KR20030033404A - Portable cd-player for compressing, saving and playing the data from audio-cd and method for controlling the same - Google Patents

Abstract

PURPOSE: A portable CD player compressively saving data recorded at an audio CD at a memory and reproducing saved data, a method for controlling the same are provided to convert audio data recorded at a general audio CD into a compressed audio file such as an MP3. CONSTITUTION: An input/output interface(10) transmits an input signal for controlling an operation of a CD player or outputs an operation state display signal. A CDP(Compact Disk Player) module(30) is mechanically controlled to read audio data from a CD, and outputs an EFM(Eight to Fourteen Modulation) signal. A digital signal processor(40) demodulates the EFM signal for generating first digital audio data and parity for error detection. An encoder(50) converts the first digital audio data into a compressed audio file. A memory(60) saves the converted compressed audio file. A decoder(70) restores the compressed audio file into second digital audio data. A multiplexer(80) outputs a signal selected in the first digital audio data and the second digital audio data. A digital-to-analog converter(90) converts the selectively output digital audio data into an analog audio signal. A microprocessor(20) controls compression, saving, and output of the data provided from the CD.

Description

PORTABLE CD-PLAYER FOR COMPRESSING, SAVING AND PLAYING THE DATA FROM AUDIO-CD AND METHOD FOR CONTROLLING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable CD player for compressing, storing, and playing back data recorded on an audio CD. More particularly, the present invention relates to converting audio data read from an audio CD into compressed audio data through an encoder, and storing the data in a memory. The present invention relates to a portable CD player for restoring and reproducing the stored compressed audio data into digital audio data through a decoder when playing music without an audio CD, and a method of controlling the same.

In general, a compact disc (CD) is a digital recording of a voice or the like on a transparent plastic disc using a pulse code modulation (PCM) method using a laser. Detect the signal. Such a record or player for a CD is called a CDP.

Also, MPEG is an abbreviation of Motion Picture Expert Group and refers to a method of decompression and compression of digital audio / video data standardized by the International Standards Organization (ISO). MPEG is divided into MPEG1 and MPEG2, and MPEG1 can process digital audio / video streams up to 1.5 Mbps, and is suitable for the video player based on the above-mentioned CD. MPEG2 includes the MPEG1 specification described above, is designed for high bit rates and multiple channels, and is adopted by DVB in Europe, and is expected to be used in next generation high definition TV (HDTV) and digital consumer audio / video environments. Doing. The MPEG1 audio is divided into layers 1, 2, and 3 according to complexity and compression ratio, and layer 3 has the most complex but the highest performance.

MP3, on the other hand, is a digital file containing music, and is a music format that is widely spreading among PC users. MP3 refers to the above-mentioned standard for the Layer 3 audio of MPEG1, and the sound quality is almost similar to that of the CD, and the compression ratio of the data is about 1/11. MP3 can store 3 ~ 4 minutes of music in about 2 ~ 5Mbytes. For example, if you store it on 650Mbytes of CD, you can enjoy as much as 14 hours of music on CD. Therefore, the advantages of MP3 are that the amount of data available is large, and it is suitable for home appliances ranging from the Internet, audio CDs, and CD-ROMs under PC environments, and can be used by record companies. MP3 is a method developed for digital audio broadcasting by Fraunhofer Institute in Germany. It uses a method of dividing the sound by frequency and compressing it.

In addition, the MP3 player, which is a portable digital audio device, is a device that can download MP3 music files through the Internet or PC communication without a tape or CD, and store them in a memory of a portable player, not a computer, to play music.

The difference between the MP3 player and the aforementioned CD player is as follows. First, the MP3 player uses MP3 data instead of PWM data, downloads MP3 data from a PC or the like instead of CD, which is a storage medium of a CD player, and stores the MP3 data in a flash memory to play the MP3 data. In the CD player or MP3 player, a DSP, a D / A converter, and the like are commonly used to perform similar operations. The conventional memory MP3 player uses a small flash memory of about 16MB to 64MB, and can store about 5 to 15 songs. Also, the manufacturing cost is expensive, and only MP3 files can be played.

Therefore, the conventional memory MP3 player has a problem that the storage capacity is insufficient because it uses a small capacity flash memory, and can play only MP3 files, and the price is expensive.

In addition, a conventional CD player cannot play MP3 files, and in the case of a vehicle CD player, there is a problem in that there is no measure for preventing data errors due to vibration or the like.

In order to solve this problem, a compact disc player having an MP3 module and a control method thereof which can store and play MP3 data instead of audio data on a CD (Korea Patent Publication No. 2000-0055520; hereinafter referred to as 'quoting invention') Has been disclosed.

However, since the cited invention does not have a function of encoding audio data into MP3 data in the CD player itself, the audio data stored in the audio CD must be converted using a medium having a built-in tool for encoding a compressed audio file such as a PC. . In addition, even after converting from a PC to an MP3 file, there is a hassle to write a CD through a CD-RW in order to play it on the player.

Accordingly, a technical problem of the present invention is to convert audio data recorded on an audio CD into a compressed audio file through an encoder, store it in a memory, and restore the original audio data through a decoder when playing the audio data. The present invention provides a portable CD player that compresses, stores, and plays back data recorded on an audio CD.

Another object of the present invention is to provide a method for controlling a portable CD player which compresses, stores and reproduces data recorded on the audio CD in a memory.

1 is a block diagram of a CD player according to the present invention.

2 is a block diagram of a compact disk player (CDP) module according to the prior art.

