JPH04109781A - Recording device and reproducing device - Google Patents

Abstract

PURPOSE:To reduce the effect of an error without increasing additional information such as error correction by including a specific SYNC pattern to a code word or a final part of linked code words and detecting the SYNC pattern when code synchronization is unlocked at reproduction. CONSTITUTION:A signal inputted from an input section 4 in a coder is inputted to a pattern selector 7. The pattern selector 7 selects an information pattern inputted from an information pattern input section 5 and an end pattern inputted from an end pattern input section 6 according to an input signal and links them and outputs the result to an output section 8. A variable length decoding section 15 in a reproduction device stops decoding when an error information input section 13 detects an error and inputted to the section 15 and restarts a variable length decoding according to a head position of a code word inputted from a SYNC pattern detection section 14. Thus, even when an error takes place at the reproduction, the code synchronization of the variable length code is simply restored.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a recording device and a reproducing device that record image information and audio information by variable length encoding.

BACKGROUND OF THE INVENTION Since the amount of image information is very large, high-efficiency encoding is often used to reduce the amount of data when transmitting or recording image information. High-efficiency encoding is a means of compressing the amount of data by removing redundant components of image information.

As high-efficiency encoding, there is a method in which input sample values are first divided into blocks each consisting of a plurality of adjacent pixels, orthogonal transformation is performed for each bronch, and encoding is performed for each orthogonal transformation.

Another method is predictive coding, in which a pixel to be transmitted is predicted from adjacent pixels and the prediction error is transmitted. In these high-efficiency encoding methods, the orthogonal components and prediction errors are generally quantized and variable-length coded before being transmitted.

Variable length coding is a method in which signals with low frequency of occurrence are encoded into code words with a small number of bits, and signals with high frequency of occurrence are encoded into code words with a large number of bits. This makes it possible to transmit data using a smaller number of bits on average. Therefore, in conventional devices for recording or transmitting images and audio, the amount of data is reduced by using variable length encoding as described above before recording and reproducing.

Problems to be Solved by the Invention However, when variable length coding is used, if even a single bit error occurs, code synchronization will be lost, making it impossible to decode subsequent variable length codes. For this reason, in conventional devices, the influence of transmission path errors is very large, and a large amount of error correction codes and cent signals are required to prevent such errors.

It is an object of the present invention to solve the problems of the conventional recording device and reproduction "Jl".

Means for Solving the Problem The present invention provides n uniquely decodable bit patterns (
A set of bit patterns in which all the bit patterns can be distinguished when n bit patterns are read starting from the first bit), and m bit patterns among the n bit patterns are set as an end pattern, and the end pattern is It is characterized in that n−m bit patterns other than the pattern are used as information patterns, and a sink pattern generated by concatenating a certain information pattern and an end pattern is not included in the bit patterns generated by concatenating any information pattern. , input using a variable-length code obtained by a variable-length code generation means characterized in that the end pattern is finally connected to any concatenation of the information patterns, or the end pattern itself constitutes a code word. It is a recording device that encodes and records data, and also has n uniquely decodable bit patterns (bits that can distinguish all beard patterns when n bit patterns are read from the 1st bit). a set of patterns), m bit patterns among the n bit patterns are set as end patterns, n − m bit patterns other than the end patterns are set as information patterns, and by concatenating a certain information pattern and the end pattern, The sync pattern to be generated is not included in the bit pattern generated by concatenating any information patterns, and any concatenation of the information patterns includes:
Reproducing data encoded and recorded using a variable length code obtained by a variable length code generation means characterized by concatenating the end pattern at the end or configuring a code word by the end pattern itself. when an error is detected in the encoded bit string during playback, sync pattern detection means reads the bit pattern after the error position and detects the sync pattern; This is a playback device characterized in that decoding of a code word is started assuming that the code word is at the beginning of the code word.

