JP2728654B2 - Image playback device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reproducing apparatus, and more particularly to an apparatus for reproducing image information from a video signal recorded on a recording medium. 2. Description of the Related Art As an analog VTR (Video Tape Recorder) currently known, a β-inch or VHS-type 1 / 2-inch home VTR is widely known. Other
A commercial 1-inch VTR is used as the VTR,
In any case, these VTRs all record analog signals. [0003] Also, since the form of a recording signal of a digital VTR is completely different from that of an analog VTR, an analog VT
Reproduction of magnetic tapes recorded by R is not considered at all. [0004] However, 1 /
Considering the widespread use of 2-inch VTRs, apart from the distant future, not only digital VTRs but also analog VTs
The coexistence of R becomes essential. [0005] In other words, there is a disadvantage that an analog VTR must be used when reproducing an analog image recorded in the past, and a digital VTR must be used when reproducing a digital image. Accordingly, an object of the present invention is to provide an image reproducing apparatus capable of properly reproducing a video signal recorded on a recording medium as an analog signal or a digital signal in any form. To provide. [0007] Under such a purpose,
In the image reproducing apparatus according to claim 1 of the present application, in an apparatus that reproduces image information from a recording medium in which a video signal is recorded in a digital signal form or an analog signal form, at least trace the recording medium. A reproducing means including one rotary head, an analog signal processing means for processing an analog signal reproduced by the reproducing means and outputting a reproduced video signal, and a digital signal reproduced by the reproducing means; ; and a digital signal processing means for outputting the reproduced video signal, said rotary head
Is rotated at a first rotation speed, and the reproduction signal of the reproduction means is reproduced.
Analog signal processing by the analog signal processing means.
In the reproduction mode, the rotating head is adjusted to the first rotational speed.
At a second high rotation speed, and
Data for processing a reproduced signal by the digital signal processing means.
And a digital reproduction mode . According to the above arrangement, even if the video signal recorded on the recording medium is a normal analog signal,
Even digital signals with a large amount of information
By rotating the rotating head at high speed during playback,
I can respond. An embodiment of the present invention will be described below in detail. FIG. 1 is a block diagram showing an embodiment of an analog / digital VTR to which the present invention is applied. In this figure, 2 is an input terminal of an analog video signal, SW1 is a changeover switch for selecting an analog recording mode or a digital recording mode, 4 is an analog / digital (A / D) converter, 6 is a digital signal processing circuit for recording, 7 Is an analog signal processing circuit for recording, 8 is a signal switching / distributor, 10 is
A to 10E are amplifiers, and 12 is a rotary head cylinder. H-1 to H-5 are video heads arranged at intervals of 90 °, and each head has an azimuth angle as shown. H-4 and H-2 of these video heads
Inverted azimuth heads 180 ° facing each other and used when recording / reproducing ordinary analog signals or as one mode when recording / reproducing digital signals (FIG. 6).
(B) will be described later in detail. 14 is a cylinder at 1800 rpm (standard speed) or
Cylinder motor rotating at 3600 rpm (2x speed), 16A and 16B are loading posts, 17 is capstan, 18
Is a magnetic tape, 19A to 19E are amplifiers, 20 is signal switching /
A coupler, 22 is a digital signal processing circuit for reproduction, 24 is a D / A converter, SW2 is a switch for switching an input video signal, 26 is an analog signal processing circuit for reproduction, and 28 is a signal form (analog) recorded on a magnetic tape. / Digital), a reference numeral 30 denotes a capstan control circuit, a reference numeral 32 denotes a cylinder motor control circuit, and a reference numeral 34 denotes a system controller. FIG. 2 is an operation block diagram when recording / reproducing the VTR shown in FIG. 1 in digital mode. This figure shows the configuration of the digital signal processing circuits 6 and 22 in more detail. The digital mode recording / reproducing operation is as follows.
