KR100487374B1 - Apparatus for generating thumbnail image of digital video - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thumbnail image generating device among additional functions provided by a personal video recorder or a video browser installed in a digital TV, and more particularly, a DC image generated by a DC value of an I picture. A thumbnail image generated from the DC value of the I picture is calculated by calculating the image complexity in the horizontal and vertical directions, and comparing the horizontal and vertical image complexity with a preset horizontal and vertical threshold, respectively. By determining whether the image is an image and not using the thumbnail image determined as the blank image, it is possible to provide only a thumbnail image that is meaningful to the user.

Description

Apparatus for generating thumbnail image of digital video}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a thumbnail image generating apparatus among additional functions provided by a personal video recorder (PVR) mounted on a digital TV, or other system that provides a function such as a video browser, and more particularly, a thumbnail image. The present invention relates to an apparatus for automatically generating a thumbnail image only for an image that is meaningful to the user by calculating a complexity of an image currently input during the generation process.

In general, a thumbnail image displays a specific frame of a video smaller than the original size for browsing or searching, and provides implicit information about the video to the user in the form of a still image rather than a video. Use for the purpose of providing. These thumbnail images summarize the contents of the video recorded in the PVR into several thumbnails, generate key frames for video indexing, or preview or content summary of the program in the program guide. There are various fields of application such as the generation of representative images for the purpose.

Conventional methods for generating a thumbnail image can be classified into a method of decoding a frame of video encoded with MPEG and then directly reducing a reconstructed frame and a method using a DC value of an I picture. In this case, the former method of directly reducing a frame of a video needs to decode all pixels of the frame, which requires a variable length decoder, which is a hardware burden. In addition, in the case of a B or P picture that is not an I picture, the B or P picture needs to be decoded and then converted into an intra-coded still picture using a compression method such as JPEG. On the other hand, the latter method of creating a thumbnail image using the DC of the I picture of the video does not require such a variable decoder, so it is less burdensome in hardware and the DC value is directly used as the pixel value of the thumbnail image. Therefore, this method generates the 1/64 size thumbnail image of the original image by a simple method without complicated decoding and re-encoding process, which has the advantage of ease of implementation and efficiency.

The thumbnail image generated by the above methods provides the user with a method of implicitly representing the entire contents of the video as a representative image of a smaller size, that is, a lower resolution than the original image, so that the video frame that is the source of the thumbnail image is noisy. There should be no blanks, overlaps due to scene transitions, etc., and at the same time, the delivery of information about the entire video to the user should be clear. Therefore, for the thumbnail image, an unclear image generated by camera movement such as a sudden zoom and blur due to the movement of the subject should be avoided.

However, the conventional thumbnail image generating apparatus does not provide an effective method of detecting and filtering an image that is not suitable for use as a thumbnail image. That is, in the conventional thumbnail image generating apparatus, a thumbnail is generated for an arbitrary I picture without analyzing the content of the image. In this case, a method of generating a thumbnail image for an I picture generated at a predetermined interval by a hardware preset or user input sample rate is used. However, in the digital video that is actually received, the original image may be noisy, scenes or other special effects may cause the image to be very dark or have a single color without the actual content, or may be caused by excessive zooming or close-up. Sometimes the image itself is meaningless or the amount of information contained in the image is weak. Thumbnail images generated from such images are very difficult for a user to identify the contents, and as a result, a problem arises in providing implicit information about the entire video.

That is, in the conventional thumbnail image generation method, there is no method for automatically determining the validity of the thumbnail by analyzing the thumbnail image, so that it does not effectively cope with the meaningless image, which has many problems in effectively extracting the representative image.

The present invention is to solve the above problems, an object of the present invention is to calculate the complexity of the input image to generate a thumbnail image by not generating a thumbnail image for a low complexity image, the user means more It is an object of the present invention to provide a thumbnail image generating apparatus capable of viewing only a clear thumbnail image.

An apparatus for generating a thumbnail image of a digital video according to the present invention for generating the above object generates a thumbnail image from an I picture of an MPEG encoded video stream, but has a low complexity or almost no texture in the process. Thumbnail images generated from non-existent or background-only images, single-color dominated images caused by poor lighting conditions, and low-luminance images, and meaningless images resulting from excessive zooming or close-up, and then detecting them. By blocking the use of the, there is a feature to provide a more meaningful and clear thumbnail image to the user.

