JPS607603A - Magnetic reproducing device - Google Patents

Abstract

PURPOSE:To attain voice reproduction also other than normal reproduction by providing he titled device with a memory extending the time base of a reproducing audio PCM signal and a reproducing level detector, and when the reproducing level is reduced less than a prescribed value, stopping the update of data. CONSTITUTION:Reproduced PCM audio data are written in an RAM of a time base extending circuit 106 and the writing operation is controlled by an output from an RF detecting circuit 107. The RF detecting circuit 107 detects an pream ble component recorded before the PCM audio data and supplies a detecting signal generated when the amplitude of the preamble is reduced less than the fixed value to the time base extending circuit 106. The detecting signal inhibits the update of the data stored in the RAM of the extending circuit 106. If tracking is disabled at the time of still reproducing, the update of data in the extending circuit 106 is inhibited by the output of the RF detecting circuit 107. Thus, voice is reproduced and the written audio PCM signal is repeatedly read out and outputted from the time base extending circuit 106 at the time of proper tracking.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" This invention is directed to a PCM modulated audio signal (hereinafter referred to as
The present invention relates to a magnetic reproducing device that reproduces an audio PCM signal (referred to as an audio PCM signal) together with a video signal from a magnetic tape.

"Background Art and its Problems" It has been considered to PCM-modulate a related audio signal together with a video signal and record it on a magnetic tape using a rotating head. In this case, in order to facilitate editing of the audio signal, the audio signal is recorded in a trunk separate from the trunk for the video signal.

As one of the existing analog VTRs, a C-format 1-inch helical scan VTR is known in which a vertical synchronizing signal portion is recorded by an auxiliary head separate from that for recording the video signal. Considering the need for compatibility with existing VTRs, an auxiliary head is used to record one field's worth of time-base compressed audio PCM signals.

Furthermore, the reproduced audio PCM signal is time-axis expanded, D/A converted, and returned to an analog audio signal. Processing of time axis compression and time axis expansion of an audio PCM signal is performed using a memory, and the frequencies of a write clock and a read clock for this memory are set in a predetermined relationship. By the way, when editing using a rotating head type VTR, the final editing point is often determined by listening to the reproduced audio. Therefore, as mentioned above,
When an audio PCM signal is recorded, it is desirable to be able to perform audio reproduction during reproduction operations other than normal reproduction (slow reproduction, still reproduction, high-speed reproduction).

OBJECT OF THE INVENTION The object of the present invention is to provide a magnetic reproducing device that is capable of reproducing audio even in a normal reproducing operation.

"Summary of the Invention" The present invention provides video signals and audio PCM signals from a magnetic recording medium in which a video signal is recorded by a first head, and an audio PCM signal is time-base compressed and recorded by a second head. A magnetic playback device for playing back audio PCM signals, comprising a memory for extending the time axis of the played audio PCM signal and a level detection device for detecting the playback level of the audio PCM signal. When it is detected that the value is below the value, updating of the data in the memory is stopped.

Embodiment A VTR in an embodiment of the present invention has a head arrangement shown in FIGS. 1A and 1B. In FIG. 1, 1 indicates the upper drum and 2 indicates the lower drum. The upper drum 1 and the lower drum 2 are disposed coaxially, and the upper drum 1 receives the field frequency (6 in NTSC system) in the direction of arrow a.
0Hz).

As shown by the two-dot chain line in FIG. 1B, the magnetic data 3 is wound diagonally around the circumferential surfaces of the upper drum 1 and the lower drum 2 at a distance of, for example, 24.4 cm/24.4 cm in the direction of the arrow.
The vehicle is run at a speed of sec.

The Ni drum 1 is provided with three sets each consisting of a video head as a main head and a sync head as an auxiliary head. 4A is a video head for recording and playback, 4B is a sync head for recording and playback, and 5A is a
This is an erasing head for the video signal track, and is a 5B
is the erasing head for the sink signal trunk.

Drum 1 above video head 4A and sync head 4B
Erasing heads 5A and 5B are provided at positions preceding the rotation direction. Unfortunately, a reproduction-only video head 6A and a sync head 6B are installed at a position later than the pair of the video head 4A and sync head 4B with respect to the rotational direction of the upper drum 1.