It is as described below. At the time of recording, first, the input video signal is A / D
The data is introduced into the converter 4 and converted into digital data. If the encoding method at this time is a composite encoding method according to the NTSC method, a sampling rate that is three times (3fsc) or four times (4fsc) the chrominance subcarrier frequency (fsc) is set, and a quantization level of 7 is set. Preferably, bits or 8 bits are selected. Since the digital data thus obtained has a data rate of about 100 Mbps, the information band is too wide for recording on a cassette tape such as a VHS. Therefore, the data amount is reduced to about a quarter by using the band compressor 6A. Specifically, the following is performed. Now, assuming that the effective screen is 76%, the amount of information is reduced to half by a well-known subsample, and the DPCM (difference PCM) is used.
(Encoding) to compress information of 7 bits per sample into 4 bits. Now, when the increase rate due to the addition of the redundant code in the next stage 6B is calculated as 15%, it is 0.76 × 0.5 × 4/7 × 1.15 ≒ 1/4. According to the above method, the total information amount is reduced to one-fourth. You can do it. The redundant code adding circuit 6B adds an error correction code as a measure against transmission errors and dropouts accompanying magnetic recording / reproduction, a block ID word for special reproduction, and a synchronization pulse for data reproduction. Is added. The modulation circuit 6C at the next stage performs digital code conversion having low-frequency suppression characteristics so as to obtain a spectrum suitable for the characteristics of an electromagnetic conversion system (a rotary transformer, an azimuth head, etc.). Specifically, it is preferable to use adaptive coding using the characteristics of the image signal, nm conversion for adding a redundant code, or the like. In the present embodiment, since the adaptive coding method cannot be used because DPCM coding is performed, the nm (8-10, 8-9, etc.) conversion method is adopted. Then, digital data is recorded on the magnetic tape 18 in accordance with a track forming process described later in detail (to be described with reference to FIG. 6B). FIG. 3 shows an example of a track pattern formed on the magnetic tape 18. At the time of reproduction, the demodulation circuit 22C performs a waveform equalization process, performs a conversion reverse to that at the time of modulation (use a reverse lookup table), and returns to the original code sequence. The error detection / correction circuit 22B performs error detection, and corrects errors that can be corrected. On the other hand,
For errors exceeding the correction capability, data interpolation is performed with other correct data. In addition, when an interleave process for rearranging a data sequence is performed as a countermeasure for a burst error as an error correction process at the time of recording, a de-interleave process for restoring an original data sequence is performed. As the error detection and correction code, for example, a CIRS (cross interleaved Reed-Solomon) code can be used.
However, when special reproduction and editing are considered, the interleaving process cannot be performed on all data strings, so that the range of interleaving is limited. The band extending circuit 22A performs a conversion reverse to that of the band compressor 6A. That is, PCM data is generated from DPCM-encoded difference data (4 bits → 7 bits), and data corresponding to the pixel decimated by the sub-sample is interpolated with other data and synchronized to obtain a video signal. A blanking portion such as a signal is added. The D / A converter 24 at the final stage converts the digital data reproduced in this way back into an analog signal and converts it into a signal suitable for a general monitor television. In the above description of the operation at the time of reproduction, it is assumed that the analog / digital discriminating circuit 28 has previously discriminated that the digital signal is recorded on the magnetic tape 18. FIG. 4 is a block diagram showing a detailed configuration of the reproduction analog signal processing circuit 26 shown in FIG. In the figure, blocks 26A to 26C are blocks for reproducing a luminance signal. That is, 26A is recorded on the magnetic tape 18.
