JPS63280584A - Time lapse system magnetic recorder - Google Patents

Abstract

PURPOSE:To attain audio recording in all modes by providing a means for switching the compression ratio of time compression of an audio signal into a value equal to a frame skipping ratio of a video signal in the mode or a value larger than it. CONSTITUTION:A time compression means for applying time compression to an input audio signal, recording means 3, 4 recording the audio signal subjected to time compression between a video signal on a magnetic tape and a video signal track, and a compression ratio switching means 2 for switching the compression ratio of time compression in response to the changeover of the made, are provided. The input audio signal is subjected to time compression by the time compression means 1 and recorded intermittently on the magnetic tape 12 in the same period as the period of skip of the video signal. The compression ration of the time compression is switched to a value equal to or larger than the skip of the video signal of the mode by a compression ratio changeover means 2. Thus, all information of the input audio signal in all the modes is recorded on the magnetic tape.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a time-lapse magnetic recording device that performs frame-by-frame recording on a magnetic tape.

[Conventional technology]

The time-lapse magnetic recording device is disclosed in the published patent publication 1983.
- As described in No. 62985, a field video signal of one frame is extracted from the input @ signal every fixed number of frames (for example, 240 frames) and recorded on a magnetic tape.
By intermittently sending the magnetic tape one track at a time at the same frequency as the frame-cutting cycle (4 seconds for a frame-cutting ratio of 240), the frame-cut video signal is packed and recorded on the magnetic tape, and can be recorded over a long period of time. It is possible to record. For example, in the case of a time-lapse ratio of 240, it is possible to record 480 hours using a 2-hour tape.

The time-lapse ratio can be switched to several levels, and the modes are differentiated depending on the recording time in each case. For example, a time-lapse ratio of 240 (time-lapse cycle: 4 seconds) is the 480 hour mode, and a time-lapse ratio of 120 (time-frame time: 2 seconds) is 2.
It is called 40 hours seven days.

As described above, the conventional apparatus enables long-time recording by time-lapse recording, and the time-lapse ratio can be switched to several levels. However, no consideration was given to recording audio signals.

[Problem that the invention seeks to solve]

Since the time-lapse magnetic recording device runs the tape intermittently, it is not possible to record audio on a linear audio track. Therefore, conventionally, audio recording was not performed.

Is the purpose of the present invention applicable to all modes of a time-lapse magnetic recording device? The purpose of the present invention is to make it possible to record audio using a simple circuit configuration, and also to be able to handle mode switching with a simple circuit configuration.

[Means for solving problems]

The present invention is characterized by a time compression means for time compressing an input audio signal, a recording means for recording the time compressed audio signal between video signal tracks on a magnetic tape, and mode switching. [Function] The input audio signal is time-compressed by the time compression means and recorded by the recording means according to the frame-by-frame period of the video signal. Data is intermittently recorded on the magnetic tape at the same period. The compression ratio for time compression is switched to a value equal to or larger than the frame-less ratio of the video signal in that mode by the compression ratio switching means. Therefore, in all modes, the audio signal for the frame-by-frame period must be time-compressed to within one frame. Since this time-compressed audio is recorded on the magnetic tape in one frame length at the same period as the frame extraction period, all information of the input audio signal is recorded on the magnetic tape in all modes.

(Embodiment) FIG. 1 is a block diagram of characteristic parts of an embodiment of the present invention, and FIG. 2 is a schematic block diagram of its overall configuration.

The audio signal input from the audio input terminal 10 is supplied to the audio rotary head 4 through the time compression circuit 1 and the audio signal recording circuit 5. The video signal inputted to the video input terminal 11 is also supplied to the video rotary heads 6z and 6' through the video signal recording circuit 5. rotating head 4
．． 6 and 6' are slid on the magnetic tape 12 at high speed.The audio rotating head 4 is connected to the video rotating heads 6H and 6'.
′ with a step in the direction of the axis of one rotation. The magnetic tape 12 is run by a capstan motor 9, and the capstan motor 9 is driven by a motor drive circuit 8. The system control circuit 7 includes an EE reduction printing switching circuit 2 an audio signal recording circuit 5. Control signals are supplied to the video signal recording circuit 5 and the motor drive circuit 8. The compression ratio switching circuit 2 supplies a signal to the time compression circuit 1.

The input audio signal is time compressed by the time compression circuit 1,
The sound is recorded on the magnetic tape 12 by the rotary head 4 for audio. - 10,000, the input video signal is recorded on the magnetic tape 12 by the video rotary heads 6 and 6'. A video recording gate signal t' is supplied from the system control circuit 7 to the video signal recording circuit 5.

