JPS6348660A - Sound signal discriminating circuit - Google Patents

Abstract

PURPOSE:To judge whether or not a reproduced signal is an sound signal by utilizing a start signal (start flag) recorded substantially as a reference position of signal recording and discriminating whether or not this signal is generated at a prescribed time and has a prescribed frequency. CONSTITUTION:A start flag discrimination circuit 7 generates an audio signal discrimination signal (i) when an output (b) of a time region filter 10 and an output (h) of a BPF 8 are both at H level and a trailing output (g) changes from L to H and outputs the signal (i). The start flag discriminating circuit 7 consists of an AND circuit 11 receiving the output (b) of the time region filter, the trailing output (g) and the BPF output (h) and a D flip-flop 12 giving an output signal of the AND circuit 11 to a data terminal. A DC signal (j) of H level is given to a clock terminal of the flip-flop 12 and a head access signal (k) obtained from a system controller is given to a reset terminal of the flip-flop 12 and the sound signal discriminating signal is reset to L with every head access is executed.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a device for reproducing a desired signal from a recording medium on which audio signals and other signals (for example, video signals) are recorded. This relates to an audio signal discrimination circuit equipped for system control and the like.

(Prior Art) Electronic still cameras, which have been attracting attention as still image recording devices in recent years, use flexible magnetic disks (floppy disks) as signal recording media, and use a magnetic head to record concentric circles on the signal surface of the floppy disk. 9 It is also possible to convert the explanatory audio of images recorded on a floppy disk into a compressed audio signal, and record the audio signal on an empty rack of the floppy disk. Electronic still cameras have been proposed (e.g., Television Society Report TEIES 107-5), and international standards for signal recording methods have been established (published by the Electronic Still Camera Association). Specification of
5Lill Video Floppy 5ystec
*See “s”).

FIG. 3e shows the recording format of the audio signal in the unified standard. One round of the track is divided into 1 sector, and each sector has a data star + = 1 point.
-(L'1SP) is the starting point for signal recording, and as shown in the figure, a start flag, control 1 to roll codes, time compressed audio signal, and end flag are recorded at predetermined time intervals.

A DSP uses a pulse generation yoke (
The PG yoke is set by detecting the magnetic flux of the PG yoke by a PG detector consisting of a pulse generator coil.

The start flag and end flag serve as a start signal and an end signal indicating the beginning and end of a sector, respectively. Further, the control code includes various information possessed by the audio signal (for example, the 1-rack number where the video signal for the audio signal is recorded, the audio compression ratio, etc.).

A tolerance of ±1 horizontal scanning period is allowed for the position of the DSP, which is the period 'T' from when the DSP output is obtained to the falling position of the start flag. is defined as approximately 257 μS (approximately 4 horizontal scanning periods) in a video system with 525 scanning lines and 60 fields.

As mentioned above, since there are slight variations in the position of the DSP, the positions of the control code and the time-compressed audio signal during signal recording and reproduction are accurately defined using the start flag as a reference position.

When recording a signal, an audio format signal shown in FIG. 3C is written onto a floppy disk by an FM modulated magnetic head.

On the other hand, during signal reproduction, FM is added to the output signal of the magnetic head.
After demodulation, the compressed audio signal is subjected to signal processing including time expansion based on the control code separated from the demodulated signal, thereby restoring the audio.

(Problem to be solved) When recording signals using an electronic still camera, as mentioned above, audio signals are recorded on empty tracks of the floppy disk on which video signals are recorded, and different types of signals are mixed on the same recording medium. ! -I am. However, it has been proposed to record data signals representing other information in addition to video signals and audio No. 13 on the same floppy disk, and the recording format is specified in the unified standard.

These signals are recorded in any order on any track on the same floppy disk, so when reproducing a desired signal, the signal being reproduced by the magnetic head is It is difficult to determine whether the signal is a voice signal, a data signal, or a data signal.
The key point.