In the present invention, an image that is too dark or simple colors, or because of the complexity and blur due to the cause of blur and zoom, the content or information that can be delivered to the user is very small, the image that is not suitable for generating a thumbnail image blank ( blank) Defined as an image.

In accordance with an aspect of the present invention, a thumbnail image generating apparatus according to the present invention includes a DC decoder for parsing only a DC value of an I picture from an input video stream, a temporary buffer for storing DC values output from the DC decoder, Calculates the image complexity in the horizontal and vertical directions of a memory for generating and storing a thumbnail image by receiving a DC value output in slice units from the temporary buffer, and a DC image generated by the DC value output from the DC decoder, And a blank image determining unit configured to compare the calculated horizontal and vertical image complexity with a preset horizontal and vertical threshold and determine whether the I picture is a blank image, and to store the DC value in the temporary buffer. And controlling the output and, if determined to be a blank image by the blank image determination unit, stored in the memory. It characterized in that the buffer comprises a control unit for controlling so that a nail image is used.

The blank image determiner calculates horizontal and vertical image complexity of the DC image by using the DC value of the Y component or the combination of the DC value of the Y component and the DC value of the CbCr component output from the DC decoder. do.

When the image complexity of the horizontal and vertical directions for one DC image is calculated, the blank image determiner determines whether the calculated image complexity in the horizontal direction is less than or greater than a first threshold value set in advance, and the vertical image. The method may determine whether the I picture is a blank image based on a comparison result after comparing whether the complexity is smaller than or greater than a preset first vertical threshold.

The blank image determiner is configured to perform the I when the calculated image complexity in the horizontal direction is less than the first horizontal threshold value preset and / or the image complexity in the vertical direction is less than the first vertical threshold value preset. The picture is distinguished by a blank image.

The blank image determiner is larger than the first horizontal and vertical threshold values calculated in the horizontal and vertical directions than the first horizontal and vertical threshold values set in the horizontal and vertical directions. The method determines whether the I picture is a blank image according to a comparison result after comparing whether the image complexity in the vertical direction is smaller or larger than the preset second vertical threshold value.

The blank image determiner may determine the I picture as a blank image when the calculated image complexity in the horizontal and vertical directions is greater than a preset threshold value in the second horizontal and vertical directions, respectively.

The blank image determination unit increases the image complexity in the horizontal direction when two DC values adjacent to each other in the horizontal direction are different, and increases the image complexity in the vertical direction when two DC values adjacent in the vertical direction are different from each other. The image complexity of the current DC image and the image complexity of the vertical direction are respectively obtained by applying to all DC values of the DC image.

The blank image determiner may use only upper k bits of each DC value for comparison.

If it is determined that the input I picture is a blank image, the buffer controller controls the thumbnail image generated from the next I picture to be overwritten to a position in the memory where the thumbnail image generated from the I picture is stored.

The buffer controller may include as many blank vectors as the number of thumbnail images that can be stored in the memory, and then store all the thumbnail images in the memory regardless of whether they are blank or not, according to a result of the determination of the blank image determining unit. It is characterized by displaying the presence or absence of the blank.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

Hereinafter, with reference to the accompanying drawings illustrating the configuration and operation of the embodiment of the present invention, the configuration and operation of the present invention shown in the drawings and described by it will be described as at least one embodiment, By the technical spirit of the present invention described above and its core configuration and operation is not limited.

The present invention analyzes the DC value of an I picture for generating a thumbnail image to determine whether the corresponding I picture is a blank image, and does not use a thumbnail image generated from the I picture determined as the blank image. In particular, the present invention is to calculate the image complexity in the horizontal and vertical direction in the DC image unit generated by the DC value of the I picture, respectively, and the horizontal and vertical threshold value preset in the horizontal and vertical image complexity and The characteristics of the blank image are determined by comparing them with each other.

1 is a block diagram showing an embodiment of the overall configuration of a thumbnail image generating apparatus according to the present invention, a DC decoder 101 for parsing only the DC value of an I picture in an MPEG encoded video stream, the parsing A blank image determination unit 102 determining whether a thumbnail image currently generated from the DC value is valid, a temporary buffer 103 temporarily storing the parsed DC value in line or slice units for thumbnail image generation, and the The DC value is stored in the temporary buffer 103, the DC value stored in the temporary buffer 103 is transmitted to the thumbnail dedicated memory through the thumbnail memory interface 105 in units of slices, and the blank image determination unit 102 is also used. The buffer controller 104 controls the overall flow of the system, such as controlling the use of the thumbnail image stored in the thumbnail dedicated memory in accordance with the determination result of the It is sex.

