YCbCr 8-Bit to RGB565 Converter April 2013 Reference Design RD1152 Introduction YCbCr 8-bit to RGB565 converter converts YCbCr 4:2:2 8-bit color space information to RGB565 color space. To facilitate easy insertion to practical video systems, this design example takes video stream control signals (H_SYNC, V_SYNC, FID, and DEN) and delays them appropriately, so that control signals can be easily synchronized with the output video stream. This document provides a brief description of YCbCr 8-bit to RGB565 Converter and its implementation. The design is implemented in VHDL. The Lattice iCEcube2™ Place and Route tool integrated with the Synopsys Synplify Pro® synthesis tool is used for the implementation of the design. The design can be targeted to other iCE40™ FPGA product family devices. Features • 8-bit YCbCr 4:2:2 input and RGB565 output • Pipelined implementation • Latency of 4 cycles • H_SYNC, V_SYNC, FID and DEN control signals for video synchronization • VHDL RTL and functional test bench Functional Description Figure 1. Functional Description iCE CMD YCbCr Source i_PIX_CLK IO i_RESET_B IO i_PIX_DEN IO i_PIX_HSYNC IO i_PIX_VSYNC IO i_PIX_FID IO i_Y_PIX[7:0] IO i_Cr_PIX[7:0] IO i_Cb_PIX[7:0] IO IO IO YCbCr 8-Bit to RGB565 Converter IO IO IO o_RGB_DEN o_RGB_HSYN o_RGB_VSYN o_RGB_FID RGB Device o_RGB_DATA © 2013 Lattice Semiconductor Corp. All Lattice trademarks, registered trademarks, patents, and disclaimers are as listed at www.latticesemi.com/legal. All other brand or product names are trademarks or registered trademarks of their respective holders. The specifications and information herein are subject to change without notice. www.latticesemi.com 1 rd1152_01.0 YCbCr 8-Bit to RGB565 Converter Signal Description Table 1. Signal Description Signal Width Type Description i_PIX_CLK 1 Input Input Pixel Clock i_RESET_B 1 Input Asynchronous Active high reset i_PIX_DEN 1 Input Synchronous Data Enable i_PIX_HSYNC 1 Input Horizontal Sync i_PIX_VSYNC 1 Input Vertical Sync i_PIX_FID 1 Input Input Frame ID (odd/even field indicator) i_Y_PIX 8 Input Y component of pixel i_Cr_PIX 8 Input Cr component of pixel i_Cb_PIX 8 Input Cb component of pixel o_RGB_DEN 1 Output RGB Data valid o_RGB_HSYNC 1 Output Pipelined Horizontal Sync o_RGB_VSYNC 1 Output Pipelined Vertical Sync o_RGB_FID 1 Output Output odd/even field indicator (pipelined) o_RGB_DATA 16 Output Converted RGB Component Design Module Description Figure 2. Functional Block Diagram i_PIX_CLK Y-16 F/F ADD MUL i_RESET_B F/F MIN/ MAX F/F R F/F o_RGB_DEN i_PIX_DEN o_RGB_FID i_PIX_HSYNC Cr-128 F/F o_RGB_HSYNC i_PIX_VSYNC ADD MUL F/F F/F MIN/ MAX F/F G i_PIX_FID o_RGB_VSYNC o_RGB_DATA i_Y_PIX[7:0] i_Cr_PIX[7:0] i_Cb_PIX[7:0] Cb-128 F/F ADD MUL F/F F/F MIN/ MAX F/F B Configurable parameter None 2 YCbCr 8-Bit to RGB565 Converter Register Map This design does not have any user accessible registers or memory. Design Details This module converts 8-bit YCbCr 4:2:2 to RGB565 as per the following conversion expressions: • R = 1.164(Y-16) + 1.596(Cr-128) • G = 1.164(Y-16) - 0.813(Cr-128) - 0.392(Cb-128) • B = 1.164(Y-16) + 2.017(Cb-128) The implementation comprises of a set of constant coefficient multipliers and add/sub logic arranged in pipelined fashion. Considering the large amount of data path involved here, a pipelined implementation is provided here to improve the performance. If the converted R, G and B values falls outside the allowed range, then the values are clipped and limited to the maximum/minimum possible range. This is a fully synchronous design and all the modules listed in the block diagram generates registered output through input pixel clock. To facilitate easy insertion to practical video systems, the design makes use of video synchronization signals pixel clock (i_PIX_CLK), valid data indicator (i_PIX_DEN) and generates a delayed version of i_PIX_HSYNC, i_PIX_VSYNC, i_PIX_DEN and i_PIX_FID so that control signals synchronized with the output RGB565 stream. Initialization Conditions This design does not have any user specific initialization conditions. Timing Diagram Figure 3. Timing Diagram i_PIX_CLK I_RESET_B I_PIX_HSYNC I_PIX_VSYNC i_PIX_FID i_PIX_DEN I_Y/Cr/Cb o_RGB_HSYNC o_RGB_VSYNC o_RGB_FID o_RGB_DEN o_RGB_DATA 3 YCbCr 8-Bit to RGB565 Converter Simulation Waveforms Figure 4. Simulation Waveforms Usage Examples Common YCbCr video sources include NTSC video decoders, MPEG decoders, and cameras. YCbCr to RGB converters are useful in applications like Video Surveillance, Display Systems, Image/Video processing applications, Image decompression systems etc… Example usage of this module is illustrated in the block diagram below, which interfaces TVP5150 NTSL/PAL/SECAM Video Decoder to a Display system. Video Pixelization module decodes ITU-R BT.601 YCbCr stream and generates HSync, VSync, DEN and FID control signals. Figure 5. Usage Example Control Control VideoInterface Pixelization TVP5150 Video Decoder YCrCb2RGB Converter Display Buffer and LCD Controller YCbCr Memory 4 YCbCr 8-Bit to RGB565 Converter Simulation setup comprises of a testbench which provides input Y, Cb, Cr values for various colors like red, blue, green, white etc… The DUT generated output RGB565 values are compared against the corresponding known RGB565 values. Implementation This design is implemented in VHDL. When using this design in a different device, density, speed or grade, performance and utilization may vary. Performance and Resource Utilization Table 2. Performance and Resource Utilization Family Language Utilization (LUTs) fMAX (MHz) I/Os Architecture Resources iCE401 VHDL 273 >50 49 (63/160) PLBs 1. Performance and utilization characteristics are generated using iCE40-LP1K-CM121 with iCEcube2 design software. References • iCE40 Family Handbook Technical Support Assistance Hotline: 1-800-LATTICE (North America) +1-503-268-8001 (Outside North America) e-mail: [email protected] Internet: www.latticesemi.com Revision History Date Version April 2013 01.0 Change Summary Initial release. 5