Have just bought TMPGEnc MPEG Editor (Its no longer free!) and have cut sections from a 1hr 53 min long MPEG2 video clip (1,779,089 KB),making it exactly 1hr long. When I come to save the shortened clip as a 'Common MPEG' file it fails with the message insufficient disk free space available, 6.53 GB free space needed. I am saving to a partition with 3.83 GB of free space so clearly it is not enought. But can anyone explain why such a comparatively short video clip requires such a lot of free space to be saved?

Well, here's my theory on this.

In basic terms, MPEG2 uses delta information between two key frames and these are not full frames. So, in essence you will have a key frame (I-frame) which will be a full frame with all the the image content and then you will have intermediate frames (P and B frames) which in themselves do not contain all the image data but just information on what's changed (this is very high-level btw).

When you go to transcode this to standard MPEG, then all those intermediate frames become full frames again. I believe this is why the file size increases.

Alternatively I could be talking complete and utter twaddle.

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Lloyd

That's my opinion. If you don't like it I have others

System: Apple Macbook Pro 17, and an external Freecom 500GB eSATA drive.
Software: Final Cut Studio 2 (FCP 6, Motion 3, Soundtrack Pro 2, Color, DVD Studio Pro 4, Compressor 3), Sonicfire Pro 4.5
Favourite Resources: Findsounds.com, Free DVD menus, Ken Stone's FCP Page, Wikivid

Depends on the above and the comparative bitrates. As Lloyd says, file sizes of MPEG2 video will vary according to the variables used in the encoding process. I would suggest that you use a bitrate calculator to get the right size of video for any given length.

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