That is, the buffer controller 104 may store data stored in the buffer 103 through the thumbnail memory interface 105 at a specific location of the thumbnail dedicated memory.

The DC decoder 101 has a structure that can parse only the DC value and image information parameter of the I picture in a very simple structure compared to the VLD of a general MPEG video decoder. In the present invention, since a thumbnail image is generated, the DC decoder 101 does not need to decode the P picture and the B picture, and removes the variable decoding table and hardware parts necessary to obtain other AC values.

That is, the DC decoder 101 decodes an information parameter of an image, such as a picture size, and a DC value of each block in an I picture stream of MPEG video, thereby blanking the image determining unit 102 and the thumbnail temporary buffer 103. To send).

In this case, in order to simplify the function of the blank image determining unit 102, the analysis may be performed only on the luminance component of the image. In this case, a DC value corresponding to blocks 0 to 3 of each macro block, that is, a Y component Only the DC values of the transmission are transmitted to the blank image determiner 102.

Here, each DC value has a value from 0 to 255, which is represented by 1 byte of data. In general, in an MPEG video having a 4: 2: 0 format, a DC value means an average value of each block, and since there are six blocks per macroblock, six DC values are input from one macroblock. DC values of the first four (that is, blocks 0 to 3 of each macro block) are DC values of the Y component, and the remaining two (ie blocks 4 and 5) are the Cb and Cr components, respectively. It corresponds to DC value.

On the other hand, the temporary buffer 103 must transmit all DC values necessary for the configuration of the thumbnail image. That is, the thumbnail image is stored in a thumbnail-only memory in a complete form, and under the control of the buffer controller 104, the data corresponding to one slice is stored in the temporary buffer 103, and when the slice ends, the temporary image The data in the buffer 103 is transferred to the thumbnail dedicated memory. Here, the slice refers to one horizontal line of the macro block according to the ATSC standard. The reason for generating the thumbnail image based on the slice is that the buffer 103 is controlled based on the slice based on the characteristics of the input MPEG video stream. Because it is efficient.

The buffer controller 104 controls the input and output of the temporary buffer 103, the temporary buffer 103 is implemented in the form of a double buffer for the efficiency of the input and output. That is, when the slice ends, the buffer controller 104 performs a process necessary to transfer the thumbnail data stored in the temporary buffer 103 to the thumbnail dedicated memory together with the thumbnail dedicated memory interface 105. The thumbnail dedicated memory interface 105 controls a process of directly writing data stored in the temporary buffer 103 to a thumbnail dedicated memory, and controls all other processes for accessing the thumbnail dedicated memory.

The thumbnail image generating apparatus of the present invention shown in FIG. 1 is a block diagram in consideration of scalability, and the thumbnail dedicated memory interface 105 may be used in connection with another external unit to access the thumbnail dedicated memory. That is, in addition to the thumbnail image generating apparatus according to the present invention, a block for using a thumbnail dedicated memory may be connected to the thumbnail dedicated memory interface 105. In such a case, the thumbnail dedicated memory may be expanded to enable input and output of other data in addition to the thumbnail data.

The blank image determiner 102 determines whether the current image is blank by performing a series of processes to be described later using the input DC value. As described above, when the blank image determination unit 102 intends to analyze an image using only the luminance Y component of the image, only the DC values corresponding to blocks 0 to 3 of each macro block are used. In addition, if a blank is to be determined using a specific component or a combination of several components (including chrominance components) of the other image, the blank determination function may be performed using all DC values of the corresponding components.

The blank image determination unit 102 determines whether the current image (ie, the I picture whose complexity is calculated) is blank based on the complexity calculated while the DC values of the I picture are input when the I picture ends. The corresponding signal BLANK is output. For example, when the current image is determined to be blank, a signal BLANK = '1' is output. Otherwise, a signal BLANK = '0' is output.

Therefore, when the BLANK signal has a value of '0', it can be seen that the thumbnail image generated from the DC value of the I picture and stored in the thumbnail dedicated memory is valid. On the contrary, when BLANK = '1', the user or PVR system may inform that the thumbnail image generated from the DC value of the I picture and stored in the thumbnail dedicated memory is a blank image. That is, the user or the PVR system may know whether the currently stored thumbnail image is available using the BLANK signal. For example, when BLANK = 1, the user may be a blank image, or the PVR system may prevent a thumbnail image corresponding to the blank image from being displayed on the screen.

