JPS60251790A - Quantizer - Google Patents

Abstract

PURPOSE:To obtain a stable quantizer against noise and temperature change by constituting circuits after a circuit A/D-converting a video signal of complete digital circuits to reduce the mounting area. CONSTITUTION:A video signal digital quantizer consists of following three large function blocks; a block A applies A/D conversion to a video signal voltage VV, detects further a reference black level fluctuated dut to temperature and extracts digital data only with a signal component independently of temperature change; a block B outputs digital data of an envelope level corresponding to the output of the block A; a block C outputs a quantized value decided depending on the relation between the output of the block A, that is, digital conversion data of the video signal voltage with no level fluctuation against temperature and the output of the block B, that is, digital data of an envelope level.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a video signal quantization device.

[Prior art]

FIG. 1 shows a conventional video signal quantization device.

In this device, when the video signal V has a waveform as shown in FIG. 2, the envelope detection circuit 12 and slice level setting circuit 13 produce the slice level signal VSL shown in FIG. In Figure 6, ll0111, 111
0II, +11111 indicates the slice level. The comparison circuit 14 compares the video signal VV and the slice level signal VSL, and the encoding circuit 15 obtains quantization information DSL for each pixel as shown in FIG.

However, from Hiko, in the configuration of this conventional device, the envelope detection circuit 12. Since both the slice level setting circuit 13 and the comparison circuit 14 are constructed of analog circuits, two circuit adjustments are required. Furthermore, since it is composed of discrete components such as resistors and capacitors, the mounting area becomes large. Furthermore, since high-frequency signals are processed, there are inconveniences such as the need to be careful about wiring, noise, and the like.

Further, the slice level signal VSL shown in FIG. 6 is outputted from the output signal vp of the envelope detection circuit 12 by a slice level setting circuit 13 formed of a resistive voltage dividing circuit. As a result, as shown in FIG. 5, when the black level, which is the standard of the video signal, changes due to a temperature change in the video signal generation circuit, the signal VSL changes to VSL'. Even if it is the same as the video signal shown in the figure, the encoded result has a drawback that it differs from the information shown in FIG. 4, such as the quantized information DSL' shown in FIG. 6.

[Purpose of the invention]

An object of the present invention is to provide a quantization device that does not require the adjustment required in conventional analog circuits.

The present invention also includes: The present invention aims to provide a quantization device with a reduced mounting area and number of parts.

A further object of the present invention is to provide a quantization device capable of stable quantization against noise and temperature changes.

[Structure of the invention]

The present invention is a device that is conventionally configured with an analog circuit, but is configured with a digital circuit.

That is, the quantization device according to the present invention performs analog-digital conversion (hereinafter referred to as "analog-to-digital conversion") of a video signal voltage.

A-D conversion circuit (referred to as A-D conversion), and the A-D conversion circuit.
A first register temporarily stores the output data of a reference black pixel among the outputs of the conversion circuit; A subtraction circuit that has a function of extracting only the corrected video signal component, and an envelope corresponding to the corrected video signal voltage value and the video signal voltage value one pixel before the subtraction circuit, with the output of the subtraction circuit being part of the address specification. a first storage circuit that stores an envelope voltage value determined by the line voltage value;
a second register that temporarily stores the output of the storage circuit for a time corresponding to the next one pixel and outputs it to the first storage circuit as part of the address designation data; Addressed by circuit output.

and a second storage circuit that stores a quantized value determined based on the relationship between the corrected video signal voltage value and the envelope voltage value.

Margin below [Embodiments of the invention] Embodiments of the present invention will be described with reference to the drawings.

FIG. 7 shows a block diagram of a video signal digital quantization device which is an embodiment of the present invention. In this embodiment, it is roughly divided into three large functional blocks.

That is, in Figure 2, block A has a video signal voltage VV of 4-
After performing D conversion, a reference black level that varies depending on temperature is detected, and digital data of only signal components unrelated to temperature changes is extracted by calculation.

Block B outputs digital data at an envelope level corresponding to the output of block A.

Block C outputs a quantized value determined by the relationship between the block A output, that is, the digitally converted data of the video signal voltage that does not vary in level with respect to temperature, and the block B output, that is, the envelope level digital data.

Each of the above blocks will be explained in order below. In the following explanation, DV, DS, DB, DP, etc. all indicate digital data.

Block A: When a video signal having the waveform shown in FIG. 8 is input as the video signal voltage VV, the A-D converter 71
The digital data Dv shown in the figure is converted into digital data. Digital data equal to the fluctuation level due to temperature change is set in the latch 72 in synchronization with the pulse φB shown in FIG. On #day, the pulse φB is synchronized with the video signal period. The subtracter 73 uses the A-D conversion data DV of the video signal and the digital conversion data DB of the black level from the latch 72.

The calculations DS'2DV-DB are sequentially performed to extract a signal component DS (see FIG. 10) unrelated to the black level which changes with temperature.

