Infinite Algorithms
Algorithms for Consumer Electronics, Audio, Video, Imaging, and Wireless
Tutorials
Video Scaler
Video scaler is a sub system that transforms an input video stream to fit into a given display area of Xd x Yd pixels by changing the size of the input arriving with Xi x Yi pixels. The horizontal scaling ratio is then Xd/Xi and the vertical scaling ratio is Yd/Yi. Both these ratios are usually non-integers.
For example, the standard definition video has 720 x 480 pixels. If this video is to be displayed on a screen with 800 x 600 pixels, then the horizontal scaling ratio is 800/720 = 1.1111111 and the vertical scaling ratio is 600/480 = 1.25.
This mean that a horizontal line of 720 pixels must be converted to contain 800 pixels. Similarly 480 horizontal lines must be transformed to be 600 lines. This type of conversion must happen at the frame rate of the display unit. If there is a mismatch between the input frame rate and the display frame rate, a temporal conversion is also needed. In the tutorial PDF, only the spatial scaling problem is considered.
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There is also a Video Scaler Utility that runs on Windows machines and let you design the scaler system with many different polyphase filters. Please send us an email, we will be glad to send you this utility free.