These pairs of video heads 4A, 5A, 6A and sync heads 4B, 5B, 6B are arranged with the sync head leading by an angular interval of 30 degrees, and their heights are slightly different. ing.

Furthermore, a playback-only video hendro A and a sync hendro B are attached to one end of the support plate of the piezoelectric element.
The height of these heads can be varied by an external control signal, so that the scanning trajectory of these heads coincides with the video signal trunk even in non-normal playback operations. Video heads 4A, 5A, and 6A each have 12
00 angular intervals.

FIG. 2 does not show the Forman I. recording pattern in one embodiment of the present invention. Along the upper edge of magnetic tape 3, audio 1 rank IOA, 10B is formed in parallel, and along the lower edge of magnetic tape 3 audio!
- Rack 11 is formed. Audio 1/Rack 10
Audio signals and time codes are recorded in A, 10B, and 11, respectively.

A control track 12 is formed in parallel above the lower audio track 11, and a servo control signal is recorded on this control track 12. A diagonal video signal trunk 13 is formed in the area of the audio track 10A and the control trunk section,
An audio 1 rack 11 and a control track 14 are formed. 1 video signal track 1 each
3 and a sync signal trunk 14 are formed by a video head 4A and a sync head 4B.

In the sync signal trunk 14, signals of a vertical synchronizing signal section and a subsequent vertical blanking period of several dozen H (H is one horizontal section) are recorded. In addition, the sink signal trunk 1
The signal recorded at both ends of the video signal track 4 and the signal recorded at the end and start end of the video signal track located before and after it overlap, and approximately the center of this overlap section is at the time of playback. It is used as the switching point for switching heads. FIG. 3 shows this switching point. In the first field or the third field of the color video signal, at a timing slightly later than the center of the third horizontal section, the playback output of the video output is switched to the playback output of the sync head. At the beginning of the th horizontal interval, the playback output of the sync head is switched to the playback output of the video head. In the second or fourth field of the color video signal, the 266th field
At the beginning of the 278th horizontal section, the playback output of the video head is switched to the playback output of the silk head, and at the end of the 278th horizontal section, the playback output of the sink head is switched to the playback output of the video head. .

The head arrangement and recording pattern described above are the same as those in the existing C formant 1 inch hexagonal scan VTR. In one embodiment of the present invention, an audio PCM signal subjected to error correction encoding processing and time-base compressed is recorded on the sync signal trunk 14.

FIG. 4 shows the configuration of a recording circuit according to an embodiment of the present invention, in which a recording color video signal is supplied to an input terminal 21, and two channels of recording audio signals are supplied to input terminals 22A and 22B, respectively. Supplied. The color video signal is FM modulated by an FM modulation circuit 23 and supplied to a gate circuit 24 . The gate circuit 24 has a terminal 2
From 5, game 1゛zt''v /( is supplied.・1de4
Signal 1, 2, 1? The gate circuit 24 is turned on during the corresponding period. The output of this gate circuit 24 is transmitted to the video head 4A via a recording amplifier 26 and a rotary transformer (not shown).
and recorded on the magnetic tape 3.

Further, the audio signal is supplied to A/D converters 27A and 27B, converted into a 14-bit audio PCM signal at a sampling frequency of, for example, 44.0559 KHz, and supplied to the recording data processing circuit 28. Tarock pulses and timing control signals for processing the audio PCM signal are synchronized with the color video signal synchronization signal. The clock generator 29 is supplied with a horizontal synchronization signal separated from the color video signal by a synchronization separation circuit 30, and has a horizontal frequency f.
A master clock of 1344 times H (=21.14683'2 MHz) is formed. Similarly, a horizontal synchronization signal is supplied to the timing control circuit 31 to form a pulse at the sampling frequency, and is also supplied to the recording data processing circuit 282, the time axis compression circuit 32, the preamble and synchronization generation circuit 33. Timing control signals required by each digital modulation circuit 35 are generated.

FIG. 5 shows the configuration of an example of the timing control circuit 31, in which 45 is a phase comparison circuit and 46 is a VCO (voltage controlled oscillator). VCO46 is 5376 fH-
1 (-84,46MHz), and its output is a T frequency divider 47. T divider 48. π frequency divider 49. i
The signal is supplied to the phase comparator circuit 45 via the frequency divider 50. The phase comparison circuit 45 is supplied with a horizontal synchronization signal from a terminal 51, and its phase comparison output is applied to the VCO 46 as a control voltage.

