Re: [Hampshire] Editing DVD content?

> DVD is a problem. It uses MPEG2. It uses compressions that relies of
> prediction from previous frames.

MPEG2 uses bidirectional prediction; each GOP may contain the first image
(I-frame) to be displayed, the last to be displayed (P-frame), and then
the ones in the middle (B-frames)
.
> As such, it is considerably more
> difficult to edit, because if you try to cut out one of the frames
> used to predict another frame, the editor has to re-encode the stream.

It has to re-encode the GOP. That's not exactly onerous...

> Generally, editing a MPEG2 stream results is a
> loss of quality on the output, due to the re-encoding requirement. DV
> streams do not require any re-encoding so the quality is preserved.

Errr - I don't think you're comparing apples with apples there...

Any time you re-encode video you run the risk of dropping the quality
because blocking artefact noise becomes general HF noise as soon as you do
a motion prediction - but that's not what you're seeing. You're seeing the
difference between a 25Mb/s DV stream with a DVD stream that is generally
<10Mb/s (often much less). VBR is a Good Thing(tm), but DVD I-frames are
inevitably bandwidth-limited in the general case...

Vic.