The above is a description of the overall configuration of the thumbnail image generating apparatus according to the present invention, and a detailed description of the blank image determining unit 102, which is a core function of the present invention, will be described.

FIG. 2 illustrates an embodiment of an operation flowchart of the blank image determiner 102, wherein a DC value input to the blank image determiner 102 is limited to a specific component or a combination of various components required for blank determination. do. For example, when determining whether to use a blank using only luminance components of an image, only a DC value corresponding to blocks 0 to 3 corresponding to the Y component of the image is input to one macro block.

Hereinafter, an embodiment of the blank image determining unit 102 using only the Y component will be described.

In this case, the size of the DC image (that is, the thumbnail image) generated using only the DC value of the I picture varies according to the resolution. For example, the DC video of the HD video having a resolution of 1920x1088 and the SD video having a resolution of 720x480 have a resolution of 240x136 and 90x60, respectively.

That is, when the DC value of the luminance component of the I picture parsed by the DC decoder 101 is input (step 201), the blank image determination unit 102 uses the input DC value to perform horizontal image complexity. TR_H indicating and TR_V indicating the image complexity in the vertical direction are calculated (step 202). A more detailed description of the method of calculating the horizontal image complexity TR_H and the vertical image complexity TR_V will be described later with reference to FIG. 3. In FIG. 2, this value is used to determine whether the image is blank. Describe how to do it.

At this time, a pair of TR_H and TR_V is calculated for each DC image, and this value is compared with each of the first threshold values TH1_H and TH1_V preset as shown in Equation 1 below (step 203). Here, when at least one of the two conditions of Equation 1 is satisfied, the blank image determining unit 102 determines the current image as a blank image and sets the blank signal to '1' and then the buffer control unit 104. (Step 204). If the blank signal is '1', the buffer controller 104 controls not to use a thumbnail image corresponding thereto (step 205).

Condition 1: TR_H <TH1_H

Condition 2: TR_V <TH1_V

In the embodiment of the present invention, TH1_H and TH1_V are set to h_size / 16 and v_size / 16, respectively, based on the results of experiments on various MPEG video streams, and h_size and v_size are the horizontal and vertical sizes of the DC image. it means. Therefore, when the comparison operation is hardware-configured, the comparison operation may be performed after setting the threshold values TH1_H and TH1_V except for the lower 4 bits of h_size and v_size.

For example, assuming that HD-quality video having a resolution of 1920x1088 is input, the resolution of the DC image at this time is 240 (h_size) x136 (v_size), so that TH1_H and TH1_V are 15 (= 240/16) and 8, respectively. (= 136/16) is set. That is, if the complexity TR_H of the horizontal component is less than 15, or the complexity TR_V of the vertical component is less than 8, or the complexity TR_H of the horizontal component is less than 15 and the complexity TR_V of the vertical component is less than 8, the DC image is blank. The image is judged as an image, and a thumbnail image is not generated from the DC image.

In the case where the complexity TR_H of the horizontal component and the complexity TR_V of the vertical component do not satisfy both conditions of Equation 1 in step 203, that is, when TR_H is larger than TH1_H and TR_V is larger than TH1_V, It is checked whether or not both conditions are satisfied (Equation 2) (step 206).

Condition 1: TR_H <TH2_H

Condition 2: TR_V <TH2_V

That is, when both TR_H and TR_V are smaller than each of the preset second thresholds TH2_H and TH2_V, the blank image determiner 102 determines the current image as a blank image, sets the blank signal to '1', and then buffers it. Output to control unit 104 (step 204). If the blank signal is '1', the buffer controller 104 controls not to use a thumbnail image corresponding thereto (step 205).

In the embodiment of the present invention, the second horizontal and vertical thresholds TH2_H and TH2_V are also set to h_size / 8 and v_size / 8, respectively, based on the experimental results of the actual MPEG video, which is higher than the lower 3 bits of h_size and v_size. It is easily implemented by performing comparison operation using only 5-bit values. For example, in the above-described HD video having a resolution of 1920x1088, TH2_H and TH2_V are set to 30 (= 240/8) and 17 (= 136/8), respectively. That is, when the complexity TR_H of the horizontal component is less than 30 and the complexity TR_V of the vertical component is less than 17, the DC image is determined to be a blank image, and a thumbnail image is not generated from the DC image.

