CN107592518B - A kind of composite video signal quality index determination method and device - Google Patents

Abstract

The invention discloses a kind of composite video signal quality index to determine method and device, which comprises the coenvelope line for obtaining composite video signal determines the first range value of the coenvelope line wave crest；According to first range value, the value range of luminance component amplitude in the composite video signal is determined, and determine the value range of coloration relative luminance delay in the composite video signal；To the luminance component amplitude and coloration relative luminance delay difference assignment in corresponding value range, the assignment is substituted into and be delayed with the luminance component amplitude, the coloration relative luminance as in the coenvelope line function of variable, and determines the second range value of the wave crest of the function of the coenvelope line of substitution assignment；When second range value and the first range value difference are less than preset value, the bright gain inequality of color and the bright delay inequality of color of the composite video signal are determined by each assignment that the luminance component amplitude and the coloration relative luminance are delayed.

Description

A kind of composite video signal quality index determination method and device

technical field

The invention relates to video testing technology, in particular to a method and device for determining a quality index of a composite video signal.

Background technique

Composite Video Broadcast Signal (CVBS, Composite Video Broadcast Signal) is a widely used standard, also called baseband video or RCA (Radio Corporation of American) video, which transmits data in analog waveforms. Composite video contains color difference (hue and saturation) and luminance (brightness) information, synchronized in a blanking pulse, transmitted with the same signal. In actual use, it also includes two formats: PAL (Phase Alteration Line) and National Television Standards Committee (NTSC, National Television Standards Committee), which use the same interface as CVBS, which is a more specific composite video. Signal System.

At present, many TV sets are equipped with CVBS interfaces, that is, the yellow one is the video signal, the white one is the left channel audio signal, and the red one is the right channel audio signal. Most cable TV set-top boxes and network set-top boxes are also equipped with CVBS interfaces, so that digital signals can be converted into analog signals, ie CVBS signals, and played through the TV.

There are many ways to convert digital signals into CVBS signals, generally through CVBS decoding chips, but CVBS signals are more complex composite video signals, containing a variety of analog voltage levels, time intervals and other indicators, and all video information only uses A transmission line transmits the brightness information, color information and synchronization signal into one signal. The quality of the video signal converted by different CVBS decoding chips is very different. Therefore, it is necessary to carry out strict testing before the CVBS decoding chip is put into the market to verify The quality of the CVBS decoding chip.

The test method can be to test the video signal converted by the CVBS decoding chip, or before the CVBS decoding chip is manufactured, through the register transfer level (RTL, Register Transfer Level) code of the CVBS decoding chip, and simulate the CVBS through the simulation device. signal, and test the simulated CVBS signal.

The above test methods will all affect the determination of the indicators of the video quality of the color-brightness gain difference and the color-brightness delay difference, and the error is very large, which directly affects the quality judgment of the CVBS signal.

Another test method is to send the CVBS signal into the decoder, one way into the luminance channel, and the chrominance signal is absorbed by the color load wave notch filter (4.43mhz notch filter), and the luminance signal is taken out, and the other way is passed through the bandpass filter. Take out the chrominance signal of 4.43mhz, measure the amplitude of the two signals and observe the delay of the envelope in the time domain. This test method will introduce additional amplitude distortion and timing distortion when distributing the signal, resulting in a very large error.

SUMMARY OF THE INVENTION

In order to solve the existing technical problems, the embodiments of the present invention are expected to provide a method and device for determining the quality index of a composite video signal, which can more accurately determine the color-brightness gain difference and the color-brightness delay of the CVBS signal converted by the CVBS decoding chip. Poor, judge the conversion quality of the CVBS decoding chip.

The technical solution of the embodiment of the present invention is realized as follows:

An embodiment of the present invention provides a method for determining a quality indicator of a composite video signal, the method comprising:

Obtain the upper envelope of the composite video signal, and determine the first amplitude value of the peak of the upper envelope;

According to the first amplitude value, determine the value range of the luminance component amplitude in the composite video signal, and determine the value range of the chrominance relative luminance delay in the composite video signal;

Assign values to the luminance component amplitude and chrominance relative luminance delay respectively within the corresponding value range, and substitute the assignments into the upper envelope with the luminance component amplitude and the chrominance relative luminance delay as variables function, and determine the second amplitude value of the peak of the function that is substituted into the assigned upper envelope;

When the difference between the second amplitude value and the first amplitude value is smaller than a preset value, determine the color-brightness gain of the composite video signal through the respective assignments of the luminance component amplitude and the chrominance relative luminance delay Difference and color brightness delay difference.

Preferably, the obtaining the upper envelope of the composite video signal includes:

The peak points in each cycle of the composite video signal are acquired, and the peak points are connected to form an upper envelope.

Preferably, the determining the first amplitude value of the upper envelope peak includes:

Acquire the peak point of the upper envelope, measure the amplitude of the peak point, and obtain the first amplitude value.

Preferably, the determining the value range of the luminance component amplitude in the composite video signal includes:

According to the first amplitude value, determine the value range of the luminance component amplitude in the composite video signal from zero to the first amplitude value;

The determining the value range of the chrominance relative luminance delay in the composite video signal includes:

The range of the chrominance relative luminance delay in the composite video signal is greater than or equal to -π and less than or equal to π.