As a result, one frame of field image is displayed for each fixed number of frames.
Extract and record the signal. In addition, the audio signal recording circuit 6
An audio recording gate t is supplied to the audio recording gate t, whereby the time-compressed audio signal is intermittently recorded one frame at a time in the same cycle as the frame-by-frame extraction cycle of the video signal. Furthermore, a motor drive control multiple d is supplied to the motor drive circuit 8, thereby causing the magnetic tape 12 to run intermittently at the same period as the frame removal period of the video @ signal. Video and time-compressed audio are recorded while the magnetic tape 12 is stopped.

The audio rotary head 4 has a step between one video signal track and the next video signal track so as to form a track surface. Therefore, by the above-described operation, the frame-extracted field video signal and the time-compressed audio signal are alternately recorded on the magnetic tape 12. - 10,000, the compression ratio switching circuit 2 is supplied with a mode switching signal layer corresponding to the time-lapse ratio, and the compression ratio switching circuit 2 receiving this signal changes the compression ratio of the time compression circuit 1 to the time-lapse ratio. Switch to a value equal to or greater than . For example, in the case of the 480-hour mode, the time-lapse ratio is 240, so the compression ratio is set to 240 or more. Therefore, the input audio signal for the frame extraction period is equivalent to one frame (one field time).
From then on, the time will be compressed, and the time-compressed audio signal for one frame will be recorded at a period equal to the frame removal period, so
In all modes, all information of the input audio signal is recorded on the magnetic tape 12.

In the time compression circuit 1, the input audio signal is passed through a low-pass filter 104. A/D converter 102. Memory 101°D/Ai conversion 5105. It is output through a low-pass filter 105. In response to this, the audio signal recording circuit 3 performs a pre-emphasis circuit 501. FM modulation circuit 6
02. Gate circuit 3o3. The signal is supplied to the audio rotary head 4 through a recording amplifier 504. In the compression ratio switching circuit 2, the output of the oscillator 201 is supplied to a frequency divider 202. The output of the oscillator 201 is a high-speed clock fH, and the output of the divider 202 is a low-speed clock /L.
k memory 101.

Mode switching signal -1-j from system control circuit 7: Audio recording gate signal ? to frequency divider 202? is gate circuit 6
06.

The input audio signal is band-limited by the low-pass filter 104, converted to digital data by the A/D converter 102, and written to the memory 101 at a low speed clock/L'''Q.Then, it is read out at a high speed clock fH. The time-compressed audio signal thus generated is compressed in time, restored to an analog signal by the D/A converter 103, and only the required band is extracted by the low-pass filter 105.
The high frequency frequency is emphasized, the signal is FM modulated by the FMi tone circuit 602, and recorded by the audio rotary head 4. At this time, by the gate operation of the gate circuit 606, intermittent recording is performed one frame at a time in the same cycle as the frame extraction cycle.

The low-speed clock fL is generated by frequency-dividing the high-speed clock f1i by the frequency divider 202. The compression ratio for time compression is the frequency ratio of the high speed clock /'H and the low speed clock fL, so what about the 5 frequency divider 2L12? It is equal to the Kero frequency division ratio.

In the divider 202, this division ratio is switched by the mode switching signal m, and the compression ratio? Switch to a value f equal to or larger than the time-lapse ratio available in that mode.

FIG. 3 shows spectrum diagrams of the input audio signal side and the time-compressed audio signal side in Example 2. The horizontal axis is frequency, and the vertical axis is signal level. In this example.

The maximum recording time is 480 hours. a) and b) are 4
Spectrum of input audio signal side in 80-hour mode (
2) and the spectrum diagram of the time-compressed audio side, cn and d) are the spectral diagram of the 8Gero human power round voice in 240-hour mode and the spectrum diagram of the time-compressed audio side, f''+ is 48
Frequency of high-speed Grotsach that settles in 0-hour mode, fLI
is the frequency of the slow clock/L in the 480-hour mode. Note that the frequency axis of the spectrum diagram on the input audio side is normalized by fLI, and the frequency axis of the spectrum diagram on the time compressed audio side is normalized by fM+.

This also applies to the subsequent spectrum diagrams.

1000 is the spectrum of the input audio signal band-limited by the low-pass filter 104, and 1001 is the 480 time mode? Spectrum of time-compressed audio signal, 1002
is the spectrum of the time-compressed audio signal in the 240-time mode, 1040 is the frequency characteristic of the low-pass filter 104, and 1050 is the frequency characteristic of the low-pass filter 1o5. In the 6240-time mode, the dividing ratio of the frequency divider 202 is set to 4.
Set it to half of the 80 hour mode.

Then, the frequency of the low-speed clock fb becomes /L2, which is twice the frequency fLI, as shown in FIG. Since the frequency of the high-speed clock fH does not change by 11 of fH+, the frequency carrying capacity of a low-pass filter for suppressing aliasing noise due to sampling and extracting only the necessary components is 1/1050.
Up to the point. This means that no matter what the compression ratio is, El
:Please reduce the size of the print.

