JPH0773595A - Recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain a format which has a common synchronism and a frame size and in which ratio of compression data quantity, allocation information and scale factor data quantity is optimum for plural compression ratios and transfer rates. CONSTITUTION:A phase code generation section 6 generates a first phase code and a second phase code. A data code section 5 outputs data consisting of a first frame having a synchronizing signal, the first phase code, allocation information, a scale factor and a data block, and a second frame having a synchronizing signal, the second phase code and data block.

Description

Detailed Description of the Invention

[0001]

This invention uses data compression technology to
The present invention relates to a recording data structure of an audio recording / reproducing apparatus having a plurality of bit rates and its processing.

[0002]

2. Description of the Related Art Recently, an audio recording / reproducing apparatus using data compression has been put into practical use.

As a conventional audio recording / reproducing apparatus using data compression, there is, for example, a digital compact cassette (hereinafter referred to as DCC).

A conventional voice recording / reproducing apparatus will be described below. FIG. 7 shows the configuration of this conventional audio recording apparatus. In FIG. 7, 50 is a voice input terminal and 51 is an AD
A converter, 52 is a frequency band division filter, 53 is a compression code section, 54 is a data code section, and 55 is a recording medium.

The operation of the conventional audio recording apparatus having the above structure will be described below.

First, the audio signal input to the input terminal 50 is converted into digital data by the AD converter 51. The digital data is divided into 32 frequency bands by the frequency band division filter 52 in order to realize accurate compression encoding. As the input digital signal data divided into 32 frequency bands, 384 samples of data are collected. The collected data is grouped into 32 frequency bands, the largest absolute value is selected from each group, and the value is used as a scale factor as a representative value.
Also, the collected 384-sample input signal digital data is normalized by replacing it with the amount of change with respect to the scale factor. Further, the number of quantization bits expressing the compressed data is determined for each of the 32 frequency bands by reducing unnecessary portions in terms of human hearing characteristics. The determined 32 quantization bit numbers are called allocation information. A set of compressed data corresponding to the collected data and represented by the number of bits according to the allocation information is called a data block. The scale factor, allocation information, and data block are sent to the data encoder. The data encoding unit 54 adds a synchronization signal and other control signals to the scale factor, allocation information, and data blocks to form data in units of frames.

Here, FIG. 9 is a diagram showing the structure of a frame. 31 is a synchronizing signal, 32 is a bit rate code, 3
3 is a sampling frequency code, 35 is allocation information, 36 is a scale factor, and 37 is a data block. The sync signal 31 is used for frame sync detection.
The bit rate code 32 indicates the transfer rate of compressed data. The sampling frequency code 33 indicates the sampling frequency of the AD converter 51.

A data string having the above-described frame as a unit is recorded on the recording medium 55.

FIG. 8 shows the structure of a conventional audio reproducing apparatus. In FIG. 8, 55 is a recording medium, and 56
Is a data decoding unit, 57 is a synchronous reproduction unit, 59 is a compression decoding unit, 60 is a frequency band synthesis filter, 61 is a DA converter, and 62 is an output terminal.

The operation of the conventional audio reproducing apparatus configured as described above will be described below.

First, the data recorded on the recording medium 55 is a data string in units of frames shown in FIG. The reproduced data string identifies the synchronization signal 31 in the synchronization reproduction section 57, and outputs the timing at which the synchronization signal is reproduced to the data decoding section 56. The data decoding unit 56 identifies the bit rate code 32, the sampling frequency code 33, and the allocation information 35 that are reproduced following the timing signal of the synchronous reproduction unit 57, and further identifies the scale factor 36 and the data block 37 to perform compression decoding. Part 59
Output to. The compression decoding unit 59 receives the allocation information 35 and scale factor 3 input from the data decoding unit 56.
6. Restore the original input digital signal data using the data block 37. The input digital signal data in the state of being divided into 32 frequency bands is the frequency band synthesis filter 6
The audio signal synthesized at 0 is converted into quantized digital data. Further, the DA converter 61 uses the same frequency as the sampling frequency at the time of recording, which is obtained by the sampling frequency code 33, to be converted back into an audio signal and output from the output terminal 62.