Preferably, the determining of the second amplitude value of the peak of the function substituted into the assigned upper envelope includes;

Based on the function of the upper envelope of the assignment assignment, a maximum value of the function of the upper envelope line assigned to the assignment is calculated, and the calculated maximum value is determined as the second amplitude value.

Preferably, the method further comprises;

The respective upper envelopes of the plurality of composite video signals obtained based on the plurality of composite video signals, respectively, based on the respective upper envelopes, the respective color-brightness gain differences and color-brightness delay differences of the plurality of composite video signals are determined respectively. ;

Take the average value of a plurality of color-brightness gain differences and color-brightness delay differences respectively;

The average value is used as the color-brightness gain difference and the color-brightness delay difference of the composite video signal.

The embodiment of the present invention also provides a composite video signal quality indicator determination device, the device includes an acquisition module, a first determination module, a second determination module, a third determination module and a fourth determination module; wherein,

The acquisition module is used to acquire the upper envelope of the composite video signal;

the first determining module, configured to determine the first amplitude value of the upper envelope peak;

The second determining module is configured to determine, according to the first amplitude value, the value range of the luminance component amplitude in the composite video signal, and determine the value range of the chrominance relative luminance delay in the composite video signal ;

The third determination module is configured to assign values to the luminance component amplitude and the chrominance relative luminance delay respectively within the corresponding value range, and substitute the assignment into the luminance component amplitude and the chrominance relative luminance delay. The delay is in the upper envelope function of the variable, and the second amplitude value of the peak of the function of the upper envelope of the assignment is determined;

The fourth determination module is configured to determine by each assignment of the luminance component amplitude and the chrominance relative luminance delay when the difference between the second amplitude value and the first amplitude value is less than a preset value The difference in color and brightness gain and the difference in color and brightness delay of the composite video signal.

Preferably, the acquisition module is also used for:

The peak points in each cycle of the composite video signal are acquired, and the peak points are connected to form an upper envelope.

Preferably, the first determining module is further used for:

Acquire the peak point of the upper envelope, measure the amplitude of the peak point, and obtain the first amplitude value.

Preferably, the second determining module is further used for:

According to the first amplitude value, determine the value range of the luminance component amplitude in the composite video signal from zero to the first amplitude value;

The second determination module is further configured to determine the value range of the chrominance relative luminance delay in the composite video signal: the range of the chrominance relative luminance delay in the composite video signal is greater than or equal to -π and less than or equal to pi.

Preferably, the third determining module is further used for:

Based on the function of the upper envelope of the assignment assignment, a maximum value of the function of the upper envelope line assigned to the assignment is calculated, and the calculated maximum value is determined as the second amplitude value.

Preferably, the fourth determining module is further used for:

The respective upper envelopes of the plurality of composite video signals obtained based on the plurality of composite video signals, respectively, based on the respective upper envelopes, the respective color-brightness gain differences and color-brightness delay differences of the plurality of composite video signals are determined respectively. ;

Take the average value of a plurality of color-brightness gain differences and color-brightness delay differences respectively;

The average value is used as the color-brightness gain difference and the color-brightness delay difference of the composite video signal.

Embodiments of the present invention provide a method and device for determining a quality index of a composite video signal, which acquire an upper envelope of a composite video signal, and determine a first amplitude value of the peak of the upper envelope; and determine, according to the first amplitude value, The value range of the luminance component amplitude in the composite video signal, and the value range of the chrominance relative luminance delay in the composite video signal is determined; within the corresponding value range, the luminance component amplitude and chrominance relative to The luminance delays are respectively assigned, and the assignments are substituted into the upper envelope function with the luminance component amplitude and the chrominance relative luminance delay as variables, and the peak value of the function of the upper envelope of the assignment is determined. second amplitude value; when the difference between the second amplitude value and the first amplitude value is less than a preset value, determine the composite video by assigning the luminance component amplitude and the chrominance relative luminance delay The color-brightness gain difference and the color-brightness delay difference of the signal; it can be seen that the embodiment of the present invention can more accurately determine the quality indicators of the color-brightness gain difference and the color-brightness delay difference by approximating the CVBS signal, and judge the CVBS decoding chip. conversion quality.

Description of drawings

1 is a schematic flowchart of a method for determining a quality indicator of a composite video signal according to an embodiment of the present invention;

2 is a schematic diagram of a 20T pulse waveform of a composite video signal according to an embodiment of the present invention;

3 is a schematic diagram 1 of the frequency of a composite video signal tending to positive infinity according to an embodiment of the present invention;

4 is a schematic diagram 2 of the frequency of a composite video signal tending to positive infinity according to Embodiment 1 of the present invention;

5 is a schematic diagram 3 of the frequency of a composite video signal tending to positive infinity according to Embodiment 1 of the present invention;

6 is a schematic diagram 4 of the frequency of the composite video signal tending to positive infinity according to Embodiment 1 of the present invention;

Fig. 7 is the waveform diagram formed by taking out the envelope of Fig. 3 separately;

8 is a schematic flowchart of a method for determining a quality indicator of a composite video signal according to Embodiment 2 of the present invention;

FIG. 9 is a schematic diagram of an apparatus for determining a quality indicator of a composite video signal according to Embodiment 3 of the present invention.