The same is true.

According to this embodiment, audio signals can be recorded in all modes KN of the time-lapse magnetic recording device. M1
Even if the compression ratio is changed, there is no need to change the low-pass filter. Furthermore, when the compression ratio is lowered, the time EE+
Since the band of compressed speech becomes narrower, the influence of cheese head noise is reduced.

Furthermore, since the ratio of the signal band to the frequency of the high-speed or low-speed clock is reduced, the influence of quantization noise is also reduced. In addition, there is an effect that the S/N ratio is improved in a mode where the time-lapse ratio is small.

In the second embodiment, as shown in the fourth example, a low-pass filter system 1o6191 is used instead of the low-pass filter 104.
j. The low-pass filter switching circuits 107 and 107' switch the low-pass filter 104 to the low-pass filter 104' with a wide pass band when the 240-hour mode is set.
You can also try switching to . A spectrum diagram in the 240-time mode is shown in FIG. 5, where 1006 is the spectrum of the input audio signal band-limited by the low-pass filter 104', 1004 is the spectrum of the time-compressed audio signal, and 1041jd is the frequency characteristic of the low-pass filter 104'. However, this embodiment has the effect of widening the band by using a mode with a small frame-off ratio. Note that if there are many modes, a low-pass filter may be provided for each mode, or a low-pass filter may be provided for each mode 1'''r: to increase the bandwidth, and the time-lapse ratio may be increased. In the mode where the ratio is small, the same low-pass filter may be used.In the embodiment shown in FIG.
As shown in FIG. 6, the division ratio of the divider 202' that generates the low-speed clock /L from the output of the oscillator 201 is fixed, and the high-speed clock fH is also output from the oscillator 201 by the frequency divider 205.
The output may be generated by dividing the frequency of the output, and this frequency division ratio may be switched depending on the mode. In this case, the seventh
As shown in Figure 2, it is necessary to replace the low-pass filter 105 with a low-pass filter system 1oalB, and to switch from the low-pass filter 105 to the low-pass filter 105' with a narrow pass band when the 240-hour mode is entered by the low-pass filter switching circuits 109 and 109'. There is. 2
The spectrum diagram in the 40-hour mode is shown in FIG.
1oos is the spectrum of the time-compressed audio signal, and 1051 is the frequency characteristic of the low-pass filter 105'. In this embodiment as well, when the compression ratio is reduced, the band of time-compressed audio becomes narrower and the noise from the tape head system becomes smaller, so the effect of improving the S/N ratio by switching to a mode with a small frame-less ratio is obtained. be. Note that if there are many modes, a low-pass filter may be provided for each mode.

In the case of the above embodiment, since the required memory capacity is also reduced when the compression ratio is reduced, the remaining memory may be used to time-compress and multiplex record another signal. As a recording method, another rotary head may be provided to form additional tracks.

Frequency multiplexing on a time-compressed audio signal is no problem. FIG. 9 is a block diagram of the time l:l: pongee circuit 1 in an embodiment of periodic mantissa multiplexing, in which there are two systems of memories 110 and 111, and in addition to the voice code string, the multiplex signal input terminals 1o', A /IJ converter 1
02', IJ/A converter 105', bandpass filter 114. A multiplex signal system consisting of a meeting circuit 115 is provided, and an adder 116 performs frequency multiplexing.

In the 4bO time mode, the selector 112 selects the audio signal and the gate circuit 116 is opened and the ℃ memories 110 and 11
The time compression of the audio signal is performed using the two swords of 1, and the miniting circuit 115 operates to compress the normal time pressure m.
When the 240-hour mode is set such that only audio is output, the selector 112 selects a multiplexed signal, the gate circuit 115 is closed, the audio signal is time-compressed in the memory 110, and the multiplexed signal is time-compressed in the memory 111. Since the output of 106' includes the aliasing component of the time compression multiplexed signal, if this is extracted by the bandpass filter 114, a signal obtained by frequency-converting the 1-time compression multiplexed signal No. 18 can be obtained. The mute ink circuit 115 passes the signal through, and the adder 116 frequency-multiplexes the time-compressed audio signal and the frequency-converted time-compressed multiplexed signal and outputs the resultant signal. 240
The spectral diagram in time mode is shown in the 10th factor.

1006i is the spectrum of the multiplexed signal band-limited by the low-pass filter 104''; 1007 is the spectrum of the time-compressed multiple signal after frequency conversion; 1042i is the frequency characteristic of the low-pass filter 104''; and 11401d is the cycle mantissa characteristic of the bandpass filter 114.

According to this embodiment, multi-channel recording can be performed in -M mode with a small frame-off ratio.