3 is a block diagram of an encoder of MP3 (MPEC-1 Audio Layer 3) type according to an embodiment of the present invention.

4 is a block diagram of an MP3 decoder according to an embodiment of the present invention.

5 is a flowchart of playing or storing a CD player according to an embodiment of the present invention.

6 is a flowchart for playing an audio CD according to an embodiment of the present invention.

7 is a flowchart for compressing and storing data of an audio CD according to an embodiment of the present invention.

8 is a flowchart of reproducing stored data according to an embodiment of the present invention.

9 is a diagram illustrating a CD player and a screen display unit according to an embodiment of the present invention.

10 is a diagram showing a relationship between a CD player and a peripheral memory device according to an embodiment of the present invention.

According to an aspect of the present invention, a portable CD player for storing and reproducing data recorded on an audio CD in a memory converts the audio data read from the audio CD into compressed audio data through an encoder, The present invention relates to a portable CD player which stores and stores the compressed audio data as digital audio data through a decoder when playing music without an audio CD. Specifically, a portable CD player for storing and reproducing data recorded on an audio CD according to an aspect of the present invention transmits an input signal for controlling the operation of the CD player or outputs an operation state display signal. Input / output interface; A CDP module that mechanically controls the audio data to be read from the CD, and outputs an EFM (Eight to Fourteen Modulation) signal; A digital signal processor for demodulating the EFM signal generated from the CDP module to generate first digital audio data and an error correction parity; An encoder for converting the first digital audio data demodulated by the digital signal processor into a compressed audio file; A memory for storing the converted compressed audio file; A decoder for restoring compressed audio files stored in the memory to second digital audio data; A multiplexer for outputting a signal selected from first digital audio data generated from the digital signal processor and second digital audio data reconstructed by a decoder from a compressed audio file stored in the memory; A digital / analog converter for converting digital audio data selectively output from the multiplexer into an analog audio signal; And a microprocessor for controlling the compression, storage and output of the data provided from the CD.

In the present invention, when the CD is not an audio CD in the CDP module, it is preferable not to read data and to indicate that the CD is not an audio CD through the input / output interface.

In the present invention, the method of compressing digital audio data in the encoder may be any one selected from a compression scheme of MP3 (MPEC-1 Audio Layer 3), WMA (Windows Media Audio File) and AAC (Advanced Audio Coding). The same may be applied to the present invention even if a compression scheme having better compression efficiency is developed.

In the present invention, the memory for storing the converted compressed audio file is preferably an inactive memory (Flash memory). When storing in the inert memory, data can be easily stored, deleted, and copied.

In the present invention, when the digital signal processor transmits digital audio data to the encoder for compressing, a high speed serial interface such as a service provider interface (SPI) or a scalable coherent interface (SCI) is used. Serial Interface) is preferable.

In the present invention, when the digital audio data is compressed by the encoder, the microprocessor may preset encoding quality information according to a user's setting and compress it according to the set quality information.

In the present invention, the encoding quality information set by the microprocessor,

It is possible to set to at least one selected from bitrate, bit / sample, and sampling rate. Set 128kbps for general MP3 audio data and 96kbps for WMA or AAC audio data.

In the present invention, when setting the information required for the compression, etc., it is preferable that an interface for transmitting the setting information uses a serial interface such as an Inter Intergated Circuit (IIC) interface. .

In the present invention, it is preferable to use a parallel interface to recognize and control the compressed audio data compressed by the encoder in the microprocessor.

In the present invention, when the compressed audio file is generated by the encoder, it is preferable to inform the microprocessor of the compressed file information using an input / output port (I / O port).

In the present invention, the data compressed by the encoder can be transmitted to the memory by accessing by byte unit through a parallel interface.

In the present invention, when transferring the compressed data to the memory, it is preferable to use a direct memory access (DMA) to improve the transfer speed, the control of the microprocessor when using the DMA It is possible to transmit without, increasing the efficiency and speed of the system.

In the present invention, when the audio source read from the audio CD is discontinuous, after grasping and correctly recognizing TOC (Table of contents) information stored in the CD, the file generation is completed and the new file is again. It is desirable to proceed with the procedure to generate. As described above, when the file compressed audio data is stored in a file unit, music can be easily played back and edited.

In the present invention, the method of restoring the compressed audio file to the digital audio data in the decoder is preferably restored in the reverse order of the compression method according to each method compressed in the encoder.

In the present invention, the portable CD player may further include an auxiliary memory medium capable of copying and storing the compressed file stored in the memory. It is possible to move and exchange the stored compressed audio data through the auxiliary storage medium.

In the present invention, the portable CD player may further include a connection port for copying and storing the compressed file from the memory to an external PC. Through the connection port, it is possible to facilitate data movement between sound source playback media.

According to another aspect of the present invention, there is provided a method of controlling a portable CD player for compressing, storing, and reproducing data recorded on an audio CD in a memory, the method comprising: (a) reading audio data from the CD and performing EFM; Outputting a signal; (b) demodulating the EFM signal with a digital signal processor to generate parity for digital audio data and error correction detection; (c) converting the digital audio data demodulated by the digital signal processor into a compressed audio file through an encoder; (d) storing the converted compressed audio file in an internal memory; (e) restoring the compressed audio file stored in the memory into digital audio data through a decoder; And (f) converting the digital audio data restored by the decoder into an analog audio signal through an analog / digital converter and outputting the analog audio signal through an amplifier.

In the present invention, if the CD for reading the data of the step (a) is not an audio CD, the step of indicating that the audio CD through the output means without reading the data; can proceed to include Do.