As a result, after calculating the complexity of the current image using a DC value corresponding to the Y component of the I picture, and if any one of the two conditions of Equation 1 is satisfied, the current image is determined as a blank image, two Although not satisfied, the current image is determined to be a blank image when both conditions of Equation 2 are satisfied. In this case, a thumbnail image corresponding thereto is not used.

In the present invention, the threshold values in the first horizontal and vertical directions and the threshold values in the second horizontal and vertical directions are set to h_size / 16, v_size / 16, h_size / 8, and v_size / 8, respectively. It is just one embodiment, and may vary by designer, and thus the present invention is not limited thereto.

On the other hand, if the conditions of step 203 and step 206 are not satisfied, that is, the complexity of the horizontal and vertical components, TR_H and TR_V, are both greater than the first thresholds TH1_H and TH1_V, respectively, and the TR_H and TR_V are the second thresholds TH2_H If it is not less than TH2_V, the blank image determination unit 102 determines that the current image is not the blank image and outputs the blank signal to the buffer controller 104 as '0' (step 207). If the blank signal is '0', the buffer controller 104 controls a thumbnail image corresponding thereto to be used (step 208).

3 is a flowchart illustrating an example of a process of calculating an image complexity TR_H of a horizontal component and an image complexity TR_V of a vertical component of a corresponding DC image of FIG. 2.

First, the TR_H and TR_V are initialized to 0 before the first DC value of the image is input, and then the DC value is input (step 301). When the input DC value satisfies the following Equation 3, each of them increases by one. (Step 302).

TR_H = TR_H + 1, if Q (f (i, j)) ≠ Q (f (i, j-1));

TR_V = TR_V + 1, if Q (f (i, j)) ≠ Q (f (i-1, j));

That is, TR_H is increased when there is a difference between two adjacent DC values in the DC image, and TR_V is increased when a difference between two adjacent DC values in the vertical direction occurs.

In Equation 3, f (i, j) denotes a pixel value (eg, DC value of each Y block) of an input DC image, i and j respectively mean vertical and horizontal coordinates, and Q ( .) Is a preset quantization function, which means that the parameter is divided by 8 according to an embodiment of the present invention. Therefore, each pixel value of the DC image is compared with a value corresponding to the upper 5 bits except the lower 3 bits by a quantization function. This is because a small difference in the lower bits does not really make a big difference to the naked eye, so the lower bits are not used for the comparison operation.

When the two consecutive pixel values are different from each other through the comparison operation, TR_H or TR_V is increased. The quantization function Q (.) Described above divides the parameter by 8, but this is divided by 4 by the designer (i.e., only the values corresponding to the upper 6 bits except the lower 2 bits are used for the comparison operation) or 16 (that is, only the value corresponding to the upper 4 bits except the lower 4 bits may be used for the comparison operation) and the like, and thus the present invention will not be limited to the example described above.

At this time, the comparison process first compares the difference between the two pixel values in the horizontal direction, and after comparing the one line, compares the difference between the two pixel values in the horizontal direction of the current line and at the same time the vertical direction of the previous line and the current line. The process of comparing the difference between the two pixel values is performed until the end of the DC image is detected.

That is, in step 302, if two neighboring pixel values in the horizontal direction are different from each other, the image complexity TR_H in the horizontal direction is increased by one, otherwise, the previous value is maintained as it is. In addition, when two neighboring pixel values in the vertical direction are different from each other, the image complexity TR_V in the vertical direction is increased by one, otherwise the previous value is maintained as it is.

Then, it is determined whether it is the end of the line (step 303), and if it is not the end, j is increased by 1 for comparison with the next pixel in the line (j = j + 1), and then the process returns to the step 301 as described above. Steps are repeated (step 304), and if it is the end of the line, it is determined whether it is the end of the DC image (step 305). If it is determined in step 305 that it is not the end of the DC image, it is initialized to j = 0 for comparison of the next line, i increases by 1 and then returns to step 301 to repeat the above steps (step 306).

In this case, the blank image determining unit 102 needs a temporary buffer to store one previous DC value because a comparison with the previous DC value generated in the horizontal direction is necessary to calculate the image complexity TR_H in the horizontal direction. In addition, in order to calculate the vertical image complexity TR_V, a previous DC value generated in the vertical direction is required, so a temporary buffer for storing one line of data is required.