Next, give a specific example of the compression ratio in J6 for each mode. Therefore, if you set the compression ratio to a value larger than the time-lapse ratio of the mode with the maximum time-lapse cycle,
(However, since the only change is the track usage rate (the proportion of time-compressed audio on one track that corresponds to the audio for the frame-by-frame extraction period), there seems to be no problem, and the circuit size can be reduced.) Seven ten thousand is good for your sake.

However, when we evaluated the prototype beforehand, we found that there was always a lag in the recording and playback of time-compressed audio due to uneven rotation of the rotating cylinder to which the single-rotation head was attached, so if the track utilization rate decreased to a certain extent, it would take the frame-by-frame period. The ratio of the time lag of the time-compressed audio to the length of the time-compressed audio corresponding to the audio of (The problem arises that the ratio is within 2% in order to obtain good sound quality.The maximum time lag between recording and playback of time-compressed audio is about 100 μsec, so In order for this to be within 2%, the time compressed audio corresponding to the audio for the frame-by-frame period should be about 5 m5 eC or more, that is, the track utilization rate should be about 1/6 or more.

Therefore, in the present invention, the compression ratio of each mode is switched so that the track utilization rate becomes 175 or more.

The specific value may be selected within this range so that the circuit scale is small.

Table 1 shows specific examples of compression ratios for each mode.

1st printed example? branching devices 202, 202'# and 20
A concrete block diagram of the configuration of 5 is shown in FIG. a) is a configuration block diagram of the frequency divider 202, which divides the high speed clock /H from the counter 202OK and selects the low speed clock selection circuit 2.
021, in 480 hour mode, Q, output (dividing ratio 2
), 9 outputs in 240 hour mode (branch ratio 2)
.

Select . . . and set it as low-speed clock/L.

b) is a configuration block diagram of the frequency dividers 202' and 205, where the sluggish clock /L is Q, the output, and the high-speed groutter selection circuit 2031 selects the clock input itself in the 480-hour mode, Q, the output in the 240-hour mode, etc. ... and set it to high speed clock/H.

According to this embodiment, by setting the compression ratio to a power of 2, the compression ratio switching circuit 2 can be realized with a simple circuit. Also, due to variations in the tape running bus, etc., it may appear at the end of the track? However, according to this embodiment, it is not necessary to use the signal at the end of the track.

Good sound quality without S/N deterioration can be obtained.

By the way, as mentioned above, it is sufficient that the track utilization rate in each mode is 175 or more, so there is no need to switch the compression ratio between modes with similar frame-by-frame ratios.

An example of this is shown in Table 2. According to this embodiment, fewer steps are required to switch the royal power ratio, and the circuit can be further simplified.

〔Effect of the invention〕

According to the present invention, the compression ratio for time compression of the audio signal is provided with a means for switching the compression ratio for the time compression of the audio signal to a value equal to or larger than the time-lapse ratio of the Gerobo 1-elephant signal in that mode.
It is possible to record audio in all modes of the time-lapse universal magnetic recording device, and by directly switching the compression ratio to a power of 2, which is higher than the time-lapse ratio, the circuit configuration can be simplified. You can obtain stable sound quality that is not affected by the FM envelope level drop at the end of the track.

[Brief explanation of the drawing]

The first factor is a block diagram of characteristic parts of an embodiment of the present invention, FIG. 2 is a block diagram of its overall configuration, FIG. 6 is a spectrum diagram of each part, and FIGS. 4, 6, and 7. 9 are block diagrams of characteristic parts of other embodiments, FIG. 5, FIG. 8,
FIG. 10 is a spectrum diagram of each S signal of another example,
FIG. 1 is a detailed block diagram of a compression ratio switching circuit according to an embodiment of the present invention. 1... Time compression circuit, 2... Compression ratio switching circuit. 5...Audio signal recording circuit. 4... Rotating head for audio. 7...System control circuit.

Claims (1)

[Scope of Claims] 1) Sampling means for extracting four frames of field video signals from an input video signal for every fixed number of frames of field video signals, and forming diagonal tracks on a magnetic tape for the sampled field video signals. In a time-lapse magnetic recording device, the time-lapse magnetic recording device is equipped with a recording means for recording on a magnetic tape, and a mode switching means for switching the time-lapse ratio into several stages, and performs time-lapse recording on a magnetic tape in several modes according to the time-lapse ratio. , time compression means for generating a time-compressed audio signal by time-compressing the input audio signal with the same period as the sampling period; and forming additional diagonal tracks on the magnetic tape alternately with the diagonal tracks to generate the time-compressed audio signal. and a compression ratio switching means for switching the compression ratio of the time compression to a value equal to or larger than the time-lapse ratio in that mode in response to the switching of the mode. A time-lapse magnetic recording device. 2) A time-lapse magnetic recording device according to claim 1, characterized in that the value of the compression ratio is a power of two.