The output of the VCO 46 is taken out to a terminal 52 and supplied to the digital modulation circuit 35. The output of the T frequency divider 47 is taken out to a terminal 53 and supplied to the time axis compression circuit 32.

The output of the T frequency divider 48 is taken out to a terminal 54 and supplied to the recording data processing circuit 28 as a timing control circuit. Furthermore, the output of the π frequency divider 49 is passed through the π frequency divider 55, so that the sampling frequency (4
A timing control signal of 4,0559KI-Iz) is extracted.

The recorded data processing circuit 28 encodes the two-channel audio PCM signal with an error correction code to generate recorded audio data in a predetermined format. 6th
The figure shows the structure of recorded audio data in an embodiment of the present invention.

This audio data has a structure in which IH (-1/f,) is a unit, similar to the synchronization signal of the video signal. A 4-pin synchronization signal 58 is added to the beginning of the IH, followed by 14-pin sampling words (3 words for each channel A and B), followed by two parity words of an error correction code. P, Q (14 bits each)
are arranged, and furthermore, a sampling word and a parity word P,
CRC code for error detection for Q (16 bits)
is added, and a white reference signal 59 is inserted at the end.

Therefore, data of 128 pintos is inserted into IH (168 pintos). Also, 2 in IV (1 field)
Since audio data is inserted in the 45H section, I
V contains data of 735 samples.

The error correction code forms a simple parity word P and a complex parity word Q from 6 words of data within one block, and has the ability to correct up to 2 word errors within the same block. The 6 sampling words and 2 parity words of the block are subjected to an interleaving process in which the order is different from the original arrangement order, and are converted into data of 1 i-1 units.

Note that the block synchronization signal 58 and the white reference signal 59 may not be inserted.

Recorded audio data from the recorded data processing circuit 28 is supplied to a time axis compression circuit 32. Time axis compression circuit 32
has two RAMs (random access memories), and performs compression processing on the IV yearly time axis. Figure 7A is
The time axis of the video signal is shown, and Ts indicates the section in which audio data is recorded within the section in which the recording signal is supplied to the sync head 4B in the IV. As Ts, a length of about 12H from the fourth horizontal section in the first or third field and a length of about 12H from the center of the 266th horizontal section in the second or fourth field are selected.

As shown in FIG. 7B, recording audio data is written into one RAM from the beginning of the IV. This writing is done by a write clock that is synchronized with the recorded audio data. When the writing of the data of IV is completed, the contents of the RAM are read out by the high frequency readout clock in the interval Ts. The ratio of the lengths of IV and Ts determines the frequency ratio of the write clock and read clock. Furthermore, as shown in FIG. 1C, recording audio data is written to the other RAM from the beginning of the next IV that includes the section Ts in which one RAM performs the read operation, and the section immediately after the end of this IV is written to the other RAM. At Ts, the contents of the other RAM are read. Due to this time axis compression process, the audio data is delayed by 1V with respect to the video data.

Recorded audio data compressed by the time axis compression circuit 32 is supplied to an addition circuit 34, to which a preamble signal and a synchronization signal are added. The synchronization signal is added before the recorded audio data and has a predetermined focus pattern, and the preamble signal is further added before the synchronization signal. The preamble signal is a signal that becomes a signal with a predetermined repetition frequency after digital modulation.

Furthermore, the postamble signal may be refined after recording audio data.

The output of the adder circuit 34 is supplied to a digital modulation circuit 35. The digital modulation circuit 35 converts recorded audio data in order to improve recording density. The output of this digital modulation circuit 35 is supplied to an F"-h circuit 39 via one input terminal 38 of a switch circuit 36. A gate pulse is supplied to this gate circuit 39 from a terminal 40: In the section where the signal trunk 14 is formed, the K''-1- circuit 39 is turned on. The output of the dirt circuit 39 is supplied to the sync head 4B via a recording amplifier 41 and a rotary transformer (not shown).

The output signal of the FM modulation circuit 23 is supplied to the input terminal 37 of the switch circuit 36, and when the audio PCM signal is not recorded, the video signal is recorded as the sync signal trunk 14.