As for the video signal, it is possible to easily determine that the reproduced signal is a video signal by detecting the synchronization signal included in the video signal.

However, with respect to audio signals, no valid means for determining them is known, and in the development of the electronic still camera, an audio signal determining circuit with a simple configuration was required.

(Means for Solving the Problems) An object of the present invention is to provide a simple voice discrimination circuit that can reliably discriminate voice signals when multiple types of signals are recorded in the same signal recording method. The goal is to provide the following.

The present invention achieves this objective by using a start signal (start flag) that is originally recorded as a reference position for J-word recording, and when the signal is generated at a predetermined time,
Furthermore, by determining whether the reproduced signal has a predetermined frequency or not, it was determined whether the reproduced signal was an audio signal or not.

According to the present invention, the audio discrimination circuit (related to the present invention) includes first discrimination means for discriminating whether or not a reproduction signal exceeding a predetermined level is obtained from the reproduction head during the generation period of the start signal which has elapsed for a predetermined time from the generation time of the DSP output. and 21"1 different means for determining whether or not the reproduced signal includes a signal having the same frequency as the start signal, and a 21"1 different means for determining whether or not the reproduced signal includes a signal having the same frequency as the start signal; 9 (Operation) When the reproduction signal by the reproduction head is an audio signal, the third determination means determines that the signal is an audio signal.
As shown in Figure e,
There is no recording until the time period elapses, and then a start signal having a predetermined level and a predetermined frequency (approximately 8 KHz) appears in the reproduced signal.

The first determining means detects that the reproduced signal, ie, the start signal, has a level equal to or higher than a predetermined value, and outputs a first start signal determining signal representing this.

On the other hand, the second determining means detects that the reproduced signal, ie, the start signal, has a predetermined frequency, and outputs a second start signal determining signal representing this fact.

Further, the third determining means determines that the reproduced signal is a start signal based on the first and second determining signals, and generates and outputs an audio signal determining signal without determining this fact. .

If the reproduction signal is a signal other than an audio signal, since the reproduction signal does not include a start signal, the reproduction signal is obtained from the reproduction head during the generation period of the start signal after a predetermined period of time has elapsed from the generation time of the DSP output. It is practically impossible for the signal to have a level exceeding a predetermined value and the same frequency as the start signal. Therefore, the first determining means and the second determining means
Both of the discriminating means do not output a start signal discriminating signal, so the third discriminating means does not output an audio signal discriminating signal.

In this way, it is determined whether the reproduced signal is an audio signal or not, and the determination signal obtained in the case of an audio signal is supplied to, for example, a system controller that controls the operation of the entire device, and is used for tracking control, etc. used for system control.

(Effects of the Invention) In the audio signal discrimination circuit according to the present invention, it is possible to discriminate audio signals with extremely high reliability, and as described in the embodiments below, the first to third discriminations are possible. Since the circuit can be formed with a simple circuit configuration, it is suitable as an audio signal discrimination circuit for electronic still cameras and the like.

<Embodiment> FIG. 1 shows an example in which the audio signal discrimination circuit according to the present invention is implemented in an electronic still camera, and the timing chart of FIG. 3 represents the circuit operation of FIG. 1.

A reproduction signal C obtained by scanning the signal surface of a rotating floppy disk (1) with a magnetic head (2) is amplified into an amplified reproduction signal d via a preamplifier (3), and then sent to an F Pv1 demodulator (4). ) and converted into an audio format signal e.

The audio format signal e is input to a slicing circuit (5), where it is sliced at a predetermined level at which the start flag can be detected, as shown by the chain line in FIG. 3e, resulting in a slice output f. However, the slice output r includes not only the start flag but also the sliced output of the time-compressed audio signal.

The slice output f passes through a fall detection circuit (6), where the fall position is detected and converted into a fall output 8, and the signal 8 is further supplied to a start flag discrimination circuit (7).

