KR0130875B1 - Audio signal reproducing apparatus for pcm and mpeg signal - Google Patents

Abstract

None.

Description

Pulse Code Modulation (PCM) Waveform Audio and MPEG Audio Signal Playback Devices

1 is a block diagram of a waveform audio device of a general computer.

2 is a block diagram of a typical MPEG audio decoder.

3 is a block diagram of an audio signal reproducing apparatus according to the present invention.

4 is a serial PPM data output signal timing chart for explaining the operation of the apparatus of the present invention.

5 is a 16-bit PCM data output signal timing chart for explaining the operation of the apparatus of the present invention.

6 is an 8-bit PCM data output signal timing chart for explaining the operation of the apparatus of the present invention.

* Explanation of symbols for main parts of the drawings

21: audio data decoder 22: MPEG audio decoder

23: clock generator 24: digital signal multiplexer

25: D / A Converter

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to pulse code modulation (PCM) waveform audio and Moving Picture Experts Group (MPEG) audio signal reproducing apparatus, and more particularly to a PCM used for editing when performing digital audio functions in MPEG audio reproducing apparatus It also provides a waveform audio playback function.

The digital audio functions provided by the general-purpose PC include digital waveform audio functions mainly used for digital audio editing for sound effects, digital interface between electronic instruments for transmitting digital data between electronic instruments, and CDs. The CD audio playback function is provided. In recent years, the MPEG audio standard has been stipulated as a means of compressing / restoring audio data with respect to the moving picture compression / restoration function.

Among the functions listed above, the digital waveform audio function is a signal or analog mixer in which an audio input signal such as an external input signal source (Line-in, Mic) is amplified through the amplifier 1 as shown in FIG. The analog audio signal OUT A passed through (2) is converted into digital data through a low pass filter (4) and a two-stage A / D converter (6) and applied to the audio controller (8). In this case, a waveform or audio file is stored in a memory or disk file, or a stored waveform audio file is played. In this case, a PCM method is mainly employed as a conversion method to digital data.

3 is a power amplifier, 5 is a low pass filter, 7 is a D / A converter, and 9 is a decoder.

The PCM digital audio method uses an A / D converter that converts the amplitude of the input analog audio waveform into a digital value. The PCM digital audio method quantizes and stores these values for each sampling sampling rate. In this case, the factors that represent the fidelity of the PCM method are sampling rate and sampling resolution (bits).

The sampling rate represents the frequency at which sound is converted from an analog waveform to a number, and represents a sampling rate per second.

This sampling rate requires sampling at a frequency at least twice the frequency of at least twice the highest frequency of the analog waveform to maintain the original waveform when the analog waveform is converted to a digital waveform by the Nyquist theory. There is.

Sampling analysis is also the number of bits used to quantify the amplitude of the recorded sound, which determines the dynamic range of the sound and supports sampling sizes of 8 and 16 bits.

Meanwhile, MPEG audio technology is an international standard that compresses and restores PCM waveform digital audio signals together with video compression / decompression technology in CD-Video systems using CD-ROM. Subband sample signals are decoded according to a result of analyzing information such as layer type, sampling, coding method, etc. from a frame header that extracts every frame from an input bitstream. Synthesis subband filter (Syntersis) for receiving the output of the frame unpacking unit 10 and the digital audio output data corresponding to one frame by receiving the output of the frame unpacking unit 10 Subband Filter 11).

The MPRG audio decoder features Frame Resolving and Synthesis Filerbank.

First, the frame analysis function is described. The frame header is analyzed to distinguish layers and find information such as bit allocation sampling rate and load.

Next, the bit allocation information is decoded to obtain the number of bits allocated to each band.

Next, the scale factor information is decoded to find the scale factor value of the band allocated at least two bits.

Subsequently, the subland sample is restored by referring to the number of bits and scale factor of each band, and the value of the band without bit allocation is filled with zero.

On the other hand, when the synthesis filterbank function is described, 32 new subband samples are taken.

Next, shift the 1024 shift register and discard the oldest 64 samples.

Subsequently, a new 64 sample, which is made up of 32 samples, is newly input to the shift register.

Next, 512 vectors are obtained from the 1024 vectors, and then the window with the composite bank coefficients is obtained for the 512 vectors.

Next, 32 PCM samples are obtained from the windowing result.

However, the conventional technology as described above may provide the PCM waveform audio function among the digital audio functions in the multimedia system, but in order to execute the waveform audio function in the MPRG audio reproducing apparatus, an audio board must be separately installed. As well as weighted, there was a problem that a lot of functional restrictions.

The present invention has been made to solve the problems of the prior art, and to support the digital waveform audio projection playback function which is used for editing the digital audio in the case of executing the MPEG audio playback function using a general multimedia PC. It aims to diversify functions and reduce equipment costs by allowing them to be used as an audio D / A converter for reproducing PCM waveform audio playback functions used to convert MPEG decoded digital data to analog. will be.

