Jim Tonge wrote:
IMHO, plus points for the Sony include no-light nightshot for your
Blair Witch-style fun, and a (albeit low-rent) Carl Zeiss lens. The
audio jack is the main selling point for me though.
"...the GOP length will affect the ability to edit the output."
I've never really understood GOP (I know it's to do with interlacing,
right?) - could you point me in the direction of a clear explanation
please?
No, nothing to do with interlacing (i.e. you have a GOP with any MPEG
interlaced or progressive video)
It is the Group of Pictures. In MPEG you can encode each frame as
I-Frames, P-Frames or B-Frames. I-Frames have the complete image,
P-Frames are predicted based upon changes from an I-Frame or previous
P-Frame. B-Frames are similar to P-Frames, but bi-directionally
predicted (n.b. this implies out of order frame encoding in the encoder)
from I, P and B-Frames. A GOP is a sequence of I, P and B-Frames e.g.
IBBPBBPBBPBB
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.
Broadcast contributions e.g. DV, use I-Frame only codecs to allow frame
accurate editing.
--
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*Simon Thompson MEng MIET *
Research Engineer (Electronics)
PRINCE2^TM Registered Practitioner
*BBC Future Media and Technology*