[0012]

In the structure having the above frame structure, what is recorded on the magnetic tape as a recording medium is a compressed data block corresponding to sample data and information of frame data. It has some allocation information and a scale factor. Therefore, in order to perform recording / reproduction by high-quality compression, the compressed data block corresponding to the data in sample units, the allocation information, which is the information of the data in frame units, and the scale factor are set to the optimum ratio. It is important to design the length of the frame.

However, when the transfer rate after compression is not constant and there are many cases, two types of tape speeds, that is, two types of tape speeds, such as the two-speed recording / reproduction found in the conventional microcassette tape recorder, are used. In the case of selecting one of the transfer rates and implementing it in one system, there is a problem that the above-described optimization of the frame length cannot be performed in two cases.

The present invention solves the above-mentioned problems of the prior art, and has a common frame length and a compressed data block corresponding to sample data for each of a plurality of transfer rates and a frame unit. It is an object of the present invention to provide a recording / reproducing apparatus having a frame structure in which allocation information, which is data information, and a scale factor have an optimum ratio.

[0015]

In order to achieve this object, a recording / reproducing apparatus of the present invention comprises a set number of input digital signal data divided into a plurality of frequency bands, a scale factor which is a representative value of the set. A data block, which is a set of compressed data obtained by normalizing the input digital signal data by a scale factor, and a compression encoding unit for calculating and outputting allocation information indicating the number of bits of the compressed data assigned to each frequency band. , A phase code generator that generates a phase code synchronized with the cycle of the data block, and data that outputs data in units of frames, in which the synchronization signal and the phase code are added to the data block, scale factor, and allocation information Records data in units of frames composed of a code part and a data code part A first frame having a sync signal, a first phase code, allocation information, a scale factor, and a data block, and a second frame having a sync signal, a second phase code, and a data block. This is a configuration having a data encoding unit that outputs data having a structure consisting of.

[0016]

According to the present invention, when the transfer rate after compression is reduced and the compression ratio is increased by the above configuration, the phase code representing the phase of the frame is newly defined and combined to provide data information in frame units. The ratio of the allocation information and the scale factor becomes smaller than that of the compressed data block corresponding to the data in units of samples, so that the optimum data structure for each transfer rate is realized by using a common frame.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the structure of a recording section of an audio recording / reproducing apparatus according to an embodiment of the present invention. In FIG. 1, 1 is a voice input terminal, 2 is an AD converter, 3 is a frequency band division filter, 4 is a compression code section, 5 is a data code section, 6 is a phase code generating section, and 7 is a recording medium.

The operation of the audio recording / reproducing apparatus of this embodiment constructed as above will be described below.

First, the audio signal input to the input terminal 1 is converted into digital data by the AD converter 2. The digital data is divided into 32 frequency bands by the frequency band division filter 3 in order to realize compression encoding with high accuracy. As the input digital signal data of the compression encoding unit 4 divided into 32 frequency bands, 768 samples of data are collected. This is one processing unit. The collected data is grouped into 32 frequency bands, the largest absolute value is selected from each group, and the value is used as a scale factor as a representative value. Also collected 76
The input digital signal data of 8 samples is normalized by replacing it with the amount of change with respect to the scale factor to obtain compressed data. Furthermore, the number of quantization bits for expressing the compressed data is determined by reducing unnecessary portions in terms of human hearing characteristics, and 32 types of values are determined for each of the 32 frequency bands.
The 32 numerical value sequences are called allocation information. A set of compressed data corresponding to the collected data is called a data block. As a result of the above processing, the scale factor, allocation information, and data block are sent to the data encoding unit 5. The data encoder 5 adds the sync signal, the phase code input from the phase code generator 6 and other control signals to the scale factor, the allocation information and a part of the data block to form the first frame. . Also, a second frame is formed by adding a portion of the data block corresponding to 768 samples, which is not included in the first frame, a synchronization signal, a phase code, and other control signals. The phase code generator 6 repeatedly outputs the phase code of "0" and "1" with the half of the time interval corresponding to 768 samples as the cycle, that is, in the frame cycle.
The phase code generator 6 can be realized by using an ordinary counting circuit. The phase code "0" indicates the first frame, and the phase code "1" indicates the second frame.

