Dynamic-Range Reduction of Video Signals by Amplitude Compression

摘要

Methods of recording a video signal with large dynamic range on a magnetic tape (or other recording medium) that has a smaller dynamic range than that of the signal are discussed. The useful part of the voltage range of the input signal is mapped onto the linear voltage range of the recorder. Several maps are considered with the thought of minimizing the degradation of the final signal by recorder noise. Two mapping functions are found to be useful: a logarithmic function, and a part-linear, partlogarithmic one. The use of these maps entails a reduction in signal-to-noise ratio for large input signals. The relationships among the input signal dynamic range, the recorder dynamic range, and the attainable output signalto-noise ratios are calculated. Results are presented graphically for several particular cases. (Author)