JPH0336155Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a two-system VTR that enables recording and reproduction of SECAM color signals and PAL color signals.

There are multiple standards for VTR recording and playback, and each standard specifies the recording and playback method for each color system. Therefore, as one standard, there are the following recording and reproducing methods.

The recording and playback method for PAL color signals is
Color subcarrier of 4.433619MHz (=283.75 _H +25H _Z ≒283.75 _H ) (44±1/8) _H [However, _H is the horizontal synchronization frequency] [The appendix is reversed for each field]
When recording, the low frequency conversion color subcarrier of _H (44±1/8) is converted back to the original.
It is converted to a high frequency band of 4.433619MHz. This recording and playback normally requires a multiplier circuit that multiplies the horizontal synchronization signal by a factor of (44±1/8), a PAL subcarrier oscillator, and a frequency conversion circuit. To eliminate this, it is necessary to make the multiplier circuit function as an AFC circuit and the subcarrier oscillator to function as an APC circuit.

In addition, the recording and playback method for SECAM color signals is
During recording, the (RY) color subcarrier of 4.40625MHz (= _282H ) is changed to (44±1/8) _H [sign is reversed for each track], and the (B-Y) of 4.25000MHz (= _273H ) is Color subcarrier of Y) (54±1/8) _H
[The sign is reversed for each track], the low-frequency conversion is performed and recorded, and during playback, the low-frequency conversion color subcarriers are returned to the original _282H and _272H color subcarriers. This recording/reproduction usually involves a multiplier circuit that multiplies the horizontal synchronization signal by (44±1/8) times.
A SECAM (R-Y) color subcarrier oscillator and a frequency conversion circuit are required, the subcarrier oscillator is fixed during recording, the multiplier circuit is used as an AFC circuit to remove jitter during playback, and the subcarrier oscillator functions as an APC circuit. There is a need.

Therefore, as long as you faithfully follow the recording and playback method described above,
In the case of a two-system VTR that records and reproduces both PAL color signals and SECAM color signals, it is possible to use a common multiplier circuit, but it is not possible to use a common subcarrier oscillator.

However, because the SECAM color signal consists of a color subcarrier that is FM-modulated, a slight change in the color subcarrier will only appear as a slight change in the color level on the TV screen. Therefore, with conventional 2-system VTRs and 3-system VTRs, PAL and
They shared the SECAM color subcarrier oscillator.

However, as shown in Figure 1, PAL and SECAM tapes recorded on a 2-system VTR are
There is no problem when playing on a system VTR, but
When a SECAM tape recorded on a SECAM-dedicated VTR is played back on a two-system VTR, one of the converted color subcarriers matches the PAL color subcarrier.

Therefore, there is no problem when monitoring the reproduced image with a normal two-system color television receiver that detects the presence or absence of the SECAM color subcarrier and distinguishes between PAL color signals and SECAM color signals. Two special systems that detect color subcarriers and identify color signals
When monitoring with a VTR, the PAL reception state occurred even though the SECAM color signal was being played, causing the color to disappear from the screen.

Therefore, the present invention is reproduced in view of the above points.
So that the color subcarrier frequency of SECAM does not match the color subcarrier frequency of PAL,
A new and effective configuration that identifies the SECAM color signal and switches the multiplication value of the multiplier circuit to (44-1/4) so that the SECAM color subcarrier derived from the VTR does not match the PAL color subcarrier. The purpose of this project is to propose a two-system VTR.

Below, before explaining one embodiment of the present invention, the tapes recorded by the PAL-dedicated VTR, the SECAM-dedicated VTR, and the two-system VTR of the present invention will be described. It is confirmed below that the VTR of the present invention maintains compatibility with conventional dedicated VTRs, according to FIG.

When playing a tape recorded on a PAL or SECAM dedicated VTR with the two-system VTR of this invention,
When a PAL tape is played back, it is converted back to the PAL color subcarrier frequency and derived.
When the SECAM tape is played, the color subcarrier frequency of (RY) becomes (283.5±1/8) _H ,
The color subcarrier frequency of (B-Y) is (273.5
±1/8) _H and do not match the PAL color subcarrier frequency.

In addition, when playing back a tape recorded with the two-system VTR of this invention on a dedicated VTR, when a PAL tape is played back, it is converted back to the PAL color subcarrier frequency and derived, and when a SECAM tape is played back ( The color subcarrier frequency of RY) is converted to 280.25 _H , and the color subcarrier frequency of (BY) is converted to 270.25 _H , which do not match the color subcarrier frequency of PAL.