Detailed ways

The basic principle of the embodiment of the present invention is: the chrominance component amplitude A _C , the luminance component amplitude A _Y and the chrominance relative luminance delay required to calculate the color-brightness gain difference and the color-brightness delay difference It cannot be directly measured from the composite video signal, but the measured amplitude values of the envelope peaks and troughs of the composite video signal can be measured first; variable envelope function, and then according to this function, in A _Y and Within the theoretical value range of , for A _Y and The theoretical amplitude values of the envelope peaks and troughs are obtained, and the measured amplitude values are gradually approached, and finally the A _C , A _Y and the set accuracy are obtained. The principle of the embodiment of the present invention is to obtain the quality index of the composite video signal through an approximate calculation method, and this approximate calculation method is very suitable for calculation by a computer.

The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

Example 1

FIG. 1 is a schematic flowchart of a method for determining a quality indicator of a composite video signal according to an embodiment of the present invention. The execution body of the method may be a test host, more specifically, a computer. As shown in FIG. 1 , the method includes:

Step 101: Obtain the upper envelope of the composite video signal, and determine the first amplitude value of the peak of the upper envelope;

Here, the upper envelope of the composite video signal is obtained through the test host. The composite video signal is the standard signal to be tested. Generally, it is simulated by the simulation device according to the RTL code of the composite video decoding chip, that is, the CVBS decoding chip. The composite video signal is a digital signal, which can be directly acquired by the test host; it can also be directly output from the composite video decoding chip, that is, the CVBS signal that can be received by ordinary analog TVs. It needs to go through an analog-to-digital conversion device to be tested by the host. Obtain;

The acquisition of the upper envelope is obtained by connecting the peak points of the composite video signal, and specifically, is processed by an application program, which is provided with a specific algorithm to automatically capture the The peak point of the composite video signal, then draw a tangent line tangent to the peak point, and finally connect the tangent line smoothly. The application program is generally a video signal processing application program installed on the test host.

Specifically, the video processing application of the test host may be a Matrix Laboratory (MATLAB, Matrix Laboratory).

The specific signal for testing the color gain difference and color brightness delay difference in the composite video signal is the 20T pulse waveform. The distance between them is 20T, and T is the time period; specific to the system, for PAL, T is 100ns; for NTSC, T is 125ns.

In a 20T pulse, both the chrominance and luma signals are square sine waves, and the chrominance signal is superimposed on the luma signal.

Fig. 2 shows the 20T pulse waveform in this embodiment, ω=2πf, and f is the carrier frequency of the composite video signal.

In order to better observe the 20T pulse waveform, it is assumed that the frequency of the composite video signal tends to be infinity, so that the envelope of the composite video signal is clearer, see Figure 3 to Figure 6 for details, and Figure 3 to Figure 6 are the chrominance components and four types of different features for the luminance component, where:

A _C and A _Y are the magnitudes of the chrominance and luminance components, respectively, is the delay between chrominance and luminance.

The characteristics of Fig. 3 are: A _C >A _Y , That is, the amplitude of the chrominance component is greater than that of the luminance component, and the chrominance leads the luminance;

The characteristics of Fig. 4 are: A _C >A _Y , That is, the amplitude of the chrominance component is greater than that of the luminance component, and the chrominance lags the luminance;

The characteristics of Figure 5 are: A _C <A _Y , That is, the amplitude of the chrominance component is smaller than that of the luminance component, and the chrominance leads the luminance;

The characteristics of Fig. 6 are: A _C <A _Y , That is, the amplitude of the chrominance component is smaller than that of the luminance component, and the chrominance lags the luminance;

The characteristics of the above graphs are obtained by qualitative analysis according to the shape of the envelope.

Further, the envelope shown in FIG. 3 is shown separately to obtain the envelope shown in FIG. 7 .

The first amplitude value of the upper envelope peak is the value of M shown in FIG. 7 , and the first amplitude value is determined to determine the amplitude of the luminance component and the relative luminance delay of chrominance in the composite video signal in the subsequent steps. The value range of time;

The method for determining the first amplitude value may include: acquiring a peak point of the upper envelope, measuring the amplitude of the peak point, and obtaining the first amplitude value, that is, the value of M shown in FIG. 7 .

Step 102: According to the first amplitude value, determine the value range of the luminance component amplitude in the composite video signal, and determine the value range of the chrominance relative luminance delay in the composite video signal;

After obtaining the first amplitude value, it is necessary to establish a relationship expression of the luminance component amplitude, chrominance component amplitude, chrominance relative luminance delay and M in the composite video signal, and then determine the luminance component amplitude, chrominance relative The value range of the brightness delay is as follows:

According to the principle of the composite video signal, it can be known that the chrominance and luminance waveforms of the composite video signal are sine square waves respectively, so A _C , A _Y and The variable is expressed as a standard function of the envelope of the composite video signal. Specifically, the upper envelope and the lower envelope in FIG. 7 are represented by the following equations (1) and (2), respectively.

In the above two formulas, CVBS_t is the upper envelope, CVBS_b is the lower envelope, A _C and A _Y are the amplitudes of the chrominance and luminance components, respectively, is the delay between chrominance and luminance.

According to equation (1), it is assumed that the delay of chrominance relative to luminance is zero, that is, Then we can get: M=A _Y +Ac;

And Ac is the square of the sine, greater than or equal to zero, so A _Y will not be greater than M, so the value range of A _Y can be obtained from 0 to M, that is, the value range of the luminance component amplitude in the composite video signal is zero to the first amplitude value;

From the characteristics of the sine function, it can be known that in formula (1) period is 2π, and It is the delay of chrominance relative to brightness, which may lead or lag, so it can be set The value range of is greater than or equal to -π, and less than or equal to π, The value range of can be expressed as [-π,π].

