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Advanced Video Processing and Networking
6-12
EN/LZT 790 0023/1 R16A
6.7 VCM Video Encoding Functionality
6.7.1.1 Overview
The VCMs process the video input signal into a compressed encoded bit stream in
accordance with the appropriate specification (ITU-T H.264 or ISO/IEC MPEG-4
AVC, MPEG-2 specification (ISO/IEC 13818) or JPEG 2000 specification (ITU-T
Rec. T.802 or ISO/IEC 15444-3)).
6.7.1.2 Functional Description for VCMs
Figure 6.5 CE VCM Functional Diagram
The 3G/HD/SD-SDI Video Input can be configured to accept either 25 Hz or
29.97 Hz video. The Pre-processor has a video frame re-synchronizer which allows
the video frame rate to be locked to the Unit 27 MHz clock, or to a 27 MHz clock
locked to an external sync input if an External Sync Input option card
(HWO/EXTSYNC) is fitted. If the unit is configured to be locked to video, then the
frame re-synchronizer is inactive.
The Pre-processor can perform horizontal and vertical scaling and bandwidth
filtering on the video prior to passing it on to the Video Encoder. It can also generate
a test pattern or repeat the last frame received if the video input is not valid.
The Video Encoder processes the video from the Pre-processor into a compressed
encoded bit-stream in accordance with the relevant specification.
It can produce a constant bit rate (CBR) output, which can be set in the range
1 Mbps to 200 Mbps depending upon encoder and profile.
The Video Encoder can be configured for CBR, Low Delay, Mega Low Delay
(available only for CE-x VCM variants), Ultra Low Latency (CE-a/J2K only), Stripe
Refresh or Fixed Latency buffer mode. The available modes are dependent upon
VCM type, configuration and available licenses.
CBR is the recommended buffer mode for optimum video quality, while the Low
Delay buffer modes give lower video encoding delay, where video quality may be
impacted. In non-seamless buffer modes, the compressed video output will glitch if
the video bit rate is changed.