JPH0287366A - Audio recording and playback method and device - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to an audio recording and reproducing method for a digital recording and reproducing apparatus and an apparatus thereof.

Prior Art FIG. 3 is a block diagram showing an audio signal recording device that performs a conventional audio signal recording method.The audio signal is inputted from an audio signal input terminal 1, and an AD converter 3 converts the manually generated audio signal into a quantum computer. Number of encoding bits: 14 bits, sampling frequency: 44
．． It undergoes AD conversion at 1kHz and becomes a digital audio signal 4. The still image signal is input from the still image signal input terminal 5,
A D converter 6 performs AD conversion to obtain a digital still image signal 7.

Of the 16 bits of the digital signal, the encoder 8 arranges the digital audio signal 4 in the upper 14 bits and the digital still image signal 7 in the lower 2 bits, and records them on the disk 10.

FIG. 4 is a block diagram showing an audio signal reproducing apparatus using a conventional audio signal reproducing method, in which a signal reproduced from a disc 10 recorded as described above is processed by a decoder 11 from the 16 bits of the digital signal to the upper 14 bits. The digital audio signal 12 and the 5th 2-bit digital still image signal 16 are separated and output. Digital audio signal 12 is sent to DA converter 13
The signal is DA-converted at , and output as an audio signal from the audio signal output terminal 15 . The digital still image signal 16 is DA-converted by a DA converter 17, and output as a still image signal from a still image signal output terminal 18.

Problems to be Solved by the Invention In such a conventional configuration, the lower two bits of the 16 bits of digital data are used to record the still image signal, so the number of quantization bits when quantizing the audio signal is 1
When recording and reproducing an audio signal that has only 4 bits and has a low amplitude, the amplitude of the quantization noise becomes larger than the amplitude of the audio signal, which causes a problem in terms of auditory sensation.

The present invention has been made in view of the above, and an object of the present invention is to provide an audio recording and reproducing method that can record and reproduce low-amplitude audio signals with low quantization noise even when the quantization bit number is 14 bits. .

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention expands or compresses the amplitude of an audio signal at a prescribed rate during recording, and digitizes the audio signal that has been expanded or compressed. Then, digital recording is performed using predetermined bits of the upper bits of the digital signal, and during playback, after DA conversion of the digital audio signal, compression is performed corresponding to the expansion of the amplitude of the audio signal performed at the time of recording, or expansion corresponding to compression is performed. This is an audio recording and reproducing method characterized by performing the following.

Effects According to the present invention, with the above-described configuration, when an audio signal with a low amplitude is expanded and recorded, it is compressed during playback, so that the quantization noise can be suppressed to be lower than that of the audio signal.

Embodiment FIG. 1 is a block diagram showing an audio signal recording method in an embodiment of the present invention.The audio signal is input from the audio signal input terminal 1, and the input audio signal with a low amplitude is constant at the expansion circuit 2. Stretch at a ratio of

FIG. 5 shows recording expansion characteristics 19 and playback compression characteristics 20 in one embodiment of the present invention.
If it is dB, it is expanded by 14 dB in expansion circuit 2 and -14 dB.
The amplitude will be . The expanded audio signal is quantized by the AD converter 3 with a quantization bit number of 14 bits and a sampling frequency of 44.1.
It is AD converted at kHz and becomes a digital audio signal 4. The still image signal is input from the still image signal input terminal 5, and the AD
A converter 6 performs AD conversion to obtain a digital still image signal 7.

Of the 16 bits of the digital signal, the encoder 8 arranges the digital audio signal 4 in the upper 14 bits and the digital still image signal 7 in the lower 2 bits, and records them on the disk 10.

FIG. 2 is a block diagram showing a method for reproducing an audio signal in one embodiment. The decoder 11 converts the signal reproduced from the disc 10 recorded as described above into the upper 14 bits of the digital audio signal from the 16 bits of the digital signal. 12 and bottom 2
A bit digital still image signal 16 is output separately.

The digital audio signal 12 is converted from a digital audio signal to an analog audio signal by a DA converter 13, and the amplitude of the audio signal is compressed by a compression circuit 14 using a reproduction compression characteristic 20 shown in FIG. That is, the amplitude of the audio signal input by -14 dB is compressed by 14 dB, which is the same ratio as the ratio at which the amplitude of the audio signal is expanded by the expansion circuit 2 at the time of recording, and becomes an amplitude of -28 dB.

The compressed audio signal is output from the audio signal output terminal 15. An audio signal input with an amplitude of -28 dB is expanded in amplitude by 14 dB and compressed by 14 dB, so that the amplitude of the quantization noise is reduced by 14 dB. The digital still image signal 16 is DA-converted by a DA converter 17, and output as a still image signal from a still image signal output terminal 18.

Effects of the Invention As described above, by recording a low-amplitude audio signal after decompression and compressing it during playback according to the present invention, quantization noise can be suppressed to a low level, and recording can be performed with a small number of m-bits. Even when playing back, high-quality sound with a high SN ratio and wide dynamic range can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the audio recording and reproducing method and device according to the present invention, FIG. 2 is a block diagram showing an audio signal reproducing device in the same embodiment, and FIG. 3 is a conventional audio signal recording device. FIG. 4 is a block diagram showing a conventional audio signal reproducing device, and FIG. 5 is a characteristic diagram showing recording expansion characteristics and reproduction compression characteristics in an embodiment of the present invention. 1... Audio signal input, 2... Expansion circuit, 3.6.1
3.17... AD converter, 4.12... Digital audio signal, 5... Still image signal input terminal, 7.16... Digital still image signal, 8... Encoder, 10...・Disk, 11...Decoder, 14
... compression circuit, 15 ... audio signal output terminal, 18 ... still image output terminal, 19 ... recording expansion characteristics, 20 ... playback compression characteristics. Name of agent Patent attorney Awag! P Shigetaka Haka18 Yoshi 4
figure

Claims (3)

[Claims] (1) At the time of recording, the amplitude of the audio signal is expanded at a specified rate, and the expanded audio signal is digitized,
Audio characterized in that digital recording is performed using predetermined upper bits of the digital signal, and upon playback, the digital audio signal is DA converted and then compressed in accordance with the expansion of the amplitude of the audio signal performed during recording. Recording and playback method. (2) during recording, compressing the amplitude of the audio signal at a specified rate and digitizing the compressed audio signal;
Audio characterized in that digital recording is performed using predetermined upper bits of the digital signal, and upon playback, the digital audio signal is subjected to DA conversion and then expanded in accordance with the compression of the amplitude of the audio signal performed during recording. Recording and playback method. (3) an expansion and compression circuit that expands and compresses the amplitude of an audio signal at a prescribed rate; and means that digitizes the expanded and compressed audio signal and digitally records it using predetermined upper bits of the digital signal; An audio recording system comprising: a compression/expansion circuit that performs DA conversion on a digital audio signal during playback, then compresses the audio signal by the amount by which the amplitude of the audio signal is expanded during recording, and expands the audio signal by the amount by which the amplitude of the audio signal is compressed. playback device.