Note that the 2
The analog audio signal of the channel is
Audio trunk I of magnetic tape 3 with fixed head
Recorded in OA and 10B.

Next, a reproducing circuit according to an embodiment of the present invention will be described. During reproduction, a video head 6A supported by a piezoelectric element such that its height can be changed and a fixed sync head 4B are used. As is clear from the head arrangement shown in FIG. 1, the video head 4A corresponds to the sink head L-54B. Therefore, by using the video head A, it is possible to The scanning of the video camera) y6A will be delayed from the original scanning timing. Further, due to the servo circuit and dynamic tracking control shown in FIG. 8, the audio PCM signal reproduced by the sink head 4B leads the video signal reproduced by the video head 6A by a total of 7V.

In FIG. 8, 61 is the reference video signal input terminal +
62 is a fixed head that reproduces the control signal from the control track 12, and 63 is a can 0 stun motor. 64 is a drum motor that rotates the upper drum 1, 65 is a detection element that magnetically detects the rotation phase of the upper drum 10, and 66 is a piezoelectric element that supports the video head 6A.

Generally, a phase servo is applied to the capstan motor to determine the running phase of the magnetic tape so that the reference video signal and the reproduced control signal have a constant phase relationship, and the rotational phase of the drum at that time. Control 1 performs trunking during playback so that the phase of the playback video signal matches the reference video signal. In this embodiment, in place of the output of the reproducing head, the fact that the rotational speed of the upper drum 1 is constant is used, and a detection pulse is generated by the detection element 65 from a fixed position on the upper drum 1. This detection pulse is supplied to a phase comparison circuit 68 via a delay circuit 67.

The vertical synchronization signal of the reference video signal separated by the synchronization separation circuit 69 is supplied to the phase comparison circuit 68 from the vertical synchronization separation circuit 70 . The output of the phase comparison circuit 68 is applied to the drum motor 64 via an amplifier 71.

In this embodiment, since the sync head 4B and video handler A are used, the rotational phase of the capstan motor 63 is controlled so that the scanning locus of the sync head 4B correctly scans the sync signal trunk 14. The reference video signal is supplied to a burst separation circuit 72, and a color frame discrimination circuit 73 discriminates a color frame from the phase relationship between the burst signal and the horizontal synchronization signal. Based on the color frame from which the frame pulses appearing at the output of the frame pulse separation circuit 74 have been determined, a servo reference signal having a phase that is C1 ahead of the reference video signal is generated by the pulse generation circuit 75. This servo reference signal is supplied to the phase comparator circuit 76.

A reproduction control signal that is reproduced by the fixed Hendro 2 and passed through the amplifier 79 is sent to the frame pulse separation circuit 80.
and its output is supplied to the phase comparator circuit 76. The output of this phase comparison circuit 76 is supplied to the capstan motor 63 via an amplifier 78. The phase of the magnetic tape 3 is advanced by the capstan phase servo circuit. This makes it possible to track the sink head 4B.

Further, in the drum phase servo circuit, the delay amount of the delay circuit 67 that delays the detection pulse is set so that the playback phase of the video head 6A matches the reference video signal. As a result, the color video signal reproduced by the video handler A has a predetermined phase. However, if this continues, the reproduced color video signal will lead the reference video signal by 1V.

A drive voltage from a tracking control circuit 81 is supplied via an amplifier 82 to the piezoelectric element 66 that supports the video head 6A. A reproduction RF signal of the video head 6A is supplied from a terminal 83 to the tracking control circuit 81, and the scanning position of the video head 6A is controlled so that the envelope of this reproduction RF signal is at a predetermined level, thereby ensuring good trunking. It is designed to be. As mentioned above, in order to compensate for the fact that the reproduced color video signal of the video head 6A has a phase lead of IV with respect to the reference video signal, the video signal track is delayed by one field from the terminal 84 with respect to the trunking control circuit 81. Supply an off-cent voltage such that it plays.

As described above, the audio PCM signal reproduced by the sync spatula 14B precedes the color video signal reversely reproduced by the video head 6A by 7V. Therefore, the delay of the IV audio signal caused by the time axis compression processing of the recording circuit is compensated for, and -V can be secured as the time required for the reproduction processing.