In the present invention, the method of compressing the digital audio data in the encoder of step (c) is selected from a compression scheme of MP3 (MPEC-1 Audio Layer 3), WMA (Windows Media Audio File) and AAC (Advanced Audio Coding). It may be any one, and even if an improved digital audio data compression method is developed, it is equally applicable to the present invention.

In the present invention, the memory for storing the converted compressed audio file of step (d) is preferably an inactive memory (Flash memory).

In the present invention, when the digital signal processor of step (c) transmits the digital audio data to the encoder for compression, a transmission interface (SPI) such as a service provider interface (SPI) or a scalable coherent interface (SCI) or the like is used. It is preferable to set it as a high speed serial interface.

In the present invention, when the digital audio data is compressed by the encoder of step (c), the microprocessor may preset encoding quality information according to a user's setting and compress it according to the set quality information.

In the present invention, the encoding quality information set by the microprocessor may be set to at least one selected from bitrate, bit / sample, and sampling rate.

In the present invention, when setting the information required for the compression, etc., it is preferable that an interface for transmitting the setting information uses a serial interface such as an Inter Intergated Circuit (IIC) interface. .

In the present invention, it is preferable to use a parallel interface to recognize and control the compressed audio data compressed by the encoder in the microprocessor.

In the present invention, when the compressed audio file is generated by the encoder of step (c), the compressed file information is preferably notified to the microprocessor using an input / output port.

In the present invention, the data compressed by the encoder of the step (c) is preferably transmitted to the memory by accessing (byte) unit (byte) through a parallel interface (Parallel Interface).

In the present invention, when transferring the compressed data to the memory, it is possible to use a direct memory access (DMA) to improve the transfer speed, and when using the DMA, since the control of the microprocessor is not necessary, system efficiency Can improve.

In the present invention, when the audio source read from the audio CD of step (a) is discontinuous, after grasping and accurately recognizing TOC (Table of contents) information stored in the CD, the file generation is completed. It is then possible to proceed with the process of creating a new file again.

In the present invention, the method of restoring the compressed audio file into the digital audio data in the decoder of step (e) is preferably restored in the reverse order of the compression method according to each method compressed by the encoder.

In the present invention, after the step (d), (e1) it is possible to further include the step of copying the compressed file stored in the memory, and storing in the auxiliary memory medium.

In the present invention, after the step (d), (e2) may further include the step of copying and storing the compressed file from the memory to the external PC through the access port.

In the present invention, the digital audio data generated in the step (b) may be converted into an analog audio signal directly through an analog / digital converter without being converted into a compressed audio file and output through an amplifier.

In the present invention, the digital audio data generated in the step (b) and the digital audio data reconstructed from the compressed audio file in the step (e) may be selectively output through the multiplexer.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail. However, the preferred embodiments of the present invention described below are not intended to limit the technical scope of the present invention, but are intended to more clearly and easily describe the present invention to those skilled in the art. Like reference numerals in the drawings refer to like elements.

1 is a block diagram of a CD player according to the present invention.

1, a portable CD player for compressing, storing, and reproducing data recorded on an audio CD according to the present invention transmits an input signal for controlling the operation of the CD player or outputs an operation state display signal. An input / output interface (I / O Interface) 10; A CDP module 30 which mechanically controls the audio data to be read from the CD and outputs an EFM (Eight to Fourteen Modulation) signal; A digital signal processor (40) for demodulating the EFM signal generated from the CDP module (30) to generate parity for detecting first digital audio data and error correction; An encoder (50) for converting the first digital audio data demodulated by the digital signal processor (40) into a compressed audio file; A memory 60 for storing the converted compressed audio file; A decoder (70) for restoring compressed audio files stored in the memory (60) to second digital audio data; A multiplexer for outputting a signal selected from the first digital audio data generated by the digital signal processor 40 and the second digital audio data reconstructed by the decoder 70 from the compressed audio file stored in the memory 60. (Multiplexer; 80); A digital-to-analog converter (D / A Converter) 90 for converting digital audio data selectively output from the multiplexer 80 into an analog audio signal; And a microprocessor 20 that controls the compression, storage and output of data received from the CD.

When playing an audio CD as in a general CD player, analog audio data read out from the CDP module 30 is output in the form of PCM (Pulse Code Modulation) data through the digital signal processor 40. At this time, the output data is sent to the digital-to-analog converter 90 and then passed through an amplifier (not shown), and is converted into a sound that can be heard through a speaker (not shown).

At this time, if the PCM data output is not sent to the digital / analog converter 90, but is sent to the encoder 50 as it is, the microprocessor 20 prior to encoding such as encoding quality. Set the information related to. Here, the encoding quality is information such as bitrate, bit / sample, sampling rate, and the like. The encoder 50 compresses and processes the PCM data transmitted from the CD according to the set information. That is, since the PCM data already includes information of respective bitrates, sampling rates, bits / samples, etc., the information of the digital data extracted from the PCM data is compressed and compressed using respective compression algorithms such as MP3, WMA and AAC. Is done. At this time, the final data output is based on the already set bit rate.

Before starting the compression, information necessary for compression is set in advance by using a predetermined command in the digital signal processor 40 for compression. At this time, the command uses a serial interface such as IIC. Here, the commander performs the master. That is, the master is performed in the microprocessor 20 and the slave is performed in the encoder 50. Encoded data should be recognizable and controlled by the microprocessor 20. For this purpose, a parallel interface is used. In addition, source audio for encoding uses a high speed serial interface such as SPI.

