JPH0810946B2 - Television signal playback device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television signal reproducing apparatus for mutually converting and reproducing television systems such as NTSC and PAL.

2. Description of the Related Art A recording / reproducing apparatus such as a video tape recorder generally has a different format depending on the television system of the recording signal. Therefore, it is desired to mutually convert the reproduced signals of different formats. For this reason, conventionally, a reproducing apparatus and a television system converting apparatus have been used in combination. The conversion of the television system roughly requires the conversion of the following two terms.

(1) Conversion of the number of lines and the number of fields (2) Conversion of the carrier frequency and modulation method of the color signal Among these, the conversion of the number of lines and the number of fields in (1) is performed by digital signal processing using a digital memory or the like. The conversion by is common. On the other hand, for the conversion of the color signal of (2), conventionally, decoding and encoding using analog signal processing have been general.

Hereinafter, a conventional television system conversion apparatus according to the above method will be described with reference to the drawings.

FIG. 3 is a block diagram of a conventional television system converter of the present invention. In the figure, 1 is an input terminal to which a converted television signal is input. Reference numeral 2 denotes a luminance signal / color signal separation circuit which separates the input converted television signal into a luminance signal and a carrier color signal. A carrier color signal decoding circuit (decoder) 38 by analog signal processing decodes the carrier color signal into two color difference signals U / V. Reference numeral 39 denotes an analog / digital converter (A / D converter) for color signals, which multiplexes two color difference signals and performs digital conversion. A color signal digital memory 40 converts the number of lines and the number of fields by thinning out or interpolating the digitally converted color difference signals under the control of a write clock and a read clock. 41 and 42 are digital / analog converters (A / D converters) for color signals, which perform analog conversion of two color difference signals in which the number of lines and the number of fields are converted. Reference numeral 43 denotes a carrier color signal encoding circuit (encoder) by analog signal processing, which encodes the two analog-converted color difference signals into carrier color signals. Reference numerals 6, 9 and 12 are an A / D converter, a digital memory, and a D / A converter for the luminance signal, respectively, and their operations are the same as those for the color signal processing. Reference numeral 14 is a sync separation circuit, which separates the sync signal from the luminance signal. Reference numeral 44 is a write clock generation circuit, and 45 is a read clock generation circuit. The number of lines and the number of fields are converted by controlling both clocks. An output buffer circuit 13 outputs the converted luminance signal and carrier color signal to the output terminal 19.

In the operation of the conventional television system conversion apparatus configured as described above, for example, the converted television signal input to the input terminal 1 is the NTSC system television signal, and the PAL
A case in which the system television signal is converted and output to the output terminal 19 will be described. The NTSC system carrier color signal separated by the luminance signal / color signal separation circuit 2 is demodulated by the NTSC system carrier color signal decoding circuit 38 with a right-angled two-phase carrier of 3.58 MHz to obtain the NTSC system 2 signal. Color difference signal U / V
Is decoded into. The two decoded NTSC color difference signals are digitally converted by the A / D converter 39 and then written in the digital memory 40 by the write clock generated by the write clock generation circuit 44. This write clock is the NT output from the sync separation circuit 14.
Since the two color difference signals of the NTSC system written in the digital memory 40 are generated by being locked to the sync signal of the SC system, the line and field number and the line and field address of the address space of the digital memory 40. Written to match. That is, 525 line numbers and 60 field numbers are written so as to correspond to addresses. Then, the number of lines is appropriately interpolated to 625 by being read by the read clock locked to the PAL synchronization signal generated by the read clock generation circuit 45, and the number of fields is appropriately thinned to 50. Therefore, the two color difference signals of the PAL system are converted and read. The two color difference signals of the PAL system read from the digital memory 40 in this way are converted into analog signals by the D / A converters 41 and 42, and then the carrier color signal encoding circuit 43 of the PAL system.
, It becomes a carrier color signal of the PAL system by being modulated by a 4.42MHz quadrature two-phase alternating carrier wave. For the luminance signal, the luminance signal / color signal separation circuit 2
The NTSC system luminance signal output from the same is digitally converted by the A / D converter 6 in the same manner as the color difference signal, and then the write clock locked to the NTSC system synchronization signal output from the write clock generation circuit 44 is used. Are written in the digital memory 9. And read clock generator
The number of lines is interpolated from 525 to 625 by being read by the read clock locked to the PAL system sync signal output from the 45, and the number of fields is thinned from 60 to 50 Is converted into a luminance signal, read out, and converted into an analog signal by the D / A converter 12. As mentioned above, from NTSC system to PAL
The carrier color signal and the luminance signal converted into the format are output to the output terminal 19 through the output buffer circuit 13. In this way, the NTSC television signal is converted into the PAL television signal.

