JPS62296684A - Mode discrimination for recording medium reproducing device - Google Patents

Abstract

PURPOSE:To automatically and securely decide a recording mode by extracting the DC level in a sink chip level transmission period from a reproducing video signal and comparing it with a reference level for decision making. CONSTITUTION:A reproducing video signal passed through an FM demodulator 2 and an LPF 3 is supplied to a sample holding circuit 4 and a synchronizing signal separating circuit 5. A horizontal synchronizing signal outputted by the circuit 5 is used as sampling pulses by the circuit 4 to extracts the DC level in a sink chip level transmission period which varies according to the recording mode from the luminance signal of a video signal, and the DC level is supplied to a comparing circuit 6 supplied with the reference level. Then, the circuit 6 outputs the comparison output of the recording mode decision result to securely and automatically decide the recording mode.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Industrial Field of Application The present invention relates to a T-code discriminating device for a recording medium reproducing device, and in particular, the present invention relates to a T-code discriminating device for a recording medium reproducing device, and in particular, when the reproduction of 11 video signals from a recording medium is performed in a plurality of recording modes. This invention relates to an equipment for determining the recording medium re/1 head on which the recording was recorded.

Conventional technology In recent years, tape performance and head performance have improved, and there is a demand for high-quality magnetic recording and reproducing devices with high resolution marks, and the carrier frequency has been sufficiently high compared to the carrier frequency of current home VTRs. The high image quality mode with shift 1 is considered divine.

Problem to be Solved by the Invention LN However, as mentioned above, since 171fA llI is /z I, z between the signals recorded at the key ↑, The data recorded in one mode can be replayed in the other recording mode! 1 can be A
There is a problem with this. Example λ to solve this
It is conceivable to provide a changeover switch or the like and cover it so that the changeover switch can be changed according to the recording mode.
According to this, the switching operation is extremely complicated and the usability is extremely poor. At this time, when performing this switching operation, it is necessary to judge which record was recorded in each mode. Since some files may be recorded in a different mode, you may end up switching to a different playback mode and playing back. Furthermore, there are other problems, such as the possibility that the user may make a mistake when playing in a playback mode different from the recording mode.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a mode discriminating device for a recording medium reproducing device that solves the above problem by discriminating the mode based on the self-current level of the sync chip level transmission section of the FM demodulated reproduced video signal. shall be.

Means for Solving the Problems The mode discriminating device of the recording medium reproducing apparatus according to the present invention detects the sync chip level transmission section from the reproduced video signal which is reproduced in the 1 and 1u tones on the recording medium. It is comprised of a DC level extraction means for extracting a DC level, and a recording mode discrimination means.

Function: On the recording medium described above, a video signal is recorded in one of a plurality of recording modes in which carrier frequencies of frequency modulated video offsets are different from each other. Next, the discriminating means detects the re-! from the DC level 1 drawing means. 1- Compare the DC level of the sync chip level transmission section of the video signal with a preset reference value, and determine the recording mode of the reproduced video signal according to the comparison result.

Embodiment FIG. 1 shows a block system diagram of an embodiment of a (-) code discriminating device for recording medium playback 5A according to the present invention.

Before explaining this embodiment, please refer to Figures 5 and 6.
The principle of the device of the present invention will be explained with reference to the drawings.

Frequency modulation (FM modulation) is a modulation method that replaces one signal amplitude with each frequency.For example, this modulation method is generally used for magnetic recording of video signals. The frequency spectrum of the signal (1:M luminance signal) is shown in Fig. 5 in the above standard mode.
It becomes as shown in A, and in the high image quality mode mentioned above, Se
As shown in , the carrier frequency is set higher than that of the standard frequency. In the FM luminance nail polishing signal frequency spectrum SA shown in FIG. fBs, fBP, and fBW indicate -1 near frequency at the sync tip level, pedestal level, and white peak level of the luminance signal, respectively. For example, the carrier frequency fAs in standard mode
is 3.4MHz, f AP is 3.8M1-1z
, fAw is 4.4Ml-1z, and the carrier frequency f'es in high image quality mode is 5.0Htlz.

fep is 5.6M t-IZ, few is G,
7M l-lz.

By the way, "In M demodulator, generally input frequency and output DC
Since there is a proportional relationship with the level, demodulated video image E3 in standard mode and high quality mode. The waveform of the demodulated luminance signal is as shown in YA and YB in FIG. Therefore, the -1-17 rear frequency difference between both modes appears as a DC level difference in the demodulator output. The present invention is characterized by extracting the difference in the DC level of the sync tip level, which is always kept at a substantially constant level regardless of the image content, and by stably determining the recording mode.

