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Instruction Manual: evolution 5000 E57xx DSNG and DENG Voyager Encoder Page 4-43
ST.TM.E10076.3
GOP Length Option
To access the Group of Pictures (GOP) Length option, press the GOP
Length softkey in the Video Encoder Menu.
This enables the video GOP structure length to be set. The structure length
determines how regularly an I frame is transmitted. The I frame provides a
regular reference from which predicted frames can be generated, thereby
ensuring that predictions do not become wildly inaccurate.
NOTE…
Some of the settings may not be available if they are not valid for use with other current encoding
parameters. Also, changing the GOP structure automatically changes the GOP length if the current
GOP length is not compatible with the selected structure.
Table 4.39: Group of Pictures Length Options (Long GOPs Disabled)
Valid Input Range Description
Min: 1
Max: 15
GOP lengths available depend on GOP structure selected and the frame rate.
Maximum GOP lengths are 12 for 25 Hz and 15 for 29.97 Hz.
I-Frame and IP encoding have 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15.
IBP and IB have 2, 4, 6, 8, 10, 12, 14.
IBBP and IBB have 3, 6, 9, 12, 15.
IBBBP and IBBB have 4, 8, 12.
Long GOPs Option (3.1 and later)
NOTES…
1. This option is available in Build version 3.1.0 and later.
2. Only available if M2/ESO2/PU has been purchased.
To access the Long GOPs option, press the Long GOPs softkey in the
Video Encoder Menu. This is used to enable or disable the use of GOP
structures that are longer than 500 ms in duration.
Long GOP structures can improve video encoding performance, particularly
at low bit-rates. However, it can lead to compression artefacts being visible
on scene cuts, and a periodic build-up and removal of noise at the I-frame
rate.
NOTE…
Long GOPs are not DVB compliant, and should be used with caution.
Field/Frame Option
To access the Field/Frame option, press the Field/Frame softkey in the
Video Encoder Menu. This enables the choice of field or frame based
pictures.
MPEG-2 encodes video at the field/frame level in what are known as
pictures. These are coding units within the hierarchy of the spec. Pictures
can be used in two ways, frame pictures and field pictures.