Conversely, when converting a PAL system television signal to an NTSC system television signal, the luminance signal / color signal separation circuit 2 becomes a PAL system luminance signal / color signal separation circuit, and the carrier color signal decoding circuit 38 Becomes a PAL system carrier color signal decoding circuit, and the carrier color signal encode circuit 43
It becomes the carrier color signal encoding circuit of NTSC system. Further, the write clock generation circuit 44 may generate a write clock locked to the PAL sync signal, and the read clock generation circuit 45 may generate a read clock locked to the NTSC sync signal.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the conventional television system conversion device having the above-described configuration, the carrier color signal decoding circuit 38 and the carrier color signal encode circuit 43 are respectively the type and output of the television system of the input signal. As many as the number of types of signal television systems are required, and because all of these circuits are analog signal processing circuits, the circuit scale is very large, and there are also many adjustment points. As a result, the total cost is high and the reliability is low.

Therefore, it may be considered that the carrier color signal decoding circuit and the carrier color signal encode circuit are configured by digital signal processing. However, in the conventional television system conversion apparatus shown in FIG. 3, the carrier color signal decoding circuit 38 is configured by digital signal processing, is arranged in the subsequent stage of the A / D converter 39, and the carrier color signal encoding circuit 43 is arranged. When configured by digital signal processing and arranged before the D / A converters 41 and 42, the scale of the carrier color signal decode circuit and carrier color signal encode circuit by the digital signal processing becomes considerably large. However, there was a problem that the cost increased significantly and it was not suitable for consumer use.

In view of such a point, the present invention provides a television signal reproducing apparatus in which a carrier color signal decoding circuit and a carrier color signal encoding circuit are configured by simple digital signal processing, and a large reduction in cost and no adjustment can be realized. It is intended for.

Means for Solving the Problems To achieve the above object, the present invention provides a recording signal of a first television system recorded in a format in which a carrier luminance signal is frequency-modulated and a carrier color signal is converted into a low frequency range. Reproduction means for reproducing, frequency conversion means for converting the reproduced low-frequency converted carrier color signal to a carrier frequency of the second television system, frequency-converted carrier color signal,
A / D conversion means for digitally converting with a clock corresponding to the carrier frequency of the second television system, and decoding means for digitally decoding the digitally converted carrier color signal into two color difference signals of the first television system. Scanning line conversion means for converting the decoded two color difference signals of the first television system into the number of lines and the number of fields of the second television system by thinning and interpolation processing, and scanning line conversion 2. Encoding means for digitally encoding one color difference signal into a carrier color signal of a second television system; and a second encoding means obtained by the encoding.
And a D / A conversion means for analog-converting the television system carrier color signal with a clock corresponding to the carrier frequency of the second television system.

According to the present invention having the above-mentioned configuration, when the signal of the first television system recorded in the format for converting the carrier color signal into the low frequency range is reproduced, when the signal of the first television system is converted into the signal of the second television system, The low frequency conversion carrier color signal reproduced by the frequency converting means is converted into a carrier frequency of the second television system, then digitally converted by a clock according to the carrier frequency of the second television system, and then digitally decoded. Also, by performing digital encoding, it becomes possible to configure the decoding means and the encoding means by simple digital signal processing.

Embodiment One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a television signal reproducing apparatus according to the present invention. In FIG. 1, a reproducing head 30 reproduces and outputs a frequency-modulated luminance signal and a low-frequency conversion carrier color signal. A high-pass filter 31 separates the frequency-modulated luminance signal. A low-pass filter 32 separates the low-frequency conversion carrier color signal. A frequency demodulator 33 frequency-demodulates the frequency-modulated luminance signal separated by the high-pass filter 31. 34 is a frequency converter,
The carrier frequency of the low-frequency conversion carrier color signal separated by the low-pass filter 32 is frequency-converted into the signal frequency oscillated by the oscillator 36. Reference numeral 35 is an APC circuit, which removes the phase fluctuation of the carrier due to the jitter of the reproduced low-frequency conversion carrier color signal, and stabilizes the carrier frequency of the carrier color signal whose frequency is converted by the frequency converter 34. Reference numeral 5 is an A / D converter for color signals, which digitally converts a carrier color signal whose carrier frequency has been converted. Denoted at 7 is a carrier color signal decoding circuit based on digital signal processing. It carries two color difference signals U /
Decode to V. A color signal digital memory 8 converts the number of lines and the number of fields by thinning out or interpolating the digitally decoded color difference signals under the control of a write clock and a read clock. Reference numeral 10 denotes a carrier color signal encoding circuit by digital signal processing, which encodes two color difference signals in which the number of lines and the number of fields are converted into carrier color signals. A color signal D / A converter 11 converts the encoded carrier color signal into an analog signal. Reference numerals 6, 9 and 12 are an A / D converter, a digital memory, and a D / A converter for the luminance signal, respectively, and their operations are the same as those for the color signal processing. Reference numeral 14 is a sync separation circuit, which separates the sync signal from the luminance signal. Reference numeral 16 is a clock generator, which multiplies the signal frequency output from the oscillator 36 to generate a clock for digital signal processing. Reference numeral 17 is a write clock generation circuit, and 18 is a reference clock generation circuit. The number of lines and the number of fields are converted by controlling both clocks. An output buffer circuit 13 outputs the converted luminance signal and carrier color signal to the output terminal 19.