Returning to FIG. 1 again, the device 1 of the present invention is an FM
M adjuster 2. Low pass filter (LPF) 3° sample hold circuit 4. Synchronous signal division circuit 5. 'It is composed of a comparator 6 and a reference voltage source 7.

The FMM modulator 2 demodulates the reproduced video signal (that is, the reproduced frequency-modulated luminance signal) that comes in through the input terminal 1a, and then removes the carrier with the LPF 3, and then removes the carrier as shown in FIG. 2(A).
As a reproduced luminance signal as shown in FIG.

The synchronization signal valve head circuit 5 extracts the horizontal synchronization signal in advance from the incoming reproduced video signal, and outputs the horizontal synchronization signal as shown in FIG.
→J non-pull hold circuit 4 outputs as a sampling pulse as shown in J.

The sample and hold circuit 4 calculates the DC level V+)c, J of the horizontal synchronizing signal section of the 1P1-luminance signal supplied from the PF3 based on the Doma 4 non-bringing pulse, that is,
The DC level Voc between the sink tip level is sampled and outputted to the non-inverting input terminal of the comparator 6.

On the other hand, the inverting input terminal of the comparator 6 is supplied with the base tI + voltage source 7J and the base F\voltage JTVR, and the comparator is connected to the DC level VDC of the sync depth level transmission section of the reproduced video signal. 3) Compares VR and outputs a mode discrimination signal corresponding to the comparison song to the output terminal 1b.

In this case, the V quasi-voltage VR is set, for example, to a substantially intermediate level between the two DC levels of the sync deep level transmission section for the standard mode and the high image quality mode. Therefore, when the recording mode is high image quality mode, Voc>V+<, and the mode discrimination signal becomes high level.On the other hand, when the recording mode is standard Ql- [-1 mode, Voc≦VR, and the mode discrimination signal becomes high level.
Determination 0'; The moon is [I-level.

In this way, a mode determination signal q which alternates between high level and low level depending on the recording mode is output 111.

Next, a recording system and a reproducing system of a VTR to which this embodiment is applied will be explained with reference to FIGS. 3 and 4. First, the third
To explain the recording system of a VTR in both figures, the video signal input to the input terminal 8 is passed through a low-pass filter (LPF).
and comb filter 9°10 and bandpass filter (13P
r) 11 respectively.

BPFl 1 inputs) 1ζ's image offset J, and outputs the conveyed color Ig to the C color signal recording processing circuit 12.

The color signal recording processing circuit 12 frequency-converts the carrier color signal into a low frequency converted carrier color signal and outputs it to the adder 13.

On the other hand, "P [and comb filter 9. pre-emphasis circuit 14. FM modulator 15 are for standard mode, and L P
F and comb filter 10. Pre-emphasis circuit 1
6. Each of the FM modulators 17 constitutes a brightness blockage recording processing circuit for high image quality mode. Here, both luminance signals obtained by P wave from the video signal from the input terminal 8 in the comb filter 9 and 10 are given pre-emphasis characteristics and are frequency modulated (FM modulated). The signal is output to terminals 18a and 18b of the switch circuit 18.

The switch circuit 18 is supplied via a terminal 19 with a mode switching signal corresponding to a recording mode set by a 1000-degree selection switch or the like (not shown).

Therefore, when the recording mode is set to the standard mode, the switch circuit 18 is switched to the terminal 18a side, while when the recording mode is set to the high quality mode, the switch circuit 18 is switched to the terminal 18b side.

In this way, a frequency-modulated luminance signal (FM luminance signal) that has been given a pre-emphasis characteristic according to the recording mode and has been FM-modulated at a carrier frequency according to the recording mode is sent from the switch circuit 18 to the adder 13. Output.

The adder 13 adds the M luminance signal and the low-frequency conversion carrier color signal to the rotating heads 11 and 1 via the recording amplifier 20.
2 and recorded on the magnetic tape T.

Next, to which this embodiment is applied, the reproduction system of the XVTR will be explained with reference to FIG. Here, the magnetic tape T
The reproduced video signal re-fed by the rotating head I''l, t12 is supplied to terminals 23a and 23b of the switch circuit 23 via preamplifiers 21 and 22, respectively. The switch circuit 23 is switched in response to a head switching pulse inputted from the terminal 24, whereby 1q of continuous reproduced video signals are generated.

The output of the switch circuit 23 (τ; double signal low-pass filter (LPF) 25 and high-pass filter (+-I PF)
) 26 respectively. The 1-PF 25 converts the incoming reproduced video signal J: into a low frequency converted carrier color signal into a P wave and outputs it to the color signal recording processing circuit 27 . The chrominance signal processing circuit 27 outputs the incoming low-frequency conversion signal S to a carrier chrominance signal in the original frequency band to the adder 28 after frequency conversion.

On the other hand, HP [26 is the incoming playback video signal J, and the playback '
The M luminance signal is converted into a P wave and sent to the switch circuit 31 via the riser circuit 29 and 30.

31b. The output signal of the switch circuit 31 is supplied to the limiter 33 and the mode discriminating device 1 of this embodiment through an automatic gain control circuit (circuit) 32, respectively. The output signal of the limiter 33 is transmitted to the FM demodulator 34, L
PF35, de-emphasis circuit 36 and 1M demodulator 3
7, L PF 3 B, and the de-emphasis circuit 39, the signal is demodulated and supplied to the terminals /loa and 401-) of the switch circuit 40.

As described above, the mode discrimination device 1 generates a [-mode discrimination signal] in response to the output signal of the 〇〇 circuit 32 (playback FM 1 degree signal) and outputs it to the system 1 and the roller 41. The system controller 1 roller 41 issues a mode switching signal according to the incoming mode discrimination signal/1-] and the switch circuit 3
1 and 40 to control switching between them.

Here, the equalizer 29, [M demodulator 34.1-PF3
5 and de]-nf i? cis times'j836 tl +'
iii.Standard mode Teruma signal re-A1-Installed for processing
Similarly, an equalizer 30.1M demodulator 37,
I-PF3B and de-emphasis circuit 39
It is provided immediately for brightness signal reproduction processing in high image quality mode.

Therefore, the mode discriminator 1 indicates that the recording mode is J.
When it is determined that the recording mode is 7-mode, the switch circuits 31 and 40 are connected to the terminals 31a and 40a, and when it is determined that the recording mode is high-quality mode, the switch circuits 31 and 40 are connected to the terminals 31b and 40b. connected to. As a result, the reproduced FM signal is demodulated according to the recording mode, and equalizer characteristics and de-emphasis characteristics are applied.

Thereafter, the adder 28 adds the fading signal output from the color signal reproduction processing circuit 27 and the output luminance signal from the switch circuit 40 and outputs the resulting video signal to the output terminal 42.

In addition, the mode discriminator 1 width FM demodulator 2 and L P
Omit F 3 and use net note 1-P[3 for high image quality mode.
It may be configured such that the 1-mode discrimination is performed based on the output luminance signal of 8. Furthermore, it goes without saying that the apparatus of the present invention can also be applied to the reproduction of recording media other than magnetic recording media.

Effects of the Invention As described above, according to the present invention, since the n1-stream level flow mode determination of the sync depth level transmission section of the F M i'; Mode discrimination can be performed automatically and reliably without causing malfunctions due to changes in the picture pattern of the reproduced video signal, thereby eliminating the need for cumbersome operation of changeover switches. It is very easy to use for the user, and since it can prevent playback in a playback mode different from the recording mode, it prevents the bacteria used from being misunderstood as malfunctioning. It has features such as being able to realize a mode discrimination device with a circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a block system diagram showing an embodiment of the mode discriminating device for a recording medium reproducing apparatus according to the present invention, and FIG. 2 (A>, (
13) is a signal waveform diagram for explaining the operation of the system diagram shown in Figure 1, and Figures 3 and 4 (block diagrams showing an example of the recording system and playback system of a VTR to which the system of the present invention is applied). The system diagram, FIGS. 5 and 6 are respectively explanatory diagrams of the operation of the device of the present invention. 1...Mode discrimination device, 1a...Regenerated frequency modulated luminance signal input terminal, 1b...Mode discrimination signal Output terminal, 2...FM demodulator, 3...Low pass filter (L P
r), 4...1J-mple bold circuit, 5...
Comparator signal distribution circuit, 6...]] Amparator 7... Reference voltage source.

Claims (2)

[Claims] (1) A reproduced video obtained by reproducing and demodulating a video signal recorded on a recording medium from the recording medium in one of a plurality of recording modes in which the carrier frequency of the frequency modulated video signal is different from each other. A DC level extracting means extracts the DC level of the sync chip level transmission section from the signal, compares the DC level with a preset reference value, and determines the recording mode of the reproduced video signal according to the comparison result. 1. A mode discriminating device for a recording medium reproducing device, comprising: discriminating means for discriminating. (2) The DC level extraction means includes a synchronization signal separation circuit that separates and extracts a synchronization signal from the reproduced video signal, and a synchronization signal separation circuit that samples and holds the reproduced video signal with a sampling pulse based on the synchronization signal to generate the reproduced video signal. 2. The mode determination device for a recording medium reproducing device according to claim 1, further comprising a sample and hold circuit that outputs a DC level of a sync tip level transmission section.