Resolution doesn't matter for bitrate calculation?

[Leviathan]

I was just wondering this point because bitrate calculators never seem to take the final size of the movie into consideration. It could be 720x480 or 640x272 and the bitrate still stays the same. So, my question: As long as I have the correct length, audio bitrate, and final size of the movie I want, will the video bitrate stay the same regardless of resolution?

[jggimi]

Bitrate = filesize (in bits) / time (in seconds).

You are correct. Average bitrate is determined by file size.

Therefore, when you lower the resolution, you have les pixels per frame. This means, you can get by with much less compression with the same file size.

I use GKnot. It uses bits / pixels * frames to provide an estimation of "quality" for any setting of resolution and any setting of file size. If you're unfamiliar with it, it is a bitrate calculator for SBC, DivX, and XviD codecs.

Most Gknot users start by setting the resolution to provide reasonable bits / pixels * frames, then run Gknot's compressability test. That gives a much better estimation of the compressability of the content, and a feel for final video "quality".

I hope that helps.