KR20040083699A - Method for Analog to Digital drift adjustment of Set-top box - Google Patents

Abstract

PURPOSE: A method for adjusting an ADC(Analog to Digital Converter) deviation in a set-top box is provided to independently adjust an ADC without using a reference signal generator. CONSTITUTION: ADC initialization values according to adjustment modes are set up(S10). After the ADC initialization values are set up, an ADC output digital image pixel value is read(S11-S16). The read ADC output digital image pixel value is compared with a desired pixel value. If the compared result is included in a convergence condition(S17), it is moved to a next channel. If the compared result is not included in the convergence condition, an adjustment mode is adjusted.

Description

Method for Analog to Digital drift adjustment of Set-top box}

The present invention relates to a set top box, and more particularly, to an ADC deviation adjustment method of a set top box that automatically performs mode adjustment of an analog chip (ADC), which is an essential chip set for an analog input of the set top box.

In general, there is an ADC (Analog to Digital Converter) that converts an analog video signal into digital data as a chip set essential for developing a set-top box that receives and outputs an external input such as a component or NTSC.

The ADC chip set is composed of an analog block and a digital block, and each chip variation is large in the process of converting an analog to digital. In addition, this deviation increases due to a circuit path to the ADC or errors in peripheral passive components.

Therefore, when developing a set top box with these ADCs, it is essential to adjust the internal parameters of the ADCs in each set top box to match the overall color.

1 is a diagram illustrating a connection with an external generator for ADC adjustment of a conventional set top box.

Referring to FIG. 1, an analog video signal generated from a standard pattern generator is input according to an external input mode of a set top box or a set, and the color of the ADC is adjusted based on the signal.

Since the output paths are different for each input type, color values of the ADC are generally adjusted by mode.

This method requires the purchase of a separate expensive pattern generator, and the coordinator must set the pattern generator again for the input mode to be adjusted.

And in the case of mass-produced products, there is a problem that the mistakes and work rate of the adjuster falls during this adjustment process. And if this environment is not established, adjustment is impossible.

Accordingly, an object of the present invention has been made in view of the above-mentioned problems of the prior art, and the ADC deviation adjustment method of the set top box which can be independently adjusted in the ADC adjustment of the set top box without using a standard signal generator. It is to provide.

Another object of the present invention is to provide a method for adjusting the deviation of a set top box which can be adjusted at any time and any place by simplifying a task that an adjuster needs to set separately for each input mode.

1 is a view showing connection with an external generator for ADC adjustment of a conventional set top box

2 is a view for explaining the ADC deviation adjustment method of a set top box system according to the present invention.

3 is an algorithm for explaining an ADC deviation adjustment method of a set-top box system according to the present invention.

4 is an ADC deviation adjustment signal block diagram of a set top box system according to the present invention.

According to one aspect of the present invention for achieving the above object, in the set-top box for generating a standard signal, receiving the standard signal as an input and adjusting the ADC deviation, setting the ADC initial value for each adjustment mode, After setting the initial value, reading the ADC output digital image pixel value, compares the ADC output digital image pixel value and the desired pixel value to the next channel if included in the convergence condition, and adjusts if the convergence condition is not met It consists of adjusting the mode.

First, a type of video signal input to the set top box may be classified into a component and a composite.

The composite signal is a signal in which Y (Luminance) and C (Chrominance) components are combined in one channel, and a component signal is composed of three channels of Y (Luminance) / Pb / Pr (Color DifferenceSignal).

Hereinafter, a configuration and an operation according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

2 is a view for explaining the ADC deviation adjustment method of the set-top box system according to the present invention, it shows a digital converted value for the standard signal used in the automatic adjustment.

Referring to FIG. 2, 100IRE color bars are white, yellow, cyan, green, magenta, red, blue, black. It consists of eight colors.

And for each color bar, the digitized value which is the reference for each channel of YPbPr can be known.

With this standard signal input into the set top box, the ADC parameters are adjusted so that the ADC's output follows the reference value.

The table below shows the reference color for each channel when adjusting gain and offset.

