Television – Bandwidth reduction system – Data rate reduction
Patent
1992-04-09
1994-02-01
Coles, Sr., Edward L.
Television
Bandwidth reduction system
Data rate reduction
358429, 341 76, 341 77, 375 27, 348420, H04N 141
Patent
active
052836460
ABSTRACT:
A method and apparatus for enabling a real time video encoding system to accurately deliver the desired number of bits per frame, while coding the image only once, updates the quantization step size used to quantize coefficients which describe, for example, an image to be transmitted over a communications channel. The data is divided into sectors, each sector including a plurality of blocks. The blocks are encoded, for example, using DCT coding, to generate a sequence of coefficients for each block. The coefficients can be quantized, and depending upon the quantization step, the number of bits required to describe the data will vary significantly. At the end of the transmission of each sector of data, the method and apparatus of the invention compare the accumulated actual number of bits expended with the accumulated desired number of bits expended, for a selected number of sectors associated with the particular group of data. The system then readjusts the quantization step size to target a final desired number of data bits for a plurality of sectors, for example describing an image. Various methods are described for updating the quantization step size and determining desired bit allocations.
REFERENCES:
patent: 4549304 (1985-10-01), Weirich et al.
patent: 5038209 (1991-08-01), Hang
patent: 5089888 (1992-02-01), Zdepski et al.
patent: 5144424 (1992-09-01), Savatier
patent: 5144426 (1992-09-01), Tanaka et al.
Coles Sr. Edward L.
PictureTel Corporation
Williams Kimberly A.
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