Code conversion system

• US 4,534,055 A
• Filed: 11/14/1983
• Issued: 08/06/1985
• Est. Priority Date: 08/04/1980
• Status: Expired due to Term

• Current Assignee: Nippon Electric Company Limited (NEC Corporation)
• Original Assignee: Nippon Electric Company Limited (NEC Corporation)
• Inventors: Iinuma, Kazumoto
• Primary Examiner(s): Kemeny, E. S Matt
• Application Number:
  US06/550,946
• Time in Patent Office: 631 Days
• Field of Search: 381/29-40, 364/513, 364/513.5, 340/347 DD, 370/92, 370/118
• US Class Current: 704/206
• CPC Class Codes: G06T 9/005 Statistical coding, e.g. Huffman, run length coding
• CPC Class Codes: H03M 7/40 Conversion to or from variable length codes, e.g. Shannon-Fano code, Huffman code, Morse code

Abstract

In a code conversion system comprising an encoder and a decoder in combination, the encoder comprises an input terminal for receiving a multi-level time series signal having at least three signal levels subject to a variation of occurrence frequency of levels, a circuit for detecting the highest occurrence frequency signal ("HOFS") level of said multi-level time series signal and generating a first code representative of the run-lengths of said HOFS level, a circuit for generating a second code representative of the individual levels of said multi-level time series signal, and a circuit for combining said codes from said first and second code generation circuits on the time series, and wherein the decoder comprises a circuit for separating the first and second codes and decoding the separated first and second codes into the original multi-level time series signal.

Claims

1. In a code conversion system comprising an encoder, said encoder comprising an input terminal for receiving a multi-level time series signal having at least three signal levels subject to a variation of occurrence frequency of signal levels, means for detecting the highest occurrence frequency signal ("HOFS") level of said multi-level time series signal and generating a first code representative of the run-lengths of said HOFS level;

means for generating a second code representative of the signal levels of said multi-level time series signal where the first code and second code, each include at least one first and second transition code respectively, wherein occurrences of the first transition code indicate transitions from the first code to the second code and occurences of the second transition code indicate transitions from the second code to the first code, and means for combining said codes from said first and second code generation means on the time series so as to produce a coded signal containing said first and second codes in combination.

2. A code conversion system according to claim 1 wherein said first code generating means comprises a first memory for storage of the first code, and said second code generating means comprises a second memory for storage of the second code, said first and second memories being addressed by said signal levels and run-lengths under the control of a level code generation timing pulse and a run-length code generation timing pulse generated from a timing control circuit based on the highest occurrence frequency signal level detected so that said first and second codes are read out of said first and second memories.

6. A code conversion system according to claim 1 wherein individual codes in said first code are defined with presence or absence of the transitions from the first code to the second code and individual codes in said second code are defined with presence or absence of the transitions from the second code to the first code.

3. In an encoder in which at least one multi-level time series signal having at least three signal levels is divided into unit blocks on the time series and compressed coding is effected on the signals in the individual unit blocks, the improvement which comprises means for generating a synchronizing code indicative of boundaries of said blocks, means for detecting the highest occurence frequency signal (HOFS) level in said multi-level time series signal and for generating a first code indicative of the run-lengths of said HOFS level, means for generating a second code indicative of the individual levels of the multi-level signal, means for time-sharing a multiplexing and synchronizing code and said first and second codes on parallel m-bit, m denoting an interger of 2 or more, data lines, means for generating a signal indicative of the bit number of valid or invalid codes on said parallel data lines, and a variable bit arrangement construction for eliminating invalid bits on said parallel m-bit data lines by means of said bit number indicating signal so as to arrange only valid bits onto the parallel l-bit, l denoting an optional integer, data lines in a predetermined order using a parallel to parallel conversion process.

5. In the system of claim 3 a decoder for reproducing variable length codes from compressed data divided into blocks, the improvement which comprises a memory for temporary storage of said compressed data, a synchronizing bit position detecting circuit for reading said compressed data from said memory onto parallel l-bit, l denoting an integer of 2 or more, data lines, detecting the presence or absence of a synchronizing code indicative of the boundaries of said blocks on said parallel data lines, and detecting the bit position of said synchronizing code, a variable bit arrangement inverse converter circuit being set in its initial state in response to the signal from said synchronizing bit position detecting circuit, for detecting the code length of the variable length code from the parallel data, and separating the variable length code from the parallel data by use of the code length detection signal using a parallel to parallel conversion process, and means for converting said separated variable length code into said at least one multi-level time series signal having at least three levels.

4. In a code conversion system comprising an encoder and a decoder in combination, said encoder comprising an input terminal for receiving a multi-level time series signal having at least three signal levels subject to a variation of occurrence frequency of signal levels means for detecting the highest occurrence frequency signal ("HOFS") level of said multi-level time series signal and generating a first code representative of the run-lengths of said HOFS level;

and, means for generating a second code representative of the signal levels of said multi-level time series signal where the first code and second code each include at least one first and second transition code respectively, wherein occurrences of the first transition code indicate transitions from the first code to the second code and occurrences of the second transition code indicate transitions from the second code to the first code, and means for combining said codes from said first and second code generation means on the time series so as to produce a coded signal containing said first and second codes in combination, said decoder comprising means for separating said first and second codes from said coded signal, and means for decoding the separate first and second codes into the original multi-level time series signal.