Here, FIG. 3 shows the first embodiment in FIG.
It is a figure which shows an example of a structure of this frame. Reference numeral 20 is a synchronizing signal, which uses 16 bits, for example. Reference numeral 21 is a bit rate code, for example, 8 bits are used. Reference numeral 22 is a sampling frequency code, which uses, for example, 7 bits. Reference numeral 23 is a phase code, for example, 1 bit is used. Since this frame is the first frame, the phase code data is "0". 24 is allocation information, for example, 256 bits, 25 is a scale factor, for example, 384 bits, and 26 is a data block, for example, 2400 bits are used. In the case of this example, the first frame has a total length of 3072 bits, which is one frame.

FIG. 4 is a diagram showing an example of the configuration of the second frame in the embodiment of FIG. 20 to 22 are the same as 20 to 22 in FIG. Reference numeral 23 is the same as the phase code 23 in FIG. 3, but its data is "1" indicating the second frame. 26 is the same data as the data block 26 in FIG. 3, but the data amount is 3
It has increased to 040 bits. The total length of the second frame is 3072 bits in total, which is the same as the first frame.

The above first and second frames are sequentially output from the data encoder 5 and recorded on the recording medium 7.

Next, the reproducing operation will be described. FIG. 2 shows the structure of the reproducing section of the audio recording / reproducing apparatus in an embodiment of the present invention. Reference numeral 7 is a recording medium, 8 is a data decoding section, 9 is a synchronous reproduction section, 10 is a phase reproduction section, 11 is a compression decoding section, 12 is a frequency band synthesis filter, 13 is a DA converter, and 14 is an output terminal.

As described above, the first frame shown in FIG. 3 and the second frame shown in FIG. 4 are sequentially and repeatedly recorded on the recording medium 7. At the time of reproduction, first, the synchronous reproduction section 9 identifies the synchronization signal 20 recorded on the recording medium 7. The sync reproducing unit 9 outputs the timing at which the sync signal 20 is reproduced to the phase reproducing unit 10 and the data decoding unit 8. The phase reproducing unit 10 counts the data reproduced after the timing signal of the synchronous reproducing unit 9 and detects the phase code 23 corresponding to the 16th bit to identify the first frame and the second frame. Is output. The phase regenerating unit 10 can be realized by using a normal counting circuit and a flip-flop circuit for creating a flag. The data decoding unit 8 identifies the bit rate code 21 and the sampling frequency code 22 that are reproduced following the timing signal of the synchronous reproduction unit 9, and the frame flag output from the phase reproduction unit 10 indicates the first frame. When it is present, the allocation information 24, the scale factor 25, and the data block 26 are identified and output to the compression decoding unit 11. Also,
When the frame flag output from the phase reproduction unit 10 indicates the second frame, the data block 26 is identified and output to the compression decoding unit 11. The compression decoding unit 11 includes allocation information 24 reproduced from the first frame input from the data decoding unit 8 and a scale factor 25,
Using the data block 26 reproduced from the first and second frames, the original input digital data of 768 samples corresponding to the total length of the first and second frames (two frame lengths). Restore signal data. As the recording medium 7 is sequentially reproduced as the recording medium 7 runs, the above decoding operation is repeated with two frames, which are the first and second frames, as one processing unit, and is divided into 32 frequency bands. The input digital signal data in this state is restored and output to the frequency band synthesis filter 12. The frequency band synthesis filter 12 synthesizes the restored input digital signal data and converts it into digital data in which the audio signal is quantized. Further, the DA converter 13 uses the same frequency as the sampling frequency at the time of recording obtained by the sampling frequency code 22 to restore the audio signal and outputs it from the output terminal 14.