Effect: With the above configuration, the codeword used in the present invention includes a specific sync pattern in the last part of a codeword or a concatenation of codewords. Further, the sync pattern is a pattern that does not occur in any part other than the last part of the codeword even when arbitrary codewords are concatenated. Therefore, by using this variable length code, even if code synchronization is lost due to a transmission path error during reproduction, the end of the code can be detected by detecting the sync pattern.

This makes it possible to restore code synchronization.

Therefore, it is possible to reduce the influence of errors without increasing additional information such as error correction.

EXAMPLES The present invention will be described in detail below. FIG. 1 shows an embodiment of the encoder of the present invention. In FIG. 1, 1 is an input section, 2 is a variable length encoding section, and 3 is a recording section.

Input data inputted from the input section 1 is variable-length encoded by a variable-length encoder as shown in FIG. 2, and is recorded in the recording section 3. FIG. 2 shows an embodiment of the variable length encoder of the present invention. In FIG. 2, 4 is an input section, 5 is an information pattern input section, 6 is an end pattern input section, 7 is a pattern selector, and 8 is an output section. The signal input from the input section 4 is input to the pattern selector 7. In accordance with the input signal, the pattern selector 7 selects and connects the information pattern inputted from the information pattern input section 5 and the termination pattern inputted from the termination pattern human input section 6, and outputs them to the output section 8.

Next, the information pattern, the end pattern, and the selection method shown in FIG. 2 will be explained using a specific example. First, the input signal has a sign 1 bit s representing positive/negative and 8 bits representing the absolute value (X
7. X6. X5. X4゜X3. X2. XI, Xo)t?
Suppose that it is expressed. Also, the information pattern is (1,0
) and (1,1), and the ending pattern is (0). This information pattern (1, 0) and the end pattern (
bit pattern (1,0,0
) is a pattern that cannot be generated by any combination of the two information patterns, and such a pattern is called a sink pattern. The present invention is thus characterized in that the sink pattern generated by concatenating a certain information pattern and an end pattern is not included in the bit pattern generated by concatenating any information pattern. Now, a method for selecting the above-mentioned information pattern and termination pattern for input signals will be described below.

(X7=X6=X5==X4=X3=X2=X 1 =
XO=0), end butter 7(0) is selected and used as the code word.

(2) (X7=, ......, =Xi+1-0
．． Xi+0), then the sign S and (X+-1,...
..., X0), if each bit is O, the information pattern (1, 0) is selected; if the bit is 1, the information pattern (1, 1) is selected. , and connect those i+1 information patterns to create 2
An end pattern (0) is concatenated to the end of the (i+1) bit series to form a code word.

As described above, in the present invention, a bit string formed by concatenating a termination pattern to a plurality of information patterns or a single information pattern for an input signal, or the termination pattern itself is used as a code word. Furthermore, various means can be applied to the encoding of the present invention in addition to the method described above in which the encoding operation is repeated for each bit of the input signal. A similar effect can also be obtained when all the 0's and 1's in the above encoding are inverted.

FIG. 3 is another encoding embodiment of the present invention. In Figure 3, 9 is an input section, 10 is a read-only memory (ROM)
), 11 is an output section. First, in the ROM 10, an encoded code word corresponding to the input signal is recorded at the position indicated by the input address. The input signal inputted from the input section 9 is inputted to the address of the ROM10, and the recorded code word output from the ROM10 is outputted to the output section 1 according to the input signal. In this way, it is also possible to implement the encoding operation as described above using memory.

Now, in the above encoding example, if (X7≠0), a code word of 17 bits in total is obtained from the combination of 8 information patterns and the end pattern. However, the information pattern is 9
Since there is no codeword that is concatenated with more than one codeword, this codeword can be decoded even if there is no ending pattern. Therefore, if (X7≠0), it is possible to encode into a 16-bit codeword. In this way, if the preceding k bits of a certain codeword are different from the preceding k bits of all other codewords, it becomes possible to represent the codeword only by the preceding bits.