In the compression process, the encoding process is started by a user of the CD player pressing an encoding start button mounted on a CD. The microprocessor 20 recognizes the CD on the CD tray for encoding. If the CD is a CD capable of encoding (generally limited to an audio CD), encoding is started. The microprocessor 20 sets information for encoding on the encoder 50. That is, a target bitrate is set. Set 128 kbps for general MP3 compression and 96 kbps for WMA or AAC. The microprocessor 20 prepares a correct start time from the CD, which is a sound source, and creates a new file in an inactive memory (Flash Memory) 60.

The microprocessor 20 converts the sound source into PCM data through the digital signal processor 40 and then transmits the PCM data to the compression encoder 50. At this time, a high speed serial interface such as SPI or SCI is used for transmission.

The compressed audio data transmitted to the encoder 50 is encoded and then informs the microprocessor 20 of the presence of the compressed data using a specific I / O port.

The microprocessor 20 accesses the compressed data in units of bytes through a parallel interface and transmits the data to the flash memory 60. At this time, means such as DMA can be used to speed up the transfer.

The microprocessor 20 must control a method of storing each data in order to manage a file with an efficient file system.

In addition, the microprocessor 20, when the sound source from the CD is discontinuous, that is, when there is a part that changes the song, to grasp the TOC information of the CD information and correctly recognized and complete the file generation, and again the new file You must proceed with the creation process. That is, the structure of creating one file per song must be completed.

The input / output interface 10 performs the above function to issue a user's operation command in the CD player or to output progress information in the system. When the user sends a control signal such as playback, compression, compression ratio setting, and playback after selecting a compressed file through the input / output interface 10, the microprocessor 20 performs a system according to the command. Send a control signal to each module in the module. In addition, the procedures performed in each module are controlled by the microprocessor 20 and displayed to the user through the input / output interface 10.

When a user plays an audio CD directly in the CD player or restores compressed data, it is necessary to perform a different procedure to select the output digital audio data. Accordingly, the microprocessor 20 controls the multiplexer 80 according to a signal selected and input by a user to selectively output digital audio data among the two data. The selected digital audio data is converted into analog audio data through a digital-to-analog converter 90, and is output as an audible sound through an amplifier and a speaker.

2 is a block diagram of a CDP module according to the prior art.

Referring to FIG. 2, the CDP module 30 includes a spindle motor 32a for rotating the compact disk 31; An optical pickup unit 33 for tracking and reproducing the CD 31 to convert detected light into an electrical signal; A thread motor 32b for transferring the optical pickup unit 33; An analog waveform shaping unit 34 for linear equalization and waveform shaping of the high frequency analog signal detected by the optical pickup unit 33; A synchronization detecting unit 35 for detecting a frame synchronization signal and finding a head position of each frame; A phase locked loop (PLL) 36 for generating a continuous pulse train and supplying the synchronous detection unit 35 and the digital signal processor 40; A servo unit 38 for controlling tracking and focusing of the optical pickup unit and controlling rotation of the CD; And a drive unit 37 for driving the spindle motor 32a and the thread motor 32b in accordance with the control command of the servo unit, respectively.

The operation of the CDP module according to FIG. 2 is as follows. First, when the spindle motor 32a rotates the CD 31, the optical pickup unit 33 tracks and reproduces the CD 31 to convert the detected light into an electrical signal, and thereby the tracking error signal TE. And a focusing error signal FE. In this case, the optical pickup unit 33 includes a laser diode (not shown), a photodetector (not shown), an objective lens (not shown), and the like.

The thread motor 32b transfers the optical pickup unit 33 so that the CD 31 can be tracked and reproduced, and the analog waveform shaping unit 34 detects the high frequency analog signal detected by the optical pickup unit 33. After amplifying to a predetermined level, DC components and noise are removed, linear equalization, and waveform shaping are performed.

The sync detector 35 detects a frame sync signal among the digital signals and finds a head position of each frame. In this case, the PLL 36 generates a continuous pulse sequence to generate the sync detector 35 and the digital signal processor 40. ) Will be supplied.

The servo unit 38 includes a tracking servo, a focusing servo, and a rotation servo. The servo unit 38 controls the tracking and focusing of the optical pickup and the rotation of the CD 31. The driving unit 37 includes the servo unit ( According to the control command of 38, the spindle motor 32a and the thread motor 32b are respectively driven.

3 is a block diagram of an encoder of MP3 (MPEC-1 Audio Layer 3) scheme according to an embodiment of the present invention.

Referring to FIG. 3, a process of converting PCM data into compressed audio data by the encoder 50 shown in FIG. 1 is disclosed. 3 illustrates a representative MP3 compression method among MP3, WMA, and AAC compression methods.

The audio layers of MPEG use a compression coding technique called perceptual coding or perceptual coding, which is a technique of analyzing and applying a human auditory model, which is a kind of trick using the insensitivity of the human ear called the masking effect. Can be.

The human ear can usually hear sounds from 20Hz to 20kHz, which is called the audible frequency, and the sensitivity of hearing varies with each frequency range, especially the most sensitive in the 2kHz to 5kHz band.

For example, when several people listen to the piano, when the player does not play the piano, they can hear the sound of the strings on the piano, but the moment they play the keyboard again, they can no longer hear it. This is not because the sound is lost, but because the sound is small compared to the sound produced when you play the keyboard. In other words, in the state where a large mask exists, a sound in a predetermined range near the note, i.e., below the critical band, is not heard even though the sound is quite high level. This principle is called the frequency masking effect, and the threshold of the masked sound varies according to the frequency band, and the threshold of the masked sound becomes smaller in the ear-sensitive part, and the masked sound threshold has a large masking threshold.