[Table 1] When adjusting gain

signal Usage pattern Remarks Y black Adjust Y offset value using black signal Cb black White Use this because the Cb value is the same for the black and white signals Cr black White Use this because black and white signals have the same Cb value

[Table 2] Offset Adjustment

signal Usage pattern Remarks Y black White Use the difference between white with maximum Y and black with minimum Y Cb Yellow, blue Uses the difference between yellow with minimal Cb and blue signal with maximum Cb Cr Cyan, Red Use the difference between Cyan with the smallest Cr and Red signal with the largest Cr

3 is an algorithm for explaining the ADC deviation adjustment method of the set-top box system according to the present invention.

Before the algorithm runs, the ADC is initially set to 128 gain and offset 64. (S10)

If the average value of the image data μ _i deviates from the tolerance, it moves to the offset adjusting stage S12, and if it is included in the tolerance, it moves to the gain adjusting stage S14 (S11).

When the average value of the image data is out of the tolerance, the difference between the average image data value and the target average value is multiplied by the change amount (beta) of the offset coefficient to update the current offset value. If the difference between the target average value is large, the offset change amount is large, and if the difference is small, the offset change amount is also small.

The offset or gain adjustment of the ADC is applied only as an integer, so in some cases it may not be within the tolerance of S11 for the offset of the integer.

Therefore, if the difference between the current offset value and the updated offset value is 1, the internal counter is assumed to be an escape condition for this case. (S13)

However, if the difference between the two offset value is 1 or more, it is determined that it has not converged and resets the current counter value to zero.

If the counter value reaches 10, it is considered that the change in the average value due to the offset adjustment does not come within the allowable error but is converged, and the process proceeds to the next step of gain adjustment (S15).

However, if the counter is less than 10, it can be said that convergence is not certain for the changed offset. (S16)

In this case, after updating the screen with the image output by the changed ADC offset, perform the offset adjustment (S12) again. (S17)

In this way, the ADC is set as the initial initial value, and in this state, the ADC output digital image pixel value is read from the memory.

Compare the desired pixel value with the pixel value stored in the real memory and move to the next channel if it is included in the convergence condition.If the convergence condition is not satisfied, adjust the gain or offset and then adjust the ADC output digital image pixel value in this state. Read back from memory.

This process is repeated over and over again if there is no change in gain and offset overall.

In addition, the program termination occurs only when the convergence condition of the gain or offset value of the algorithm falls within -0.5 <e <0.5. Most ADCs show a convergence condition at a constant gain or offset value, but some ADCs do not meet this convergence condition at a specific gain or offset value, and continue to change if O ↔ O + 1, G ↔ G + 1 may occur.

Therefore, focusing on the change pattern of ADC gain or offset value that does not satisfy the above convergence condition, O ↔O + 1, G ↔G + 1, if the change pattern appears about 10 using a separate internal counter, It can be recognized as a condition to prevent infinite repetition.

4 is a block diagram illustrating an ADC deviation adjustment signal in the set top box system according to the present invention. The component (DVD) and composite (A / V) external inputs are possible, and the output specification diagram of the set top box or set is shown in FIG. Both (DVD) and composite (A / V) can be output.

The usual method is to route the output of the external standard equipment to the set top box or set input and make advanced adjustments. That is, the user needs to adjust the two inputs, so that the user may set an external device and adjust the set-top box or set. However, the present invention generates an internal test pattern of the display processor itself. This is internally received by the AC input.

For example, HDTV chip sets can output their own internal test patterns. Since these test patterns are generated by the chip itself, they are more reliable than standard equipment. This allows the software to automatically process the two inputs by generating test patterns on the set-top box or set itself and externally feeding back them, without the need for connecting external equipment.

As described above, the present invention can bring more efficient workability than that used in the conventional method in the adjustment of ADC, which is an essential chip set of a set top box or set.

In addition, no expensive standard equipment is required to make adjustments, resulting in cost savings in terms of simple cost comparisons and without the need for time and space constraints. Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the examples, but should be defined by the claims.

Claims (1)

In a set-top box that generates a standard signal, takes this standard signal as input and adjusts the ADC deviation, Setting an ADC initial value for each adjustment mode; Reading the ADC output digital image pixel value after setting the initial value; Comparing the ADC output digital image pixel value with a desired pixel value and moving to the next channel if it is included in the convergence condition, and adjusting the adjustment mode if the convergence condition is not satisfied. How to adjust the deviation.