Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1987-10-13
1989-06-13
Groody, James J.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358135, 382 56, 375 25, 370 83, H04N 712
Patent
active
048397245
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is concerned with a process for the digital transmission of information especially for digital video signals obtained fromm analog signals, in which groups of data are processed by a source coder and are sent via a channel coder to a transmission channel and from the transmission channel via a channel decoder to a source decoder.
European Patent Application Publication No. 0,084,270 corresponding to U.S. Ser. No. 336,984 of Apr. 1st, 1982, now U.S. Pat. No. 4,541,012 discloses a process for the encoding of transformed coefficients. A plurality of code tables are used to generate a block of address codes, a DC-coefficient code, and a sequence of codes for transformed coefficients.
SUMMARY OF THE INVENTION
The invention is based on the task to improve transmission processes and/or to optimize the information content of a signal or information, respectively.
The task is solved, in general according to the present invention by encoding the signals from the source coder according to a variable codeword length code, and adapting the variable cordeword length code, at time intervals, according to a statistical value of the signal values actually being processed and transmitted.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block circuit diagram of a basic known transmission system for use with the method according to the invention;
FIG. 2 is a more detailed block diagram of a source coder for use in the circuit of FIG. 1;
FIG. 3 shows a coefficient block or matrix whose values are to be transmitted;
FIG. 4 is a table showing the relationship between the values of FIG. 3 and a Huffman coding process;
FIG. 5 shows a Huffman coding arrangment;
FIG. 6 shows a zigzag scan for the transmission of the coefficients of FIG. 3;
FIGS. 7A and 7B each show a block of coefficients with zigzag-scan sampling and the resulting Huffman code according to the table of FIG. 4;
FIG. 8 shows a transmission quantities according to the preferred embodiment of the invention;
FIG. 9 shows a display screen;
FIG. 10 is a block circuit diagram of an embodiment of a transmitter for use in the method according to the invention;
FIG. 11 is a block circuit diagram of an embodiment of a receiver for use in the method according to the invention;
FIG. 12 is a more detailed block circuit diagram of a portion of a transmitter for use with the method according to the invention and particularly a preferred embodiment of the Huffman coder arrangement;
FIG. 13 is a more detailed block circuit diagram of a portion of a receiver for use with the method according to the invention and particularly a preferred embodiment of the Huffman decoder.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a transmission system including an information source 1, an ADC 2 (analog-digital converter), a source coder 3, a channel coder 4, a channel 5, a channel decoder 6, a source decoder 7, a DAC 8 (digital-analog converter) and an information sink 9. The channel 5 can, for instance, represent a HF transmission line or a digital videorecorder. A digital videorecorder, line or a digital videorecorder. A digital videorecorder, however, can also represent the ADC 2, the source coder 3, the channel coder 4, the channel 5, the channel decoder 6, the source decoder 7 and the DAC 8. The source 1 is then formed by a HF transmission line, the channel 5 by a magnetic tape and a magnetic head of the videorecorder, and the sink by a television set.
FIG. 2 shows that in the source coder 3, a digital signal runs, firstly, through a ADCT 10 (adaptive discrete cosine transformer), secondly, through a weighting member 11, thirdly, through a block quantizer 12, fourthly, through a coder 13 and, fifthly, through a buffer 14. Especially if images are sent to a source coder 3 without intermediate storage, the block quantizer 12 must be controlled so that, at the receiving end, sufficient data for the production of an image with acceptable image quality are always available.
FIG. 3 shows a block of distribution coefficients as it arr
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W. Chen; "Scene Adaptive Coder"; International Conference on Communication; vol. 2, pp. 22.5.1-22.5.6; Jun. 14-18, 1981.
Dukhovich; "A DPCM System Based on a Composite Image Model"; National Telecommunications Conference; Band 2, vol. 4; pp. 36.2.1-36.2.6; Nov. 30-Dec. 4, 1980.
Keesen Heinz-Werner
Peters Hartmut
Deutsche AG fur Unterhaltungselectronic OHG
Groody James J.
Peng John K.
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