Step 103: Assign values to the luminance component amplitude and the chrominance relative luminance delay respectively within the corresponding value range, and substitute the assignments into the upper value with the luminance component amplitude and the chrominance relative luminance delay as variables. In the envelope function, and determine the second amplitude value of the peak of the function that is substituted into the assigned upper envelope;

When the difference between the second amplitude value and the first amplitude value is smaller than a preset value, determine the color-brightness gain of the composite video signal through the respective assignments of the luminance component amplitude and the chrominance relative luminance delay Difference and color brightness delay difference.

Specifically, in order to determine the second amplitude value of the peak of the upper envelope function after assigning the luminance component amplitude and the chrominance relative luminance delay respectively within the corresponding value range, it is necessary to The envelope standard function is transformed to obtain the relationship between the luminance component amplitude and the chrominance relative luminance delay and the second amplitude value of the envelope peak;

Of course, in the process of assignment trial calculation, some other formulas are needed. In order to describe clearly, all formulas used in the calculation process are deduced one by one:

Note that when ωt∈[0,π], there is a maximum value in formula (1), and a maximum value and a minimum value in formula (2). Therefore, formula (1) and formula (2) are respectively derived with respect to t to obtain formula (3) and formula (4).

When equations (1) and (2) reach a maximum value or a minimum value, equations (3) and (4) are respectively equal to 0, and equations (5) and (6) are obtained.

Let t that satisfies Equation (5) be t _{t , and t} that satisfies Equation (6) be t _b1 and t _b2 ; according to the relationship between t _b1 and t _b2 , Equation (7) can be obtained:

Combined with Figure 7, t _t , t _b1 , t _b2 and formula (7) are substituted into formula (1) and formula (2) to obtain formulas (8), (9), (10):

Equation (9) and Equation (10) are added to obtain Equation (11):

A _Y -A _C =Y1+Y2 (11)

Then formula (12) is derived from formula (5):

Finally, formula (13) is obtained:

Similarly, formula (14) can be derived from formula (6):

After deriving the above formula, for A _Y and Assign values respectively within the value range, and use formula (11) to obtain the corresponding A _C according to the assignment; after obtaining A _C , assign A _C , A _Y and Substitute into equation (13) to find ωt _t ;

Substitute the obtained ωt _t into Equation (8) to determine the second amplitude value of the upper envelope, that is, to calculate the maximum value of the function of the upper envelope of the substituted assignment, denoted as M',

for A _Y and Continue to assign values in the set value range to obtain the second amplitude values of multiple upper envelopes;

When the difference between the second amplitude value and the first amplitude value is smaller than a preset value, determine the color-brightness gain of the composite video signal through the respective assignments of the luminance component amplitude and the chrominance relative luminance delay Difference and color brightness delay difference;

Specifically, it is calculated by the following formula:

The result obtained by formula (15) is the difference in color and brightness gain, and the unit is %;

The result obtained by formula (16) is the color-brightness delay difference, and the unit is ns; if the calculation result is negative, it means that the chroma lags; if the calculation result is positive, it means that the chroma is ahead;

Among them, N is a constant, because it is a 20T pulse, so take 20, and T is the time period; specific to the system, for PAL, T is 100ns; for NTSC, T is 125ns;

The preset difference value is determined according to the requirements of the composite video decoding chip, that is, the CVBS decoding chip, and will not be repeated here.

Further, in order to make the calculation result more accurate, multiple waveforms can be extracted from the composite video signal, and the color-brightness gain difference and the color-brightness delay difference are calculated respectively;

Specifically, based on the respective upper envelopes of the multiple composite video signals obtained from the multiple composite video signals, the respective color brightness gain differences and color brightness of the multiple composite video signals are determined based on the respective upper envelopes. delay difference;

Take the average value of a plurality of color-brightness gain differences and color-brightness delay differences respectively;

Taking the average value as the difference in color and brightness gain and the difference in color and brightness delay of the composite video signal

More specifically, according to the principle of composite video signal, it can be known that the waveform of the 20T pulse is four waveform cycles with initial phases of zero, 90, 180 and 270 degrees, and the shapes of zero, 180 and 90 and 270 degrees are exactly the same. , but the direction of the peaks and troughs is opposite, so just calculate the indicators of the two waveforms of zero degree and 90 degrees, and take the average value, namely:

According to the composite video signal whose initial phase is zero, calculate the first color brightness gain difference and the first color brightness delay difference:

Calculate the second color brightness gain difference and the second color brightness delay difference according to the composite video signal with an initial phase of 90 degrees;

The color brightness gain difference is obtained according to the average value of the first color brightness gain difference and the second color brightness gain difference, and the color brightness delay difference is obtained according to the average value of the first color brightness delay difference and the second color brightness delay difference.

