Internal Modules
79
SPRUHI7A – December 2012 – Revised June 2016
Copyright © 2012–2016, Texas Instruments Incorporated
High-Definition Video Processing Subsystem (HDVPSS)
1.2.4 Constrained Image Generator (CIG)
The Constrained Image Generator (CIG) module is used to generate a resolution constrained version of
the high-quality video to meet the CableCard Copy Protection Specification`s requirement on the handling
of Constrained Image Trigger (CIT) information.
1.2.4.1
Features
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Generates both constrained and non-constrained output from a single input video source
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1/4x vertical/horizontal resolution reduction using 3-tap vertical/horizontal decimation filters
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2x vertical/horizontal resolution restoration using 2-tap average interpolation
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Video Interlacing to match final scan format
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PIP window framer: Positions a PIP window onto a full display screen.
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Individual Chroma keying and blend value application for all outputs
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Can generate interlaced output on both PIP and main window from a progressive input
1.2.4.2
Functional Description
Copy control information (CCI) is passed from the video service provider across the data channel to inform
the Set Top Box of the level of copy protection required. Product shall be able to constrain, when required
by the CIT CCI bit, the resolution of content that is High Definition to be output through a connection
capable of transmitting content in High Definition Analogue Form, to a Constrained Image. The basic
requirement of a constrained image is that it contains the visual equivalent of not more than 520,000
Pixels per frame (e.g. an image with resolution of 540 vertical lines by 960 horizontal lines for a 16:9
aspect ratio). A Constrained Image can be output or displayed using video processing techniques such as
line doubling or sharpening to improve the perceived quality of the image.
Although not specifically mentioned in these sources, it is also generally accepted that the degraded video
will still need to look better than standard DVDs, which generally are encoded at 720x480.
The CIG module takes in a single non-constrained HD video and generates following two outputs:
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The same non-constrained video which may optionally be interlaced
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The same or constrained version of the source video which may optionally be interlaced
The first output is sent to the DVO1 (HDMI)/ HDCOMP output (via COMP/HD_VENC_A) and the second
output is sent to the digital HD output HD_DVO2 (via COMP/HD_VENC_D).
In addition, the CIG module takes in a second video input and positions the video in a full display output
screen if the input video is a PIP sized. The PIP video output from CIG module can optionally be
interlaced. This path is enabled for following two use cases:
•
Displaying un-constrained PIP with constrained/unconstrained main Video (PIP mode)
•
Displaying aux video channel output directly on the HD_DVO2 output (Dual-Video Channel mode)
The block diagram of CIG module is shown in