System for computer video leaking information capture is designed, which employs USB2.0 as bi-directional data transfer channel. Considering that there is no valid data in the vertical blanking intervals of the video signal, bulk transfer with one field as a unit is used in the input channel. In the output channel, the host computer transfers the line and field synchronization parameters to DSP via USB bus and DSP generates high precision synchronization signal. The output process is allocated in the gaps of the input bulks. Therefore bi-directional transfer channel is established. Successful acquisition and display of sto-chastic video signals with line-period 15. 625 kHz and field-frequency 50 Hz and the video leaky signals of computer display with line-period 31. 656 kHz and field-frequency 60 Hz respectively demonstrate that this plan is feasible.%为了实现计算机视频泄漏信号的实时采集,设计了以USB2.0为双向传输通道的泄漏信息采集系统.针对视频图像场消隐期间无有效数据的特点,输入通道中外设以场为单位分块传输实时泄漏截获数据至主机.输出通道中主机将计算出的行、场同步信号通过USB传输至外设,外设由此产生高精度同步信号;该过程在输入通道的块间隙间进行,从而实现了实时双向数据传输.实验采集了行周期为15.625 kHz、场频为50 Hz的CCD视频信号和行周期为31.656 kHz、场频为60 Hz的计算机显示器视频信号,截获图像显示稳定,证明本系统方案切实可行.
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