KR100223169B1 - System for recording and reproducing of pcm digital audio signals - Google Patents

Abstract

An audio recording system according to the present invention converts audio samples in a predetermined reference unit of a digital audio signal into frequency-domain transform coefficients, and formats the change coefficients according to a preset recording format. The formatted signal is recorded on a recording medium. A corresponding audio reproduction system converts an audio signal in a frequency domain contained in data read from a recording medium based on an operation frequency related to the digital-analog conversion and a sampling frequency value of a signal recorded on the recording medium, Format and invert. The inverse formatting unit in the audio reproducing system extracts only a part of data belonging to the low frequency region of the audio signal in the frequency domain when the sampling frequency of the audio signal recorded on the recording medium is larger than the operating frequency. If the sampling frequency of the recorded audio signal is less than the operating frequency, the inverse formatter performs inverse formatting to output all data in the frequency domain. The changing part converts the audio signal in the frequency domain into a signal in the time domain, and performs zero padding in the frequency domain with respect to the audio signal having a sampling frequency less than the operating frequency.

Description

A system for recording and reproducing a pulse code modulated digital audio signal

FIG. 1 is a schematic block diagram of a digital audio signal recording apparatus according to a preferred embodiment of the present invention. FIG.

FIG. 2 is a detailed block diagram of the first degree formatting unit 30,

3 (a) - (d) illustrate recording formats according to the present invention,

FIG. 4 is a schematic block diagram of an audio reproducing apparatus according to an embodiment of the present invention;

FIG. 5 is a block diagram showing another embodiment of an audio reproducing apparatus according to the present invention;

DESCRIPTION OF THE REFERENCE NUMERALS

10: reference unit generator 20:

30: formatting section 40: recording section

50: Reading section 60: Inverse formatting section

71, 73: inverting section 81, 83: D / A converter

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for recording and reproducing pulse code modulation (PCM) digital audio signals, and more particularly to a system for recording and reproducing pulse code modulated digital audio signals To a system for recording and reproducing a PCM digital audio signal, which makes it possible to reproduce an audio signal read from the recording medium.

All devices up to now using a PCM digital audio signal use a reference unit, which is a data unit that can be error corrected when played back. The size of the reference unit is determined by the characteristics of the transmission medium. A digital audio signal sampled according to a predetermined sampling frequency is recorded in the recording medium in the form of blocks having a size, i.e., a data amount, determined according to data recording characteristics in a recording medium such as CD, DAT (digital audio tape) When a reproduction operation is performed on such a recording medium, the D / A converter in the reproduction apparatus performs digital-analog conversion of the digital audio signal in the order in which data is output from the recording medium.

With respect to PCM digital audio signals, new audio recording schemes using sampling frequencies of 88.2 KHz and 96 KHz, replacing the conventional method using sampling frequencies of 44.1 KHz and 48 KHz, in Japan and around the world, for example, , And Japanese Advanced Digital Audio (ADA) method. However, existing reproduction systems using sampling frequencies of 44.1 KHz and 48 KHz can not properly reproduce digitally recorded audio signals according to the newly proposed methods. Therefore, in order to enable a conventional reproducing system to reproduce a digital audio signal of a new recording system, a separate digital signal processing is required to enable the number of bits representing each sample to be handled without much noise. Examples of required digital signal processing include low pass filtering to remove frequency components greater than 44.1 KHz or 48 KHz from the signal read from the recording medium, low pass filtered signal to a signal with a sampling frequency of 44.1 KHz, 48 KHz Decimation filtering, and subsequent processing for playback. For this reason, since an audio apparatus according to a conventional recording method for processing an audio signal according to a new recording method must process all input audio data, the operation cycle of the digital processor required must be faster than the sampling frequency of the input data. For this reason, there is a disadvantage that the price for upgrading the existing reproducing system to reproduce the digital audio signal of the newly proposed signal recording system becomes very high. In addition, the above-mentioned digital signal processing requires an additional amount of RAM, and the price required for improvement is further increased. However, a playback system having a D / A converter with a sampling frequency of 88.2 KHz or 96 KHz does not require a digital processor or a large amount of RAM to process the audio data, since the received data is immediately sent to the output stage. However, when this recording method is presented to another recording method using a sampling frequency higher than 88.2 KHz or 96 KHz, the same problem as the conventional recording method is obtained.

