Appendix A — General Registry Settings
83
GOP Structure and Size
Let’s look at some examples:
When determining which settings to choose, you must consider whether it is more
important to end the encode precisely on the mark-out, or if it is more important
to achieve the optimum video quality. Including B-frames in each GOP improves
video quality, especially at low bit rates. On the other hand, setting both I-frame
distance and Ref-frame distance to 1 guarantees frame-accurate stops.
I-Frame
Distance
(N Value)
Ref-Frame
Distance
(M Value)
Open or Closed
GOP Structure
1
1
Either
II…(I-Only)
2
1
Either
IPIP…
4
1
Either
IPPPIPPP…
2
2
Open
IBIBIB…
6
2
Open
IBPBPBIBPBPB…
3
2
Closed
IPBIPBIPB…
7
2
Closed
IPBPBPBIPBPBPB…
3
3
Open
IBBIBBIBB…
6
3
Open
IBBPBBIBBPBB…
4
3
Closed
IPBBIPBB…
7
3
Closed
IPBBPBBIPBBPBB…
Table A-3. GOP Structure Examples