Block B: FROM (rewritable read-only memory, hereinafter abbreviated as FROM) 74 stores the following contents. That is, the digital data DS of the video signal
When is the data string shown in FIG. 11, the data string shown in FIG. 12 is obtained. The value of the envelope level of data DPn in FIG. 12 is the data DPn-
1 and the video signal data DSn at the time of determining the data DPn. That is.

The following relationship holds true: DPn=f (DSn, DPn-1). Here, n indicates the currently considered pixel number,
n-1 indicates the pixel number at the previous point. F.R.O.
When M74 is given a pair of data DSn and data DPn-i as address data as shown in FIG.
Data DP determined by the above relationship as the content of this address
Store the value of n.

The latch 75 temporarily stores the data DPn-1 before it is applied to the FROM 74, and is set by a pulse φP synchronized with each pixel data. In the manner described above, block B can extract digital data at the envelope level. Also.

By changing the relationship DPn=f (DSn, DPn-1) in advance, arbitrary envelope level data can be obtained from the video signal data in Fig. 11 as shown in Figs. 14 and 15. can get.

Block C In block C, video signal data DS and envelope data D
P Toyoshi quantization is performed.

When considering quantization in an analog circuit, when a video signal as shown in Figure 2 is input, the slice level VSL is determined by the envelope signal vp of the video signal and the resistance division voltage, as shown in Figure 6. quantization is performed by comparing this slice level with the video signal. That is, the quantization value of each pixel is determined only by its video signal voltage value and envelope signal voltage value. Video signal voltage value.

The envelope signal voltage value and the pixel quantization value are VV, respectively.
Assuming VP and DSL.

It is considered that DSL=fA(VV, VP). Further, if vv and vp are expressed as A-D converted digital values, and are respectively Dv and DP.

DSIL = fD(DV, DP) In this case, since the digital value DV also includes a reference black level that changes with temperature, the output DS of the subtracter 73 can be used instead of the digital value DV.

DSL = fD (DS, DP) It can be expressed as

In this embodiment, the address specification of FROM 76 in FIG.
As shown in FIG. 16, this is performed using DS and DP, and the digital values DS and DP at that time are assigned to each address.

Store the value of DSL=fD (DS, DP). In this way, F ROM76
It is possible to obtain the quantization information DSL.

〔Effect of the invention〕

This embodiment provides the following effects.

That is, in this embodiment, all of the nine circuits after the A-D converter circuit are constructed of digital circuits.

The circuit adjustment that was conventionally required in analog circuits is completely unnecessary.

In addition, by using a digital circuit, the effects of noise and oscillation caused by wiring, which were problems in the past, are significantly reduced.

Since there are no discrete components such as resistors and capacitances, the mounting space can be reduced.

Furthermore, the problem of the quantization value of the video signal fluctuating due to fluctuations in the reference black level in the video signal due to temperature changes in the video signal source elements and changes over time has been solved, making it possible to obtain stable quantization values. It becomes possible to obtain.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional video signal quantization device using an analog circuit, Fig. 2 shows an example of an analog video signal, Fig. 3 shows an analog envelope signal vp and a slice level signal VSL, and Fig. 4 shows an example of an analog video signal. shows the quantized output, FIG. 5 shows the analog video signal when the reference black level fluctuates, and FIG. 6 shows the fluctuation of the quantized value due to temperature change. FIG. 7 shows a quantization device according to an embodiment of the present invention. FIG. 8 shows an example of an analog video signal VV. Figure 9 shows the A-D converted video signal and the synchronizing pulse φ8.
Show. FIG. 10 shows the extracted digital data DS. FIG. 11 is an enlarged view of the white and dotted portions of the digital data DS. FIG. 12 shows the relationship between data DS and DP. FIG. 13 shows the structure of address data given to FROM 74 in FIG. FIGS. 14 and 15 are diagrams for explaining that changes in DP can be set arbitrarily depending on the contents stored in the FROM block 4, respectively. FIG. 16 shows the structure of address designation data given to FROM 76 in FIG. In the figure, 71 is an A-D conversion circuit, and 72.75 is a lunch. 73 is a subtraction circuit, and 74.76 is FROM.・Figure 4 Figure 8 Figure 9 Voice Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Voice Figure 15

Claims (1)

[Claims] 1 Analog-digital conversion (hereinafter referred to as A
-A-D conversion circuit (referred to as "D conversion"). A first register temporarily stores data of a reference black pixel among the outputs of the A-D converter circuit, and offset is corrected by subtracting the output of the first register and the output of the A-D converter circuit. A subtraction circuit that extracts a video signal and an envelope signal that follows a white signal in the main scanning direction are configured to be extracted by giving the video signal after offset correction and the envelope signal of one pixel before the offset correction as an address. a first memory circuit that stores a table in advance, and an output of the first memory circuit for one pixel in order to input data of one pixel before the video signal after the offset correction to the first memory circuit; A quantization value determined by the envelope signal and the offset-corrected video signal is stored in a second register held for a corresponding period, and at an address represented by the first storage circuit output and the subtraction circuit output. and a second storage circuit in which data is stored in advance, and the envelope signal outputted from the first storage circuit is used as a slice level reference for the offset-corrected video signal outputted from the subtraction circuit. A quantization device that performs quantization as follows.