JP4186769B2 - GOP cycle detector - Google Patents

Description

  The present invention is a GOP (Group Of Pictures) of a moving image obtained by decoding image information encoded by a high-efficiency encoding method of image information proposed by MPEG (Moving Picture Experts Group) (hereinafter referred to as MPEG method for convenience). The present invention relates to a cycle detection method, a GOP cycle detection device, a video processing method, a video processing device, and a recording medium on which the GOP cycle detection method and the video processing method are recorded.

  In digital broadcasting, DVD (Digital Versatile Disc), etc., encoding is performed by the MPEG method, and the reproduction side decodes this to obtain a video signal. In general, a moving image is composed of a plurality of still images (hereinafter referred to as pictures). In the MPEG system, these still images are compression-coded in units called GOPs. The GOP is composed of at least one I picture (Intra-coded Picture), P picture (Predictive-coded Picture), and B picture (Bidirectionally-coded Picture).

  Each picture is divided according to the method of motion compensation prediction. An I picture is encoded only with information in a frame or field, and motion compensation prediction is not performed. The P picture is encoded by prediction from one direction using the closest one of the immediately preceding I picture and P picture. The B picture is encoded by predicting from two directions using not only the immediately preceding but also the immediately following I picture or P picture. From the viewpoint of the image compression rate, I pictures have the lowest compression rate, followed by P pictures and B pictures.

  On the other hand, the decoded video signal may have a specific image distortion called MPEG noise. What is generated on the mosaic on the screen is called block noise, and what is generated so that the edges of a tree branch, subtitles, etc. are cluttered together is called mosquito noise.

  These image distortions change periodically, and the period is related to the period of the GOP. That is, since these image distortions generated in the I picture continue to affect the P picture or B picture until the next I picture arrives, the I picture period (in many cases coincides with the GOP period) or the P picture period ( The integer fraction of the GOP period is known as the image distortion period.

  As a method for reducing such image distortion, there is a noise reduction method and a video processing apparatus disclosed in Japanese Patent Laid-Open No. 2003-32685. FIG. 14 is a block diagram thereof. In FIG. 14, 1 is an input terminal to which an MPEG-encoded video signal Se is input, and 1001 is a decoder that decodes the encoded video signal supplied to the input terminal 1 and outputs the decoded video signal Sd. An MPEG video decoder for output. Reference numeral 1002 denotes a noise reduction unit that receives Sd and reduces noise. Reference numeral 1003 denotes a picture that is extracted from the GOP layer of the encoded video signal and is currently decoded. This is a detection control unit that detects the noise and controls the noise reduction unit 1002. Reference numeral 2 denotes an output terminal that outputs a video signal in which noise is reduced by the noise reduction unit.

As described above, in the conventional noise reduction method and video processing apparatus, the detection control unit adaptively changes the noise reduction amount of the noise reduction unit according to the picture being decoded by the MPEG video decoder. And a video signal having a high S / N can be decoded (see, for example, Patent Document 1).
JP 2003-32685 A

  However, since it is determined using the GOP header information from the MPEG video decoder whether the picture being decoded is an I, B, or P picture, it has already been decoded by another device or the like. When GOP header information cannot be obtained as in a video signal, it is impossible to determine whether the current picture is I, P, or B, their period, noise reduction effect, or the like.

  In addition, since only MPEG encoded signals are handled, video signals of various sources that have been decoded cannot be handled.

  Further, it was impossible to determine whether the source was MPEG-coded from the decoded video signal.

  The present invention has been made in view of the above problem, and an object thereof is to enable detection of a GOP cycle from a decoded video signal. Another object of the present invention is to make it possible to determine whether a source is MPEG-coded from a video signal. It is another object of the present invention to provide an apparatus for performing optimum image quality correction from a decoded video signal. Another object of the present invention is to provide a storage medium on which means for enabling the GOP cycle to be detected even from a decoded video signal is recorded. It is another object of the present invention to provide a storage medium having recorded thereon means for determining whether a source is MPEG-coded from a video signal. It is another object of the present invention to provide a storage medium storing means for performing optimum image quality correction from a decoded video signal.

In order to solve the above-described problem, a GOP cycle detection device according to the present invention includes a timing signal generating means for generating a timing signal indicating a predetermined period synchronized with a vertical synchronizing signal of an input video signal, and a timing signal from the timing signal generating means. specific frequency component extraction means, and a fluctuation feature amount detecting means for detecting a GOP period of the input video signal, the variation characteristic for extracting a specific frequency component of the input video signal in the predetermined period according to The amount detection means includes a comb filter group that extracts different specific frequencies from the output of the specific frequency component amount extraction means according to each timing signal, and an absolute value calculation that calculates an absolute value of each output from the comb filter group For comparing each output from the means group, an integration means group that integrates each output from the absolute value calculation means group, and each output from the integration means group Ri detects the period of the periodic and P-pictures of the I picture, it is characterized in that it comprises a comparison operation means for detecting the GOP period, the.