The present invention for achieving this purpose will be described in detail according to the accompanying drawings.

3 is a block diagram of an audio signal reproducing apparatus according to the present invention, which decodes audio data output from a PC data bus line and transmits the decoded audio data to a clock generator 23 at a later stage. Data decoder 21, which transmits the data to the MPEG audio decoder 22, the data DATA, the address ADDRESS, the control signal CONTROL and the state of the MPEG stream which are output from the PCCOM bus. An MPEG audio decoder 22 which decodes and transmits the decoded digital signal to the digital signal multiplexer 24, a clock generator 23 which generates a clock oscillation frequency for waveform audio and applies it to the digital signal multiplexer 24; A digital signal multiplexer 24 for selectively outputting one data of MPEG audio and waveform digital data, and the digital data signal multiplexer 24 Daemon inputted digital audio has been configured as a multi-audio D / A converter 25 for converting an analog signal Ata.

The present invention configured as described above will be described as follows.

First, the MPEG audio reproduction operation process will be described. In the MPEG audio reproduction operation, it is determined that the audio data from the PC data bus is in an MPEG audio stream (MPEG STREAM) state through the audio data decoder 21. It is input to the decoder 22.

The audio data input to the audio data decoder 21 may be an MPEG audio data stream encoded with PCM waveform data, and the file header information of the input audio data is read by the audio data decoder 21. The PCM waveform data (PCM WAVE) is sent to the clock generator 23, and the MPEG audio stream (MPEG STREAM) is sent to the MPEG audio decoder 22.

The stream data input to the MPEG audio decoder 22 is decoded by the corresponding information (bit allocation, sampling, ratio, scale ratio, channel mode, etc.), and thus 16-bit serial data (SER 12) and sampling clock (SCLK2). ), Left and right channel clocks (LRCLK 2) are generated and sent to the digital signal multiplexer 24.

The serial PCM data SER1, clocks SCLK, and LRCLK0 output from the digital signal multiplexer 24 are shown as timing charts shown in FIG. 4 and FIG.

FIG. 4 shows the serial PCM data output state, and FIG. 5 shows the 16-bit PCM data output state.

The audio data SER12 and the clocks SCLK 2 and LRCLK 2 output from the MPEG audio decoder 22 are inputted to the digital signal multiplexer 24 and are subjected to D / A in accordance with the audio selection signal SEL. Audio data is output to the converter 25.

That is, the digital signal multiplexer 24 outputs PCM waveform audio data when the audio selection signal SEL is in a logic low state, and outputs MPEG decoded audio data when in a logic high state.

Next, the PCM waveform audio reproduction operation procedure will be described. The waveform audio data in the PC (computation) includes a sampling rate (11.025KHZ, 22.05KHZ, 32KHZ, 44.1KHZ), the number of sample bits (8 bits, 16 bits) and Since channels (stereo, mono) are various, the corresponding clock is applied to the D / A converter 25.

Subsequently, the waveform data PCM WAVE determined by the audio data decoder 21 is input to the clock generator 23, and the clock generator 23 receives a clock corresponding to the corresponding information (sample rate, sample bits, channel). It is generated and applied to the D / A converter 25.

At this time, the sample rate clock SCLK of 16 bits, 32 KHZ, 44.1 KHZ, and 48 KHZ is generated in the same manner as the output of the MPEG audio decoder 22 as shown in FIG. 4 and FIG.

In case of 8-bit PCM data, the left and right clocks (LRCLK 1) are divided and outputted as shown in FIG. ) Is output.

The PCM waveform data PCMCLK 1 and clocks SERI 1, SCLK 1, and LRCLK 1 output from the clock generator 23 are input to the digital signal multiplexer 24 so that the selection signal SEL is logic. In the low state, a signal is output to the audio D / A converter 25, and is converted into an analog signal through the D / A converter 25 and output.

As described above, in the present invention, when the MPEG audio playback function is to be implemented in a general personal computer, the D / A converter can be used in common, so that the PCM waveform audio can be played smoothly without a separate multimedia card. It is possible to provide an effect that can provide the effect of diversifying functions and reducing equipment costs.

Claims (1)

An audio data decoder which decodes audio data output from a PC data bus line and delivers it to a subsequent clock generator, and simultaneously delivers an MPEG stream signal to an MPEG audio decoder, and data, address and control signals output from the PC data service line. An MPEG audio decoder that decodes the MPEG stream state and delivers it to the digital signal multiplexer, a clock generator that generates the clock oscillation frequency for waveform audio and applies it to the digital signal multiplexer, and optionally, MPEG audio and waveform digital data. Pulse code modulation (PCM), comprising: a digital signal multiplexer for outputting one data; and multiple audio D / A converters for converting digital audio data input from the digital signal multiplexer into an analog signal. A) waveform audio And MPEG audio signal reproducing apparatus.