I've ripped some CGI videos from a game and I wish to upscale them for a number of reasons (mainly because Youtube allows a much higher bitrate for videos that are uploaded in HD) but I don't know which is the best method/algorithm for doing so.

Normally when I need to resize videos I use the built in Resizer in Avidemux with the Lanczos3 algorithm. While this gives a much better result than letting the video player do the upscaling, it's far from perfect. Ideally, I want something that won't lose too much sharpness over the whole scene, similar to what was used to upscale FF VII Advent Children for the Blu-Ray release (it was rendered at less than 1080p for those who didn't know).

If anyone can suggest their preferred method I'd be grateful. Free software is greatly preferred but if the results are good enough I wouldn't disregard a paid solution.

avisynth, need a really steep learning curve though.

With most resize algorithms there's usually a trade-off between the sharpness and the unwanted visual artifacts (usually "ringing" - sort of shadows around sharp edges). The sharper the result is, the more unwanted artifacts it usually has. Avidemux supports the 3 major resize methods (from sharpest to softest): Lanczos(3), bicubic, bilinear.

Bilinear probably will not be sharp enough for a nice upscaling, but bicubic might do the trick nicely and with little artifacts.

If your source is very low resolution and upto 256 colors (e.g. 8-bit game consoles), there are specific scalers for such images, you can read about it here. I'm not sure Avidemux supports them, but mencoder might, as well as avisynth, possibly with some plugins.

Good luck.

BTW, I had exactly the same issue as yours, and same upscale solution, also using Avidemux, with this video. Though now that I look at it, it probably could be sharper...