On the other hand, the DSP output a obtained from the PG detector (9) is
By passing through a time domain filter (10),
“H” during a predetermined period that overlaps with the falling timing of the start flag.
A time-domain filter output screen is created that serves as a time-domain filter.The time-domain filter (10) includes, for example, a counter that counts the period 1 from the DSP output to immediately after the start flag rises, and a time-domain filter output screen.
It can be easily constructed from a multi-bye break that sets the level maintenance time (pulse t, +=) t2.

The time domain filter output is supplied to a start flag discrimination circuit (7).

In addition, the audio format signal e output from the FM demodulator (4) passes through the BPF (8) with a pass center frequency of 8Kl-1z through which the start flag can pass, and is output as BPF output 1.
1, and the start flag discrimination circuit (7)/\ is supplied.

In the start flag discrimination circuit (7), the time domain filter output and BPF output 1] are both at the "H" level,
Moreover, when the falling output 8 changes from "L" to "H" degree, one layer of audio signal discrimination signal i that changes from "L" to "H" is generated and output. The start flag discrimination circuit (
For example, as shown in FIG. 2, 7) is an AND circuit (11) to which the time domain filter output I], falling output g, and BPF output are input, and the output signal of the AND circuit (11) is connected to a data terminal. A D type flip-flop connected to (
12).

The clock terminal of the flip-flop 7 (12) has "H"
A head access signal k provided by the system controller 6t is connected to the DC signal j of level 7) and the reset terminal, and the audio signal discrimination signal is reset to "L" every time the head is accessed 7).

The operation of the circuit will be described below when the signal reproduced by the magnetic head (2) is an audio signal, a video signal, and a data signal.

A. In the case of an audio signal, the FM demodulator (4) obtains the audio format signal e shown in Figure 3, so the slice output f contains a signal r1 in which the start flag is sliced, and a signal r1 in which the time-compressed audio signal is sliced. A signal f2 appears.

Therefore, the falling edge detection circuit (6) detects not only the falling edge of the start flag but also the falling edge of the time-compressed audio signal as shown in 312I.

However, the fall of the start flag can be detected by selecting j'A the falling output which becomes "H" during the period when the time domain filter output becomes "■Z".

The time domain filter (10), the slice circuit (5) and the falling detection circuit (6) are connected to the magnetic head (2).
) constitutes a first determining means for detecting a start flag by determining whether or not a reproduced signal exceeding a predetermined level has been detected.

On the other hand, the BPF (8) passes the start flag and end flag of the audio format signal e, and supplies the BPF output 11 to the start flag discrimination circuit (7). still,
According to the unified standard, the lowest frequency of the compressed audio signal is approximately 30 Kl-(z, 30 KHz, and 120 KHz at time compression rates of 320 times, 640 times, and 1280 times, respectively).
, which is much higher than the passband of BPF(8),
No compressed audio signal appears at the BPF output.

At this time, it is not possible to distinguish whether the pulse that appears at the BPF output 11 is due to the passage of the start flag or the end flag, but during the period when the time domain filter output I] is at the 'H' level, By selecting a pulse that becomes "H", a pulse caused by the start flag can be detected.

Therefore, the time domain filter <10) and B P F
(8) constitutes a second determining means for detecting the Sufu-I flag by determining whether or not a signal having the same frequency as the start flag is read in the reproduced signal.

The start flag discrimination circuit (7) serving as the third discrimination means,
When the falling output g and the BPF output 11 both become 'H' during the period when the time-order filter output is at the 'tr' level, the audio signal discrimination signal i switches from 'L' to 'H'. Create.

B. In the case of video signals, in the unified standard for electronic still cameras, as shown in Figure 4, the phase difference θ between the DSP output and vertical synchronization No. 13 is
corresponds to 7 horizontal scanning periods (7T-1 = 444.5 μs), so the time domain filter output is “H”.
This period occurs within the 7H, and the video signal demodulated within this period is connected to the BPF (8).

However, even if the screen is solid white, the video signal always includes a horizontal synchronization signal, so the lowest frequency of the video signal No. 13 is 15.7 KHz, and this signal must pass through the BPF (8>). Yes; 2.