A high-pass filter (HPF) for extracting an FM signal, 26B is an FM demodulator for restoring a black and white image, and 26C is a delay line for performing time alignment with a chrominance signal. The other blocks 26D to 26F are blocks for reproducing color signals. That is, 26D
The low-pass filter for extracting a low-band converting chrominance signal, 26E are frequency converter for performing frequency conversion _{(767kH Z → 3.58MH Z),} 26
F is a band pass filter (BPF) for removing unnecessary frequency components generated by the frequency conversion. Also, 2
6G is a mixer that restores composite color television signals. However, as a prerequisite for setting the operation mode shown in FIG. 4, it is necessary for the analog / digital discriminating circuit 28 to identify in advance that an analog signal is recorded on the magnetic tape 18. That is, the analog / digital discriminating circuit 28
When it is determined that the analog signal is recorded by the two video heads H-2 and H-4 (having opposite azimuth angles), the video heads are mounted opposite to the rotary head cylinder 12. The resulting signal is
The signals are supplied to a high-pass filter 26A and a low-pass filter 26D via 19B and 19D. Subsequent signal processing steps are well known and will not be described. Thus, a video output is obtained via the changeover switch SW2. FIG. 5 is a block diagram showing another embodiment for reproducing an analog signal from a magnetic tape. In this embodiment, the video heads H-2 and H- described with reference to FIG.
4 and the amplifiers 19B and 19D are used, but the analog signal processing circuit 26 for reproduction is not used. Instead of using the analog signal processing circuit 26, the present embodiment shown in FIG.
The digital processing is performed using the converter 4, the digital signal processing circuit 22, and the D / A converter 24. That is, in this embodiment, instead of using a separate and independent circuit as the A / D converter, the A / D converter 4 (FIG. 1) already provided in the recording side circuit for recording digital signals.
See). Similarly, a digital signal processing circuit for reproduction 22 already provided for digital signal reproduction.
And the D / A converter 24 (see FIG. 1) is used as it is. In order to realize such sharing, it is necessary to cascade the above-mentioned blocks by a changeover switch or the like (not shown). However, since the blocks can be realized by using a normal switching technique, detailed description is omitted. . Thus, the video heads H-2 and H-4
By converting the analog signal obtained from the digital signal and processing it, various image processing (for example, stop motion display, overlap display, split display) can be performed, and A / D converters required as digital VTRs, etc. Can be shared, so that the production cost is not increased. FIGS. 6A and 6B show the rotary head cylinder 12.
FIG. 4 is a diagram for explaining a relationship between a rotation speed of a capstan 17 and a recording / reproduction track pattern. The numbers “1” to “5” in the track pattern shown on the right side of FIG.
The video heads H-1 to H-5 respectively indicate that they are currently located at the illustrated positions. Further, the hatched portion in the track indicates that the tracing has already been completed. FIG. 6A is an explanatory diagram of an operation for recording / reproducing an analog signal. Here, the rotating head cylinder is set at 1800 rpm (standard speed: X1), and the capstan is rotated at the standard speed (X1). In addition, as the video head, the inverted azimuth heads H-2 and H-
Use 4. Here, the rotation speeds of the rotary head cylinder and the capstan are controlled by the system controller 34 (see FIG. 1). FIG. 6B is a diagram showing an operation mode for recording / reproducing a digital signal. In this embodiment, the system controller 34 controls the rotating head cylinder to operate at a double speed.
(X2), the capstan is set to quadruple speed (X4). In the traced completed portion (hatched portion) shown on the right side of the figure, the portions indicated by “(5)” and “(4)”
The tracing is completed by heads H-5 and H-4, respectively. [0037] by the amount of information to be recorded / reproduced by the digital recording / reproducing mode of FIG. 6 described above (B), the contents of the restoration process in the encoding and bandwidth expander 22A in the band compressor 6A (number of quantization levels, bits rate, etc.)
Is set. Each track shown in FIGS. 6A and 6B has the same width. In other words, in this embodiment, the physical shapes of the heads H-1 to H-5 are made uniform, and the heads H-1 to H-5 can be applied to any of the analog / digital systems. 6 (A) and 6 (B) have been described using a four-head type in which video heads are arranged at intervals of 90 °. However, as shown in FIG. Thus, various tracks can be formed. FIG. 7 shows 180 ° where the azimuth angle is ± 6 °.
FIG. 3 is a view showing opposing heads A and B. By setting the rotation speed of the rotary head cylinder 40 to the standard speed (1800 rpm) and setting the capstan to the standard speed as well, FIG.
