Method and apparatus for detecting scene changes and adjusting picture coding type in high definition television encoder

Abstract

Methods and apparatus are provided for detecting scene changes between successive fields in a digital television signal. Adjusts the picture encoding type to optimize the encoding efficiency of the video encoder when a scene change including flashes or bad fields caused by improper editing is detected. Aligning I-frames starting a new GOP with scene changes greatly improves the coding efficiency of the MPEG encoder (100). In a pre-processing stage (205, 210), the change in the sum of pixel differences between successive odd fields or successive even fields is calculated for each successive input field. A scene change is detected when a large positive value is followed by a large negative value in the change in neutral. The decision of which picture type to use is not made until the final encoding stage (225, 235). I-frames can be disabled when the encoder buffer level is too high. A counter (counting down) resets the scene change indication in order to avoid a permanent scene change state for the transition from stationary to motion. For the MPEG film mode frame picture determined as a scene change frame, when the scene change may occur on the field boundary (such as there is no redundant field in the picture), the frame-based discrete cosine transform (DCT) and predictive coding recommended by MPEG will be withdrawn. .

Description

Background of the invention [0001] This application claims the benefit of US Provisional Application No. 60 / 102,234, filed September 29,1998. [0002] The present invention relates to video compression, and more particularly to methods and apparatus for detecting scene changes and adjusting picture encoding types to optimize encoding efficiency of video encoders. The invention is particularly useful for picture encoding type determination and scene change detection in digital HDTV encoders. [0003] Aligning intra-coded (I) frames with scene changes can greatly improve the coding efficiency of MPEG (Moving Picture Experts Group) video encoders. In the past, such scene change detection has been provided, for example, by detecting changes in luminance values. [0004] In some existing scene change detection proposals, encoding of I-frames is avoided until the scene change is complete and a new GOP (Group of Pictures) starts. However, scene change detection is performed on a f...

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Therefore, this method can produce incorrect results in the presence of bad editing, special effe

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