Grass Valley PROFILE FAMILY v.2.5 - Manual (Page 170)

Chapter 4 Using VdrPanel
170 Profile Family
4. For MPEG settings:
- Select 4:2:2 or 4:2:0 chroma sampling.
- # P per GOP is the number of P pictures (predictive pictures) in a group
of pictures (GOP).
- # B per I/P is the number of B pictures (bidirectionally predictive
pictures) for every I-frame or P picture. B pictures improve compression
efficiency.
NOTE: Placing zeros in both # P per GOP and # B per I/P boxes
forces pictures to be I-frame only.
- Open GOP is a group of pictures that has a B picture as its last picture type
for the next I-frame, such as IBBPBBPBBI, and so on. An Open GOP
depends on the next GOP’s anchor to define its last B picture.
- First encoded line is the number of first encoded line of video. Lines in
a 525 system are in the range 21–260; 625 lines are in the range 7–310.
- Last encoded line is the number of the last encoded line of video.
- Bit rate in megabits per second. The higher the bit rate, the higher the
video quality, though more disk space is used. In other words, the higher
the video quality, the fewer hours of video you can store on disk.
5. Click OK .
Table 9. Factory set values for MPEG compression presets
Preset Name Bit Rate
(Mb/sec)
P Pictures
per GOP
B Pictures
per I/P
Chrom Open GOP
Highest quality 24 5 2 4:2:2 No
Best compromise 15 5 2 4:2:2 No
Most recording time 4 5 2 4:2:0 No
Custom setting 4–44 2 2 4:2:0 Yes