Masking effects include temporal masking in addition to the frequency masking. This means that there is a certain delay after you hear a loud sound before you can hear a smaller sound. For example, if 60dB of sound is heard for 5ms and 40dB of sound is continuously heard, the sound can be detected after about 5ms. This delay time also has a different value depending on the frequency band.

MP3 uses this person's auditory psychological model to allow quantization noise caused by quantization according to frequency bands within the masking threshold and delay time to reduce the bitrate of audio data without loss of sound quality. It is to be able to compress.

In order to more efficiently use the hearing psychology such as the critical band, it is important to first divide the signal into frequency components. For this purpose, audio inputted using the filterbank 32 Subbands 51 of FIG. After dividing the entire band of the PCM sample into 32 equally spaced frequency bands, each signal is encoded by subsampling to 1/32 of the original sampling frequency (band division coding).

However, if the conventional filter takes 1/32 frequency band, it is not an ideal filter, so it does not remove 'aliasing' at the time of subsampling, that is, removes frequency components higher than 1/2 of the sampling frequency. In this case, a noise returned to the low frequency signal is generated, so that a filter called a polyphase filter bank is used or an MDCT 52 section and an aliasing reduction section (not shown) of FIG. 3 are used. By performing MDCT (Modified Discret Cosine Transform), 32 bands of aliasing noises are canceled from each other so that degradation due to the filter is eliminated.

MDCT 52 is a DCT for the value sampled as the threshold so that if no quantization has been done, it is fully recoverable to the original signal. In practice, however, quantization is performed, resulting in discontinuities between the respective transport blocks.

In other words, the audio input is divided into 32 frequency bands through the 32 filter banks 51, and then, for each frequency band, the masking influence by the components of the adjacent frequency bands is calculated to apply quantization bits only to signals above the masking threshold. In this case, the quantization bits are allocated such that the quantization noise is less than or equal to the masking threshold in a given frequency band.

In the quantizer 53, the sample data in the 32 subbands is separated into a waveform and a magnification, and the waveform is normalized to have a maximum amplitude of 1.0, and the magnification at that time is encoded as a scale factor. do. This coding allows the generation of quantization noise by restricting the generation of quantization noise by allowing the frequency and time to enter within a close range even for a large signal component. At this time, the signal passing through the FFT 1024 Points 56 and the Psycho-acoustic Model 57 gives information so that the signal encoded by the quantizer 53 can be compressed into a signal that is not detected by humans.

In the Huffman Encoder (54) block, coding called a variable length encoding or entropy encoding is performed. A redundancy reduction method that eliminates redundancy of bits using statistical characteristics of digital data, that is, a code generation probability By assigning a short code to a value having a high probability of occurrence and a long code to a value having a low probability of occurrence, the average code length of all coded data is reduced.

The side information information extracted through the Hoffman encoder 54 is encoded through the side information encoder 58, and then the auxiliary data 59 is added to the bitstream formatting block 55 from the Hoffman encoder 54. Reconstructed in the form of code and bitstream to be compressed. In addition, the bitstream formatting block 55 also performs an error check (CRC-Check) function.

As for the compression efficiency when using the above MP3 encoding, in the conventional digital audio equipment, PCM codes of 32 kHz, 44.1 kHz, and 48 kHz with sampling frequencies of 16 bits per sample are widely used, for example, two-channel stereo, 44.1 kHz sampling, In the case of 16-bit quantization bits, the bit rate is 16 * 44100 * 2 = 1411200 (about 1.4 Mbps), whereas in MP3, such a signal can be encoded at 128-256 kbps. This corresponds to about 1/12 to 1/6 of the original PCM code, saving about 1.5 to 3 bits of the original 16 bits per sample.

4 is a block diagram of an MP3 decoder according to an embodiment of the present invention.

Referring to FIG. 4, the MP3 decoder 70 includes a demultiplexer 71 for separately outputting an input MP3 audio bit stream into a plurality of characteristic data; A side information decoder (76) for reading and interpreting side information data among the separated output data; A Huffman decoder 72 for Huffman decoding the separated output audio data; An inverse quantizer (73) for restoring the Hoffman decoded data to an actual sample energy value in the frequency domain; An inverse MDCT unit 74 for restoring the restored data to data before MDCT; And a synthesis filter bank 75 for synthesizing each subband value of the reconstructed data and outputting the final PCM sample.

Auxiliary data 77 is added to the demultiplexer 71 to separately output side information which is information on how a frame is encoded, a scale factor for controlling gain values of each frequency band, and Hoffman coded data in order. The side information decoder 76 may decode the side information data outputted separately, and then may know how to process data contained in the corresponding frame based on this information.

When the audio data to be decoded is identified based on the side information, the Hoffman decoder 72 separates and outputs the output based on the Hoffman tree and the side information used according to data characteristics in order to reduce the total bit amount during encoding. Huffman decoding is performed on Hoffman coded data.

After restoring audio data to the Hoffman decoder 72 before the Hoffman coding, the dequantization unit 73 restores the Hoffman decoded result to the actual sample energy value in the frequency domain. The Hoffman decoded value is multiplied by the scale value obtained from the scale factor to restore the actual spectral energy value. In this process, if the bit stream is encoded as a stereo signal, each channel may be transmitted separately from each other, but often uses a method of removing redundancy between two channels by transmitting a sum and a difference between the two channels. If encoded using the method, perform stereo recovery.

