JP2621346B2 - Video signal processing circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing circuit, and more particularly to a video signal processing circuit for obtaining a predetermined analog signal from a plurality of types of digital video signals.
The present invention relates to an arrangement of a D / A conversion circuit and an interpolation filter circuit for removing quantization noise.

Conventional technology To obtain a predetermined analog signal from a digital video signal
D / A conversion processing and interpolation filter processing for removing quantization noise components included in the D / A converted signal are required, and circuits for performing these signal processing are usually connected in series. Placed in If the video signal to be processed such that a plurality of kinds of specifications, for example, the luminance Y ₁ signal and two color difference from the first signal input terminal group 10 through 12 as shown in FIG. 4 (C _1, C ₂₎ The signal is applied to the second signal input terminal group 20 to 22.
One of the luminance (Y ₁ ′) signal and the color difference (C ₁ ′, C ₂ ′) signal is selected from the first signal selection circuit groups 30 to 32.
The signals are supplied to the D / A conversion circuit groups 40 to 42, respectively. These D / A
The analog signal transmitted by the conversion circuit group includes a quantization noise component. To remove these unwanted noise components, D / D
An analog low-pass filter (hereinafter abbreviated as LPF) is required to extract only the signal component at or below the A-conversion speed, that is, approximately half the clock frequency for driving the D / A conversion circuit. If the video signal to be processed has a plurality of specifications, that is, if the signal bandwidth between the first video signal group and the second video signal group is, for example, approximately 1: 2, the LPF bandwidth is also approximately 1: 2. It is necessary to. In the prior art for such a purpose, the signals transmitted by the D / A conversion circuit groups 40 to 42 are transmitted to any one of the first LPF groups 61 to 63 and the second LPF groups 64 to 66 via the second signal selection circuit groups 50 to 52. R, G, and B primary color signals are obtained by a first matrix 70 and a second matrix 80 to which the output signals of the first and second LPF groups are respectively supplied. It is configured to send three primary color signals to signal output terminals 93, 94 and 95 via 92. The first to third signal selection circuit groups are the first
This shows a case where a video signal group is processed, and when the second video signal group is processed, the connection on the other side is made.

SUMMARY OF THE INVENTION In the above-described related art, the first and second LPF groups are arranged in parallel, and the input signal and the output signal are switched according to the video signal to be processed. Two systems are required, and when the D / A conversion circuit, the signal selection circuit group, and the like are configured as an integrated circuit, the number of terminals for interconnection with the LPF is required twice, which impairs economic efficiency. .

The video signal processing circuit of the present invention is suitable for providing a circuit configuration capable of eliminating a signal selection circuit required when a plurality of types of digital video signal groups are processed by a common D / A conversion circuit group, and also suitable for integration into an integrated circuit. It is to provide a video signal processing circuit.

Means for Solving the Problems In the video signal processing circuit of the present invention, one of the first and second digital video signals having a relatively wide band and a narrow band signal band is selectively supplied and supplied. An A / A conversion circuit, and an interpolation filter circuit connected to the output side of the D / A conversion circuit and connected in series with first and second analog filters having wideband and narrowband low-pass characteristics. The first output signal sent by the first analog filter when the D / A conversion circuit processes the first digital video signal, and the second output signal when the D / A conversion circuit processes the second digital video signal. Output the second output signals transmitted by the analog filters.

According to the present invention, with the above configuration, one of the first and second digital video signals is supplied to the D / A conversion circuit,
When processing a digital video signal, the first output signal sent by the first analog filter is processed. When processing a second digital video signal, the second output signal is connected in series to the first analog filter. Respectively output the second output signals transmitted by the analog filters.

Embodiments Hereinafter, embodiments of the video signal processing circuit of the present invention will be described with reference to the drawings. In FIGS. 1 to 3, common elements are denoted by the same reference numerals.

FIG. 1 shows a first embodiment of the present invention. In FIG. 1, digital video signals of the first channel are supplied to first signal input terminal groups 100 to 120, and second video input signals are supplied to second signal input terminal groups 200 to 220. The digital video signals of the respective channels are supplied, and the first channel is selected by the switch groups 300 to 320 constituting the first signal selection circuit, and the LPF 60 is selected via the D / A conversion circuit groups 400 to 420.
Each supplies Y ₁ signals and C _1, C ₂ signal to the input terminal a1 to a3 of 0. The first LPF groups 610 to 630 have characteristics corresponding to the signal bandwidth of the second channel digital video signal described above, and the first channel digital video signal selected by the first signal selection circuit as described above is For the signals it has, it sends out virtually all information components and quantization noise components on output conductors 611 through 631. This first LPF group 610 to 630
The second LPF groups 640 to 660 connected in series to each remove the quantization noise component included in the signal supplied from the first LPF group, and output the first matrix circuit 700 through the output terminals b1 to b3.
After converting into three primary color signals of R ₁ , G ₁ , and B ₁ , a signal output terminal via switches 900 to 920 constituting a second signal selection circuit
Analog signals R ₁ , G ₁ , and B ₁ corresponding to the digital video signals of the first channel are transmitted to 930 to 950. The switches 300 to 320 constituting the first signal selection circuit select the digital video signal of the second channel and supply the Y ₁ ′ signal and the C ₁ ′, C ₂ ′ signal to the D / A conversion circuit groups 400 to 420 respectively. If you do
The switches 900 to 920 constituting the second signal selection circuit are the first
And the output terminals C _{1 to} C ₃ from the coupling midpoint of the second LPF group,
A signal supplied from the conductors 801 to 803 via the matrix circuit 800 is selected, and the signal output terminals 930 to 950 correspond to the digital video signal of the second channel and have a wider band analog than the signal of the first channel. Transmits R ₂ , G ₂ , and B ₂ signals.