Therefore, even if the falling output 8 is "H" during the period when the time-order filter output is "H", the BPF output 11 is "L", so the audio signal discrimination signal i is "
It remains at "L".

In the unified standard for C data signals, the recording format of data signals is as follows:
As shown in Fig. 5, GapO, I
ndex, Gap 1, 5ector9
0, Gap2. 5ecLor#1 etc., and the period t2 during which the time domain filter output is °゛H'' is the second half of Gapl and SecLor#O
It will straddle an area of width LH in the first half of .

Since it is specified that Gapl is set to a non-recording state, the Gapl signal becomes a DC signal, and when the DC signal is FM demodulated, noise is added to the demodulated signal and the signal is sent to the FM demodulator (4). ) will output a high frequency signal. The high frequency signal cannot pass through BPF (8).

In addition, in the IH width area of 5ecLorlO, “Pre-
A binary signal called 'amble' and '5yncl -5
It is specified that a binary signal called ync2°' is recorded. The channel focus rate is 14.31
8,180b i L/s.

“P rcamble” was released in N RZ I in '011.
111111'' continuous signal, and the signal is 3.58
This includes a MHz signal component and a 7.16 MHz signal component.

When such a signal is FM demodulated, 1.・132MH2
1. It becomes a fallen tone signal.

On the other hand, "5yncl ・5ync2" is a continuous signal of "X1000100011100010001" in NRZI, and this signal has a signal component of 1.79MHz and 7
．． This means that it contains a 16 MHz signal component. When such a signal is FM demodulated, it becomes a demodulated signal of 357 KHz.

That is, when the data signal is modulated by FM (i), the lowest frequency of the demodulated signal that can exist is 357K!-1z, and the summer tone signal is transmitted through a BPF with a center frequency of 8KHz.
(8) will not be passed.

Therefore, even when the reproduced signal from the magnetic head (2) is a data signal, the time domain filter output is
During the period of 4°°, the BPF output becomes "°I-"',
The audio signal discrimination signal i remains at "L".

As mentioned above, according to the audio signal discrimination circuit according to the present invention,
Regardless of whether the reproduced signal is an audio signal, a video signal, or a data signal, it can be accurately determined whether it is an audio signal or not based on the binary state of the audio signal discrimination signal. Further, as shown in the first (2I) and FIG. 2, the circuit configuration is simple.

It should be noted that the configuration of each part of the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made within the technical scope of the claims.

For example, in the configuration of the first determining means, the start flag can be detected by detecting the rise of the slice output.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an audio signal discrimination circuit according to the present invention;
FIG. 2 is a diagram showing a start flag discrimination circuit, FIG. 3 is a timing chart, FIG. 4 is an explanatory diagram of a recording state of a video signal, and FIG. 5 is a diagram showing a recording format of a data signal. (1)...Floppy disk (2)...Magnetic head (5)...Slave/fs circuit (7)...Sfu-l-flag discrimination circuit (8)...B
P F (10)...Time domain filter No. 50

Claims (1)

[Claims] (1) A disk-shaped signal recording medium is equipped with a PG yoke that serves as a starting point for signal recording, and on the signal surface of the recording medium, multiple types of signals including audio signals are recorded concentrically in an arbitrary track order, The audio signal recording format consists of a time-compressed audio signal recording section, and a start signal recording section and an end signal recording section provided at predetermined positions in front and behind the recording section. In a device for reproducing recorded signals, the output signal of the PG yoke (
a first determining means for determining whether or not a reproduction signal exceeding a predetermined level is obtained from the reproduction head during a generation period of the start signal after a predetermined period of time has elapsed from the generation of the DSP output;
a second determining means for determining whether or not the reproduced signal includes a signal having the same frequency as the start signal; and the reproduced signal is an audio signal when the start signal is detected by both the determining means. and a third determining means for determining the audio signal discriminating circuit.