Embodiment 2

8 is a schematic flowchart of a method for determining a quality indicator of a composite video signal according to Embodiment 2 of the present invention. The execution body of the method may be a test host, more specifically, a computer. As shown in FIG. 8 , the method includes:

Step 201: Determine the measured amplitude values of the upper envelope, the lower envelope, and the trough of the composite video signal;

Since the value ranges of the luminance component amplitude and chrominance relative to the luminance delay determined in the first embodiment are relatively large, and the calculation workload is relatively large, this step tries to reduce the luminance component amplitude and color on the basis of the first embodiment. The value range of the relative brightness delay;

Specifically, on the basis of step 101 of the first embodiment, in addition to the upper envelope of the composite video signal, the lower envelope of the composite video signal is also obtained, and the upper envelope and lower envelope are determined. The measured amplitude values of the peak and trough of the network line correspond to M, Y1 and Y2 respectively in Figure 7;

In this way, in the subsequent steps, the value ranges of the luminance component amplitude and the chrominance relative luminance delay can be determined more accurately.

Step 202: Determine the value range of the luminance component amplitude and the chrominance relative luminance delay in the composite video signal;

On the basis of step 102 in the first embodiment, this step further determines the value ranges of the luminance component amplitude and the chrominance relative luminance delay, as follows:

1) Determine the value range of the luminance component amplitude:

Substituting the aforementioned formula (11) into formula (8), the value range of A _Y can be obtained as:

2) Determine the value range of the chrominance relative luminance delay:

In the first embodiment, in step 102, it is determined that the value range of the chrominance relative luminance delay is [-π, π];

but is the square of the sine function. According to the characteristics of the sine function, the period after the square is reduced by half, so the value range of the chrominance relative luminance delay can be set to [-π/2, π/2];

Further, Equation (13) is used to calculate ωt, which is directly related to determining the second amplitude value. Some of the previous formulas are only for deriving Equation (13). In Equation (13) The value range of tg(2ωt) determines the value range of the chrominance relative to luminance delay. Therefore, further qualitative analysis of formula (13) is carried out. It can be seen from (13) that tg(2ωt) is a tangent function, and the period of the tangent function is is π, and tg(2ωt) is 2 times ωt, the period is reduced by half, and the period is π/2, so the value range of the chrominance relative luminance delay can also be π/2, so the chrominance relative luminance delay The value range of can be set to [-π/4,π/4].

Step 203: Assign values to the luminance component amplitude and the chrominance relative luminance delay respectively within the corresponding value range, and substitute the assignments into the upper value with the luminance component amplitude and the chrominance relative luminance delay as variables. In the envelope and lower envelope functions, and determine the theoretical amplitude values of the peaks and troughs of the upper envelope and lower envelope functions that are substituted into the assignment;

When the difference between the theoretical amplitude value and the measured amplitude value is less than a preset value, determine the color-brightness gain difference of the composite video signal by assigning the luminance component amplitude and the chrominance relative luminance delay and color brightness delay difference.

On the basis of step 103 in the first embodiment, this step also needs to calculate the theoretical amplitude values of the peaks and troughs of the lower envelope function;

Specifically, for A _Y and Assign values respectively within the value range, and use formula (11) to obtain the corresponding A _C according to the assignment; after obtaining A _C , assign A _C , A _Y and Substitute into Equation (13), Equation (14) and Equation (7) to find ωt _t , ωt _b1 and ωt _b2 , note that if ωt _b1 is less than 0, then add ωt _b1 to π/2 as the ωt _b1 calculated below, namely

Substitute the obtained ωt _t , ωt _b1 and ωt _b2 into equations (8)(9)(10) to determine the theoretical amplitude values of the peaks and valleys of the upper and lower envelope functions, namely M', Y1' and Y2', respectively subtract the measured amplitude values M, Y1 and Y2 of the peaks and troughs of the upper envelope and lower envelope, and add the absolute values of the three differences, and the sum of the three differences Set to S.

for A _Y and Continue to assign values in the set value range to obtain a plurality of theoretical amplitude values of the peaks and valleys of the upper envelope and lower envelope functions;

Calculate the theoretical amplitude values of the peaks and troughs of multiple upper envelope and lower envelope functions, and calculate with the measured amplitude values of the peaks and troughs of the upper envelope and lower envelope respectively, and obtain multiple S, when When S is less than the preset difference value, determine the color-brightness gain difference and the color-brightness delay difference of the composite video signal through the assignments of the luminance component amplitude, the chrominance component amplitude, and the chrominance relative luminance delay, and calculate The formulas are shown in formulas (15) and (16).

Embodiment 3

FIG. 9 is a schematic diagram of an apparatus for determining a quality indicator of a composite video signal according to Embodiment 3 of the present invention. As shown in FIG. 9 , the apparatus includes: an acquisition module 31 , a first determination module 32 , a second determination module 33 , and a third determination module 34 and the fourth determination module 35; wherein,

The acquisition module 31 is used to acquire the upper envelope of the composite video signal;

The first determining module 32 is configured to determine the first amplitude value of the upper envelope peak;

The second determining module 33 is configured to determine, according to the first amplitude value, the value range of the luminance component amplitude in the composite video signal, and determine the value of the chrominance relative luminance delay in the composite video signal scope;

The third determination module 34 is configured to assign values to the luminance component amplitude and the chrominance relative luminance delay respectively within the corresponding value range, and substitute the assignment into the luminance component amplitude and the chrominance relative luminance delay. The luminance delay is in the upper envelope function of the variable, and the second amplitude value of the peak of the function of the assigned upper envelope is determined;

The fourth determination module 35 is configured to, when the difference between the second amplitude value and the first amplitude value is less than a preset value, pass the respective assignments of the luminance component amplitude and the chrominance relative luminance delay Determine the color-brightness gain difference and the color-brightness delay difference of the composite video signal.

