Question about video size

[dark.soft]

I have a really stupid question: I know that videos' height and width should be divisible by 16 because the mpeg4 macroblocks are 16x16, but if I make, say, a video with a resolution of 640x360, does this decrease the encoding quality? So, it's better to encode at that resolution or add small black bars to have an height divisible by 16?

[Backflip]

Not sizing by 16w x 16h or 32w x 16h risks also introducing video anomalies that wouldn't otherwise appear.

[sysKin]

If vertically, there shouldn't be any problems. It's horizontal resolution that is not handled well by some players/video cards, if not mod16.

Compression-wise, it's better to keep 360 than add black bars.

[dark.soft]

Not sizing by 16w x 16h or 32w x 16h risks also introducing video anomalies that wouldn't otherwise appear.

For example?

[Backflip]

Your common artifacting I guess - blockiness, discolouration, ya know your average-joe artifacts. Mind you I don't make it a habit of testing how much artifacting I get when I use non-recommended sizing because I know I shouldn't be sizing like that when it comes to XviD anyway :)

It'd be better to crop into it as much as possible so you don't need to encode any black bar.

Why not just use a DAR if you want to keep all of the picture etc?

[dark.soft]

It'd be better to crop into it as much as possible so you don't need to encode any black bar.

You mean that I should crop actual video in order to achieve a height divisible by 16? Yes I thought this solution, but I want all the resolution, and I don't know how dar (Display Aspect Ratio, right?) can help me.

[Teegedeck]

Crop, then resize. That's what Gordian Knot is there for (among other uses). GKnot has a 1:1 AR setting that lets you keep the original PAR.