An object of the present invention is to solve the above-mentioned problems, and it is an object of the present invention to provide a method and apparatus for converting audio samples in a predetermined reference unit of a digital audio signal into frequency-domain transform coefficients, A system in which an audio signal sampled according to a recording system and an audio signal sampled according to a new recording system can be recorded and reproduced in both an existing audio apparatus and an audio apparatus manufactured according to a new recording system.

According to another aspect of the present invention, there is provided an audio recording system for recording a digital audio signal on a digital recording medium. The audio recording system includes a reference unit sequence having a predetermined size, sequence converting unit for receiving the reference unit sequence, converting the audio samples in each reference unit into frequency-domain transform coefficients, and outputting a reference unit sequence containing the transform coefficients; A formatting unit that receives the reference unit series of the conversion unit, formats each reference unit into recording units according to a predetermined recording format, and outputs a series of recording units obtained as a result of the formatting, And recording means for recording on the digital recording medium,

An audio reproduction system for reproducing an audio signal in a frequency domain recorded on the digital recording medium includes a D / A converter having a preset operating frequency, a signal processing unit for reading a signal recorded on the recording medium, A first means for determining a frequency and a recording format, and for outputting an audio signal together with a frequency discrimination result and recording format data; a second means for receiving output data from the first means, the sampling frequency and recording format corresponding to the received data, Second means for inversely formatting the audio signal contained in the received data based on a sampling frequency corresponding to the operating frequency of the D / A converter, and second means for inverting the audio signal in the frequency domain output from the second means, And a third means for supplying audio samples to the D / A converter.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic block diagram of a digital audio signal recording apparatus according to an embodiment of the present invention. The apparatus of FIG. 1 according to an embodiment of the present invention not only has an audio signal having a sampling frequency of 88.2 KHz or 96 KHz according to a new audio recording method, but also has a sampling frequency of 44.1 KHz or 48 KHz according to a conventional audio recording method The audio signal can be recorded on the recording medium using the recording format proposed by the present invention. Hereinafter, for convenience of explanation, a relatively high sampling frequency is referred to as a first sampling frequency, and a relatively low sampling frequency is referred to as a second sampling frequency.

The sampled time-domain audio signals are quantized using a linear PCM or the like and input to the reference unit generator 10 of FIG. 1. The reference unit generator 10 divides an input digital audio signal into reference units of a predetermined size. The reference unit and the recording unit to be mentioned later are determined according to the sound quality and characteristics of the transmission medium. An example of a reference unit obtained by segmentation is shown in Figure 3 (a). The reference unit of FIG. 3 (a) consists of a sequence of 2m audio samples. The reference unit generator (10) sequentially supplies the reference units obtained by the division to the converter (20). The converting unit 20 converts the audio samples into frequency-domain transform coefficients. This performance of the conversion unit 20 is determined according to the sound quality of the target audio signal. The conversion coefficients obtained by the area conversion of the individual reference units are output to the formatting unit 30 in a form that is divided for each reference unit. The formatting unit 30 uses one of the first recording formats related to FIG. 3 (b) and the second recording formats related to FIG. 3 (c) and (d) Format. The detailed configuration and operation of the formatting section 30 will be described in detail with reference to FIGS. 2 and 3 (b) - (d). The recording unit 30 digitally records a signal formatted by the formatting unit 30 in a recording medium (not shown) such as a CD, a DAT, or the like.