The operation of the television signal reproducing apparatus of the present invention configured as described above, for example, the reproducing signal output from the reproducing head 30 is an NTSC system television signal, is converted to a PAL system television signal and the output terminal 19 The case of outputting to will be described. Separated by low pass filter 32
NTSC low frequency conversion carrier color signal is a frequency converter
The APC circuit 35 controls so that the frequency is converted to the carrier frequency of the PAL system (4.43 MHz) which is the signal frequency output from the oscillator 36 at 34. The carrier color signal converted into the carrier frequency of the PAL system is input to the A / D converter 5 and fed back to the APC circuit 35. The clock generator 16 multiplies the carrier frequency of the PAL system output from the oscillator 36 by 4 to generate a digital signal processing clock (17.7
MHz) and supplies it to the write clock generation circuit 17 and the reference clock generation circuit 18. The write clock generation circuit 17 creates a write clock locked to the NTSC sync signal by phase-modulating the clock for digital signal processing according to the NTSC sync signal output from the sync separation circuit 14. It is supplied to the A / D converter 6 and the digital memory 9 as a write clock for luminance signal processing. Further, the reference clock generation circuit 18 creates a reference clock locked to the carrier signal of the PAL system by waveform-shaping the clock for digital signal processing, and uses it as a read clock for luminance signal processing and a clock for chrominance signal processing. The signals are supplied to the / D converter 5, the carrier color signal decoding circuit 7, the digital memories 8 and 9, the carrier color signal encode circuit 10, and the D / A converters 11 and 12, respectively. A / D
In the converter 5, the carrier color signal converted to the carrier frequency of the PAL system is digitally converted by the reference clock locked to 4 times the carrier frequency of the PAL system, and then the carrier color signal decoding circuit 7 performs two PAL system carrier signals. It is decoded into a color difference signal. Here, the carrier color signal decoding circuit 7
Since the input signal is a clock that is locked at 4 times the carrier frequency and is a carrier color signal that has been digitally converted, decoding processing can be performed by simple signal processing without using a multiplier or the like. Then, the two decoded PAL color difference signals are written into the digital memory 8. At this time, the digital memory 8 is arranged so that the line and field number of the color difference signal and the line and field address of the address space of the digital memory 8 match.
Address is reset in accordance with the NTSC sync signal output from the sync separation circuit 14. That is, 525 line numbers and 60 field numbers are written so as to correspond to addresses. Then, by the read clock locked to the carrier signal of the PAL system generated by the reference clock generation circuit 18, while reading the address while resetting the address according to the synchronizing signal of the PAL system, the number of lines is appropriately interpolated to 625 lines. Further, the number of fields is appropriately thinned out to 50, which is converted into two color difference signals of the PAL system and read. The two color difference signals of the PAL system read out from the digital memory 8 in this manner are encoded by the carrier color signal encoding circuit 10 into the carrier color signals of the PAL system. Since the color difference signals input to the carrier color signal encoding circuit 10 are digitized by the reference clock locked to 4 times the carrier frequency of the PAL system, encoding is performed by simple signal processing without using a multiplier or the like. Can be processed. Then, the encoded PAL-system carrier color signal is converted into an analog signal by the D / A converter 11. On the other hand, in the luminance signal, the NTSC system fractional modulation luminance signal output from the high-pass filter 21 is frequency-demodulated by the frequency demodulator 33 and then digitally converted by the A / D converter 6 in the same manner as the color difference signal. Is
It is written in the digital memory 9 by the write clock locked to the NTSC sync signal output from the write clock generation circuit 17. Then, by the read clock locked to the carrier signal of the PAL system output from the reference clock generation circuit 18, the address is reset while being read according to the synchronization signal of the PAL system, and the number of lines is changed from 525 to 625. It is interpolated and the number of fields is thinned out from 60 to 50, and it can be read by converting it into a PAL luminance signal. And then D /
An analog signal is converted by the A converter 12.

