Chapter 5 Video Configuration
© 2013 Harmonic Inc. Harmonic All rights reserved.
127
Ellipse 3000 Release 3.0, Rev. B
Encoding Sub-Menu/Box
5.4.1
Latency Control (MPEG-2/MPEG-4 AVC)
Use the
Latency Control
parameter to set the low-delay activation mode for the video profile.
When you set latency control to Ultra Low for H.264 or Low for MPEG-2, the video profile is 4:2:0.
Ultra Low and Low delay is generally used for distance interviews, where latency must be
minimized. Ultra Low and Low delay use P-Only GOP mode, where all frames are coded as
P-frames. Thus, the coding order is identical to the display order yielding a lower latency.
The available options are:
■
Ultra Low
– Use this option to set latency to ultra low. The latency is close to 300 msec
depending on video format and PVR configuration. The user cannot change the parameter
settings, they are hidden. Sync Mode should be set to
Internal Clock
.
■
Low
– Use this option to set latency to low. The latency is close to 850 msecs. See Table 5–1 for
Low Latency parameter settings. The user cannot change the parameter settings, they are
hidden. The System Clock should be set to
Internal
.
■
Standard
– Latency control is disabled. Delay is set to normal. The latency is close to 2 seconds.
(Default)
■
Manual
– This mode can have a negative effect on the video quality and is not recommended.
Manual mode enables the user to set the following parameters:
❑
GOP Structure
❑
GOP Length
❑
IDR Interval
❑
VBV Delay
NOTE:
When setting the Latency control to Ultra Low Delay, the audio bit-rate must be set to a high rate. If
the audio bit-rate is not high enough, the encoder displays the dependency check message,
avsync mismatch.
audio# and video#
.
The Latency Control default is
Standard
.
Table 5–1: Low Latency Parameter Settings
Parameter
Setting
FPGA Scene Cut Detection
Disabled
GOP structure
IBP
GOP length
64
VBV delay
0.5 sec
IDR interval
0
