360 and crop to 352, or 720/704x400. It doesn't particularly matter if your framesize is not the correct aspect ratio, it's the actual video that matters.

Have a read at this, I go into much more detail about it here. You might even find it interesting:
http://forums.animesuki.com/showpost.ph ... ostcount=8