FIG. 2 is a detailed block diagram of the first degree formatting unit 30. FIG. The recording format specification unit 22 of the formatting unit 30 designates one of two recording formats for the reference units obtained by the reference unit formatter 10. [ The recording format specification of the recording format specification unit 22 can be designed to be performed by a user who wants to record an audio signal. When the first recording format is selected, the recording format determiner 32 outputs the series of the conversion coefficients received from the conversion unit 20 to the first data formatting unit 34. [ The first data formatting unit 34 formats the conversion coefficients in the individual reference units into the first recording unit. FIG. 3 (b) shows a first recording unit composed of the transform coefficients F [0], F [1], F [2], ..., F [2m]. In FIG. 3 (b), F [0] represents the transform coefficient of the lowest frequency, and F [2m] represents the transform coefficient of the highest frequency. The first data formatting unit 34 forms one first recording unit with the conversion coefficients in one reference unit and outputs the sequence of the first recording units to the first additional data inserter 35. The first additional data inserter 35 inserts the first additional data indicating the audio sampling frequency of the received recording unit series and the second additional data indicating the number of audio samples in the individual recording unit at the front end of the recording unit series. Since the first and second additional data are inserted in the front end of the recording unit series, the first and second additional data are appropriately inserted into the recording unit series according to the characteristics of the transmission channel or recording medium It will be clear to those skilled in the art to modify the first data formatter 34.

When the second recording format is selected, the recording format specification unit 32 outputs the sequence of reference units received from the conversion unit 20 to the second data formatting unit 36. The second data formatting unit 36 formats the conversion coefficients in the individual reference units applied from the recording formatting unit 32 into two recording units. More specifically, the second data formatting unit 36 divides the conversion coefficients in each reference unit to generate a second recording unit having relatively low frequency conversion coefficients and a second recording unit having relatively high frequency conversion coefficients Three recording units are formed. Therefore, two recording units are obtained from one reference unit. Figure 3 (c) shows a second recording unit containing the transform coefficients F [0], F [1], F [2], ..., F [m] Contains the transform coefficients F [m], F [m + 1], F [m + 2], ..., F [2m] And outputs a series of recording units obtained by two per reference unit to the second additional data inserter 27. In the sequence of recording units, the second and third recording units corresponding to the relatively preceding reference unit are the reference unit In the case of recording units corresponding to the same reference unit, the second recording unit has a position ahead of the third recording unit. The second additional data inserter 37 for receiving the recording unit series from the second data formatting unit 34 outputs the above first additional data to the front end of the recording unit sequence output from the second data formatting unit 36 Sikimyeo inserted, and also insert the third additional data to distinguish from each other the second and third recording units obtained from the same reference unit in front of the second and third recording units, respectively.

The apparatus of FIG. 1 described above has been described as capable of using both recording formats. However, in a practical implementation, it is preferable to use only one specific recording format. If the first-degree device uses both recording formats, additional additional data, i.e., recording format data, capable of distinguishing the two recording formats is required. In this case, the recording unit 40 of the first drawing device inserts the recording format data in the front end of the formatted data.

The reproducing apparatus of FIG. 4 reproduces a digital audio signal from a recording medium (not shown) on which a digital audio signal is recorded, and has a D / A converter 81 having the same operating frequency as the second sampling frequency. The reading unit 50 reads the audio signal from the recording medium by the digital audio signal converted into the frequency domain by the above-described first drawing apparatus. The audio signal may have the first sampling frequency or the second sampling frequency described above. The frequency discriminator 51 in the reading unit 50 discriminates the sampling frequency of the read signal and outputs the discrimination result to the recording type discriminator 53. [ The recording type discriminating device 53 discriminates the recording format of the read signal by using the additional data contained in the read signal. If the signal recorded on the recording medium is a signal formatted according to the first recording format, the signal contains the first and second additional data and the recording format data. If the recorded signal is a signal formatted according to the second recording format, the signal contains the first and third additional data and the recording format data. The reading unit 50 supplies the data read from the recording medium together with the frequency discrimination result and the determined recording format data to the inverse formatting unit 60 (1). It is possible to design such that the reading unit 50 supplies data to the inverse formatting unit 60 (1) based on the frequency discrimination result and the recording format data. Alternatively, the reading unit 50 supplies all the read data, the frequency discrimination result and the recording format data to the inverse formatting unit 60 (1), and the inverse formatting unit 60 (1) And may be designed to supply data to the device contained therein.