Next, a case where the present invention is applied to a tape recorder capable of performing a standard tape traveling speed recording / reproducing operation and a long-time recording / reproducing operation at a half tape traveling speed will be described.

FIG. 5 is a diagram showing the structure of the recording unit. In the figure, 1 is a voice input terminal, 2 is an AD converter, 3
Is a frequency band division filter, 4 is a compression code section, 5 is a data code section, 6 is a phase code generation section, and 7 is a magnetic tape as a recording medium, which has the same structure as that of FIG. The difference from FIG. 1 is that a tape drive motor 15 is added in order to explain the tape traveling speed in this application example.

In the configuration of FIG. 5, first, consider the standard tape running speed recording / reproducing operation. At this time, the tape drive motor 15 rotates so that the magnetic tape 7 runs at the first speed. The compression encoding unit 4 outputs the optimal allocation information, scale factor, and data block for the first transfer rate. The unit of processing at this time is 384 samples (1
The frame length is basically used, but 768 samples (2 frame length) is also possible. The data encoding unit 5 sets the bit rate code 21 in the first data to form the first frame shown in FIG. 3 and does not use the second frame. At this time, the phase data is unnecessary.

Next, let us consider a long-time recording / reproducing operation at a half tape running speed. At this time, the tape drive motor 15 rotates so that the magnetic tape 7 runs at the second speed. The compression encoding unit 4 outputs allocation information, scale factors, and data blocks that are optimal for the second transfer rate. The unit of processing at this time is 768 samples (2 frame length). The data encoding unit 5 sets the bit rate code 21 in the second data. In addition, the output of the phase code generator 6 includes the phase code and forms the first and second frames shown in FIGS. 3 and 4, and sequentially outputs the frames. Data composed of the first and second frames is recorded on the magnetic tape 7.

Next, FIG. 6 is a diagram showing the structure of the reproducing section. In the figure, 7 is a magnetic tape as a recording medium, and 8 is
Is a data decoding unit, 9 is a synchronous reproducing unit, 10 is a phase reproducing unit,
Reference numeral 11 is a compression decoding unit, 12 is a frequency band synthesis filter, and 13
Is a DA converter, and 14 is an output terminal, which has the same configuration as in FIG. The difference from FIG. 2 is that a tape drive motor 15 is added in order to explain the tape traveling speed in this application example.

In the configuration of FIG. 6, first, consider a standard tape running speed recording / reproducing operation. At this time, the tape drive motor 15 rotates so that the magnetic tape 7 runs at the first speed. The data composed of the first frame of FIG. 3 is reproduced on the magnetic tape 7. Since the bit rate code 21 is set in the first data, it is identified as the first frame. At this time, the phase data is unnecessary. The subsequent reproducing operation is the same as the conventional example.

Next, consider a long-time recording / reproducing operation at a tape traveling speed of half speed. First, tape drive motor 1
5 rotates so that the magnetic tape 7 runs at the first speed. At this time, the first and second frames are sequentially recorded on the magnetic tape 7. The data decoding unit 8 identifies that the bit rate code 21 is the second data and sends a signal indicating the second speed to the tape drive motor 15, so that the tape drive motor 15 operates at the second speed. Rotates to run. From the first and second frames that are sequentially recorded on the magnetic tape 7, the data decoding unit 8 causes the phase reproducing unit 10 to operate.
Is used to identify the first frame. The compression decoding unit 11 first uses the allocation information 24 and the scale factor 25 read from the first frame to make a first
The original input digital signal data corresponding to the data of the data block in the frame is restored.

Further, the second frame to be reproduced subsequently uses the allocation information 24 and the scale factor 25 read out in the first frame again and corresponds to the data block in the second frame. Restore the input digital signal data of. The sum of the above original input digital signal data corresponding to the data of the data block in the first frame and the original input digital signal data corresponding to the data block in the second frame is the processing at the time of recording. The data is the number of 768 samples, which is a unit.