The carrier color signal and the luminance signal converted from the NTSC system to the PAL system as described above are output to the output terminal 19 through the output buffer circuit 13. In this way, the NTSC television signal is converted into the PAL television signal.

On the contrary, from PAL playback television signals to NTSC
When converting to a television signal of the system, the signal frequency output from the oscillator 36 is set to the carrier frequency of the NTSC system, and the frequency converter 4 converts the low frequency conversion carrier color signal to NTSC.
The frequency shall be converted to the carrier frequency of the system. Further, the write clock generation circuit 17 may generate a write clock locked to the PAL synchronization signal, and the reference clock generation circuit 18 may generate a reference clock locked to the NTSC carrier signal.

Next, a specific configuration example of the write clock generation circuit 17 will be described. FIG. 2 is a block diagram of the write clock generation circuit. In FIG. 2, reference numeral 20 is a sync input terminal to which the sync signal output from the sync separation circuit 14 is input, and 21 is a clock input terminal to which the digital signal processing clock output from the clock generator 16 is input. 22 is an output terminal for outputting a write clock. Reference numeral 25 is a clock delay unit that delays the clock input from the clock input terminal 21 and outputs a delayed clock group (Cl to Cn), and 23 is a delayed clock group and the synchronization signal input from the synchronization input terminal 20. Is a phase detector for comparing the phases of and, and 24 is a phase selector for selecting one clock from the delay clock group according to the phase detection result of the phase detector 23.

The write clock generator 17 configured in this way is
For example, if a clock obtained by multiplying a PAL system carrier signal is input to the clock input terminal 21 and an NTSC system synchronization signal is input to the synchronization input terminal 20, from the delay clock group output from the clock delay unit 25, The phase detector 23 detects the clock having the phase closest to the NTSC sync signal, and the phase selector 24 selects the clock having the phase and outputs the selected clock to the output terminal 22. As a result, the write clock output from the output terminal 22 becomes a clock locked to the NTSC sync signal while its frequency is a multiplication of the carrier frequency of the PAL system. In this way, the write clock locked to the synchronization signal can be generated with a simple structure.

As described above, according to the present invention, the carrier frequency of the low frequency conversion carrier color signal is converted by the frequency converter 4 and then digitally converted to perform the carrier decoding process by the digital signal processing. The circuit 10 can be realized with a very simple structure.

As described above, according to the present invention, the carrier color signal decoding circuit and the carrier color signal encoding circuit can be configured by simple digital signal processing, and a significant reduction in cost and no adjustment can be realized. As a result, it is possible to obtain a highly reliable television signal reproducing apparatus which is inexpensive as the entire apparatus and has little variation.

[Brief description of drawings]

1 is a block diagram showing the configuration of a television signal reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram showing the internal configuration of the write clock generating circuit of FIG. 1, and FIG. 3 is a conventional television. It is a block diagram showing the composition of the John system conversion device. 5,6 …… A / D converter, 7 …… Carrier color signal decoding circuit, 8,
9 ... Digital memory, 10 ... Carrier color signal encoding circuit, 11, 12 ... D / A converter, 13 ... Output buffer circuit,
14 ... Sync separation circuit, 16 ... Clock generator, 17 ... Write clock generation circuit, 18 ... Reference clock generation circuit, 19 ... Output terminal, 30 ... Playback head, 31 ... High-pass filter, 32 ... … Low pass filter, 33 …… Frequency demodulator, 34 …… Frequency converter, 35 …… APC circuit, 36 …… Oscillator.

Claims (1)

[Claims] 1. A reproducing means for reproducing a recording signal of a first television system recorded in a format in which a luminance signal is frequency-modulated and a carrier color signal is converted into a low frequency range, and the reproduced frequency-modulated luminance. Frequency demodulation means for frequency demodulating the signal to obtain a luminance signal of the first television system, and frequency conversion means for converting the reproduced low frequency conversion carrier color signal to a carrier frequency of the second television system. An A / D conversion means for digitally converting the frequency-converted carrier color signal and the luminance signal of the first television system with a clock corresponding to a carrier frequency of the second television system; Decoding means for digitally decoding the converted carrier color signal into two color difference signals of the first television system, and the decoded first video signal. Scan lines for converting two color difference signals of the vision system and the digitally converted luminance signal of the first television system into the number of lines and the number of fields of the second television system by thinning and interpolation processing, respectively. Converting means; encoding means for digitally encoding the two color difference signals subjected to the scanning line conversion into a carrier color signal of a second television system; and a carrier color signal of the second television system obtained by the encoding. And D / A conversion means for analog-converting the second television luminance signal obtained by the scanning line conversion with a clock corresponding to the carrier frequency of the second television. Television signal reproduction device.