JPS61233472A - Recording system for digital audio data - Google Patents

Abstract

PURPOSE:To prevent the deviation of lip synchronization of digital video data and digital audio data on a recording medium by cutting off digital audio data at every specified period relating to vertical period of video signals and recording in a recording medium together with discriminating data that discriminate the number of samples and thereby recording in a digital VTR easily. CONSTITUTION:Biphase series data of digital audio data having proper specified sampling frequency are supplied to a synchronizing separator demodulating circuit 1, converted to parallel data and outputted and supplied to a selector 7. An encoder 8 cuts off audio data from the selector 7 at every vertical period to make it one block and supplied to a rotary magnetic head 10 for recording through a recording amplifier 9 adding it an error correction code and recording is made in a magnetic tape 11 to form slanted tracks. Digital audio data are fetched by the encoder 8 from the selector 7 in next vertical period according to the number of samples in the vertical period.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a digital audio data recording method [Summary of the Invention] The digital audio data recording method according to the present invention comprises:
By dividing digital audio data having a unique predetermined sampling frequency into predetermined periods related to the vertical period of the video signal and recording them on a recording medium together with discrimination data that distinguishes the number of samples of the digital audio data in each predetermined period. Even digital audio data that is asynchronous to digital video data can be recorded on a digital VTR.

[Conventional technology]

When recording digital audio data (PCM audio data) on a digital VTR, the servo system of the digital VTR is configured to synchronize with the vertical synchronization signal or frame synchronization signal of the video signal, so the sampling frequency of the digital audio data also changes. , vertical synchronization signal of the video signal (59.9411z in the case of NTSSC system)
), for example, 44.056kHz, is usually used. In addition to this sampling frequency, recently 44.1kHz, 48kHz,
32kHz etc. are used. All of these sampling frequencies are signals synchronized with the vertical synchronization signal of the video signal.

Therefore, when recording digital audio data from a digital interface onto a digital VTR, the side sending out the recording signal must receive a word synchronization signal from the VTR and send out the recording signal in synchronization with this.

An audio-only digital audio tape recorder that supplies digital audio data to a VTR via an interface and records it from digital audio equipment that does not have synchronization input or that operates with a synchronization signal specific to digital audio data. There are times when it is necessary to do so.

[Problem that the invention seeks to solve]

In view of this, the present invention proposes a digital audio data recording method that allows digital audio data having a unique predetermined sampling frequency asynchronous to a synchronizing signal of a video signal to be recorded on a digital VTR. It is something.

[Means for solving problems]

The digital audio data recording method according to the present invention is as follows:
Digital audio data having a unique predetermined sampling frequency is divided into predetermined periods related to the vertical period of the video signal, and is recorded on a recording medium together with discrimination data that distinguishes the number of samples of the digital audio data for each predetermined period. That is.

[Effect]

According to the present invention, digital audio data having a unique predetermined sampling frequency can be recorded on a recording medium using a digital VTR.

〔Example〕

Referring to the figures below, digital video/video using the present invention is shown below.
An audio data recording and reproducing device (digital VTR) will be explained. The bi-phase serial data of digital audio data (output of the digital interface) having a unique predetermined sampling frequency from the input terminal T1 is supplied to the synchronization separation/11m circuit (1), and a synchronization signal is output from the preamble part. It is detected, biphase demodulated, converted into parallel data, output, and supplied to the selector (7). Furthermore, in the circuit (1), the word clock is separated from the serial data and supplied to the sample counter (2) and to the clock generator (5) via the on-off switch SW1, respectively. Since this word clock is asynchronous with the vertical synchronization signal of the video signal, it is supplied to a sample counter (2) and the number of samples thereof is counted every vertical period. This sample counter (2
) is supplied with a vertical synchronizing signal from the input terminal T2 as a reset pulse.

The output of the counter (2) is supplied to the latch (3) and latched by the vertical synchronization signal from the input terminal T2, and the latch output (only LSB is required) is sent to the encoder (8).
supplied to

(4) is a clock generator, which has an input terminal T2.
A vertical synchronization signal is supplied from the encoder (8) and a clock generated therefrom is supplied to the encoder (8) and the decoder (16). The clock from this clock generator (4) is
It is asynchronous with the audio serial data supplied to the input terminal T1, and is usually in a synchronous relationship with the vertical synchronization signal of the video signal, but it does not necessarily have to be in a synchronous relationship.

(6) is a D/A converter which D/A converts the analog audio signal from the input terminal T5, and the output digital audio signal is supplied to the selector (7).

(5) is a clock generator, to which a word clock is supplied via an on/off switch SWt, or a horizontal synchronization signal from an input terminal T4 via an on/off switch SW2.

These on/off switches SW1 . By switching SW2 on and off in the opposite way, the clock generator (5) synchronizes the selector (7) in the mode in which the signal to be recorded is supplied to the reproduction system (EE mode) and in the recording mode. When audio parallel data from the separation/demodulation circuit (1) is selected, a clock synchronized with the word clock obtained from the synchronous separation/demodulation circuit (1) is generated, and at other times, input terminal T4 is generated. A clock is generated in synchronization with the horizontal synchronization signal from the

The clock from the clock generator (5) is supplied to the A/D converter (6) and the D/A converter (18) via the changeover switch SW3.