Since the signals obtained so far are in the frequency domain, energy conversion to the time domain must be performed in order to synthesize the actual output samples, which is a reverse process of the time-frequency conversion used in the encoder. Is restored to the actual sample energy value.

Layer 3 additionally uses MDCT to achieve better frequency resolution than other layers, and this transform is a DCT for critically sampled values, so if no quantization is done, it can be completely recovered to the original signal. Since quantization is performed, there is a discontinuity between each transport block.

Accordingly, in the inverse MDCT 74 performed in units of blocks, discontinuities are generated between the respective transport blocks, and such discontinuities create noise and click sounds, which have a fatal effect on sound quality. For the result value, 50% overlap with the value in the previous block is used.

After the inverse MDCT transformation is performed by the inverse MDCT unit 74 and the result of 50% overlap addition processing is obtained, the final procedure before outputting the actual audio sample is to synthesize the original time samples by synthesizing the samples divided into subbands. A subband synthesis process for reconstructing a signal, which is a process of subband synthesis, in which the input samples are separated into 32 frequency bands during encoding, and an interpolation process for synthesizing the samples of each subband into one temporal sequence of samples. interpolation) process.

In the subband synthesis filter 75, the filter input of the previous frame is delayed and needs the filter input value of the previous frame. The filter bank for the synthesis filter is defined in the MPEG standard and can be decoded using this.

5 is a flowchart of playing or storing a CD player according to an embodiment of the present invention.

Referring to Fig. 5, there is shown a procedure of compressing, storing, and playing music using a portable CD player that compresses, stores, and plays back the data recorded on the audio CD.

When a user inserts an audio CD to compress and store audio data or to play music using compressed and stored data without an audio CD, the user can make a selection (S100) for a job through a function button mounted in the player. .

When playing the audio CD is selected (S110), the CD can be played while compressing and storing the data. The CD can be played through the audio CD, which is a unique function of the general CD player. Alternatively, the preset mode allows the data compression, storage and playback operations to be executed simultaneously with the CD insertion. At this time, if the inserted audio CD has already stored data in the memory through compression and storage operations, only the playback operation can be executed.

In the above procedure, when only the audio CD playback operation is executed without compressing or storing the data, the operation is performed by the same data flow as the playback operation S112 in a general audio CD player.

If the data is compressed and stored simultaneously with the playback of the audio CD, and if the data is compressed and stored without the playback (S120), the data recorded on the CD may be compressed or stored. It is determined whether the data (S121). In this case, in the case of normal data, the data is compressed and stored in the memory (S122). In case of abnormal data, the operation is terminated with an error message (S123).

The user may select and play the stored data without inserting the CD into the CD player (S130). In order to reproduce the stored data, first, it is necessary to check whether the stored data exists through the memory search (S131). If the stored data does not exist, it is terminated with an error message (S134). If the stored data exists, the file list of the stored data is displayed to the user by displaying it on the surface of the CD player. The user selects a file to be played back from the displayed list of stored files (S132) and plays it (S133).

If the stored compressed audio data is to be transmitted to an external device (S140 and S141), a storage medium such as a floppy disk may be mounted therein according to an additional function of the CD player (S142 and S143). Alternatively, it is possible to transmit data (S144, S145) to a medium such as a PC through an external line connection.

6 is a flowchart for playing an audio CD according to an embodiment of the present invention.

Referring to FIG. 6, when audio CD playback (S112) is selected in the work mode, the same procedure as the procedure of outputting audio data from a general CD player to a speaker is performed.

First, the audio CD is mounted in the CD player (S113), and then the optical pickup is driven (S114) to perform analog waveform shaping (S115).

The optical pickup unit 33 tracks and reproduces the CD 31 to convert the detected light into an electrical signal, and outputs a tracking error signal T.E. and a focusing error signal F.E. The thread motor 32b transfers the optical pickup unit 33 so that the CD 31 can be tracked and reproduced, and the analog waveform shaping unit 34 transmits the high frequency analog signal detected by the optical pickup unit 33. After amplifying to a predetermined level, DC component and noise are removed, linear equalization, and waveform shaping (S115) are performed.

The waveform-formed signal detects the frame synchronization signal among the digital signals in the synchronization detection unit (S116) and finds the head position of each frame. In this case, the PLL 36 generates a continuous pulse sequence to generate the synchronization detection unit 35 and The digital signal processor 40 is supplied.

The supplied signal demodulates the EFM signal in the digital signal processor 40 to generate parity for detecting digital audio data and error correction (S117), outputs PWM signals L and R of left and right channels, and digital / analog. The digital PWM signal is converted into an analog signal (L, R) by a converter (S118) to output the audio analog signal through a speaker (S119).

7 is a flowchart for compressing and storing data of an audio CD according to an embodiment of the present invention.

Referring to FIG. 7, in order to compress and store audio CD data (S122), a user places an audio CD on a tray of the player and drives an optical pickup (S123). The user can select (S124) and store the method to compress.

The audio data compression method is selected from among methods such as MP3, WMA and AAC, and it is obvious that other compression methods can be used. Coding is executed by each selected coding method (S125, S126, S127), and when the coding operation is completed, a compressed file is generated (S128). The generated compressed file is stored in the form of a file in the internal memory (S129).

8 is a flowchart of reproducing stored data according to an embodiment of the present invention.

Referring to FIG. 8, in order to reproduce a file stored in the internal memory (S133), a field of a file selected in the internal memory is first searched (S134). Depending on the encoding format of the retrieved file, the decoding method is different. After the search, if the decoding mode is set (S136), the compressed audio data is decoded according to each compression scheme such as MP3, WMA and AAC (S137a, S138b, and S139c).