The first data extractor 61 in the inverse formatting unit 60 (1) extracts the data (data) from the reading unit 60 (1) when the data recorded on the recording medium has the first sampling frequency and the first recording format, And extracts the transform coefficients of the low frequency region for every first recording unit of the recording unit. More specifically, the first data extractor 61 bisects the transform coefficients in the individual record unit based on the second additional data, and extracts the transform coefficients of the low-frequency domain. Here, the low frequency region means the transform coefficients corresponding to 1/2 of the lowest frequency among all the transform coefficients in each first recording unit. Then, the first data extractor 61 removes the second additional data. As a result, the output data of the reading unit 40 (1) is 2: 1 scrambled. When the data recorded on the recording medium has the first sampling frequency and the second recording format, the first inverse formatter 63 extracts the second recording units based on the third additional data contained in the input data, 3 Remove additional data. When the data recorded on the recording medium has the second sampling frequency and the first recording format, the inverse formatting unit 60 (1) removes the second additional data contained in the data input from the reading unit 50 . When the data recorded on the recording medium has the second sampling frequency and the second recording format, the first inverse formatting unit 63 stores only the second recording units only on the basis of the previously stored second recording format and the third additional data . The inverse formatting unit 60 (1) outputs the inverse transforming unit 71 the transform coefficients obtained as a result of inverse formatting of the data read from the recording medium. The inverse transform unit 71 inversely transforms the input transform coefficients. That is, into audio samples in the time domain. The audio samples output from the inverse transforming unit 71 are subjected to digital-analog conversion by the D / A converter 81. [ Therefore, the apparatus of FIG. 4 has not only an audio signal having a sampling frequency corresponding to the operating frequency of the D / A converter 81 but also a sampling frequency corresponding to twice the operating frequency of the D / A converter 81 An audio signal can be reproduced. Therefore, when the audio signal recorded on the recording medium has the first sampling frequency and the D / A converter 61 operates according to the second sampling frequency, the device of FIG. 4 is not nearly distinguished by the human auditory system It is possible to provide the listener with an audio signal of a sound quality of