The encoder (8) divides the audio data from the selector (7) into vertical periods, sets the audio data within each vertical period as one block, adds an error correction code to this block, and sends the audio data to the recording amplifier (9). The magnetic tape (11) is supplied to the recording rotary magnetic head (lO) via the
The recording is performed so as to form an inclined track. In this case, the predetermined period for dividing the audio data may be an integral number or an integral multiple of the vertical period. This encoder (8) is also supplied with a synchronized timing signal from a sample counter (2) and a clock from a clock generator (4).

For example, when the sampling frequency of digital audio data is 48 kHz, the vertical frequency of the NTSC video signal is 59.94 Hz, so the number of samples of digital audio data within one vertical period is 800.8.
Become an individual. Therefore, the number of samples within l vertical period is 8
The sample counter (2) determines whether the number of samples for each vertical cycle is 800 or 801 alternately. Note that when the vertical frequency is 80.00Hz, the number of samples is 799 (I
I, 8.00 pieces, and 801 pieces are sequentially and cyclically selected. Therefore, 800 cells divided by vertical period
or 801 audio sampling data,
Together with a 1-bit or 2-pin discrimination signal that distinguishes the number of samples within each vertical cycle period, the signal is supplied to the recording rotary magnetic head (10) via the recording amplifier (9), and is then applied to the magnetic tape (12) to create an inclined track. Record it as it forms.

Here, there are two ways in which the encoder (8) can take in digital audio data in one vertical cycle section. One is to use an internal counter of the encoder (8) to determine whether the encoder (8) itself will be able to control itself in the next vertical period depending on the number of samples in a certain vertical period that is supplied from the latch (3) to the encoder (8). is the method of importing audio data from the selector (7).

Another method is to use a synchronous reset type counter as the sample counter (2), synchronize the vertical synchronization signal with the word clock from the synchronous separation/demodulation circuit (1), and send it as a reset signal to the sample counter (2). The encoder (8) separates the digital audio data from the selector (7) every vertical cycle at the timing edge when all the parallel outputs of the counter (2) become O.
The output of lunch (3) is recorded on a magnetic tape (12
) to record on.

Next, the reproduction system will be explained. Rotating magnetic head for reproduction (
13) reproduces the digital audio data recorded on the magnetic tape (12), and the reproduction amplifier (14) reproduces the digital audio data recorded on the magnetic tape (12).
) is supplied to an equalizer/synchronization separation circuit (15), and its output is supplied to a decoder (16). In the decoder (16), after correcting and interpolating the digital audio data using a correction code, the digital audio data is sequentially stored in a memory (FIFO is possible) (1
7).

The number of sample data at this time is determined by a discrimination signal representing the number of data recorded in the same block. The write address generator (19) consists of a counter that is incremented by the word clock output from the decoder (16), and from this the write address signal is supplied to the memory (17).

(20) is a read address generator which supplies a read address signal from this to the memory (17) to read out the digital audio data stored therein;
The read data is supplied to the D/A converter (18) and the modulation circuit (21) through the reproduction side fixed contact PB of the changeover switch SW3.

Note that when the output of the selector (7) is in the EE mode, it is connected to the D/A converter (1) through the fixed contact EE of the changeover switch SW3.
8) and a modulation circuit (21).

The read address generator (20) is a clock generator (
5) is incremented by the clock from 5). The read signal from the memory (17) is passed through the changeover switch SW3 to the D/A converter (18) and the modulation circuit (2).
1), the write address generator (19
) An address offset by the system delay of the memory (17) is loaded from the write address generator (19) to the read address generator (20), and the read address generator (20) starts operating. .

The digital data read from the memory (17) is
This becomes digital audio data that is synchronized to an internal clock that is synchronized to the vertical synchronization signal of the video signal. An analog audio signal from the D/A converter (18) is output to the output terminal T6, and audio serial data (digital audio signal) from the modulation circuit (21) is output to the output terminal T7.

Such a recording method of digital audio data is such that, as time passes, the frequency difference between digital video data and digital audio data at the time of recording is
Although the digital video data and digital audio data recorded on the magnetic tape (12) along with the digital audio data are slightly out of phase, editing is easy because the audio playback data is synchronized with the vertical synchronization signal of the video data during editing. It is. In addition, in the case of editing, since the cuts are short, the phase shift between the video and audio is not a big problem.

〔Effect of the invention〕

According to the present invention described above, even digital audio data having a unique predetermined sampling frequency asynchronous to a vertical synchronization signal of a video signal can be easily recorded on a digital VTR.

Furthermore, since the digital audio data is recorded on the recording medium asynchronously with respect to the sampling frequency of the digital video data, there is no possibility that the lip synchronization between the digital video data and the digital audio data will be out of sync on the recording medium.

[Brief explanation of drawings]

The figure is a block diagram showing an example of a digital recording/reproducing apparatus that uses the method of the present invention.

Claims (1)

[Claims] Digital audio data having a unique predetermined sampling frequency is divided into predetermined periods related to the vertical period of the video signal, and recorded on a recording medium together with discrimination data that distinguishes the number of samples of the digital audio data for each predetermined period. A digital audio data recording method characterized by: