JPS61293091A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To exactly discriminate a multitrack system MTS mode by providing a means to detect the burst signal of a reproducing chrominance signal and to discriminate the mode based on the detected burst signal. CONSTITUTION:The burst signal extracted by a burst extraction circuit 23 and the output of a standard crystal oscillator XO 24 have a phase difference of pi/2 as shown in figure (b). After phase-delaying the output of the XO 24 by a phase shifter 26 by 90 deg. as shown in figure (c), the output is phase-detected against the burst signal by a phase comparator 27. The output signal amplitude of the comparator 27 behaves as a reference that is its highest level, and its level varies due to the burst phase as shown in figure (d). When the burst signal lacks, the output level of the comparator 27 lowers and gets out of the threshold of a comparator 28, and therefore, the output of the comparator 28 reverses as shown in figure (e). Consequently, the MTS mode can be discriminated by means of this output signal of the comparator 28.

Description

Detailed Description of the Invention [Field of Industrial Application] This invention relates to mode determination of a magnetic recording/reproducing device @ (hereinafter referred to as rVTRJ). V that uses the multi-track system (MTS) method that records and plays back multiple PCM audio signals.
Regarding TR mode determination.

[Prior Art] The so-called 8mm video, which has been rated as a worldwide standard/TR, has a tape winding angle of about 220°, of which about 80° is used as a deo FM audio track. 40' is used as a PCM audio signal track.

Furthermore, by taking advantage of the fact that the PCM audio signal is time-compressed and recorded, in addition to the original PCM audio signal track 1, five video-1M audio tracks 1 to 1 are recorded as shown in FIG. A proposal has been made to record PCM audio signals on all tracks (tracks 2 to F and rack 6) and record and play back high-quality audio signals for a long time. Multi-proposal 1
~ called the rank system (M T S ), - the above-mentioned P
The recording and playback mode for only CM audio signals will be referred to as MTS mode). In such a multi-track system, there are two modes: recording of one normal video signal (which may include only the video signal or the video signal and the FN1 audio signal).

Since there is a playback mode (normal recording/playback mode) and an MTS mode, a circuit is required to determine in which mode the signal is recorded during playback.

The conventional discrimination circuit will be explained below with reference to FIG. The conventional circuit outputs a signal of approximately 228 KHz as a pilot signal for mode detection during MTS mode.
It was recorded superimposed on the CM audio signal and tracking pilot signal.

FIG. 4(a) shows the recording system, and FIG. 4(b) shows the reproducing system. First, during recording, the oscillator 1 generates a continuous wave of about 228 KHz. Also, PCMMT
The S processing circuit 2 performs PCM on the audio signal and outputs an FM modulated signal.

Both output signals from the oscillator 1 and the PCMMTS processing circuit 2 are mixed by a mixer 3, and the output thereof is amplified by a recording amplifier 4 and recorded on a magnetic tape by a recording head 5.

The recorded signal spectrum at this time is as shown in FIG. As can be seen from FIG. 5, a tracking pilot signal, which is a tracking control signal, is also recorded at the same time.

Next, during reproduction, the signal reproduced by the head 6 is amplified by the reproduction preamplifier 7. The output signal of the regenerative preamplifier 7 is given to the bandpass filter 8.
Only signals around 228KHz are extracted.

The output signal of the bandpass filter 8 is input to a synchronous detector 9,
The amplitude of the 228 KHz component is detected, and it is determined whether the mode is MTS mode or not.

[Problems to be solved by the invention] However, in the conventional circuit, as can be seen from the recorded spectrum in Fig. 5, the tracking pilot signal and the MT
Since the pilot signal for S mode detection is close to each other, it has a slight N effect on tracking, and the lower side wave of the audio PCM signal and the MTS pilot signal overlap, resulting in errors in the PCM audio. The disadvantage was that it worsened the ratio.

In addition, the conventional detection circuit requires many new circuits, making the circuit complicated, and also has the disadvantage that it interferes with the servo circuit and worsens echo light.

Therefore, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a VTR that has a simple circuit and that includes a circuit that can reliably determine the MTS mode.

[Means for Solving the Problems] The present invention includes means for detecting a burst signal of a reproduced color signal and determining the mode based on the detected burst signal in order to determine the MTS mode.

[Operation] The mode discrimination means detects the level of the detected burst signal, and when the level is below or above a predetermined value,
Determine TS mode.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.
Explain in detail.

FIG. 1 is a diagram showing the main circuit configuration of an embodiment of the present invention. In FIG. 1, information recorded on a tape is converted into an electrical signal by a reproducing head 10, and then input to a preamplifier 11, where it is amplified to a predetermined level.

Next, the output signal of the preamplifier 11 is first input to the high-pass filter 12. The high-pass filter 12 uses the FMW of the luminance signal in the normal recording mode among the input signals.
Pass through area I. The output signal of the high-pass filter 12 is F
The signal is supplied to the MtliIII unit 13 and returned to a baseband luminance signal. The output signal is then passed through a low-pass filter 14 for removing carrier components to a synchronization separation circuit 1.
given to 5. In the synchronization separation circuit 15, the synchronization portion is extracted from the output signal of the low-pass filter 14. and,
The extracted synchronous portion signal is given to a one-shot multivibrator 16, and a pulse corresponding to a burst portion in a color signal, which will be described later, ie, a burst gate pulse is created.

On the other hand, the output signal of the preamplifier 11 is transmitted through the low-pass filter 1.
7, and the low frequency converted color signal is extracted.

Then, the low-frequency converted color signal is returned to the high frequency signal, but in this case, the following configuration is adopted in order to cancel jitter included in the reproduced signal. That is,
The output signal of the synchronization separation circuit 15 is multiplied by the PLL multiplication circuit 18 to the same frequency as the low frequency conversion color signal carrier.

The output of the PLL multiplier circuit 18 is a high frequency color signal carrier frequency (3°58 MHz in the NTSC system).
) is input to the frequency converter 20 together with the output signal of the voltage-controlled crystal oscillator 19 having a center frequency of 0.01, and the frequency component of the sum of the two is obtained by the bandpass filter 21. The output signal of this bandpass filter 21 and the low-pass converted color signal output from the low-pass filter 17 described above are applied to a frequency converter 22, and the output signal includes a high-frequency converted color signal.
A color signal with jitter canceled is obtained.

The output signal of the frequency converter 22 is sent to the burst sampling circuit 23.
, only the burst portion is extracted. At this time, the output of the one-shot multivibrator 16 described above is used as a switch control signal. The burst signal extracted by the burst extraction circuit 23 is sent to a reference crystal oscillator (hereinafter referred to as rXOJ) 2 by a phase comparator 25.
The phase is compared with the output of 4. And phase comparator 25
A signal corresponding to the phase difference between the two appears at the output. This signal controls the frequency of the voltage controlled crystal oscillator 19 mentioned above. Thereby, the output frequency of X024 and the burst frequency are always controlled to be the same.

The luminance and color signal processing described above is performed on general home VT.
It is also an overview of the signal processing used in R. In such a VTR, a PC using a multi-track system
When an M audio signal is written to a video track, the reproduced signal always includes a portion where some or all of the luminance and color signals are not recorded. Therefore, by monitoring the output potential of the phase comparator circuit 25, it is possible to detect a lack of a color signal, or in other words, the recording mode.

Next, the detection operation will be explained.

In general, the detection characteristics of an analog signal detector are shown in Figure 2 (a
), it can swing up and down around π/2. Therefore, the burst signal extracted by the burst extraction circuit 23 shown in FIG. 1 and the output of X024 are usually π/
It is stable with a phase difference of 2. Here, if the burst signal and the output of X024 have a phase relationship as shown in FIG.
), if the phase of the output of Depending on the phase, Figure 2 (d
), the level fluctuates like this. Here, if the burst signal is missing, the output level of the phase comparator 27 becomes small and exceeds the threshold of the comparator 28, and the output signal of the comparator 28 is inverted as shown in FIG. 2(e).

Therefore, in the end, with the output signal of the comparator 28,
Multi-track system mode can be determined.

[Effects of the Invention] As described above, according to the present invention, by using a color burst signal with a high S/N ratio, there is no need to record a pilot signal with high accuracy, and there is no need to record a pilot signal, which affects the PCM audio signal. Therefore, it is possible to provide a VTR capable of easily detecting a multi-track system mode.

Moreover, since most of the circuits can be used for the conventional color signal processing system in a VTR, it can be constructed at low cost.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the main parts of an embodiment of the present invention. FIG. 2 is a diagram showing the operation of one embodiment of the present invention. FIG. 3 is a diagram for explaining the PCM multi-track system. FIG. 4 is a diagram showing an embodiment of a conventional mode detection circuit. FIG. 5 is a diagram showing a recorded spectrum in a conventional example. In the diagram, 13 is 11! 15 is a synchronous separation circuit, 1
6 is a burst gate generation circuit, 22 is a frequency converter, 2
4 is a crystal oscillator, 26 is a phase shifter, 27 is a phase detector, 2
8 indicates a comparator. Agent Masu Oiwa F-
Tamami procedural amendment (voluntary) 2. Name of the invention Magnetic recording and reproducing device 3. Person making the amendment 5. Detailed description of the invention of the subject of the amendment Contents of the amendment 1) Specification page 3 No. 5 Line "about 80'J to 180°"
Correct. (2) "Detect the level and the level is below a predetermined value" on page 6, line 14 of the specification is corrected to "Detect the phase and the phase error is below a predetermined value". that's all

Claims (3)

[Claims] (1) A two-head helical scan method is adopted, and there is a normal recording/playback mode in which video signals or audio signals are recorded and played back on predetermined tracks of the recording medium, and a plurality of time-compressed audio signals are recorded on the predetermined tracks. A magnetic recording and reproducing device capable of selecting a time-compressed audio recording/reproducing mode for recording and reproducing, comprising: demodulating means for demodulating a reproduced signal reproduced from the predetermined track; and a synchronizing means for separating a synchronizing signal from the output of the demodulating means. separating means; converting means for separating the color signal from the reproduced signal and converting it into a predetermined frequency band; means for extracting a burst signal from the output of the converting means based on the output of the synchronization separating means; a detection means for detecting the burst signal generated by the detection; and a mode for determining which of the two modes the recording mode of the signal recorded on the recording medium is, based on the output of the detection means. A magnetic recording/reproducing device, comprising: a determining means. (2) The magnetic recording and reproducing apparatus according to claim 1, wherein the demodulating means and the synchronization separating means are shared with each means included in a luminance signal reproducing processing circuit. (3) The magnetic recording and reproducing apparatus according to claim 1, wherein the converting means and the detection means are shared with each means included in a reproduction color signal processing circuit.