  According to the above invention, a GOP cycle detection method, a GOP cycle detection device, and a video capable of detecting a GOP cycle from a decoded video signal in order to obtain a GOP cycle from a feature amount in fluctuation of a specific frequency component amount of an input video signal. It is possible to provide a processing method, a video processing apparatus, and a storage medium.

  According to the present invention, a GOP cycle detection method and a GOP cycle detection device capable of detecting a GOP cycle even from a decoded video signal in order to obtain a GOP cycle from a feature amount in fluctuation of a specific frequency component amount of an input video signal. Can be provided.

  Further, according to the present invention, it is possible to provide a video processing method, a video processing apparatus, and a storage medium that can perform optimal video signal processing according to the GOP cycle even for a decoded video signal. Become.

(Embodiment 1)
FIG. 1 is a block diagram of a GOP cycle detection apparatus according to the first embodiment of the present invention. In FIG. 1, 1 is an input terminal for receiving a video signal, and 3 is an input terminal for inputting a synchronizing signal of the video signal. 7 is a timing generating means for generating a timing signal indicating a predetermined period synchronized with the synchronizing signal, and 4 is for extracting a specific frequency component amount of the input video signal in the predetermined period according to the timing signal from the timing signal generating means. Specific frequency component amount extraction means. Reference numeral 6 denotes calculation means for detecting the GOP cycle of the input signal from the output result of the variation feature quantity detection means. An output terminal 8 outputs the detected GOP cycle.

  The operation of the GOP cycle detection apparatus configured as described above will be described with reference to FIGS. FIG. 2 is a timing diagram showing an example of a timing signal generated by the timing generating means. Reference numeral 20 denotes a valid period of the video signal at the vertical (V) rate. For convenience of explanation, the effective period of the horizontal (H) rate is omitted. Reference numeral 21 denotes a V synchronization signal. 22 is a reset / capture signal given to the specific frequency component extracting means by the timing generating means, and 23 is an enable signal indicating a period during which the frequency components are extracted.

  The specific frequency component extracting unit 4 extracts a specific frequency component of the video signal through a BPF (Band Pass Filter), an HPF (High Pass Filter), or the like. In order to extract the amount of the extracted frequency component in a predetermined period, these absolute values are cumulatively added during the period of the enable signal 23 described above. The cumulative addition result is latched by the reset / capture signal 22 and passed to the variation feature amount detection means 6. The cumulative addition result is reset after latching.

  As another example, a method of performing orthogonal transformation such as FFT (Fast Fourier Transform) or DCT (Discrete Cosine Transform) and using the amplitude characteristic as a result may be used. A two-dimensional filter may be used. A two-dimensional filter using an operator such as Laplacian, Sobel, Prewitt, Kirsch, Robinson or the like is well known.

  When the results obtained as described above are plotted, for example, for each field, the result becomes 30 in FIG. The vertical axis is a standardized detection result in an arbitrary unit, and the horizontal axis is a field. 31 is a result of detecting the same scene as 30 under the same condition as 30 in a state before MPEG encoding / decoding.

  Thus, a specific period is detected in the plot 30 of the MPEG encoded and decoded video signal based on the difference in information amount of each of the I picture, P picture, and B picture. In this example, the GOP cycle at this time, that is, the cycle of the I picture is 30 V cycle, and the cycle of the P picture is 6 V cycle.

  In general, in moving image compression, the human eye uses the fact that the sensitivity of the high frequency component is low and cuts off the information on the high frequency side. Therefore, the frequency component extraction means 4 extracts the high frequency side signal as much as possible. desirable.

  The variation feature amount detection means 6 sequentially receives the result of the frequency component extraction means 4 and detects the periodicity of the result. As a method for detecting periodicity, for example, a BPF or the like that extracts a specific period such as a 30 V period or a 6 V period is configured, and the absolute value thereof is obtained by cumulative addition or integration by an IIR (Infinite Impulse Response) filter or the like. As another method, it can be obtained from the amplitude characteristic using an orthogonal transform such as FFT.

  In order to output a result from each periodic component amount detected in this way, for example, it is obtained by calculating a ratio or difference between the periodic component amount of interest and the average value of other periodic component amounts.

  As described above, the first embodiment of the present invention provides a GOP detection method, a GOP cycle detection device, and a storage medium storing a GOP detection method capable of detecting a GOP cycle even from a decoded video signal. Can do.