The track shown in (A) can be formed. The track shown in FIG. 6B can be formed by rotating both the rotating head cylinder and the capstan at 4 × speed. Next, various circuit configurations of the analog / digital discriminating circuit 28 (see FIG. 1) will be described with reference to FIGS. The circuit shown in FIG. 7 discriminates whether or not a color burst signal is recorded on the magnetic tape 18 to determine whether the recording is analog recording or digital recording. That is, low frequency components are small in digital recording because of the low-frequency suppression modulation scheme, whereas color burst signals are included in analog recording, so there is a difference in the level difference between the low frequency components. Occurs. Therefore, the configuration shown in the figure is adopted to detect such a level difference. [0044] In FIG. 8, 42 bandpass which passes RF input signal inputted, around the carrier frequency of the low-band converting chrominance signal a predetermined low frequency (700kH _Z hereinafter) signal obtained through the video head Filter (BPF). Reference numeral 44 denotes a level detector, and reference numeral 46 denotes a comparator which sends an H (high) level or L (low) level signal as compared with the threshold value Th. As a result, when the H-level signal is output from the comparator 46, it is determined that analog recording is being performed, and when the L-level signal is being output, digital recording is being performed. The circuit shown in FIG. 9 has a function of demodulated luminance (Y).
The determination of analog recording / digital recording is performed based on whether or not the signal includes the horizontal synchronization signal _Hsync . In the figure, reference numeral 26B denotes the FM demodulator shown in FIG. 4, which sends out a demodulated luminance signal. Reference numeral 50 denotes a horizontal synchronization signal extraction circuit, which outputs a synchronization pulse a. 52 is a counter that counts the synchronization pulse a, 54 is a 1 / N divider that outputs a reset pulse b to the counter 52, and 56 is a comparator that determines whether or not the output of the counter is “N”. It is. According to this circuit, when the output of the comparator 56 is = N, it can be determined that digital recording has been performed when analog recording ≠ N. The circuit shown in FIG. 10 performs analog / digital recording depending on whether a "clock run-in" (preamble) signal or "synchronization pulse" recorded along with digital image data is detected. The determination is performed. The “clock run-in” here is VT
A signal for synchronizing the oscillator inside the R and the clock on the tape, and the "synchronization pulse" is a signal indicating a recording start point of digital image data. In FIG. 10, 58 is a preamplifier for inputting an output signal from a video head, 60 is a waveform equalizer, 62 is a phase lock circuit, 64 is a gate circuit, 66 is a synchronization signal generation circuit, and 68 is data It is a processing circuit. In addition, a is a PLL lock flag, and b is a synchronization pulse (sync) detection signal. The phase lock circuit 62 includes a phase comparator
62A, a voltage-controlled oscillator 62B, and a comparator 62. Then, the PLL lock flag a or sync
Analog recording / digital recording can be determined based on the presence or absence of the detection signal b. The circuit shown in FIG. 11 includes an error detection / correction circuit 22B included in the digital signal processor 22 for reproduction.
The number of times an error flag is sent out from (see FIGS. 1 and 2) is counted to determine whether the signal is a digital signal. That is, when an analog signal is supplied to the error detection / correction circuit 22B, it is determined that an analog signal is recorded because error detection is performed continuously. In FIG. 11, reference numeral 22B denotes an error detection / correction circuit for outputting an error flag every time an error is detected;
Is a counter for counting the number of error flags, and 72 is a comparator. As a result, when the count value of the counter 70 is larger than N (threshold), it is determined that analog recording is being performed, and otherwise, digital recording is being performed. In this embodiment, in addition to the control track (CTL) servo method described so far, a method in which a servo pilot signal is superimposed on each track can be adopted. In the conventional servo pilot signal system, pilot signals f _{1 to} f ₄ of a predetermined frequency are sequentially written for each track in a frequency region lower than the low-frequency conversion color signal. On the other hand, since the digitally recorded data is low-frequency-suppressed, no low-level signal component exists in the frequency domain of the pilot signal. Therefore, in one embodiment of the present invention, as shown in FIG. 11, four types of pilot signals f ₁ to f _{1 are} output.
