BT656 - Wishbone Video Capture Controller

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Figure 1. BT656 Wishbone Video Capture Controller.

There are many video decoder ICs on the market that take S-Video or Composite video signals as input, and convert these signals to the ITU-R BT.656 format. One example is the TVP5150A from Texas Instruments. Altium Designer's BT656 Video Capture Controller takes this standard video stream format, decodes it, and reformats it into a simple memory image – stored in external video memory. The content of this memory can then be read by, and output onto, a VGA monitor using one of Altium Designer's 32-bit VGA Controllers.

Features at-a-glance

  • 8-bit parallel ITU-R BT.656-compatible interface
  • Supports 6 color modes:
    • Grey-scale: 8, 16, or 32 bits per pixel
    • RGB: 8, 16, or 32 bits per pixel
  • Writes directly to external memory without processor intervention
  • Supports zoom functionality:
    • Image width (X-scaling): reduce number of converted pixels in a line
    • Image height (Y-scaling): reduce number of converted lines in a frame
  • Ability to set frame rate – how many frames to discard for each one captured
  • Wishbone-compliant
  • Separate Wishbone Master interface for direct connection to external memory.


From an OpenBus System document, the Video Capture Controller component can be found in the Peripherals region of the OpenBus Palette panel.

From a schematic document, the BT656 component can be found in the FPGA Peripherals (Wishbone) integrated library (FPGA Peripherals (Wishbone).IntLib), located in the \Library\Fpga folder of the installation.

Designing with the BT656

Use the following links to explore use of the BT656 in more detail:

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