Why is DV easier to edit?

[Rudyard]

When reading around here about camcorders I always read that minDV is easier to edit than mpeg (HDD&miniDVD) camcorders. This is also true for when reading about AVI vs MPEG editing wise.

I am just curious as to what you actually cant do with the more compressed formats (mpeg) that you can with less/uncompressed (dv/avi)??

For example in Sony vegas and Ulead video studio I have been able to import all the above formats and apply whatever editing I would like (I am not advanced though and as such my editing is basic at this stage).

I understand the opinion that you should do all your editing and then compress to maximise quality as oppsed to edit a compressed file and then recompress your edited footage.

But is it just a quality thing or is there certain things you are unable to do when working with MPEG video over DV/AVI, what do people mean when they say it is easier to edit??

[jimmalenko]

AFAIK the main issue is that every frame in DV-AVI is equivalent to an I-Frame or keyframe, whereas MPEG and other codecs used in AVI generally either have a GOP or keyframe structure.

For example, for MPEG every 15th frame is an I-Frame (PAL DVD-compliant MPEG) and for the popular MPEG-4 codecs every 250th frame is a keyframe (XVID/DivX default).

What this means is that with DV, you can cut on a frame-accurate basis with no re-encoding required, whereas if you try to cut MPEG or other AVI on a non I-frame or keyframe then you need to re-encode the GOP either side of the cut points.

[guns1inger]

DV is designed from the ground up as an editing format. As Jimmalenko has explained, each frame is effectively an I-frame, or completely self contained. Mpeg2 and mpeg4 are designed as delivery formats. They are much more effective at compression, but the trade off comes from the way they compress the data. This means they are much more dofficult to edit at the frame-accurate level without using specialised software. Have a read of this for a 'simplified' explaination of how mpeg2 encoding works -> http://en.wikipedia.org/wiki/MPEG-2