Coding and decoding method and system for variable-length sequences of digital data

• US 4,573,074 A
• Filed: 12/09/1983
• Issued: 02/25/1986
• Est. Priority Date: 12/09/1982
• Status: Expired due to Fees

• Current Assignee: CSELT Centro Studi e Laboratori Telecomunicazioni SpA (Telecom Italia S.p.A.)
• Original Assignee: CSELT Centro Studi e Laboratori Telecomunicazioni SpA (Telecom Italia S.p.A.)
• Inventors: Destefanis, Paolo, Alaria, Gian B., Poggio, Cesare
• Primary Examiner(s): Britton, Howard W.
• Assistant Examiner(s): Kostak, Victor R.
• Application Number:
  US06/559,917
• Time in Patent Office: 809 Days
• Field of Search: 358/136, 358/133, 358/135, 358/138, 358/260, 358/261, 340/347 DD, 382/56
• US Class Current: 375/240.12
• CPC Class Codes: H04N 19/503 involving temporal prediction adaptive coding with adaptive selection between spatial and temporal predictive coding H04N19/107; adaptive coding with adaptive selection among a plurality of temporal predictive coding modes H04N19/109
• CPC Class Codes: H04N 21/236 Assembling of a multiplex stream, e.g. transport stream, by combining a video stream with other content or additional data, e.g. inserting a URL [Uniform Resource Locator] into a video stream, multiplexing software data into a video stream; Remultiplexing of multiplex streams; Insertion of stuffing bits into the multiplex stream, e.g. to obtain a constant bit-rate; Assembling of a packetised elementary stream multiplexing of data packets for data networks, e.g. RTP/UDP H04L65/00
• CPC Class Codes: H04N 21/434 Disassembling of a multiplex stream, e.g. demultiplexing audio and video streams, extraction of additional data from a video stream; Remultiplexing of multiplex streams; Extraction or processing of SI; Disassembling of packetised elementary stream demultiplexing of data packets for data networks, e.g. RTP/UDP H04L65/00
• CPC Class Codes: H04N 7/54 the signals being synchronous H04N21/23602, H04N21/23614, H04N21/2365, H04N21/2368, H04N21/4341, H04N21/4342, H04N21/4347, H04N21/4348 take precedence
• CPC Class Codes: H04N 7/56 Synchronising systems therefor

Abstract

Television signals generated at a transmitting station are digitized and are then transformed into bit groups by a precoder reducing their information content by eliminating redundancies, as by comparing each pixel of a given frame with the homologous pixel of the immediately preceding frame and, upon detecting their equality, emitting a particular reduction code in lieu of an otherwise emitted luminance signal. A message encoder following the precoder generates outgoing data words which may comprise a luminance value accompanied by an integrity code, a changeover signal accompanied by a reduction code, a numerical value specifying the number of consecutive pixels remaining unchanged from the preceding frame, or a synchronizing code. The bits of the outgoing data words are serialized and are temporarily stored in a buffer register in order to be sent at regular intervals, via a communication channel, to a receiving station where a message decoder regroups them in their original order. The decoder separates the luminance data from the reduction codes under the control of a local clock, re-expands the reduced information and, after checking for transmission errors, converts the received data into luminosity signals designed to reproduce the original television picture.

Claims

1. A method of conveying a sequence or original message signals from a transmitting station over a communication channel to a receiving station in the form of digital data words of reduced information content corresponding to the data-handling capacity of said channel, comprising the steps of:

(a) encoding said original message signals, at said transmitting station, into a plurality of different types of bit groups with at least partial elimination of redundancies, a first of said types, referred to as magnitude-indicating mode, representing magnitudes of a number of said message signals when said number of said message signals is not equal to corresponding message signals of a previous sequence, a second of said types being a qualitative code representing an information-reducing mode, when a number of said message signals is equal to corresponding message signals of a previous sequence thus eliminating a number of signal cycles due to redundancies in said sequence, a third of said types being a quantitative code representing a count of the number of signal cycles eliminated, a fourth of said types representing synchronization signals, a fifth of said types representing a changeover mode whereby said changeover mode indicates either a changeover from said magnitude-indication mode to said information reduction mode or a changeover from said information reduction mode to said magnitude indication mode;

(b) accumulating the bits of a predetermined number of said groups at said transmitting station;

(c) sending the accumulated bits at regular intervals over said channel to said receiving station;

(d) temporarily storing at said receiving station the bits arriving over said channel;

(e) reorienting the stored bits in groups corresponding to those of step (a) with decoding of said groups and separation of different types thereof from one another; and

(f) reconstituting the sequence of original message signals, with re-expansion of the information contained in the groups of said first, second and third types, under the control of locally generated timing signals correlated with the synchronization signals represented by the groups of said fourth type.