(Embodiment 2)
FIG. 4 is a block diagram of the specific frequency component amount extraction means of the GOP period detection device according to the second embodiment of the present invention. Note that blocks having the same functions as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  41 is a memory for storing data of n pixels of the video signal, 42 is a differentiator for calculating the difference between the output of the memory 41 and the video signal, 43 is an absolute value calculating means for calculating the absolute value of the output of the differencer 42, Reference numeral 44 denotes cumulative addition means for cumulatively adding the output of the absolute value calculation means while the effective cumulative addition period signal is H and resetting the cumulative addition result in accordance with the reset / capture signal. Reference numeral 45 denotes latch means for latching the output of the cumulative addition means 44 in accordance with the reset / capture signal.

  A difference between n pixels is calculated by the memory 41 and the differentiator 42. n may be an arbitrary integer. For example, if n is 1, the difference between pixels adjacent in the horizontal direction can be calculated. That is, it becomes HPF at the Nyquist frequency, and high frequency components can be easily and efficiently extracted. If n is 2, 3, or 4, a comb filter is formed, and by adjusting the trap position, the influence of unnecessary frequency interference can be removed. The total amount of the high-frequency components in one field can be extracted by accumulating the absolute values of the frequency components thus determined for a predetermined period, for example, one field period.

  As described above, in the second embodiment of the present invention, it is possible to provide a storage medium storing a GOP detection method, a GOP cycle detection device, and a GOP detection method, with a specific frequency component extraction unit having a simple configuration. it can.

(Embodiment 3)
When digital processing such as CG (Computer Graphics) or nonlinear editing is performed, a video signal is usually processed in units of frames. Thereafter, when converted to an interlace signal such as NTSC (National Television System Committee) method or high-definition method, a 2V period may be detected in the above-described embodiment.

  In particular, when a simple cumulative addition of absolute values of BPF output is used for the variation feature quantity detection means 6, the effect will be output. The object of the present embodiment is to prevent the detection of a period originally unrelated to GOP due to such an interlaced signal.

  FIG. 5 is a timing chart showing the operation of the timing generating means 7 in the third embodiment of the present invention.

  In the figure, reference numeral 52 denotes a reset / capture signal B, which is cumulatively added by the specific frequency component extracting means over a 2V period. In this way, since cumulative addition is performed for two field periods, detection that is not affected by the 2V cycle is possible.

  As described above, in this embodiment, since a frequency component in one frame period is extracted, it is possible to provide a video display device that can absorb fluctuation due to interlace with a simple circuit.

(Embodiment 4)
Various periods are temporarily detected when the scene on the screen is switched or there is intense movement, but these are not related to the GOP period. In the above-described embodiment, this may cause a malfunction. In addition, in the method of detecting the frequency distribution by the orthogonal transformation represented by FFT or the like, there is a problem that the amount of calculation is greatly increased from the viewpoint of resolution if detection of a long period such as 30 V period or a period that is not a multiple of 2 is performed. It was. The purpose of this embodiment is to improve the above problems.

  FIG. 6 is a block diagram of a GOP period detection device according to the fourth embodiment of the present invention. Note that blocks having the same functions as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  In FIG. 6, reference numeral 61 denotes a filter group that receives the result from the specific frequency component amount extraction means 4 and performs a filter process, and each filter has a different frequency characteristic. Reference numeral 62 denotes an absolute value calculation means group that performs an absolute value calculation for each output from the filter group 61, and 63 denotes an integration means group that performs integration for each output from the absolute value calculation means group 62. Reference numeral 64 denotes comparison operation means for comparing magnitude relationships and ratios from the outputs of the integrating means group 62 and outputting the results as GOP cycle detection results.

  FIG. 7 is a graph plotting the output of the integration means group at a certain point in time. The vertical axis is an output value normalized by a predetermined value, and the horizontal axis is a frequency component meaning each integrating means group 62. The BPF is configured so that each frequency component can be extracted by a corresponding filter. For example, according to the graph of FIG. 7, it can be seen that the output of the integrating means connected to the filter for detecting the 6V period and the 30V period shows a large value. For example, the comparison calculation means 64 can determine that the 6V period 30V period is detected by comparing the magnitude relation. Furthermore, the strengths of the 6V period and the 30V period can be easily determined by obtaining the ratio and difference from the average values of the other graph results.

  As described above, in the present embodiment, the fluctuation of the result obtained by the specific frequency extracting means is obtained from the magnitude relation of the plurality of results obtained by smoothing the absolute values of the filters having different characteristics. It is possible to provide a storage medium storing a GOP detection method, a GOP cycle detection device, and a GOP detection method that are simple and have few malfunctions.