FIG. 2 shows a second embodiment of the present invention.
In the figure, a switch 900 constituting a second signal selection circuit is shown.
After performing the selection processing of the first LPE group 610 to 630 and the second LPF group 640 to 660 at 920 to 920, the three primary color signals are transmitted to the signal output terminals 930 to 95 via the matrix circuit 780. If the video signals of the first and second channels differ substantially only in the signal bandwidth, the matrix circuit can be shared.

FIG. 3 shows a third embodiment of the present invention.
To the first signal input terminal group 100 to 120 in FIG, Y ₁ signals and C _1, second channel video signal of the first channel consisting of C ₂ signal is the RGB signal to a second signal input terminal group 200 to 220 When each of the video signals is supplied, the signal output terminal
Output terminals C ₁ to C ₃ of the LPF block 600 in order to be either also sends a three primary color signals 930 to 950 to switch groups 900 constituting the direct second signal selecting circuit without passing through the matrix circuit 920 is coupled to one input terminal, and the other input is supplied with signals from the second LPF groups 640 to 660 via the matrix circuit 700 as in FIG. 1 showing the first embodiment. This third embodiment has a first channel and a second channel.
This shows that the video signal of the channel can be processed not only when the signal bandwidth is different but also when the information component is different.

In the above-described embodiment of the video signal processing circuit according to the present invention, quantization noise components corresponding to different signal bandwidths of the first and second channel digital video signals and included in the analog signal after D / A conversion are removed. The first to do
And the second LPFs are connected in series so that they sequentially reduce the signal passing bandwidth, so that not only the D / A conversion circuit and the LPF can be coupled without a signal selection circuit, but also the LPF and the other. Can be reduced in the number of terminals required for electrical connection with the circuit. In the embodiment, the case where the video signal is processed by two systems is shown, but the present invention can be applied to the case of three or more systems.

According to the present invention, the signal selection means can be eliminated when the D / A conversion means and the LPF means are combined, so that the required number of signal selection means in the analog signal processing circuit can be reduced by half and this type of circuit can be used. In the case of the configuration in the form of an integrated circuit, the industrial value is large, for example, the number of terminals required for coupling the LPF and the integrated circuit chip, which need to be arranged outside the integrated circuit chip, can be reduced.

[Brief description of the drawings]

1 to 3 are block diagrams of video signal processing circuits according to different embodiments of the present invention, and FIG. 4 is a block diagram of a video signal processing circuit in a conventional example. 100, 110, 120 ... first signal input terminal, 200, 210, 220 ... second signal input terminal, 300, 310, 320, 900, 910, 920 ... signal selection circuit, 400, 410, 420 ... D / A conversion circuit, 610, 620, 630, 64
0,650,660 …… LPF.

Claims (6)

(57) [Claims] 1. A D / A conversion circuit for selectively supplying one of a first digital video signal and a second digital video signal having a relatively wide band and a narrow signal band, and the D / A conversion circuit And an interpolation filter circuit in which first and second analog filters having a wide band and a narrow band low-pass characteristic are connected in series, and the D / A conversion circuit is connected to the first / second analog filter. When processing a digital video signal, the first output signal sent from the first analog filter is output to the second analog filter.
A video signal processing circuit for outputting a second output signal transmitted by a second analog filter when the digital video signal is processed. 2. The video signal processing circuit according to claim 1, wherein the D / A conversion circuit sends out RGB signals for both the first and second digital video signals. 3. The video signal processing circuit according to claim 1, wherein the D / A conversion circuit sends out a luminance signal and two color difference signals for the first and second digital video signals. 4. A first output signal and a second output signal are each subjected to matrix processing to obtain first and second RGB signals, and one of them is provided corresponding to an input signal of a D / A conversion circuit. 2. The video signal processing circuit according to claim 1, wherein the video signal processing circuit is selected. 5. An RGB signal is obtained by selecting one of a first output signal and a second output signal in accordance with an input signal of a D / A conversion circuit and then performing matrix processing. Item 3. The video signal processing circuit according to Item 3. 6. A D / A conversion circuit sends an RGB signal and a YC signal to each of the first and second digital video signals, and performs a matrix process on the second output signal to obtain an RGB signal. 2. The video signal processing circuit according to claim 1, wherein said signal and said first output signal are selected in accordance with an input signal of a D / A conversion circuit.