As described above, according to the present embodiment, since the first and second frames having the phase code are provided, the data structure of the bit rate code 21 and that of the synchronous reproduction section are made common. It is possible to detect the tape speed at the time of recording regardless of which of the first speed and the second speed the detection of 21 is initially set, and the detection circuit can be made common and rationalized. Further, by providing the allocation information and scale factor common to the first and second frames, it is possible to make the data block relatively large and improve the sound quality of compression.

In the above-described embodiment, the second frame shown in FIG. 4 has the sync signal 20, the bit rate code 21, the sampling frequency code 22 and the data block 26. Either the shared allocation information 24 or the scale factor 25 may be added to the frame.

[0036]

As described above, according to the present invention, the first aspect includes the phase code generator, the synchronization signal, the first phase code, the allocation information, the scale factor, and the data block.
And a data encoding section for outputting data having a structure including a synchronization signal, a second phase code and a second frame having a data block.
And a tape recorder having a second speed, the first
It is possible to provide not only a frame structure that can be optimally compressed at the second speed but also a frame structure that can be optimally compressed at the second speed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a recording unit of an audio recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a reproducing unit of the audio recording / reproducing apparatus according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a configuration of a first frame according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a configuration of a second frame according to an embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a recording unit of an audio recording / reproducing apparatus in an application example of the present invention.

FIG. 6 is a block diagram showing a configuration of a reproducing unit of an audio recording / reproducing apparatus in an application example of the present invention.

FIG. 7 is a block diagram showing a configuration of a recording unit of a conventional audio recording / reproducing apparatus.

FIG. 8 is a block diagram showing a configuration of a reproducing unit of a conventional audio recording / reproducing apparatus.

FIG. 9 is an explanatory diagram showing a frame structure in a conventional audio recording / reproducing apparatus.

[Explanation of symbols]

 1 Input Terminal 4 Compression Code Section 5 Data Code Section 6 Phase Code Generation Section 7 Recording Medium 8 Data Decoding Section 10 Phase Reproduction Section 11 Compression Decoding Section 20 Synchronization Signal 23 Phase Code 24 Allocation Information 25 Scale Factor 26 Data Block

Claims (6)