Next, a block diagram of the reproducing apparatus of the present invention shown in FIG. 4 is shown. 12 in FIG. 4 is an input section of the present invention, ]3 is an error information input section,
14 is a sync pattern detection section, 15 is a variable length decoding section, 1
6 is an output section. The reproduced signal inputted from the input section 12 is inputted to the sync pattern detection section 14. The sync pattern detection unit 14 detects a sync pattern from the reproduced signal when an error occurs based on the error information of the reproduced signal inputted from the error information input unit 13, and encodes the position of the next bit of the sync pattern. This is input to the variable length decoding unit 15 as the starting position of the word. When the error information input unit 13 inputs that an error has been detected, the variable length decoding unit 15 stops decoding at that point and decodes the variable length according to the starting position of the code word input from the sync pattern detection unit 14. Resume decryption. The data decoded in this way is output from the output section 16. Since the sync pattern of the variable length code used in the present invention occurs only in the last part of the code word, by detecting this sync pattern, the beginning position of the next code word can be detected. For example, in the above example of the variable length code, the sync pattern is (0, 0), so it is possible to detect the start position of the code word simply by detecting two consecutive 0 bits. As described above, with the reproducing apparatus of the present invention, even if an error occurs during reproduction, it is possible to easily restore code synchronization of variable length codes. This makes it possible to minimize the influence of errors.

Effects of the Invention With the above configuration, the codeword used in the present invention includes a specific sync pattern in the last part of a codeword or a concatenation of codewords. Furthermore, even if the sync pattern is concatenated with any code word, it is a pattern that does not occur in any part other than the last part of the code word. Therefore, by using this variable length code, even if code synchronization is lost due to a transmission path error during reproduction, the end of the code can be detected by detecting the sync pattern.

This makes it possible to restore code synchronization.

Therefore, it is possible to reduce the influence of errors without increasing additional information such as error correction.

Furthermore, since the sync pattern generated by the present invention is a relatively short pattern, detection of the sync pattern is easy and has a great practical effect.

[Brief explanation of the drawing]

Figure 1 is a process diagram of the first recording device of the present invention;
V is a block diagram of the variable length encoding of the present invention, the second and third views are the block diagrams of the second variable length encoding of the present invention, and FIG. 4 is a block diagram of the reproducing apparatus of the present invention. 5...Information pattern input section, 6...End Bakun input section, 7...Pattern i5J saw device, 1
4...Nck pattern detection section. Name of agent: Patent attorney Haruaki Ogata and two others arrested＼←Hane

Claims (14)

