Jeremy James wrote:
Simon Thompson wrote:
The GOP length is the number of frames between successive I-Frames. A
long GOP length will, for example, cause a delay on video appearing on
changing channels on a STB or, as editing cuts can only start from an
I-Frame will mean you can't do frame accurate editing.
I disagree with "can't" - the Sony XDCAM EX1 is a serious camera
intended for broadcast use that uses long-GOP MPEG2. However, editing is
indeed harder since the software needs to be clever about how it handles
the content. You potentially have to decode a fair number of frames to
show the one you want, and (unless re-rendering) you need to keep up to
the previous I-frame before any edits made in your source material
throughout the editing process.
BBC R&D did some work on this a few years back - here's a white paper
from 2006, for example, if anyone's interested:
http://www.bbc.co.uk/rd/pubs/whp/whp138.shtml
The basic finding was more or less what Jeremy said - that long-GOP
video encoding makes life harder for the people who write video editing
software, but doesn't make frame-accurate editing impossible by any
means. You have to trade the advantages and disadvantages of recording
with a long-GOP codec according to circumstances - a state of affairs
that will probably surprise nobody. :-)
S
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