With reference to FIG. 9, the processing of the playback output of the video Henro A and the playback output of the sync head 4B will be described.

The reproduction output of the video head 6A is supplied to a switching and equalizer circuit 92 via a reproduction amplifier 91 and a rotary transformer (not shown).

On the other hand, the playback output of the sink head 4B is output from the playback amplifier 93.
The signal is supplied to a switching and equalization circuit 92 via a two-turn transformer (not shown) and a switching 94.

The switching and equalizing circuit 92 switches the reproduction outputs of the video controller A and the sync head 4B at a predetermined switching timing (see FIG. 3) to make the signals of the two continuous. This switching pulse is applied to the upper drum 1
It is formed based on the detection pulse from the detection element 65 that detects 0 rotation.

The output of the switching and equalization circuit 92 is supplied to an FM demodulation circuit 95, and a reproduced color video signal example is taken out at an output terminal 96. This reproduced color video signal is supplied to a sync separation circuit 97, and the separated sync signal is supplied to a sequence control circuit 98. A reference video signal from a terminal 99 is supplied to a sync separation circuit 100,
The separated reference synchronization signal is supplied to the sequence control circuit 98. The sequence control circuit 98 is supplied with a detection pulse from a terminal 101, a reproduced clock pulse etc. from a clock generation circuit 109, and a data synchronization signal from a data synchronization separation circuit 105.

In addition, the output of the reproduction amplifier 93 is transmitted to the PCM equalizer 102.
The amplitude characteristics of the tape head system during recording and reproduction are corrected, and the eye pattern of the reproduced digital signal is corrected. The output of this PCMC coil eye 102 is supplied to a comparator 103, the levels are compared at the zero-crossing point of the eye pattern, and the output is shaped into a pulse signal. The output of this comparator 103 is sent to the digital demodulation circuit 104.
and channel decoding is performed. The output of this digital demodulation circuit 104 is supplied to a data synchronization separation circuit 105 and a time axis expansion circuit 106. The data synchronization separation circuit 105 detects a synchronization pattern added to the beginning of the audio PCM signal recorded on the sync signal track 14.

The output of the PCM equalizer 102 is supplied to an RF detection circuit 107 and a discrimination circuit 108. The output of comparator 103 is supplied to clock generation circuit 109. The clock generation circuit 109 has a PLL configuration and generates a clock synchronized with the output signal of the comparator 103. This clock is used by the sequence control circuit 98. The signal is supplied to a digital demodulation circuit 104 and a time axis expansion circuit 106.

A control voltage for CO of the clock generation circuit 109 is supplied to the discrimination circuit 108, and the AC component of this control voltage causes the playback output of the sink head 4B to change to audio PCM.
It is determined whether the signal is a signal or a video signal. PCM equal +r
This determination is made during a period in which a reproduced signal is generated at the output of 102. When a video signal is reproduced, if the PLL of the clock generation circuit 109 is in a locked state, control cannot be achieved. The AC component of pressure exceeds a predetermined value. On the other hand, PC
When the M audio signal is reproduced, the clock generation circuit 1090PLL is in a locked state, and the alternating current component of the control voltage does not exceed a certain value. The switch circuit 94 is controlled by the discrimination output obtained in this way. Therefore, the switch circuit 94 is turned off when the PCM audio signal is played back, and turned on when the video signal is played back.

The time axis expansion circuit 106 is constituted by two RAMs, in which PCM audio signals are written alternately for each IV, and the written PCM audio signals are read out over the interval of the IV.

The output of clock generation circuit 109 is used as the write clock. The output clock of the clock generation circuit 110, which is synchronized with the synchronization signal of the reference video signal, is used as the read clock. Furthermore, the PCM audio data reproduced from the sync signal track 14 is written into the RAM of the time axis expansion circuit 106 according to the timing signal generated by the sequence control circuit 98 .

Writing to this RAM is controlled by the output of the RF detection circuit 107. The RF detection circuit 107 detects the preamble component recorded before the PCM audio data, and a detection signal generated when the amplitude of the preamble becomes less than a certain value is supplied to the time axis expansion circuit 106. Ru. This detection signal causes the time axis expansion circuit 106
Update of data in RAM is prohibited. During editing, the running speed of the magnetic tape is different from the normal speed, resulting in high-speed playback.