(Embodiment 5)
FIG. 8 is a block diagram of one filter in the filter group 61 of the GOP period detection device according to the fifth embodiment of the present invention.

  In FIG. 8, 81 is a memory for storing m pieces of data, where m is an arbitrary natural number, and 82 is a subtractor. This filter is called a comb filter. FIG. 9 shows the amplitude characteristics of the comb filter when m changes. As described above, the comb filter has notches at equal intervals on the frequency axis. For example, when m = 4 and m = 2, the notch is entered at the normalized frequency of 0.5.

  FIG. 10 is a graph plotting the output of the integrating means group 62 for a certain input signal when the filter group 61 is composed of comb filters having various m. Small values are obtained in the order of m = 30, m = 6, and m = 24. On the other hand, m = 3 is a large value compared to them. Therefore, it is considered that there is no 3V periodic component and a 6V periodic component is detected. In addition, 24 is a multiple of 6, but the value at m = 24 is larger than the value at m = 6, and hence the 6V periodic component is considered to be dominant. Similarly, 30 is a multiple of 6, but the value of m = 30 is smaller than the value of m = 6, so the 30V periodic component is considered to be larger than the 6V periodic component. From the above, it can be determined that the largest frequency component is 30V period and then 6V period. When detecting the GOP cycle, it is sufficient if at least two of the cycle of the I picture and the cycle of the P picture can be detected, and it is sufficient if the upper two cycle components can be detected. The detected value tends to be different when m is an even number and when it is an odd number because the 2V period is detected. In this way, by comparing the magnitude relationships of a plurality of comb filters having different m values, the GOP cycle can be detected with a simple circuit.

  As described above, the present embodiment stores a GOP detection method, a GOP cycle detection device, and a GOP detection method that can detect a GOP cycle with a small amount of calculation such as comparison between a memory, a subtractor, and a magnitude relationship. Storage media can be provided.

(Embodiment 6)
FIG. 11 is a block diagram of the sixth embodiment of the present invention. Note that blocks having the same functions as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  In FIG. 11, reference numeral 111 denotes signal processing means for performing signal processing on the input video signal based on the result of the variation feature amount detection means 6.

  For example, if the signal processing unit 111 performs a process for reducing image distortion caused by an MPEG system such as an ε-Δ filter, if the threshold value is increased in order to enhance the effect, screen blur occurs as a side effect, and screen blur is suppressed. There is a problem that the effect is reduced if the threshold is lowered. When the input source is changed and a non-MPEG signal is input, the effect should be as small as possible. If the result of the variation feature amount detection means 6 is used, the threshold value can be controlled in accordance with the detected amount of the GOP cycle.

  As described above, according to the present embodiment, since the GOP cycle can be detected even with a decoded video signal, there is an advantageous effect that the optimum video signal processing can be performed according to the detected GOP cycle.

(Embodiment 7)
There is a tendency that a GOP cycle component is detected small in an image in which an input signal is greatly compressed and a signal in which no high frequency component is present in the source, and strongly detected in a high-definition video signal. If signal processing parameters such as noise reduction are controlled as they are, there is a problem that the effect is controlled to be reversed. If the control sign is reversed, an adverse effect occurs when a signal other than the MPEG system is input. The object of the present embodiment is to solve such a problem.

  FIG. 12 is a block diagram according to the seventh embodiment of the present invention. Note that blocks having the same functions as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  In FIG. 12, reference numeral 120 denotes frequency characteristic detection means for detecting the frequency characteristic of the input video signal. Reference numeral 121 denotes parameter control means for controlling the parameters of the signal processing means 111 using the results of the output of the variation feature quantity detection means 6 and the output of the frequency characteristic detection means 120. The frequency characteristic detection unit 120 may detect the frequency that the video processing unit 111 wants to focus on.

  For example, when the side effect of a parameter controlled by the signal processing unit 111 is a high-frequency screen blur such as noise reduction, the screen blur is not noticeable if the original image frequency characteristics are known. Therefore, when the frequency characteristic detection unit 120 determines that the high range is relatively small with respect to the middle and low range, the parameter control unit 121 can control the parameter more strongly, thereby enhancing the effect.

  As described above, according to the present embodiment, a video processing method, a video processing apparatus, and a video which can achieve both control and effect based on the GOP detection result by strengthening the effect even when a side effect occurs is not noticeable. A storage medium storing the processing method can be provided.

(Embodiment 8)
When the image of the input signal is accompanied by intense movement, there is a problem that the detection of the GOP periodic component amount is small or cannot be detected. The object of the present embodiment is to solve such a problem.