2. A method as defined in claim 1 wherein said original message signals are luminance values of individual picture elements of a television image scanned in a multiplicity of lines of a recurrent frame, said information-reducing mode comprising a comparison of the luminance values of currently scanned picture elements with those of homologous picture elements on an immediately preceding frame and generation of bit groups of said firt type only for picture elements whose luminance values significantly differ from those of their respective homologs, a substantially unchanged luminance value and the number of consecutive occurrences thereof in a frame scan being respectively indicated by said qualitative and quantitative codes.

3. A system for conveying a sequence of original message signals from a transmitting station over a communication channel to a receiving station in the form of digital data words of reduced information content corresponding to the data-handling capacity of said channel, comprising:

coding means connected at said transmitting station to a video camera with scanning means generating said original message signals in conformity with luminance values of picture elements forming a multiplicity of lines of a recurrent frame, for at least partially eliminating redundancies by converting only some of said message signals into respective bit groups of a first type representing same in a magnitude-indicating mode, replacing redundancy-containing groupings of other message signals by single bit groups of a second type representing a qualitative code indicate of an information-reducing mode with elimination of a number of signal cycles in said sequence, generating for each bit group of said second type a bit group of a third type representing a quantitative code indicating the number of cycles eliminated, and adding a recurrent bit group of a fourth type representing synchronization signals, whereby said coding means comprising a precoding stage with storage means for retaining the luminance values of the picture elements of a previously scanned frame and comparison means for ascertaining substantial equalities between a newly scanned picture and a homologous picture element of said previously scanned frame, said coding means further comprising a message encoder connected to said precoding means for receiving therefrom bit groups of said first type for picture elements not substantially equal to their homologs and a bit group of said second type for a grouping of consecutive picture elements substantially equal to their homologs, said message coder further including memory means for reading out a bit group of said second type in response to an equality signal from said precoder and counting means for determining the number of picture elements giving rise to said equality signal and generating a bit group of said third type representing the number so determined,

first storage means connected to said coding means for accumulating the bits of a predetermined number of said groups;

interface means responsive to the accumulation of said predetermined number of groups in said first storage means for serially emitting the bits thereof at regular intervals over said channel to said receiving station;

second storage means connected at said receiving station to said channel for temporarily registering the arriving bits of said groups;

decoding means connected to said second storage means for reorienting the registered bits in groups corresponding to those previously contained in said first storage means and reconstituting the sequence of original message signals with re-expansion of the information contained in the groups of said first, second and third types; and

timing means at said receiving station for controlling the operation of said decoding means by locally generated clock pulses correlated with said synchronization signals.

4. A system for conveying a sequence of original message signals from a transmitting station over a communication channel to a receiving station in the form of digital data words of reduced information corresponding to the data-handling capacity of said channel, comprising:

coding means connected at said transmitting station to a video camera with scanning means generating said original message signals in conformity with luminance values of picture elements forming a multiplicity of lines of a recurrent frame, for at least partially eliminating redundancies by converting only some of said message signals into respective bit groups of a first type representing same in a magnitude-indicating mode, replacing redundancy-containing groupings of other message signals by single bit groups of a second type representing a qualitative code indicative of an information-reducing mode with elimination of a number of signal cycles in said sequence, generating for each bit group of said second type a bit group of a third type representing a quantitative code indicating the number of cycles eliminated, and adding a recurrent bit group of a fourth type repesenting synchronization signals, whereby said coding means comprising a precoding stage with storage means for retaining the luminance values of the picture elements of a previously scanned frame and comparison means for ascertaining substantial equalities between a newly scanned picture and a homologous picture element of said previously scanned frame, said coding means further comprising a message encoder connected to said precoding means for receiving therefrom bit groups of said first type for picture elements not substantially equal to their homologs and a bit group of said second type for a grouping of consecutive picture elements substantially equal to their homologs, said message coder further including memory means for reading out a bit group of said second type in response to an equality signal from said precoder and counting means for determining the number of picture elements giving rise to said equality signal and generating a bit group of said third type representing the number so determined wherein said message encoder further comprises multiplexing means with a set of first inputs connected to said precoder, to said memory means and to said counting means for receiving therefrom the bit groups of said first, second and third types, said multiplexer means being switchable by a synchronizing signal from said precoder to a second input for receiving a bit group of said fourth type in response thereto, register means connected to an output of said multiplexer means for temporarily storing said bit groups, and summing means controlled by said memory means for keeping track of the number of bit groups delivered by said multiplexer means to said register means to load said first storage means with the bit groups so stored in said register means;

first storage means connected to said coding means for accumulating the bits of a predetermined number of said groups;

interface means responsive to the accumulation of said predetermined number of groups in said first storage means for serially emitting the bits thereof at regular intervals over said channel to said receiving station;

second storage means connected at said receiving station to said channel for temporarily registering the arriving bits of said groups;

decoding means connected to said second storage means for reorienting the registered bits in groups corresponding to those previously contained in said first storage means and reconstituting the sequence of original message signals with re-expansion of the information contained in the groups of said first, second and third types; and

timing means at said receiving station for controlling the operation of said decoding means by locally generated clock pulses correlated with said synchronization signals.