Therefore, the minimum size of the temporary buffer required by the blank image determining unit 102 of the thumbnail image generating apparatus according to the present invention is (h_size + 1) * 5 bits. Here, (h_size + 1) is one line size of the temporary buffer 103 necessary for calculating the vertical image complexity TR_V. The reason why the size of the temporary buffer 103 for storing one previous DC value is 5 bits in order to calculate the image complexity TR_H in the horizontal direction is because the lower 3 bits are excluded in the comparison operation of the pixels. Is because it is 5 bits.

If it is determined in step 305 that the DC image is the end, that is, when the last DC value of the current image is input, TR_H and TR_V are divided into (v_size-1) and (h_size-1), respectively (ie ) (Step 307). As a result, TR_H and TR_V mean an average value of difference occurrence frequencies of adjacent pixels in the horizontal direction and the vertical direction, and are used as parameters in the present invention to determine the complexity of the texture of the current image.

On the other hand, if the current image is determined to be blank through the above-described process, the system using the PVR or other thumbnail image should not display the thumbnail image of the corresponding image through software or hardware methods. For example, if the current thumbnail image is blank, a method such as overwriting the next thumbnail image in a location where the current thumbnail image is already stored in the thumbnail dedicated memory may be used, or by using a blank vector or the like. Only thumbnails with a blank value of '0' can be software-selected for use in thumbnail displays or other applications.

FIG. 4 illustrates an embodiment of a thumbnail image control method using an address value of a thumbnail dedicated memory when the current image is determined to be a blank image. FIG. 4A is an operation flowchart and FIG. 4B is a thumbnail dedicated memory. The map state is showing.

That is, in step 401, it is determined whether the BLANK signal is '1'. If it is '1', it is determined as a blank image, and if it is '0', it is determined that it is not a blank image.

In step 402 and 403, ThmAddrStart refers to a start address in a thumbnail dedicated memory in which a thumbnail image to be generated next is stored. CurrThmStart represents the start address of the thumbnail image currently stored in the thumbnail dedicated memory. ThmPictSize refers to the size of each thumbnail and represents the size of the space occupied by each thumbnail image in the thumbnail dedicated memory. That is, when the current video is finally determined as a blank, the thumbnail for the current video is already stored in the thumbnail dedicated memory. This is because thumbnails are stored in slices. In other words, it is not possible to determine whether to blank the image until the last slice of the current image is finished, and the DC values corresponding to the slices of the previous image are already stored in the thumbnail dedicated memory.

Therefore, if the current image is determined to be blank in step 401, step 402 overwrites the next thumbnail image to a thumbnail dedicated memory space in which the current thumbnail image is stored, thereby using the thumbnail image generated from the image determined as blank. (ThmAddrStart = CurrThmStart). In this case, only thumbnail images, not blanks, may be stored in the thumbnail dedicated memory, thereby increasing memory efficiency. For example, assuming that the second and fourth images are determined to be blank images, the thumbnail image corresponding to the third image is overwritten at the position where the thumbnail image corresponding to the second image is stored, and the original fourth image is overwritten. The thumbnail image corresponding to the fifth image is overwritten at the position where the corresponding thumbnail image is stored. As a result, as shown in FIG. 4B, the thumbnail images for the second and fourth images are deleted in the thumbnail dedicated memory.

However, this method should provide a space for storing IDs of each thumbnail separately. That is, a list indicating which thumbnails are currently stored in the thumbnail dedicated memory must be separately prepared. The thumbnail ID indicates from which image in the original video the generated thumbnail is extracted.

If the current image is not determined as the blank image in step 401, the start address (ThmAddrStart) in the thumbnail dedicated memory in which the next thumbnail image is stored is the start address of the currently stored thumbnail image in the thumbnail dedicated memory (CurrThmStart). The sum of the space (ThmPictSize) occupied by each thumbnail image is equal to (ThmAddrStart = CurrThmStart + ThmPictSize).

On the other hand, if a blank vector is simply placed without using a list indicating which thumbnails are currently stored in the thumbnail dedicated memory as shown in FIG. 4, thumbnail ID management may be easier.