  FIG. 13 is a block diagram according to the eighth embodiment of the present invention. Note that blocks having the same functions as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  In FIG. 13, reference numeral 122 denotes APL fluctuation detecting means for detecting fluctuation of APL (Average Picture Level) of the input video signal. A parameter control unit 123 controls the parameters of the signal processing unit 111 using the results of the output of the variation feature amount detection unit 6 and the output of the APL variation detection unit 122.

  The operation of the present embodiment configured as described above will be described. The APL fluctuation detecting means 122 obtains the average luminance (APL) of the video signal by accumulating each pixel of the input signal and dividing by the number of additions. Next, the amount of change is detected from the past APL. For example, a value obtained by performing HPF processing (differentiation) and integrating the absolute value (LPF) may be used. If the APL change amount obtained in this way is multiplied by, for example, a GOP cycle detection result by the parameter control means 123, the above-described problem can be solved. Further, if the APL change amount is large and the GOP cycle detection result is equal to or larger than a predetermined value, the parameter control unit 123 may control the parameter of the signal processing unit 111 to be large.

  As described above, according to the present embodiment, the video processing method and the video processing improved in the problem that the detection of the GOP periodic component amount becomes small or cannot be detected when the image of the input signal is accompanied by intense motion. A storage medium storing the apparatus and the video processing method can be provided.

  The GOP cycle detection method, the GOP cycle detection device, the video processing method, the video processing device, and the storage medium according to the present invention have the effect that the GOP cycle can be detected even from the decoded video signal, The present invention is useful in a cycle detection method, a GOP cycle detection device, a video processing method, a video processing device, and a recording medium on which these GOP cycle detection method and video processing method are recorded.

Block diagram of the GOP cycle detection device in the first embodiment Timing diagram from timing signal generator Graph plotting the results of specific frequency component extraction means Block diagram of GOP cycle detection apparatus in second embodiment Timing diagram from timing signal generating means in the third embodiment Block diagram of GOP cycle detection device in fourth embodiment Graph plotting the output of the integration means group Block diagram of one filter in the filter group 61 of the GOP period detection device in the fifth embodiment Diagram showing amplitude characteristics of comb filter Graph plotting the output of the integration means group Block diagram of a video processing apparatus in the sixth embodiment Block diagram of a video processing apparatus in the seventh embodiment Block diagram of a video processing apparatus in the eighth embodiment Block diagram of conventional noise reduction method and video processing apparatus

Explanation of symbols

1, video signal input terminal 2, video signal output terminal 3, synchronization signal input terminal 4, specific frequency component extraction means 6, fluctuation feature quantity detection means 7, timing generation means 8, result output terminal 20, video signal V rate Valid period 21, V sync signal 22, reset / capture signal 23, enable signal 30, video signal plot 31 after MPEG decoding, source video signal plot 41, memory 42 for storing data for n pixels, difference unit 43, absolute value calculation means 44, cumulative addition means 45, latch means 52, reset / capture signal B
61, filter group 62, absolute value means group 63, integration means group 64, comparison operation means 81, memory 82, differentiator 110, video signal output terminal 111, signal processing means 120, frequency characteristic detection means 121, parameter control means 122 , APL fluctuation detection means 123, parameter control means 1001, MPEG video decoder 1002, noise reduction section 1003, detection control section 1005, limiter 1006, multiplier 1007, subtractor

Claims (3)

Timing signal generating means for generating a timing signal indicating a predetermined period synchronized with a vertical synchronization signal of the input video signal, and a specific frequency component amount of the input video signal in the predetermined period according to the timing signal from the timing signal generating means with a specific frequency component extraction means for extracting, and a fluctuation feature amount detecting means for detecting a GOP period of the input video signal, the variation characteristic amount detection means, said specific frequency component in accordance with each of the timing signals A comb filter group for extracting different specific frequencies from the output of the quantity extracting means, an absolute value calculating means group for calculating an absolute value of each output from the comb filter group, and integrating each output from the absolute value calculating means group And a period of I picture and a period of P picture are detected by comparing each output from the integration means group, and GO GOP period detection apparatus characterized by comprising: a comparison operation means for detecting the period, the. The specific frequency component amount extraction unit includes: a pixel difference calculation unit that calculates an absolute value of a level difference between predetermined pixels in the predetermined period; and a cumulative addition unit that cumulatively adds the output of the pixel difference calculation unit for a predetermined period. The GOP cycle detection device according to claim 1, wherein the GOP cycle detection device is configured. 2. The GOP cycle detection device according to claim 1, wherein the predetermined period extends over two vertical periods.

Images