In order to explain more clearly, each module will be described in detail below:

The acquisition module 31 is used to acquire the upper envelope of the composite video signal;

The composite video signal is a standard signal to be tested, and is generally a composite video signal simulated by an analog device according to the RTL code of the composite video decoding chip, which is a digital signal and can be directly obtained by the obtaining module 31; The CVBS signal directly output by the video decoding chip, that is, the CVBS signal that can be received by an ordinary analog TV, needs to be acquired by the acquisition module 31 through an analog-to-digital conversion device;

The acquisition of the upper envelope is obtained by connecting the peak points of the waveform of the composite video signal. Specifically, it is processed by an application program. The application program is provided with a specific algorithm, which can automatically capture the The peak point of the composite video signal, then draw a tangent line tangent to the peak point, and finally connect the tangent line smoothly. The application program is generally a video signal processing application program installed on the test host.

Specifically, the video processing application may be MatrixLaboratory (MATLAB, MatrixLaboratory).

The first determining module 32 is configured to determine the first amplitude value of the upper envelope peak;

According to the relevant standards, the specific signal for testing the color gain difference and color brightness delay difference in the composite video signal is the 20T pulse waveform. The distance between the two time points is 20T, and T is the time period. Specifically, for the system, for PAL, T is 100 ns; for NTSC, T is 125 ns.

In a 20T pulse, both the chrominance and luma signals are square sine waves, and the chrominance signal is superimposed on the luma signal.

Fig. 2 shows the 20T pulse waveform in this embodiment, ω=2πf, and f is the carrier frequency of the composite video signal.

In order to better observe the 20T pulse waveform, it is assumed that the frequency of the composite video signal tends to be infinity, so that the envelope of the composite video signal is clearer, see Figure 3 to Figure 6 for details, and Figure 3 to Figure 6 are the chrominance components and four types of different features for the luminance component, where:

A _C and A _Y are the magnitudes of the chrominance and luminance components, respectively, is the delay between chrominance and luminance.

The characteristics of Fig. 3 are: A _C >A _Y , That is, the amplitude of the chrominance component is greater than that of the luminance component, and the chrominance leads the luminance;

The characteristics of Fig. 4 are: A _C >A _Y , That is, the amplitude of the chrominance component is greater than that of the luminance component, and the chrominance lags the luminance;

The characteristics of Figure 5 are: A _C <A _Y , That is, the amplitude of the chrominance component is smaller than that of the luminance component, and the chrominance leads the luminance;

The characteristics of Fig. 6 are: A _C <A _Y , That is, the amplitude of the chrominance component is smaller than that of the luminance component, and the chrominance lags the luminance;

The characteristics of the above graphs are obtained by qualitative analysis according to the shape of the envelope, and the analysis methods are known to those skilled in the art, and will not be described in detail.

Further, the envelope shown in FIG. 3 is shown separately to obtain the envelope shown in FIG. 7 .

The first amplitude value of the upper envelope peak is the value of M shown in FIG. 7 , and the first amplitude value is determined to determine the amplitude of the luminance component and the relative luminance delay of chrominance in the composite video signal in the subsequent steps. The value range of time;

The method for determining the first amplitude value may include: acquiring a peak point of the upper envelope, measuring the amplitude of the peak point, and obtaining the first amplitude value, that is, the value of M shown in FIG. 7 .

The second determining module 33 is configured to determine, according to the first amplitude value, the value range of the luminance component amplitude in the composite video signal, and determine the value of the chrominance relative luminance delay in the composite video signal scope;

After obtaining the first amplitude value, it is necessary to establish a relational expression of the luminance component amplitude, chrominance component amplitude, chrominance relative luminance delay and M in the composite video signal, and then determine the luminance component amplitude, chrominance component according to this. The value range of the relative brightness delay is as follows:

According to the principle of the composite video signal, it can be known that the chrominance and luminance waveforms of the composite video signal are sine square waves respectively, so A _C , A _Y and The variable is expressed as a standard function of the envelope of the composite video signal. Specifically, the upper envelope and the lower envelope in FIG. 7 are respectively represented by the aforementioned equations (1) and (2).

In the above two formulas, CVBS_t is the upper envelope, CVBS_b is the lower envelope, A _C and A _Y are the amplitudes of the chrominance and luminance components, respectively, is the delay between chrominance and luminance.

According to equation (1), it is assumed that the delay of chrominance relative to luminance is zero, that is, Then we can get: M=A _Y +Ac;

And Ac is the square of the sine, greater than or equal to zero, so A _Y will not be greater than M, so the value range of A _Y can be obtained from 0 to M, that is, the value range of the luminance component amplitude in the composite video signal is zero to the first amplitude value;

From the characteristics of the sine function, it can be known that in formula (1) period is 2π, and It is the delay of chrominance relative to brightness, which may lead or lag, so it can be set The value range of is greater than or equal to -π, and less than or equal to π, The value range of can be expressed as [-π,π].