[Claims] 1. A scale factor which is a representative value of a set of input digital signal data divided into a plurality of frequency bands, and a set of compressed data obtained by normalizing the input digital signal data by the scale factor. A compression code unit that calculates and outputs a certain data block and allocation information indicating the number of bits of the compressed data assigned to each frequency band, and a phase code generation that generates a phase code synchronized with the cycle of the data block. A data encoder, a data encoder that outputs data in units of frames, in which a synchronization signal and the phase code are added to the data block, the scale factor, and the allocation information, and the data encoder. And a medium for recording data in units of frames, the synchronization signal and A first frame having one phase code, the allocation information, the scale factor, and the data block; and a second frame having the synchronization signal, a second phase code, and the data block. A recording / reproducing apparatus having a data encoding unit for outputting data. 2. A set of a predetermined number of sets of input digital signal data divided into a plurality of frequency bands, a scale factor that is a representative value of the set, and a set of compressed data obtained by normalizing the input digital signal data by the scale factor. A data block, allocation information indicating the number of bits of the compressed data allocated for each frequency band, a sync signal, a medium in which a frame including a phase code is recorded, and a sync signal from a reproduction output of the medium. A synchronization reproducing unit for identifying, a phase reproducing unit for identifying the phase code, a data decoding unit for outputting the data block, the scale factor, and the allocation information using the identified synchronization signal and the phase code And a compression decoding unit that reproduces digital signal data from the output of the data decoding unit, A first frame having the synchronization signal, the first phase code, the allocation information, the scale factor, and the data block; and a second frame having the synchronization signal, the second phase code, and the data block. Reproduction data having a structure consisting of the following phase, and reproducing the allocation information, the scale factor, and the data block from the first frame having the first phase code, and the second phase code. A recording / reproducing apparatus having a data decoding unit configured to discriminate the data block from the second frame having. 3. A scale factor which is a representative value of a set of input digital signal data divided into a plurality of frequency bands, and a set of compressed data obtained by normalizing the input digital signal data by the scale factor. A compression code unit that calculates and outputs a certain data block and allocation information indicating the number of bits of the compressed data assigned to each frequency band, and a phase code generation that generates a phase code synchronized with the cycle of the data block. A data encoder, a data encoder that outputs data in units of frames, in which a synchronization signal and the phase code are added to the data block, the scale factor, and the allocation information, and the data encoder. And a medium for recording data in units of frames, the synchronization signal and A first frame having one phase code, the allocation information, the scale factor, and the data block; the sync signal, a second phase code, one of the allocation information or the scale factor, and the data block. A recording / reproducing apparatus having a data encoding unit for outputting data having a structure including a second frame having 4. A scale factor which is a representative value of a set of input digital signal data divided into a plurality of frequency bands, and a set of compressed data obtained by normalizing the input digital signal data by the scale factor. A data block, allocation information indicating the number of bits of the compressed data allocated for each frequency band, a sync signal, a medium in which a frame including a phase code is recorded, and a sync signal from a reproduction output of the medium. A synchronization reproducing section for identifying, a phase reproducing section for identifying the phase code, a data decoding section for outputting a data block, a scale factor, and allocation information using the identified synchronization signal and the phase code, A compression decoding unit for reproducing digital signal data from the output of the data decoding unit, A first frame having a synchronization signal, a first phase code, the allocation information, the scale factor, and the data block; either the synchronization signal, the second phase code, the allocation information, or the scale factor. And reproduction data having a structure consisting of a second frame including the data block, and the allocation information, the scale factor, and the data block from the first frame having the first phase code. A recording / reproducing apparatus having a data decoding unit configured to reproduce and discriminate either the allocation information or the scale factor and the data block from the second frame having the second phase code. 5. A set of a predetermined number of sets of input digital signal data divided into a plurality of frequency bands, a scale factor that is a representative value of the set, and a set of compressed data obtained by normalizing the input digital signal data by the scale factor. A compression code unit that calculates and outputs a certain data block and allocation information indicating the number of bits of the compressed data assigned to each frequency band, and a phase code generation that generates a phase code synchronized with the cycle of the data block. A data encoder, a data encoder that outputs data in units of frames, in which a synchronization signal and the phase code are added to the data block, the scale factor, and the allocation information, and the data encoder. And a medium for recording data in units of frames. A first compression unit having a compression coding unit that sets the number of pieces of signal data corresponding to two frame lengths into one processing unit, the synchronization signal, the first phase code, the allocation information, the scale factor, and the data block. Data of a structure including a frame and a second frame having the synchronization signal, the second phase code, and the data block is output, and compressed data of one processing unit is used as the data block of the first frame. A recording / reproducing apparatus having a data encoding section assigned to the data block of the second frame. 6. A set of a predetermined number of sets of input digital signal data divided into a plurality of frequency bands, a scale factor that is a representative value of the set, and a set of compressed data obtained by normalizing the input digital signal data by the scale factor. A data block, allocation information indicating the number of bits of the compressed data allocated for each frequency band, a sync signal, a medium in which a frame including a phase code is recorded, and a sync signal from a reproduction output of the medium. A synchronization reproducing unit for identifying, a phase reproducing unit for identifying the phase code, a data decoding unit for outputting the data block, the scale factor, and the allocation information using the identified synchronization signal and the phase code And a compression decoding unit that reproduces digital signal data from the output of the data decoding unit, A first frame having the synchronization signal, the first phase code, the allocation information, the scale factor, and the data block; and a second frame having the synchronization signal, the second phase code, and the data block. And the reproduction data having a structure consisting of the following frames are read, the allocation information, the scale factor, and the data block are read from the first frame having the first phase code, and the second phase code is read. A data decoding unit configured to determine the data block from the second frame, the allocation information and the scale factor read from the first frame are read from the first frame. The compressed data of the data block and the second frame to be reproduced subsequently? Recording and reproducing apparatus having a compression decoder for processing as data common to both the compressed frame of said data blocks to be read.