[Claims] (1) n uniquely decodable bit patterns, m bit patterns among the n bit patterns as end patterns, and n−m bit patterns other than the end patterns as information patterns. , a part or all of a bit pattern generated by concatenating a certain information pattern and an end pattern is a sink pattern, and the sink pattern is not included in the bit pattern generated by concatenating any information pattern, A record of encoding and recording input data using variable length encoding means, characterized in that the end pattern is finally connected to any combination of the information patterns, or the end pattern itself constitutes a code word. Device. (2) In the set of codewords obtained by the variable length encoding means, if k bits from the front of a certain codeword differ from k bits from the front of all other codewords, the codeword is changed from the previous codeword. k
2. The recording device according to claim 1, wherein the recording device represents only bits. (3) Claim (1) characterized in that there are two types of information patterns: (1, 0) and (1, 1), an end pattern is (0), and a sink pattern is (0, 0). ) or the recording device described in (3). (4) The input signal has a sign bit S representing positive/negative and 8 bits representing the absolute value (X7, X6, X5, X4, X3,
2, X1, X0), (X7=X6=
If X5=X4=X3=X2=X1=X0=0), output the code word 0,
), then the sign S and (Xi-1,...,
For a total i+1 bit sequence of X0), if each bit is 0, (1, 0) is assigned, and if it is 1, (1,
1), concatenate 0 at the end of the resulting 2(i+1) bit series and output it as a code word, and in the case of (X7≠0), the code S and (X6,...
..., X0), if each bit is 0, (1, 0) is assigned, and if each bit is 1, (1,
, 1) and outputs and encodes a 16-bit sequence created by concatenating the data as a code word. (5) A claim ( The recording device described in 1) or (2). (6) Claim (1) characterized in that the variable length encoding means stores code words for all or part of the input signal in advance in a memory, and obtains the code words for the input signal by using this memory. , (2), (3) or (5)
Recording device as described. (7) The input signal has 1 sign bit S representing positive/negative and 8 bits representing the absolute value (X7, X6, X5, X4, X3,
2, X1, X0), (X7=X6=
If X5=X4=X3=X2=X1=X0=0), code word 1 is output and (X7=,...,=Xi+
1=0, Xi≠0), then the sign S and (Xi-1
, ..., X0), if each bit is 0, (0, 0) is assigned, and 1
In this case, assign (0, 1) and concatenate to create 2(
i+1) concatenate 1 at the end of the bit sequence and output it as a code word, and if (X7≠0), the code S and (X6, 2...
, X0), each bit is 0.
If , assign (0, 0), if 1, assign (0, 1
), and a 16-bit sequence created by concatenation is output as a code word and encoded.
), (2) or (5). (8) n uniquely decodable bit patterns, m bit patterns among the n bit patterns as end patterns, and n−m bit patterns other than the end patterns as information patterns. , a sink pattern generated by concatenating a certain information pattern and an end pattern is not included in a bit pattern generated by concatenating any information pattern, and the end pattern is included in any concatenation of the information patterns. When reproducing data encoded and recorded using a variable length encoding means characterized by concatenation at the end or constituting a code word by the end pattern itself, the encoded sync pattern detection means for reading the bit pattern after the error position and detecting the sync pattern when an error is detected in the bit string; A playback device that starts decoding. (9) In a set of codewords obtained by the variable length encoding means, if k bits from the front of a certain codeword differ from k bits from the front of all other codewords, the codeword is changed from the previous codeword. k
9. The playback device according to claim 8, wherein the playback device is represented by only bits. (10) A claim ( 8) or the reproduction device according to (9). (11) The input signal has a sign 1 bit S representing positive/negative and 8 bits representing the absolute value (X7, X6, X5, X4, X3,
X2, X1, X0), (X7=X6
=X5=X4=X3=X2=X1=X0=0), the code word 0 is output, (X7=,..., =Xi+1=0, Xi≠0)
In the case, the sign S and (Xi-1,...,X
0) for a total of i+1 bits, each bit is 0
If , assign (1, 0); if 1, assign (1, 1
), concatenate 0 at the end of the resulting 2(i+1) bit series and output it as a code word, and if (X7≠0), the code S and (X6,...
..., X0), if each bit is 0, (1, 0) is assigned, and if each bit is 1, (1,
, 1), and outputs and encodes a 16-bit sequence created by concatenating them as a code word. (12) Claim ( 8) or the reproduction device described in (9). (13) Claim (8) characterized in that the variable length encoding means stores code words for all or part of the input signals in a memory in advance, and obtains code words for the input signals by using this memory. , (9), (10) or (
12) The reproducing device described. (14) The input signal has a sign 1 bit S representing the positive/negative and 8 bits representing the absolute value (X7, X6, X5, X4, X3,
X2, X1, X0), (X7=X6
=X5=X4=X=3=X2=X1=X0=0), output code word 1, (X7=,..., =Xi+1=0, Xi≠0)
In the case, the sign S and (Xi-1,...,X
0) for a total of i+1 bits, each bit is 0
If , assign (0, 0), if 1, assign (0, 1
), concatenate 1 at the end of the resulting 2(i+1) bit series and output it as a code word, and if (X7≠0), the code S and (X6,...
..., X0), if each bit is 0, (0, 0) is assigned, and if each bit is 1, (0,
, 1), and outputs and encodes a 16-bit sequence created by concatenating them as a code word.