Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1987-09-28
1989-08-08
Groody, James J.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358136, 358141, H04N 704, H04N 712
Patent
active
048558257
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for detecting the most powerfully changed and thus for the human eye the most important picture areas in a video image in order to compress the live image into a transmission channel functioning at the rates of narrow bandwidth data connections, in which method the digitized picture information read in to the video memory is compared to the already transferred picture information which is stored in the reference memory, and the difference value, i.e. the change value between these picture data is compared to the present change, threshold, and if the difference value surpasses the chanbe threshold, the picture information of the specific picture elements (pels) and/or area of image in question is coded and transmitted, and the respective picture information is stored into the reference memory preparatory to a new comparison operation.
The invention also relates to an apparatus for realizing the method, the said apparatus comprising at least an analogue-to-digital converter where the video signal is digitized; a vido memory, whereinto the digitized picture information is read; a reference memory, which contains the data of the transmitted picture information; a comparator or equivalent where the contents of the video memory and the reference memory are compared to each other with respect to each corresponding pel and/or area of image; a thresholding unit, where the change value between the respective picture data, received from the comparator, is compared to the change thresholding set for the thresholding unit; a coder, where the picture information contained in the spot and/or area of the image is coded if the change value surpasses the change threshold and which coded picture information is transmitted into the transmission channel; a replenishment unit for the reference memory, via which replenishment unit the transmitted picture information is read into the reference memory.
In the prior art, various transmission arrangements for videoconferencing images have been realized at the trunk rates 2 Mbit/s (Europe), 1.54 Mbit/s (U.S.A.) of digital telephone networks or at their multiple rates from 512 kbit/s upwards, as well as at the rates 64 kbit/s (Europe) or 56 kbit/s (U.S.A.) of the simple and economical subscriber line of the data network. However, the prior art methods have not succeeded in detecting the changed picture areas in a video image so that the most important areas of change were recognized and the best possible quality achieved for the image.
While transmitting a videoconferencing or a teleconferencing image, the basic principle is generally the fact that while the camera remains stable, only that portion of the picture area which represents the object is changed. Thus the picture information concerning an area which represents a stable background must in principle be transmitted only once. By means of this method, the conditional replenishment method, a live video signal can up to certain limit be transmitted along a transmission channel with a considerably narrower bandwidth than is normally required by a standard-shaped video signal. The majority of the known compression methods for a live video signal are based on the said basic principle.
The conditional replenishment method can be optimized and improved by means of several additional methods. The U.S. Pat. No. 3,582,546 introduces a method where the size of the required frame memory can be for instance decreased by employing a system where certain indicator words are chosen per each group of pels of images, the number of bits of each indicator word being lesser than the number of bits of respective pels of images. The scanning of the frame groupwise instead of detecting every pel individually, improves the noise tolerance and the coding efficiency. The size of required picture memory can be decreased, and the image contrast improved, by aid of various histogram modifications connected to the amplitude of the video signal, for example according to the GB patent application No. 2,112,602 and the
REFERENCES:
patent: 3582546 (1971-06-01), Brown
patent: 4389672 (1983-06-01), Bowen et al.
patent: 4575756 (1986-03-01), Furukawa
patent: 4591908 (1986-05-01), Hiramo
patent: 4698672 (1987-10-01), Chen et al.
patent: 4717957 (1988-01-01), Santamaki et al.
Haikonen Pentti O.
Korhonen Ilkka O.
Santamaki Harry J.
Groody James J.
Peng John K.
Valtion teknillinen tutkimuskeskus
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