The restored compressed digital audio data is converted into analog audio data by a digital analog converter (S138). The converted analog audio data is output as an audio signal that can be heard by a person through an amplifier and a speaker (S139).

9 is a diagram illustrating a CD player and a screen display unit according to an embodiment of the present invention.

Referring to FIG. 9, a CD player 200 for compressing, storing, and playing the audio CD may be configured as shown in FIG. 9. First, a screen 210 capable of displaying data files such as compressed, stored MP3, WMA, and AAC to a user should be configured. On the displayed screen, stored file information 220, for example, go away.mp3, after breaking up.mp3, bite.wma, first.aac and the like should be presented. The file selected from the presented file information should be displayed so as to be identified by the user (230), and the selected file may be reproduced through the speaker of the player after being restored by the decoder.

A recording (compression and storage) button 240, a play button 250, a stop button 260, and up / down scroll buttons 270 and 280 may be provided below the screen unit to control the user. have.

10 is a diagram showing a relationship between a CD player and a peripheral memory device according to an embodiment of the present invention.

Referring to FIG. 10, it is possible to copy data stored in an internal memory to an external device in the CD player 200 which compresses, stores and reproduces data of the audio CD.

Inside the player 200, a removable memory or a floppy disk 300 similar to that of a conventional MP3 player may be mounted. Through the above function, it is possible to copy or move data such as MP3, WMA and AAC stored in the internal memory to the outside.

In addition, the compressed data may be copied to a device capable of reproducing a compressed data file such as a PC 310 having a data cable 320 that can be connected to the outside.

In the above described with reference to the accompanying drawings, preferred embodiments of the present invention in detail. However, the technical idea according to the present invention is not limited thereto, and various modifications or improvements are possible by those skilled in the art.

According to an aspect of the present invention, it is possible to convert the audio data contained in a general audio CD into a compressed audio file such as MP3 through the CD player with built-in encoding function.

According to another aspect of the present invention, music can be played without a CD by playing compressed and stored audio files through the CD player.

According to another aspect of the present invention, it is possible to play the audio CD while converting the audio data stored in the audio CD into compressed audio data via the CD player.

According to another aspect of the present invention, it is possible to store and move compressed audio data stored in the CD player through an auxiliary storage medium mounted in the player.

According to another aspect of the present invention, it is possible to transmit compressed audio data through the data transmission cable to the CD player and other playback media, that is, a PC or an MP3 player.

According to another aspect of the present invention, it is possible to transmit and exchange compressed audio data between the CD players via the data transmission cable.

According to another aspect of the present invention, by directly compressing, storing and playing back audio data stored in an audio CD without a device including an encoder function such as a PC, the compressed audio data converted in the PC is stored in CD or auxiliary. There is no need to move it to the storage medium.

Claims (34)