The third determination module 34 is configured to assign values to the luminance component amplitude and the chrominance relative luminance delay respectively within the corresponding value range, and substitute the assignment into the luminance component amplitude and the chrominance relative luminance delay. The luminance delay is in the upper envelope function of the variable, and the second amplitude value of the peak of the function of the assigned upper envelope is determined;

Specifically, in order to determine the second amplitude value of the peak of the upper envelope function after assigning the luminance component amplitude and the chrominance relative luminance delay respectively within the corresponding value range, it is necessary to assign the The envelope standard function is transformed to obtain the relationship between the luminance component amplitude and the chrominance relative luminance delay and the second amplitude value of the envelope peak;

Of course, in the process of assignment trial calculation, some other formulas are needed. In order to describe clearly, all formulas used in the calculation process are deduced one by one:

Note that when ωt∈[0,π], there is a maximum value in formula (1), and a maximum value and a minimum value in formula (2). Therefore, formula (1) and formula (2) are respectively derived with respect to t to obtain formula (3) and formula (4).

When equations (1) and (2) reach a maximum value or a minimum value, equations (3) and (4) are respectively equal to 0, and equations (5) and (6) are obtained.

Let t that satisfies Equation (5) be t _{t , and t} that satisfies Equation (6) be t _b1 and t _b2 ; according to the relationship between t _b1 and t _b2 , Equation (7) can be obtained:

Combined with Figure 7, t _t , t _b1 , t _b2 and formula (7) are substituted into formula (1) and formula (2) to obtain formulas (8), (9), (10):

Equation (9) and Equation (10) are added to obtain Equation (11):

Then formula (12) is derived from formula (5):

Finally, formula (13) is obtained:

Similarly, equation (14) can be derived from equation (6):

After deriving the above formula, for A _Y and Assign values respectively within the value range, and use formula (11) to obtain the corresponding A _C according to the assignment; after obtaining A _C , assign A _C , A _Y and Substitute into equation (13) to find ωt _t ;

Substitute the obtained ωt _t into Equation (8) to determine the second amplitude value of the upper envelope, that is, to calculate the maximum value of the function of the upper envelope of the substituted assignment, denoted as M',

for A _Y and Continue to assign values in the set value range to obtain the second amplitude values of multiple upper envelopes;

The fourth determination module 35 is configured to, when the difference between the second amplitude value and the first amplitude value is less than a preset value, pass the respective assignments of the luminance component amplitude and the chrominance relative luminance delay Determine the color-brightness gain difference and the color-brightness delay difference of the composite video signal.

When the difference between the second amplitude value and the first amplitude value is smaller than a preset value, determine the color-brightness gain of the composite video signal through the respective assignments of the luminance component amplitude and the chrominance relative luminance delay Difference and color brightness delay difference;

Specifically, it is calculated by formulas (15) and (16):

The result obtained by formula (15) is the difference in color and brightness gain, and the unit is %;

The result obtained by formula (16) is the color-brightness delay difference, and the unit is ns; if the calculation result is negative, it means that the chroma lags; if the calculation result is positive, it means that the chroma is ahead;

Among them, N is a constant, because it is a 20T pulse, so take 20, and T is the time period; specific to the system, for PAL, T is 100ns; for NTSC, T is 125ns;

The preset difference value is determined according to the requirements of the composite video decoding chip, and will not be repeated.

Further, in order to make the calculation result more accurate, multiple waveforms can be extracted from the composite video signal, and the color-brightness gain difference and the color-brightness delay difference are calculated respectively;

Specifically, based on the respective upper envelopes of the multiple composite video signals obtained from the multiple composite video signals, the respective color brightness gain differences and color brightness of the multiple composite video signals are determined based on the respective upper envelopes. delay difference;

Take the average value of a plurality of color-brightness gain differences and color-brightness delay differences respectively;

Taking the average value as the difference in color and brightness gain and the difference in color and brightness delay of the composite video signal

More specifically, according to the principle of composite video signal, it can be known that the waveform of the 20T pulse is four waveform cycles with initial phases of zero, 90, 180 and 270 degrees, and the shapes of zero, 180 and 90 and 270 degrees are exactly the same. , but the direction of the peaks and troughs is opposite, so just calculate the indicators of the two waveforms of zero degree and 90 degrees, and take the average value, namely:

According to the composite video signal whose initial phase is zero, calculate the first color brightness gain difference and the first color brightness delay difference:

Calculate the second color brightness gain difference and the second color brightness delay difference according to the composite video signal with an initial phase of 90 degrees;

The color brightness gain difference is obtained according to the average value of the first color brightness gain difference and the second color brightness gain difference, and the color brightness delay difference is obtained according to the average value of the first color brightness delay difference and the second color brightness delay difference.

In practical applications, the acquisition module 31 , the first determination module 32 , the second determination module 33 , the third determination module 34 and the fourth determination module 35 can all be composed of a central processing unit (CPU), a microprocessor located in the test host (MPU), digital signal processor (DSP), or field programmable gate array (FPGA), etc.

As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the invention may take the form of a hardware embodiment, a software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media having computer-usable program code embodied therein, including but not limited to disk storage, optical storage, and the like.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each process and/or block in the flowchart illustrations and/or block diagrams, and combinations of processes and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to the processor of a general purpose computer, special purpose computer, embedded processor or other programmable data processing device to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing device produce Means for implementing the functions specified in a flow or flow of a flowchart and/or a block or blocks of a block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory result in an article of manufacture comprising instruction means, the instructions The apparatus implements the functions specified in the flow or flow of the flowcharts and/or the block or blocks of the block diagrams.