5 is a view illustrating an embodiment of a control method using a blank vector when a blank image is generated in the thumbnail image generating apparatus according to the present invention. FIG. 5A is an operation flowchart, and FIG. 5B is a map state and a blank of a thumbnail dedicated memory at this time. A vector is used to indicate whether each thumbnail image stored in the thumbnail dedicated memory is blank. That is, as shown in FIG. 5B, all of the generated thumbnail images are stored in a dedicated memory of a thumbnail, and a value of a blank signal corresponding to each thumbnail is stored together in a blank vector. If the N thumbnail images are stored in the thumbnail dedicated memory, a blank vector of size N bits is required. Each bit indicates whether a thumbnail image corresponding to the sequence is blank. For example, if the n th bit of the blank vector is '0' and the m th bit is '1', the n th thumbnail image is available and the m th thumbnail image is not used because it is a blank image.

This process is illustrated in Figure 5a. In FIG. 5A, when the current image is determined to be blank, the blank vector value is set to 1, and when not determined to be blank, the blank vector value is set to 0.

That is, in step 501, it is determined whether the i-th blank vector is 1 or 0, and if it is 1, a thumbnail image corresponding to the i-th blank vector is not displayed on the screen (step 502). In addition, if it is determined as 0 in step 501, a thumbnail image corresponding to the i-th blank vector is displayed on the screen (step 503). After the step 502 or 503 is performed, the value of i is increased by one (step 504), and if the value of i is not N (step 505), it is not the end of the thumbnail dedicated memory, so the process returns to step 501 where i + 1th Extract the black vector value. If it is determined in step 504, the end of the thumbnail dedicated memory moves to the beginning or terminates the program.

As described above, when using the method of FIG. 5, the system that wants to use the thumbnail image may know whether to use each thumbnail image by referring to the blank vector when reading the thumbnail from the thumbnail dedicated memory. In this case, since thumbnails generated collectively according to a rule determined in advance by the system are all stored in a thumbnail dedicated memory regardless of whether each image is blank, there is an advantage that no separate thumbnail ID management is required.

Therefore, the present invention is applied to a summary of a video stream provided by a PVR or a video library and a browser installed in a digital TV, a program preview, a representative image generation function of a program guide, and other application fields related to implicit information delivery of a video. As a result, an effective and automatic thumbnail image can be provided to the user.

As described above, according to the apparatus for generating a thumbnail image of a digital video according to the present invention, a thumbnail image is generated using a DC value of an I picture of an input MPEG video stream, and in this process, the complexity of the thumbnail image is analyzed to blank the image. Determine whether or not. In this case, when the input image is determined to be blank, no thumbnail is generated from the image determined by the blank, or the generated thumbnail is not used. Therefore, the user can provide only thumbnails that are meaningful in content, not blank.

In particular, the present invention is generated from an image that is difficult to deliver the content as a representative image, such as a low complexity image due to the meaningless image due to excessive zoom or close-up that may occur in the video stream received in the actual broadcast, low brightness image due to lighting conditions, etc. There is an effect that can prevent the use of the thumbnail image, which enables the user to automatically obtain a more meaningful and clear thumbnail image.

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 embodiments, but should be defined by the claims.

1 is a block diagram showing an embodiment of a thumbnail image generating apparatus according to the present invention

2 is a flowchart illustrating an embodiment of a blank image determining unit of a thumbnail image generating apparatus according to the present invention;

3 is a flowchart illustrating a process of calculating TR_H and TR_V in a blank image determination unit of a thumbnail image generating apparatus according to the present invention.

4A is a flowchart illustrating an embodiment of a method of controlling a thumbnail image using an address value of a thumbnail dedicated memory when a blank image is generated in the thumbnail image generating apparatus according to the present invention.

4B is a view illustrating a map state of a thumbnail dedicated memory in FIG. 4A.

5A is a flowchart illustrating an embodiment of a control method using a blank vector when generating a blank image in a thumbnail image generating apparatus according to the present invention;

FIG. 5B is a diagram illustrating an embodiment of whether each thumbnail image stored in the thumbnail dedicated memory is blank by using the map state and the blank vector of the thumbnail dedicated memory in FIG. 5A; FIG.

Explanation of symbols for main parts of the drawings

101: DC decoder 102: blank image determination unit

103: temporary buffer 104: buffer controller

105: thumbnail memory interface

Claims (15)

