Television – Bandwidth reduction system
Patent
1996-12-02
2000-04-04
Tung, Bryan
Television
Bandwidth reduction system
348390, 382233, 382234, H04N 730, H04N 732
Patent
active
060467738
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Field of the Invention
The invention relates to an apparatus and method for decoding video images, especially for decoding a video sequence, compressed according to a known data modelling method suitable for transmission or storage, into decompressed frames, suitable for viewing, said encoded data model comprising a plurality of spatial intensity change patterns, called intensity loads, a plurality of spatial address change patterns, called address loads, and a plurality of values, called scores, specifying for each frame how much of each load should be present. The invention further relates to a method for transforming a source image, consisting of picture elements given in integer positions in a first two-dimensional coordinate system, into a target image consisting of picture elements given in integer positions in a second two-dimensional coordinate system.
2. Background of the Invention
The use of digital techniques for transmission and storage of images is becoming more and more widespread. However, the high number of bits required to represent digital images in raw form is often a problem, demanding high transmission band width or large amounts of storage media. This is the motivation for using compression techniques, which aim at reducing the number of bits required to represent the images without impairing image quality too much.
Early methods of digital image transmission and storage used Pulse Code Modulation (PCM). More recent systems use digital compression techniques. One such compression technique is JPEG, where each frame is compressed as a still image, independent of the other frames. The frame is digitized into picture elements, called pixels, and the pixels are grouped together into blocks of 8.times.8 pixels. Each block is transformed using DCT (Discrete Cosine Transform). The transform coefficients are quantized and run length coded, and the result is then coded with a Variable Length Code like Huffman code or Arithmetic Coding. The resulting bit stream is then transmitted or stored.
In a TV signal, subsequent frames are often related to each other, in that the same objects can be seen in several frames, possibly at differing positions in the frame corresponding to object or camera motion. This gives rise to the family of motion compensated compression techniques. One such technique is MPEG. In MPEG, some frames are compressed using still image coding similar to JPEG. Other frames are coded by prediction and motion compensation: For each block, the encoder performs a search for the most similar block in a small search region around the current block position but in a previously transmitted frame. Only the position of the found best match relative to the current block position, called the motion vector for the block, need to be transferred, together with a DCT coded residual. The decoder can then reconstruct the frame by collecting pixels according to the motion vector, perform an inverse DCT on the coded residual and can then add the results together.
Research is being done on model based compression techniques, like wire frames or object-based region coding, but a commercial breakthrough has not come yet.
One possible application for digital compression and decompression techniques is the storage of video films on CD-ROMs. Without compression, less than one minute of a digitized video film can be put on a single disk. In order to store a full video film on a disk, compression techniques must be used. The resulting data must then be decompressed before or when it is viewed.
Another possible application is Video On Demand, implemented so that many users are connected to one common distribution central. Each user has the possibility to choose one from a large number of films for immediate playback, and the distribution central must then transmit the wanted film to this user. A highest possible number of users is wanted, and they should be interconnected using a least possible expensive cable network. The distribution central therefore often uses compression techniques, cre
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Martens Harald Aagaard
Reberg Jan Otto
IDT International Digital Technologies Deutschland GmbH
Le Vu
Tung Bryan
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