BT656 Decoder with Colour-Space Converter

BT_656_DECODER is a digital video decoder with integrated colour-space converter. It's function is to extract the valid pixels from a BT.656 video stream and convert them to 24-bit RGB for subsequent processing.

Video decoding begins after reset is de-asserted and on the rising-edge of clk when the video_val signal is asserted high. (The signal video_val is a clock-enable signal that enables the sampling and processing of each input byte).

Pixels are extracted from the BT.656 input stream and converted to RGB888 format. These pixels are then presented at the output of the decoder together with field and sync flags. All signals are synchronous with the input clock.

The video output from the decoder follows a simple valid-ready streaming protocol that is common to all other Zipcores video IP. Output pixels and flags are sampled on a rising clock-edge when pixout_val and pixout_rdy are both high.

The decoder features an internal FIFO that is sufficient to buffer two lines of input video. If the pixout_rdy signal is de-asserted for more than two lines worth of active pixels then the FIFO will fill to capacity and the overflow flag will be asserted. In the event of an overflow then the decoder must be reset in order to cleanly re-align to the input video stream.

Note that the pixout_rdy signal may be tied high if it is known that the downstream interface can always accept output pixels.

• Synthesizable, technology independent VHDL Core
• Converts industry standard BT.656 digital video to 24-bit RGB
• Integrated 4:2:2 YCbCr to RGB888 colour-space converter
• Both PAL and NTSC (576i and 480i) input formats supported
• All signals synchronous with the pixel clock
• Small implementation size ideal for all types of FPGA
• Compatible with a wide range of SD video decoder ICs

• BT.656 input video capture and processing
• PAL & NTSC SDTV interlaced format conversion
• Connectivity with a wide range of commercially available video decoder ICs
• Simple and cost-effective method for capturing digital video into your FPGA or ASIC