FIG. 5 shows a reproducing apparatus having a D / A converter 83 having an operating frequency corresponding to a first sampling frequency, unlike the apparatus shown in FIG. In FIG. 5, the blocks having the same reference numerals as those in FIG. 4 perform the same functions as the corresponding blocks in FIG. 4, and a detailed description thereof will be omitted. The reading unit 50 outputs the frequency discrimination result obtained using the data read from the recording medium and the discriminated recording format data to the inverse formatting unit 60 (2) together with the data read from the recording medium. When the data recorded on the recording medium has the first sampling frequency and the first recording format, the second data extractor 65 in the inverse formatting unit 60 (2) receives the data input from the reading unit 50 And extracts the transform coefficients. Thereafter, the inverse formatting unit 60 (2) outputs the frequency determination result to the inverse transform unit 73 together with the first recording units. The inverse transform unit 73 converts each recording unit of input data into a frequency domain. Even if the data recorded on the recording medium has the second sampling frequency and the first recording format, the second data extractor 65 in the inverse formatting unit 60 (2) And outputs the first recording units to the inverse transform unit 73 together with the frequency discrimination result. In this case, when the transform coefficients belonging to the first recording unit are directly transformed into audio samples in the time domain, the number of audio samples at that time becomes smaller than the number of audio samples belonging to the reference unit related to the signal processing of the fifth view apparatus . For this reason, the data padding unit 75 in the inverse transform unit 73 performs zero padding to fill the data in the frequency domain. The inverse transform unit 73 transforms the transform coefficients of the zero-filled first recording unit into time-domain audio samples. When the audio signal recorded on the recording medium has the first sampling frequency and the second recording format, the second inverse formatter 67 in the inverse formatting unit 60 (2) outputs the data supplied from the reading unit 50 Formatted according to the previously stored second recording format. More specifically, the second inverse formatter 67 inversely formats the second recording unit and the third recording unit corresponding to the same reference unit on the basis of the third additional data and the second recording format in the corresponding reference unit . After that, the inverse formatting unit 60 (2) removes the third additional data, and outputs a sequence of reference units to the inverse transform unit 73 together with the frequency discrimination result. The inverse transform unit 73 receives the reference unit sequence from the inverse formatting unit 60 (2), and converts the change coefficients of each reference unit into audio samples in the time domain. The D / A converter 83 digital-analog converts audio samples output from the inverse transform unit 73. When the audio signal recorded on the recording medium has the second sampling frequency and the second recording format, the second inverse formatter 67 outputs the third additional data and the second recording format from the reading unit 50 Thereby inversely formatting the second and third recording units to be applied. In this case as well, the number of audio samples in the time domain is less than the number of audio samples required for signal processing in the fifth-degree device. The data padding unit 75 performs the above-described zero padding, and the resulting reference units are converted into time-domain audio samples by the inverse transform unit 73. Then, these audio samples are subjected to digital-analog conversion by a D / A converter 83. Therefore, the apparatus of FIG. 6 can provide a listener with a digital audio signal having an existing sampling frequency and an acoustic signal having a sound quality almost equal to a signal having a sampling frequency according to a new recording method.

When the first sampling frequency is L and the second sampling frequency is M, each of the reference units is made up of K transform coefficients, and the conversion coefficient required by the existing reproducing apparatus having the operating frequency corresponding to the second sampling frequency Is calculated according to the expression Int ((K x M) / L). Here, Int is an operator that discards a value smaller than an integer value. Therefore, in this case, the number of transform coefficients obtained by the above equation is converted into time-domain audio samples. With this concept, the system of the present invention can be directly applied to an audio apparatus in a case where the sampling frequency of the audio signal is continuously increased by an integer multiple of the first sampling frequency.

Although the embodiments have been described with reference to the first sampling frequency and the second sampling frequency, the present invention can be similarly applied to an audio signal having a sampling frequency greater than the first sampling frequency.

As described above, the system for recording and reproducing audio signals according to the present invention enables audio signals having different sampling frequencies to be reproduced both in an audio apparatus having a relatively low sampling frequency and in an audio apparatus having a relatively high sampling frequency Effect. In addition, it can be applied to an audio apparatus adopting a new sampling frequency that is fixed to an integer multiple.

Claims (2)

An audio signal recording system for recording a digital audio signal on a digital recording medium, A reference unit forming means for forming a reference unit sequence in which each reference unit has a predetermined size from the received digital audio signal; Conversion means for receiving the reference unit sequence, converting audio samples in each reference unit into frequency-domain transform coefficients, and outputting a reference unit sequence containing transform coefficients; Formatting means for receiving a reference unit series of the conversion means, formatting each reference unit in a recording unit according to a predetermined recording format, and outputting a series of recording units obtained as a result of formatting; And And recording means for recording the recording unit series of the formatting means onto the digital recording medium. 1. An audio reproduction system for reproducing an audio signal in a frequency domain recorded on a digital recording medium, A D / A converter having a predetermined operating frequency; A first means for reading a signal recorded on the recording medium, determining a sampling frequency and a recording format of the read audio signal, and outputting an audio signal together with a frequency discrimination result and recording format data; And an audio signal contained in the received data based on a sampling frequency corresponding to the sampling frequency and the recording format corresponding to the received data and the sampling frequency corresponding to the operating frequency of the D / A second means for reverberating; And Third means for converting an audio signal in the frequency domain output from the second means into audio samples in the time domain and supplying audio samples to the D / A converter.