Coded data generation or conversion – Digital code to digital code converters – To or from number of pulses
Reexamination Certificate
2001-04-06
2002-07-16
Tokar, Michael (Department: 2819)
Coded data generation or conversion
Digital code to digital code converters
To or from number of pulses
C341S050000, C341S059000, C341S063000, C341S067000, C341S087000
Reexamination Certificate
active
06420980
ABSTRACT:
TECHNICAL FIELD
The present invention relates to encoding and compression for transmitting and recording super-audio signals having a quality of reproduced sound much higher than that of compact disk.
BACKGROUND ART
There are a variety of techniques for compression of audio signals. Two major techniques are known. One of them is a lossless compression where redundant data which depend on self-correlation or relative-correlation of the data of music signals are extracted, and only the redundant components are compressed for transmission and recording. The other is perceptual encoding where dull components are allowed to be deleted based on the ambiguity of the human audible properties to perform a high efficiency of the encoding (or the quality is degraded). The latter is commonly used together with the former for low bit rate communication and package media. However, it is essential in the super-audio technology for targeting a much higher level of the sound quality than the compact disk (hereinafter referred to as CD) technology to employ the lossless compression which does not cause degradation of the quality. The following description is hence limited to the lossless compression.
One of such conventional techniques is disclosed in “Serial transmission apparatus with data compression function” in Japanese Patent laid-open Publication 7-74675(1995). The object thereof is to improve the transmission rate in a serial transmission apparatus. An output of an analog-to-digital converter which converts. input analog signal to digital signal is processed by a differential process, and the signals are compressed by the Huffman conversion. As the high-rate data is compressed and transmitted over a line having a given communication speed, the substantial transmission rate is increased, and this prior art is similar to the present invention on this point. The differential process functions to bias the profile of appearance probability of digital data, and this improves the compression efficiency in the Huffman conversion at the later stage. In other words, the differential circuit can increase its advantage by cooperating with the Huffman conversion circuit. For example, it is said that the compression rate for converting audio data directly by the Huffman compression is generally 90 to 95%, and similar data have been confirmed through a series of experiments by the inventors. When the Huffman compression is performed after the differential process, the rate may slightly be increased to 85 to 90%.
Meanwhile, as a variety of high-density recording media including DVD have been developed so far, the pulse code modulation (PCM) super-audio technology can be realized in a wider frequency range and in a wider dynamic range. The DVD audio technology is just on the stage of standardizing its format. Its draft version, Book 0.9, was explained in a meeting at Tokyo on Apr. 21, 1998. One of publications that introduces the meeting is “Radio Technology”, June 1998, Vol. 52, No. 6, Serial No. 695, by IA Publishing, pp. 73-77. According to the report, the major parameters of the DVD audio technology include sampling frequencies of 48 kHz/96 kHz/192 kHz and 44.1 kHz/88.2 kHz/176.4 kHz, number of linear PCM quantization bits of 16/20/24, and maximum number of channels (ch) of 6. It is to be noted that the maximum bit rate is set to 9.6 Mbps. Any combination of the above parameters can be accepted as far as the bit rate is not greater than the determined level. For instance, a combination of 96 kHz, 24 bits, and 4 ch has bit rate of 9.216 Mbps, and it can be utilized. However, another combination of 96 kHz, 24 bits, and 5 ch has bit rate of 11.52 Mbpts which exceeds 9.6 Mbps, and it cannot be used. A further combination of 96 kHz, 24 bits, and 6 ch has bit rate of 13.824 Mbps exceeding 9.6 Mbps, and it cannot be used.
As to the movie, multi-channel systems becomes popular particularly in the United States of America. Some of home appliances employ multi-channel systems such as 5.1 channel (three channels at front center, left, and right, two channels at rear left and right, and one channel for a subwoofer), and others may follow before long. In view of such a background, a multi-channel system is also desired to employ the super-audio format. It is known that a combination of 96 kHz, 24 bits, and 6 ch is feasible with the use of high performance recording equipments available. It is then proposed to transmit and record DVD audio signals without degradation. Hence, the DVD audio technique is now demanded for the application of 96 kHz, 24 bits, and 6 ch.
In addition, besides the application of 96 kHz, 24 bits, and 6 ch to the DVD audio system, the recording time of 74 minutes on a single recording side is also desired, similarly to CD. This resides on the facts that most music workpieces are finished within 74 minutes and that master sources produced in the music industry are designated to fall in the length of 74 minutes. If its playback period stays within 74 minutes, both of the CD and DVD can favorably be planned, manufactured, and marketed. It is hence crucial for storage on a given size of disk medium that 4.7 GB (gigabytes) data in the DVD format are compressed so that its bit rate calculated by dividing 4.7 GB with the playback period (74 minutes) is not higher than 8.47 Mbps.
The foregoing requirements are now compiles below.
(a) The data compression shall be conducted by lossless compression which permits reversible conversion.
(b) The transmission rate shall be not higher than 9.6 Mbps defined as the maximum level in the DVD audio format.
(c) The average transmission rate shall be not higher than 8.47 Mbps for not exceeding the playback time of 74 minutes.
(d) Preferably, the data shall be compressed to 60% or less for allowing the playback time of 74 minutes at the mode of 96 kHz, 24 bits, and 6 ch.
DISCLOSURE OF INVENTION
The invention is developed to achieve the above requirements, and its object is to provide a method and an apparatus for carrying outlossless compression encoding and decoding of data (a) in a perfectly reversible mode, (b) at a peak transmission rate of not higher than 9.6 Mbps, (c) at average transmission rate of not higher than 8.47 Mbps or playback time of 74 minutes, and (d) at compression ate of 60% or less when playback time of 74 minutes is attained in the format of 96 kHz, 24 bits, and 6 ch.
In a method and in an apparatus for lossless compression encoding according to the invention, a given number of input data samples in a predetermined length of time is grouped to blocks, correlation between the samples in each block is deleted, redundant run lengths are determined in the data after subjected to the correlation deletion, and minimum of the redundant run length or run length of a common redundant portion in the samples is detected. Then, the common redundant portion is deleted from each sample, the data which have been subjected to the deleting the common redundant portion are subjected to the Huffman conversion, and the run length data of the common redundant portion and the Huffman-converted data for each sample are provided.
In a method and in a apparatus for lossless compression decoding according to the invention, code data are received which comprises run length data of a common redundant portion and data subjected to Huffman conversion in each sample, the data having been obtained by the steps of grouping a given number of input data samples in a predetermined length of time to blocks, deleting correlation between the samples in each block, determining redundant run length or run length of a common redundant portion in the samples after the correlation deletion, and deleting the redundant run length from each sample. Then, a conversion algorithm is get from the input data, and it is used for the Huffman decoding, and the run length data of the common redundant portion is gotten and added to the decoded data after the Huffman decoding. Then, correlation decoding is performed on the data to which the redundant portion is added.
Thus, in the method and the a
Matsushita Electric - Industrial Co., Ltd.
Nguyen Khai
Tokar Michael
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