Slow playback, still playback, etc. are performed. For this reason,
Scanning locus of sync head 4B and sync signal l/rack 1
4 may only match partially or not match at all.

As an example, if tracking is no longer achieved during still playback after transitioning from high-speed playback to normal playback and then still playback, updating of data to the time axis expansion circuit 106 is prohibited by the output of the RF detection circuit 107. Ru. As a result, the audio PCM signal that was reproduced and written when tracking was good is repeatedly read out and output from the time axis expansion circuit 106. Even if the audio signal is at a time of IV (auspicious seconds in the NTSC system), it is possible to hear audio with a normal pitch.

Therefore, the editing point can be determined.

Of course, the same applies when playing at high speed or slow play.

It is possible to reproduce sound with normal pitch.

Audio PCM data in a format as shown in FIG. 6 is obtained at the output of the time axis expansion circuit 106, and is supplied to the reproduction processing circuit 111. The reproduction processing circuit 111 is
A control signal from the sequence control circuit 98 performs dinterleap and error correction processing. For sampled words that cannot be error corrected,
Errors are corrected so that they are not noticeable. Furthermore, the muting circuit provided in the reproduction processing circuit 111 is operated by the detection signal of the discrimination circuit 1o8 when the audio PCM signal is not reproduced. The playback audio of the two channels of this playback processing circuit 111 is D
/A converters 112A and 112B, and two channels of reproduced analog audio signals are output to output terminals 113A and 113B.

In one embodiment of this invention, the audio signal trunk? O
Since A and IDBK also record analog audio signals, the muting described above is performed and the audio signal trunk 10A.

Alternatively, an analog audio signal reproduced from 10B may be used.

"Effect of the invention" This invention provides variable speed playback other than normal playback operation.

When tracking is lost due to still playback operations, and the audio PCM signal is not played back,
This is to stop updating the data in the time axis expansion memory. Therefore, even during variable speed playback or still playback, it is possible to obtain playback sound with a normal pitch, and it is possible to determine an editing point while listening to the playback sound.

[Brief explanation of drawings]

1A and 1B are a plan view and a side view showing the structure of the head arrangement according to an embodiment of the present invention, FIG. 2 is a route map of a trunk putter according to an embodiment of the present invention, and FIG. 3 4 is a waveform diagram used to explain the switching points for switching the playback outputs of the video head P and the sync head, FIG. 4 is a block diagram of a recording circuit according to an embodiment of the present invention, and FIG. 5 is a part of this recording circuit. 6 is a route diagram showing the data structure of the audio PCM signal, and FIG. 7 is a time chart used to explain the operation of the time axis compression circuit.
FIG. 8 is a block diagram showing the configuration of a servo circuit according to an embodiment of the invention, and FIG. 9 is a block diagram of a reproducing circuit according to an embodiment of the invention. 3...Magnetic tape, 4A, '6A...Video head, 4B, 6B...Synchend, 5A, 5B
... Erasing head, 13... Video signal trunk, 14... Sink signal track, 21...
・Input terminal for recording color video signal, 22A, 22B・
... Recorded audio signal input terminal, 32 ... One-time axis compression circuit, 62 ... Fixed head for control signal reproduction, 63 ... Capstar/motor, 64 ... Drum motor, 66... piezoelectric element, 81...
...Trunking control circuit, 96...Output terminal for reproduced color video signal, 106...Time axis expansion circuit, 107...RF detection circuit, 108
...Discrimination circuit, 113A, 113B...
・Output terminal for playback audio signal. Agent: Tomo Sugiura Figure 5 Figure 7 Figure 8

Claims (1)

[Scope of Claims] A video signal is recorded by a first head, and a PCM-modulated audio signal is compressed in the time axis by a second head, and the video signal and the audio PCM signal are recorded from a magnetic recording medium. A magnetic reproducing device for reproducing the audio PCM signal, comprising a memory for expanding the time axis of the reproduced audio PCM signal, and a level detection device for detecting the reproduction level of the audio PCM signal, and the level detection device detects the reproduction level of the audio PCM signal. A magnetic reproducing device characterized in that updating of data in the memory is stopped when it is detected that a reproducing level becomes less than a predetermined value.