Other f ₄ recorded beforehand a signal "f _0" representing that they are "digital recording". The frequency spectrum at this time is as shown in FIG. Also, in the case of performing DTF (Dynamic Track Following) control for moving the video head to follow a track by using the four types of pilot signals f _{1 to} f ₄ , if a conventionally known method is adopted, Description is omitted because it is good. [0056] Figure 13 is a circuit diagram for discriminating the analog recording / digital recording by detecting the pilot signal f _0. In the figure, 74 is f ₀ detector for detecting the presence or absence of the pilot signal f _0, bandpass filter for passing signals of clock frequency near 76, 78 threshold signal detected by the f ₀ detector 74 A comparator which outputs a signal of logic "1" when the level is equal to or higher than Th1, a comparator which outputs a signal of logic "1" when the output level of the band-pass filter is equal to or higher than the threshold value Th2, 82 is an AND gate. When a signal of logic "1" is output from the AND gate 82, it can be determined that digital recording has been performed on the magnetic tape 18. [0057] As has been described in the foregoing, according to the image reproducing apparatus according to claim 1 of the present application, even Ana in case the video signal recorded on the recording medium is a digital signal <br /> Even if it is a log signal, the rotating heads
Analog and digital playback modes with different rotation speeds
Since the recording mode is provided, it is possible to reproduce the digital signal and the analog signal in accordance with the recording form.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an entire embodiment of the present invention. FIG. 2 is a block diagram showing an operation in a digital recording / digital reproduction mode. FIG. 3 is a diagram showing an example of a digitally recorded video track. FIG. 4 is a block diagram showing an operation in an analog reproduction mode. FIG. 5 is a block diagram showing another operation in the analog reproduction mode. FIG. 6 is a diagram showing a video track formed by the embodiment shown in FIG. 1; FIG. 7 is a diagram showing a 180 ° opposed reverse azimuth head. FIG. 8 is a block diagram for performing analog / digital discrimination based on the presence or absence of a color burst. FIG. 9 is a block diagram for performing analog / digital discrimination based on the presence / absence of a horizontal synchronization signal. FIG. 10 is a block diagram for performing analog / digital discrimination based on the presence or absence of a pre-angle or a synchronization pulse. FIG. 11 is a block diagram for performing analog / digital discrimination based on the magnitude of an error rate. FIG. 12 shows a pilot signal recorded on a video track.
is a diagram showing the f ₀ ~f _4. FIG. 13 is a spectrum diagram showing a relationship between a pilot signal and a video signal. 14 is a block diagram for performing analog-digital determination based on the presence or absence of the pilot signal f _0. [Description of Signs] 4 A / D converter 6 Digital signal processing circuit 8 for recording 8 Switching / distributor 12 Rotating head cylinders 16A, 16B Loading post 18 Magnetic tape 20 Switching / combiner 22 Digital signal processing circuit 24 for reproduction A converter 26 Analog signal processing circuit for reproduction 28 Analog / digital discrimination circuit 30 Capstan control circuit 32 Cylinder motor control circuit 34 System controller

Claims (1)

(57) [Claims] An apparatus for reproducing image information from a recording medium on which a video signal is recorded in the form of a digital signal or an analog signal, comprising: a reproducing unit including at least one rotating head for tracing the recording medium; Analog signal processing means for processing an analog signal reproduced by the means and outputting a reproduced video signal; and digital signal processing means for processing a digital signal reproduced by the reproducing means and outputting a reproduced video signal. Preparation
Then, the rotating head is rotated at a first rotation speed, and
The reproduced signal of the generating means is processed by the analog signal processing means.
Analog playback mode, and a second rotation speed higher than the first rotation speed.
Rotate at the rotation speed, and the reproduced signal of the reproducing means is
Digital playback mode for processing by digital signal processing means
Image reproducing apparatus characterized by having a de.