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Table Of Contents
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Burn to Disc (VCD, SVCD, DVD)
GOP
GOP (Group of Pictures) relates to the sequence of I, P and B frames used for MPEG compression. I
frames (intra-codec picture) store the contents of an image at their full resolution; P and B frames each
store changes in the image that occur between I frame and I frame. P stands for forward Predictive pic-
tures and B stands for Bi-directional pictures. GOPs are very basic elements of an MPEG stream. A GOP
can have the following appearance:
I-B-B-P-B-B-P-B-B-P-B-B-P-B-B-I
I-frame only
In the case of the Elementary Stream and Program Stream Destination formats: Click this option to
export a stream consisting entirely of I-frames. Afterwards, the N and M value can no longer be changed.
GOP Size
The GOP size (aka N value) is measured from I frame to I frame. The shorter the GOP, the more I frames
with relation to the overall MPEG sequence; the longer the GOP, the fewer the I frames in an MPEG
stream. Short GOPs require a higher bit rate because more I frames also means more data.
Keep this in mind if you want to modify the GOP.
GOP sizes:
Software Encoding (export):
- NTSC 16 (4..16); closed GOP
- PAL 13 (4..13); closed GOP
(A closed GOP ends on a P frame; an open on a B frame.)
- NTSC 18 (4..18); open GOP
- PAL 15 (3..15) open GOP
Recommended for DVD: open GOP (standard), PAL 12, NTSC 15.
IPB-Capture (Logging Tool):
NTSC 15 (4..16); closed GOP; recommended for DVD: 15
PAL 12 (3..15); closed GOP; recommended for DVD: 12