Does resolution effect bitrate

[jpc82]

I've been playing around with bitrate calculators, and I confused whether the resolution effects the bitrate at all.

I used a calculator to set the length(118min), resolution(352x288), and the size I wanted (800MB), which told me the bitrate would be 877. I then upped the res to 512x400, and it had no effect on the bitrate. Now I'm fairly new to Xvid, but I would assume that as I upped the res it would use up more of the bitrate.

Can anyone explain to me what is happening.

BTW. I used the bitrate calculator byNitroGen, and the one built into Dvd::Rip for linux.

[ZippyP.]

The only thing that affects the size of the file is the running time and the bitrate. Seconds x bits-per-second = total bits

Now resolution is something you need to consider when selecting a bitrate. Higher resolutions need a higher rate to keep looking good, conversely, at lower rates it's better to have a lower resolution. What bitrate-resolution combo looks good to you is for you to decide.

[zedolfblack]

You might want to do a little research on the 'bits per pixel' quality factor of a movie.

Increasing the resolution of a video without increasing the bitrate will mean less bits per pixel - and an overall reduction in the movie's quality.
Using a lower resoltuion with the same bitrate equals more bits per pixel and a movie that should look better.

I use a utility called Aspect it's a fancy bitrate calc that tells you the bits per pixel value of your video.
In it's help file it states:
'To achieve good video quality bit/pixel value must be kept at the level of 0.15 or higher. If you get lesser value, either increase movie size (burn it on two cds instead of one) or decrease frame size.'

Aspect homepage http://www.geocities.com/vestadomain/videoutils.html

Martin.

[jpc82]

Thanks for the explanation, it makes alot more sence now.

BTW aspect is a great app, thanks for the recomendation