Re-encoding .avi's (to higher resolution)

[prOnorama]

I'm looking to make a compilation movie from several .avi sources (DivX/XviD) mainly. I want them all to the same resolution so I can join them to 1 (Xvid) compilation. They have various resolutions (mainly 512 x 384 though some 640 x 480, 576 x 432 or 448 x 336)

I would prefer 512 x 384 resolution. What would be the best way to go: re-encode the ones with 448 x 336 to 512 x 384 or re-encode everything to the lowest resolution (448 x 336)? (I fear there might be be heavy macro blocking if I upscale the resolution of a clip, but I'm not sure hence my post here).

Re-encoding to 512 x 384 would be the least work by far, so if the ones with 448 x 336 resolution can be upscaled without much loss of quality that would be the way to go ;)

Maybe anyone with re-encoding experience can shed some light on this :)

[BigCondor]

Since the resolution isn't differed by a high percentage so I think you wouldn't see any noticable change.
Perhaps you can experiment with small clips first to try things out and see what suit you most.

[prOnorama]

They are actually almost all 4:3 PAL, I might have to convert a few from NTSC to PAL to get 25 FPS, but the main thing should be there's not too much quality loss if I upscale from 448 x 336 to 512 x 384

[Brother John]

Upscaling itself will not create any macroblocking. Those are encoding artefacts. Only problem might be, if your source clips already are of low quality. Then already present blocks will grow larger and easier to spot.

512x384 seems the most reasonable way to go. Because every re-encoding means loss of quality, the less clips you have to re-encode the better.