What determines the amount of compression

[tenznet]

This is what I got with the following movies. These results are from clonedvd2, BTW DVDShrink gave me pretty much same results ratio without menues.

The Negotiator: 2h:19m:27s got 83% compression with menues
audio: english dolby AC-3/6
subtitles: english

Die Hard 3 : 2h:08m:24s got 66% compression with menues
audio: english dolby AC-3/6
subtitles: english

Air Force One : 2h:04m:28s got 67% compression with menues
audio: english dolby AC-3/6
subtitles: english

Why is it that a longer movie like The Negotiator got better compression than a shorder movie like Die Hard 3 or Air Force One. Obviously length of movie is not the only factor.

[johns0]

Bitrate.

[ZippyP.]

Obviously length of movie is not the only factor.

It's the size of the movie file that matters. The size of the file was set when it was made and it's the bitrate used and the running time which determines the size of any video file. Higher bitrate generally means better quality (up to a point) and high action movies need a higher rate to keep quality. Hope that helps.

[adam]

These programs you mention are compressed domain transcoders. They work by compressing DCT data. So the more DCT data present in the source, the more there is to compress. Basically, regardless of length, one movie might be compressed with a great deal more bitrate then another. This adds up to more DCT data, and thus you can compress it more then another source and maybe even still achieve overall better quality.

[yoda313]

Hello,

Also the amount of audio data will effect it too. If you have just a stereo ac3 track it takes up less space then a 5.1 track. Also if it includes more than one track or includes DTS (which is VERY large) it will effect the quality of the video to make room for the larger audio.

Kevin