Furthermore, when playing back a tape recorded with the two-system VTR of the present invention, with the two-system VTR of the present invention,
When a PAL tape is played back, it is converted back to the PAL color subcarrier frequency and derived.
When a SECAM tape is played back, the color subcarrier frequency of (R-Y) is converted to (281.75±1/8) _H and the color subcarrier frequency of (B-Y) is converted to (271.75±1/8) _H , respectively. It does not match the PAL color subcarrier frequency.

The present invention will be explained below according to an embodiment shown in FIG. FIG. 3 shows a circuit block diagram of the color signal frequency conversion circuit of this embodiment, which is roughly divided into an input/output switching circuit, a frequency conversion circuit A, a carrier oscillator B, a multiplier circuit C, and a color discrimination circuit D. Become. First, the input/output switching circuit consists of an input switching circuit 1 and an output switching circuit 2, which switch input or output according to the recording/playback signal (R/P), and converts high-frequency color signals to low-frequency signals during recording. The signal is input to a low-pass filter 3, and during reproduction, the low-frequency color signal is converted to a high frequency and input to a band-pass filter 4.
The frequency conversion circuit A also includes a first frequency conversion circuit 5 that converts the frequency of the output of the multiplier circuit C and the output of the carrier oscillator B, and a second frequency conversion circuit 6 that converts the frequency of the input signal using the output.
It consists of Further, the carrier oscillator B is
Equivalent to PAL color subcarrier frequency [≒
It consists of a fixed crystal oscillation circuit that provides an oscillation output of 283.75 _H +25Hz, and unlike PAL and SECAM dedicated VTRs, it does not function as an APC circuit during playback. Furthermore, the multiplier circuit C which is the main part of this embodiment
The multiplication value is switched only when reproducing the SECAM signal, and the 1/8 frequency divider circuit 7 divides the variable oscillation output into 1/8.
(44-1/4) _H when playing SECAM tape.
The multiplied output of (44±1/8) _H
The multiplied output of is derived. That is, the voltage-controlled variable oscillation circuit 8 is configured as a PLL circuit that can change the multiplication value using the horizontal synchronization signal as a reference, and the first frequency dividing circuit 9 divides the variable oscillation output by 1/352±1. The respective outputs of the second frequency dividing circuit 10, which divides the frequency by 1/350, are switched by a frequency division value switching circuit 11, and the switching outputs are used as comparison inputs and outputs of a phase comparison circuit 12, which uses the horizontal synchronization signal as a reference input. Therefore, the oscillation of the variable oscillation circuit 8 is controlled, and the frequency division value switching circuit 11
uses the SECAM identification output as a control input and selects the second frequency division value only when reproducing the SECAM signal. Furthermore, the color identification circuit D has an FM detection frequency 13 and
The FM detection circuit 13 performs FM detection on the burst portion of the reproduced color signal after high-frequency conversion, and the SECAM identification circuit 14
is SECAM's (B-Y) burst ID signal.
Using the low frequency of 4.3 MHz or less, the presence of a detection output below a predetermined level is detected and a SECAM identification output is issued.

Therefore, according to this embodiment, the multiplication value is changed by (44-1/4) only when playing back the SECAM tape.
When playing SECAM tapes recorded on a SECAM-dedicated VTR, the two-system television receiver does not malfunction, and the effect is great.

[Brief explanation of drawings]

Figure 1 is a diagram explaining the conversion frequency of the conventional VTR, Figure 2 is a diagram explaining the conversion frequency of the VTR of the present invention, and Figure 3 is a diagram explaining the conversion frequency of the VTR of the present invention.
The figures each reveal a circuit block diagram showing one embodiment of the present invention. Explanation of main drawing numbers, C... Multiplier circuit, B... Carrier oscillator, D... Color identification circuit.

Claims (1)

[Claims for Utility Model Registration] The input color signal is frequency-converted by the output of the PAL color subcarrier oscillator and the output of the horizontal synchronization signal multiplier circuit, and a high-frequency converted color signal or a low-frequency converted color signal is generated. Deriving PAL and SECAM
In the two-system VTR, the frequency division value of the comparison signal of the PLL circuit included in the multiplier circuit is switched by the output of the color identification circuit that identifies reproduction of the SECAM color signal from the burst signal after high frequency conversion. When reproducing the signal, set the multiplication value to (44-1/4) _H [where _H is the horizontal sync frequency],
Multiplying value (44±1/8) except when reproducing SECAM signals
A two-system VTR characterized by each setting being set to _H [however, the sign is reversed for each field].