ECE532H1S Final Report FLASH ACTIVATED STILL IMAGE CAPTURER Team Members Andrew Michell 990879144 Enrico Baldovino 990884101 Submitted to Professor Paul Chow April 12 2004 Contents 1 0 Overview 3 2 0 Results and Future Improvements 4 3 0 Block Description 5 3 1 MicroBlaze Processor 5 3 2 OPB External Memory Controller EMC 5 3 3 OPB General Purpose I O GPIO 6 3 4 Video Processor vidcap 6 3 5 YCrCb Buffer Viewer 8 4 0 Design Tree Description 10 2 1 0 Overview This report describes the implementation of a Flash Activated Still Image Capturer a video processing project proposed by Professor Steve Mann The basic operation of the overall system is as follows 1 A camcorder provides a continuous video signal to the Xilinx Multimedia Board through the board s component video input connection 2 The ADV7185 video decoder in the board samples the incoming video signal and converts it to YCrCb digital format 3 A video processing unit which is enabled through the GPIO measures the luminance of each incoming video frame and compares it to a luminance threshold also specified at runtime through the GPIO 4 A bright camera flash in the video picture causes the frame s luminance to exceed the threshold value prompting the video processing unit to store the subsequent frame into external ZBT RAM 5 The memory where the picture is stored is read and written to a file by an XMD command line script 6 This file is read by YCrCb Buffer Viewer a custom viewing application written in Java which displays the captured picture by sequentially drawing each pixel The system was built upon the zbt test design by Lesley Shannon This design included a MicroBlaze processor and one ZBT RAM bank connected to the OPB bus through an External Memory Controller EMC The video input core vidcap was connected to the OPB bus in master configuration This core was enabled by the user at runtime through the GPIO The original vidcap core written by Monty Nandra continuously read YCrCb digital video data from the board s video decoder and stored it in 32 bit format on the ZBT RAM module Modifications were made to the vidcap core to enable measurement of the energy of each frame The core s operation was changed such that it would only write frames into memory once it has found a frame with an energy measurement that exceeds a certain threshold A more detailed description of the system s components can be found in section 3 0 of this document 3 2 0 Results and Future Improvements The Flash Activated Still Image Capturer successfully measures the brightness of each incoming frame by summing the values of each luminance sample sent by the video decoder This sum is compared to a threshold level which can be set by writing the desired value in the GPIO register The value written must end with the last two bits set high as these two bits also function as switches which enable the video capture module to write frames to memory Frames are not written to memory until after the module senses a frame above the set threshold level Although the system works and achieves its objectives there are some drawbacks that can potentially be improved upon 1 Due to time constraints we were unable to develop a hardware module that displays the captured frame on a VGA or TV monitor once it is stored in memory This would eliminate the need to transfer the memory contents to a file and open display it using the YCrCb Buffer Viewer Java application 2 It was observed that the system is quite dependent on the light conditions where it is being used In rooms with bright fluorescent lighting flash frames become less differentiable from regular frames This problem may be solved by modifying the method by which the energy of each frame is measured such that there is a larger discrepancy between normal frames and those with a flash 3 Ideally only one frame should be captured and written to memory However we found that when only one frame is written blank spots appear in the picture This may be due to the fact that since the video capture module is connected to the OPB as a master it must be granted permission to write to the RAM This process might not be happening fast enough for every sample to be written Note that this is only a hypothesis the system should be simulated and tested further in order to find the exact cause of the problem Thus it was necessary to allow the module to write several frames into the same location on the external memory 4 One might consider modifying the operation of the video processing core so that frames are continually written to memory until a flash frame is found at which point writing is halted In this case the last frame written to memory would be the flash frame instead of the subsequent frames This is essentially the inverse of the system previously described 4 3 0 Block Description The following figure is a schematic diagram of the overall system as it was implemented on the Xilinx Multimedia Development Board The hardware modules shaded in red will be described in further detail in this section 3 1 Microblaze Processor The Microblaze processor does not take part in digital video processing as this is done by the video processing module see section 3 4 However it still plays a relatively important role in the system by running the Microblaze Debug Module MDM The user must be able to write values to the GPIO to specify the brightness threshold and enable the video processing module to write to memory The user must also be able to access the ZBT RAM directly to transfer its contents to a file Access to the GPIO and the RAM as far as we know can only be done by connecting to the MDM stub through XMD 3 2 OPB External Memory Controller EMC The EMC module is used to control reads and writes to the external memory The EMC is connected to one bank of external memory Our project used Lesley Shannon s zbt test project to implement the external memory There is an extra module gen zbt addr which as stated in the project s README file flips the address bus to select the correct bits 5 The following changes were made in Add Edit Cores set the base address to 0x80100000 set the end address to 0x801fffff 3 3 OPB General Purpose I O GPIO The GPIO module is used to start the flash detector stop the flash detector and set the threshold of the energy The GPIO core was added to the project in Add Edit Cores using the following steps set the base address of the GPIO core to 0x80000300 add the GPIO core to the OPB bus as a slave connect the GPIO d