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Compressed quantized image-data transmission technique suitable for use in teleconferencing

  • US 4,663,660 A
  • Filed: 06/20/1986
  • Issued: 05/05/1987
  • Est. Priority Date: 06/20/1986
  • Status: Expired due to Term
First Claim
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1. In a method for transmitting in real time compressed image-data, derived from a given video signal that defines the gray-scale level value of each successive pixel of each of successive frames of uncompressed original television images that exhibit a given relatively high pixel density, over a limited bandwidth communication channel to a receiver, and for displaying at said receiver successive frames of synthesized television images derived from said transmitted compressed image-data;

  • the improvement comprising the steps of;

    (a) deriving from a combination of said given video signal and a feedback signal that defines the difference in level values of corresponding pixels of at least each pair of successive frames of said original television images, an ordinally-arranged set of (N+1) separate video signals, where N is a specified positive integer, the first separate video signal of said set defining the highest spatial frequency bandpass sub-spectrum image component of the spatial frequency spectrum of a differential image corresponding to at least that pair of successive frames of said original television images, the image component of said differential image defined by said first separate video signal of said set exhibiting a first pixel density that is equal to or less than said given pixel density, each other separate video signal of said set except said last separate video signal of said set defining a spatial frequency bandpass sub-spectrum image component of said spatial frequency spectrum that is lower than that defined by its immediately preceding separate video signal of said set, the image component of said differential image defined by each other separate video signal of said set exhibiting a pixel density that is less than the pixel density exhibited by the image component defined by its immediately preceding separate video signal of said set, and said last separate video signal of said set defining a spatial frequency low pass sub-spectrum image component of said spatial frequency spectrum that is lower than that defined by its immediately preceding separate video signal of said set, the pixel density of the image component of said differential image defined by said last separate video signal of said set being no greater than the pixel density exhibited by the image component defined by its immediately preceding separate video signal of said set;

    (b) quantizing said video signals of said set to reduce the number of gray-scale level values of the pixels of at least one of said separate video signals of said set;

    (c) subsequent to said quantizing, separately compression-encoding each separate video signal of said set, and transmitting said separately compression-encoded video signals to said receiver over said limited bandwidth communication channel; and

    (d) subsequent to said quantizing, deriving said feedback signal from said separate video signals of said set.

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