A DC decoder for parsing only a DC value of an I picture from an input video stream; A temporary buffer for storing DC values output from the DC decoder; A memory configured to receive a DC value output in units of slices from the temporary buffer to generate and store a thumbnail image; Calculate the horizontal and vertical image complexity of the DC image generated by the DC value output from the DC decoder, and compare the calculated horizontal and vertical image complexity with the preset horizontal and vertical thresholds, respectively. A blank image determination unit to determine whether the I picture is a blank image; And And a buffer controller for controlling the storage and output of the DC value in the temporary buffer, and controlling not to use the corresponding thumbnail image stored in the memory when the blank image determination unit determines the blank image. Device for generating thumbnail images of video. The method of claim 1, wherein the blank image determination unit An apparatus for generating thumbnail images of digital video, comprising calculating horizontal and vertical image complexity of a corresponding DC image using only the DC value of the Y component output from the DC decoder. The method of claim 1, wherein the blank image determination unit And a horizontal and vertical image complexity of the corresponding DC image is calculated using a combination of the DC value of the Y component and the DC value of the CbCr component output from the DC decoder. The method of claim 1, wherein the blank image determination unit When the horizontal and vertical image complexity of one DC image is calculated, whether the calculated horizontal image complexity is less than or greater than a preset first horizontal threshold value, and the vertical image complexity is preset. And determining whether the I picture is a blank image according to a comparison result after comparing whether the first vertical threshold value is smaller or larger than the first vertical threshold value. The method of claim 4, wherein the blank image determination unit If the calculated image complexity in the horizontal direction is less than the first horizontal threshold value preset and / or the image complexity in the vertical direction is smaller than the first vertical threshold value preset, the I picture is a blank image. The apparatus for generating a thumbnail image of digital video, characterized in that the discriminating. The method of claim 4, wherein The first horizontal threshold value is set to a value obtained by dividing the horizontal size of the DC image by 2 ⁴ , and the first vertical threshold value is set to a value obtained by dividing the vertical size of the DC image by 2 ⁴ . An apparatus for generating thumbnail images of digital video. The method of claim 4, wherein the blank image determination unit If the calculated horizontal and vertical image complexity is greater than a preset first horizontal and vertical threshold, whether the calculated horizontal image complexity is less than or greater than a preset second horizontal threshold; and And comparing whether the I picture is a blank image according to a comparison result after comparing whether the image complexity in the vertical direction is smaller than or greater than a second preset vertical threshold value. The method of claim 7, wherein the blank image determination unit And determining the I picture as a blank image when the calculated image complexity in the horizontal and vertical directions is greater than a preset second horizontal and vertical threshold value, respectively. The method of claim 7, wherein The second horizontal threshold value is set to a value obtained by dividing the horizontal size of the DC image by 2 ³ , and the second vertical threshold value is set to a value obtained by dividing the vertical size of the DC image by 2 ³ . An apparatus for generating thumbnail images of digital video. The method of claim 1, wherein the blank image determination unit If two DC values in the horizontal direction are different from each other, the image complexity in the horizontal direction is increased, and if the two DC values in the vertical direction are different, the image complexity in the vertical direction is increased. Apparatus for generating a thumbnail image of the digital video, characterized in that the image complexity in the horizontal direction and the vertical image complexity of the current DC image is obtained by applying to a value. The apparatus of claim 10, wherein the blank image determiner An apparatus for generating thumbnail images of digital video, characterized in that only upper 5 bits of each DC value are used for comparison. The apparatus of claim 10, wherein the blank image determiner And a horizontal image complexity (TR_H) and a vertical image complexity (TR_V) of the current DC image are obtained by applying the following equation. TR_H = TR_H + 1, if Q (f (i, j)) ≠ Q (f (i, j-1)); TR_V = TR_V + 1, if Q (f (i, j)) ≠ Q (f (i-1, j)); Here, f (i, j) denotes pixel values of the input DC image, i and j denote vertical and horizontal coordinates, respectively, and Q (.) Is a preset quantization function. Divided by ³ The apparatus of claim 10, wherein the blank image determiner When the last DC value of the current DC image is input, the horizontal image complexity is divided by the vertical size of the DC image, and the vertical image complexity is divided by the vertical size of the DC image. Device for generating a thumbnail image of the digital video, characterized in that for determining. The method of claim 1, wherein the buffer control unit If the input I picture is determined to be a blank image, the thumbnail image of the digital video is controlled so that the thumbnail image generated from the next I picture is overwritten at a position in the memory where the thumbnail image generated from the I picture is stored. Generating device. The method of claim 1, wherein the buffer control unit After having as many blank vectors as the number of thumbnail images that can be stored in the memory, whether or not a blank of a corresponding thumbnail image is included in the blank vector according to a determination result of the blank image determining unit while all thumbnail images are stored in the memory regardless of blanks. Thumbnail image generating device for digital video, characterized in that for displaying.