Digital Video Overlay Module

VID_OVERLAY is a highly versatile video multiplexer that allows one video stream to be inserted over another. By cascading a series of video overlay modules together, any number of video sources may be multiplexed together. The module supports input video streams of any resolution or aspect ratio up to 216 x 216 pixels in size. Video overlay parameters may be changed on a frame-by-frame basis to dynamically change the size and position of the video overlay.

Pixels and syncs flow in and out of the video overlay module in accordance with the valid-ready pipeline protocol. Pixels and syncs are sampled at the module inputs on a rising clock-edge when 'val' is high and 'rdy' is high. Likewise, pixels and syncs are transferred out of the module on a rising clock-edge when 'val' is high and 'rdy' is high. The pipeline protocol allows both input and output interfaces to be stalled independently.

The dimensions of the output video are controlled entirely by the background video stream (pixin0) . This means that if the source video input at stream '0' is 1024x768 pixels then the output video will also be 1024x768 pixels in resolution. The video overlay enters the module via stream '1' and must be smaller or equal in size to the background video stream.

In addition, the overlay module supports a number of blending operations including an 8-bit alpha channel and bitwise AND, OR and XOR functions. Figure 1 shows the architecture of the digital video overlay module in more detail

• Synthesizable, technology independent VHDL IP Core
• Video overlays on 24-bit RGB or YCbCr 4:4:4 video
• Supports all video resolutions up to 216 x 216 pixels
• Supports any number of input video streams or video overlays  (by cascading modules together in series)
• Programmable video-overlay position and size
• Per pixel 8-bit alpha transparency
• Choice of ROP commands including AND, OR and XOR
• Simple input and output interfaces
• No complex programming required
• Easily integrates with all Zipcores Video IP
• Small implementation size
• Supports FPGA clock rates in excess of 250 MHz

• Digital TV and home-media solutions
• Broadcast TV and film production
• Digital-video special effects
• Multiple video windows
• Animated video windows
• Picture-in-Picture (PiP) applications
• Instrumentation and monitoring
• Network and Tactical operations centres
• CCTV and security camera systems