These computer program instructions can also be loaded on a computer or other programmable data processing device to cause a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process such that The instructions provide steps for implementing the functions specified in the flow or blocks of the flowcharts and/or the block or blocks of the block diagrams.

The above are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the within the protection scope of the present invention.

Claims (12)

1. a composite video signal quality index determination method, is characterized in that, described method comprises: Obtain the upper envelope of the composite video signal, and determine the first amplitude value of the peak of the upper envelope; According to the first amplitude value, determine the value range of the luminance component amplitude in the composite video signal, and determine the value range of the chrominance relative luminance delay in the composite video signal; Assign values to the luminance component amplitude and chrominance relative luminance delay respectively within the corresponding value range, and substitute the assignments into the upper envelope with the luminance component amplitude and the chrominance relative luminance delay as variables function, and determine the second amplitude value of the peak of the function that is substituted into the assigned upper envelope; When the difference between the second amplitude value and the first amplitude value is less than a preset value, determine the color-brightness gain of the composite video signal through the respective assignments of the luminance component amplitude and the chrominance relative luminance delay Difference and color brightness delay difference. 2. The method according to claim 1, wherein the obtaining the upper envelope of the composite video signal comprises: The peak points in each cycle of the composite video signal are acquired, and the peak points are connected to form an upper envelope. 3. The method according to claim 2, wherein the determining the first amplitude value of the upper envelope peak comprises: Acquire the peak point of the upper envelope, measure the amplitude of the peak point, and obtain the first amplitude value. 4. The method according to claim 1, wherein the determining the value range of the luminance component amplitude in the composite video signal comprises: According to the first amplitude value, determine the value range of the luminance component amplitude in the composite video signal from zero to the first amplitude value; The determining the value range of the chrominance relative luminance delay in the composite video signal includes: The range of the chrominance relative luminance delay in the composite video signal is greater than or equal to -π and less than or equal to π. 5. The method according to claim 1, characterized in that, the second amplitude value of the wave crest of the function of the upper envelope curve that is determined to be substituted into the assignment comprises; Based on the function of the upper envelope of the assignment assignment, a maximum value of the function of the upper envelope line assigned to the assignment is calculated, and the calculated maximum value is determined as the second amplitude value. 6. The method of claim 1, wherein the method further comprises: The respective upper envelopes of the plurality of composite video signals obtained based on the plurality of composite video signals, respectively, based on the respective upper envelopes, the respective color-brightness gain differences and color-brightness delay differences of the plurality of composite video signals are determined respectively. ; Take the average value of a plurality of color-brightness gain differences and color-brightness delay differences respectively; The average value is used as the color-brightness gain difference and the color-brightness delay difference of the composite video signal. 7. An apparatus for determining a quality index of a composite video signal, wherein the apparatus comprises an acquisition module, a first determination module, a second determination module, a third determination module and a fourth determination module; wherein, The acquisition module is used to acquire the upper envelope of the composite video signal; the first determining module, configured to determine the first amplitude value of the upper envelope peak; The second determining module is configured to determine, according to the first amplitude value, the value range of the luminance component amplitude in the composite video signal, and determine the value range of the chrominance relative luminance delay in the composite video signal ; The third determination module is configured to assign values to the luminance component amplitude and the chrominance relative luminance delay respectively within the corresponding value range, and substitute the assignment into the luminance component amplitude and the chrominance relative luminance delay. The delay is in the upper envelope function of the variable, and the second amplitude value of the peak of the function of the upper envelope of the assignment is determined; The fourth determination module is configured to determine by each assignment of the luminance component amplitude and the chrominance relative luminance delay when the difference between the second amplitude value and the first amplitude value is less than a preset value The difference in color and brightness gain and the difference in color and brightness delay of the composite video signal. 8. The device according to claim 7, wherein the acquisition module is further configured to: The peak points in each cycle of the composite video signal are acquired, and the peak points are connected to form an upper envelope. 9. The apparatus according to claim 8, wherein the first determining module is further configured to: Acquire the peak point of the upper envelope, measure the amplitude of the peak point, and obtain the first amplitude value. 10. The apparatus according to claim 7, wherein the second determining module is further configured to: According to the first amplitude value, determine the value range of the luminance component amplitude in the composite video signal from zero to the first amplitude value; The second determination module is further configured to determine the value range of the chrominance relative luminance delay in the composite video signal: the range of the chrominance relative luminance delay in the composite video signal is greater than or equal to -π and less than or equal to pi. 11. The apparatus according to claim 7, wherein the third determining module is further configured to: Based on the function of the upper envelope of the assignment assignment, a maximum value of the function of the upper envelope line assigned to the assignment is calculated, and the calculated maximum value is determined as the second amplitude value. 12. The apparatus according to claim 7, wherein the fourth determining module is further configured to: The respective upper envelopes of the plurality of composite video signals obtained based on the plurality of composite video signals, respectively, based on the respective upper envelopes, the respective color-brightness gain differences and color-brightness delay differences of the plurality of composite video signals are determined respectively. ; Take the average value of a plurality of color-brightness gain differences and color-brightness delay differences respectively; The average value is used as the color-brightness gain difference and the color-brightness delay difference of the composite video signal.