Hybrid encoder

US4825285A · kind A · utility

Assignee

• The United States of America, as represented by Director National Security Agency · US

Inventors

• Joachim Speidel · Nürnberg, DE
• Peter Vogel · Diepersdorf, DE

Key dates

• Filing date: Apr 15, 1987
• Grant date: Apr 25, 1989
• Expiry date: Apr 15, 2007

Classification

• Technology area (CPC H): Electricity
• CPC primary: H04N19/61
• WIPO field: Audio-visual technology
• WIPO sector: Electrical engineering

Abstract

In the hybrid encoder for video signals described the picture elements of a video picture are arranged into equally large data blocks and each newly entered data block, is compared with a data block of the previous video picture by means of a subtractor (SR). The data blocks of the previous picture are stored in a picture store (BS). In order to maintain the transmission bit rates as small as possible, the data blocks are conventionally subjected to a transformation (for example, a Fourier transformation) (F) and a subsequent quantization (Q). For the required strong bit rate reduction a rough quantization is necessary, which leads to a strong quantization noise. To eliminate the quantization noise a blockwise adaptive low-pass filtering (T,FTI) is performed in two signal paths of the hybrid encoder. The quantizer (Q) may then have a refined design or it may be omitted altogether. The result of the low-pass filtering (T,FTI) is a low-definition video picture which is, however, free from the occasionally occurring picture distortions caused by the quantization noise.