In a portable CD player, An input / output interface for transmitting an input signal for controlling the operation of the CD player or for outputting an operation state display signal; A CDP module that mechanically controls the audio data to be read from the CD, and outputs an EFM (Eight to Fourteen Modulation) signal; A digital signal processor for demodulating the EFM signal generated from the CDP module to generate first digital audio data and an error correction parity; An encoder for converting the first digital audio data demodulated by the digital signal processor into a compressed audio file; A memory for storing the converted compressed audio file; A decoder for restoring compressed audio files stored in the memory to second digital audio data; A multiplexer for outputting a signal selected from first digital audio data generated from the digital signal processor and second digital audio data reconstructed by a decoder from a compressed audio file stored in the memory; A digital / analog converter for converting digital audio data selectively output from the multiplexer into an analog audio signal; And A portable CD player for compressing, storing, and playing back data recorded on an audio CD including a microprocessor that controls compression, storage, and output of data received from the CD. The method of claim 1, In the CDP module, if the CD is not an audio CD, the data recorded on the audio CD is compressed and stored in the memory, not indicating that the data is read, but indicating that the CD is not an audio CD through the input / output interface. Portable CD player to play. The method of claim 1, The method of compressing the digital audio data in the encoder is any one selected from a compression scheme of MP3 (MPEC-1 Audio Layer 3), WMA (Windows Media Audio File) and AAC (Advanced Audio Coding). Portable CD player that compresses, saves and plays recorded data in memory. The method of claim 1, The memory for storing the converted compressed audio file, A portable CD player for compressing, storing, and playing back data recorded on an audio CD, characterized by being an inactive memory. The method of claim 1, When the digital signal processor transmits the digital audio data to the encoder for compression, the transmission interface may be a high speed serial interface such as a service provider interface (SPI) or a scalable coherent interface (SCI). A portable CD player that compresses, stores and plays back data recorded on an audio CD. The method of claim 1, When the encoder compresses the digital audio data, the microprocessor compresses the data recorded on the audio CD into a memory, wherein the microprocessor presets encoding quality information according to a user's setting and compresses it according to the set quality information. Portable CD player to save and play. The method of claim 6, The encoding quality information set by the microprocessor is A portable CD that compresses, stores and reproduces data recorded on an audio CD, which is set to at least one selected from bitrate, bit / sample, and sampling rate. player. The method according to claim 6 or 7, When setting the information necessary for the compression, the interface for transmitting the setting information uses a serial interface such as an Inter Intergated Circuit (IIC) interface to compress data recorded on an audio CD into a memory. Portable CD player for storing and playing. The method according to claim 6 or 7, And a parallel interface for using the microprocessor to recognize and control compressed audio data compressed by the encoder. The method of claim 1, When generating the compressed audio file in the encoder, the compressed file information is notified to the microprocessor using an input / output port (I / O port). Portable CD player. The method of claim 1, Compressed data stored in the audio CD is stored in the memory, and is reproduced by accessing the data compressed by the encoder to a memory unit through a parallel interface. Portable CD Player. The method of claim 11, A portable CD player for compressing, storing, and playing back data recorded on an audio CD, wherein the compressed data is transferred to a memory, using direct memory access (DMA) to improve a transfer speed. The method of claim 1, If the audio source read from the audio CD is discontinuous, the TOC (Table of contents) information stored in the CD is identified and correctly recognized, and then the file creation is completed and a new file is created again. A portable CD player for compressing, storing, and playing back data recorded on an audio CD, characterized by the progression. The method of claim 1, The method for restoring the compressed audio file into the digital audio data in the decoder is to restore and store the data recorded on the audio CD in memory according to the respective methods compressed by the encoder. Portable CD player to play. The method of claim 1, The portable CD player further comprises an auxiliary memory medium capable of copying and storing the compressed file stored in the memory. The portable CD player compresses, stores and reproduces the data recorded in the audio CD. player. The method of claim 1, The portable CD player further comprises a connection port for copying and storing the compressed file from the memory to an external PC. The portable CD player further comprises compressing, storing and reproducing the data recorded in the audio CD. Portable CD Player. In the method of controlling a portable CD player, (a) reading audio data from the CD and outputting an EFM signal; (b) demodulating the EFM signal with a digital signal processor to generate parity for detecting digital audio data and error correction; (c) converting the digital audio data demodulated by the digital signal processor into a compressed audio file through an encoder; (d) storing the converted compressed audio file in an internal memory; (e) restoring the compressed audio file stored in the memory into digital audio data through a decoder; And (f) converting the digital audio data restored by the decoder into an analog audio signal through an analog / digital converter, and outputting the data through an amplifier. To save, play the video in memory. The method of claim 17, If the CD for reading the data of step (a) is not an audio CD, indicating that the audio CD is not read through the output means without reading the data; and a portable CD player comprising: To record, store and play back data recorded on an audio CD in the The method of claim 17, The method of compressing the digital audio data in the encoder of step (c) may be any one selected from a compression scheme of MP3 (MPEC-1 Audio Layer 3), WMA (Windows Media Audio File) and AAC (Advanced Audio Coding). A method of compressing, storing, and playing back data recorded on an audio CD in a portable CD player. The method of claim 17, The memory for storing the converted compressed audio file of step (d), A portable CD player, characterized in that it is a flash memory, which compresses, stores and plays data recorded on an audio CD in a memory. The method of claim 17, When the digital signal processor of step (c) transmits the digital audio data to the encoder for compressing, the high speed serial interface such as a service provider interface (SPI) or a scalable coherent interface (SCI) is used. A method of compressing, storing, and playing back data recorded on an audio CD in a portable CD player. The method of claim 17, When the digital audio data is compressed by the encoder of step (c), the microprocessor presets the encoding quality information by the user's setting and compresses the audio data according to the set quality information. To record, store and play back the data recorded in the memory. The method of claim 22, The encoding quality information set by the microprocessor is Compressed and stored data recorded on an audio CD in a memory in a portable CD player, characterized in that it is set to at least one selected from bitrate, bit / sample, and sampling rate. How to play. The method of claim 22 or 23, When setting the information required for the compression, the interface for transmitting the setting information is a data recorded on an audio CD in a portable CD player, characterized in that for using a serial interface such as an Inter Intergated Circuit (IIC) interface. To save the file in memory and play it back. The method of claim 22 or 23, A portable CD player, which uses a parallel interface to recognize and control compressed audio data compressed by the encoder, controls and stores data recorded on an audio CD in a memory. Way. The method of claim 17, When the compressed audio file is generated by the encoder of step (c), the compressed file information is notified to the microprocessor using an I / O port. A method of compressing, storing and playing back data in memory. The method of claim 17, In the portable CD player, the data compressed in the encoder of step (c) is transmitted to the memory by accessing the unit of byte through a parallel interface and stored in the memory. How to play by. The method of claim 27, A method of compressing, storing, and playing back data recorded on an audio CD in a memory in a portable CD player, characterized by using direct memory access (DMA) to improve the transfer speed when transferring the compressed data to a memory. The method of claim 17, If the audio source read from the audio CD of step (a) is discontinuous, the TOC (Table of contents) information stored in the CD is identified and correctly recognized, and the file generation is completed, and the new file In the portable CD player, characterized in that for proceeding to create a compressed data stored in the audio CD, stored in the memory to play. The method of claim 17, The method of restoring the compressed audio file into the digital audio data in the decoder of step (e) is performed in the reverse order of the compression method according to each method compressed by the encoder. A method of compressing, storing, and playing back recorded data in memory. The method of claim 17, After step (d), (e1) copying the compressed file stored in the memory and storing it in an auxiliary memory medium; Way. The method of claim 17, After step (d), (e2) copying and storing the compressed file from the memory to an external PC through an access port, and compressing and storing the data recorded on the audio CD in the memory in the portable CD player. How to play by. The method of claim 17, Instead of converting the digital audio data generated in the step (b) into a compressed audio file, the analog audio signal is directly converted through an analog / digital converter and output through an amplifier. A method of compressing, storing and playing back recorded data in memory. The method of claim 17 or 33, The digital audio data generated in step (b) and the digital audio data reconstructed from the compressed audio file in step (e) are selectively output through a multiplexer. Compressed, stored and played back in memory.