JP4530671B2 - Image reproducing apparatus and image reproducing method - Google Patents

Description

  The present invention relates to an image reproducing apparatus and an image reproducing method for reproducing encoded image data.

  In recent years, still images and moving images are recorded on removable media such as a memory card, and the media is a portable information device such as a PDA (Personal Digital Assistants) or a TV using an FPD (Flat Panel Display) such as a liquid crystal TV. For example, there is a use for connecting and playing. In these devices, a fixed pixel type display device such as a liquid crystal display is used as a display for displaying an image. Since image data is very large as it is, when recording images to removable media such as a memory card, it is generally saved using a compression technique to greatly reduce the data size. Has been done. Various encoding methods have been proposed for the purpose of such image compression. As these encoding systems, the JPEG system is standardized as a still picture compression system, and MPEG-1, MPEG-2, MPEG-4, etc. are standardized as international standards as video compression systems. Used in.

A display method with different sizes for displaying the decoded image on the display screen when the image is displayed on a device that decodes and displays such a compressed image is considered. For example, FIG. As shown in FIG. 6, the same size display in which the same number of pixels as the decoded image is displayed on the display screen without enlargement or reduction , or the decoded image is the size of the display screen as shown in FIG. A full-screen display so that the decoded image is displayed in the same size as shown in FIG. 6C, or a method of displaying the image by enlarging or reducing it so that the decoded image becomes equal to a predetermined size in the display screen as shown in FIG. There is. Hereinafter, these are called display methods.

In a terminal capable of such a plurality of display methods, as shown in Patent Document 1, for example, there is a method of switching by a user's operation by means of a remote controller or the like as disclosed in Patent Document 1.
Japanese Patent Application No. 2002-283311

FIG. 7 is a block diagram showing a configuration of an image reproducing apparatus that includes recording means such as a memory card and displays one of a plurality of display methods by selecting one of the display methods. .
In the figure, reference numeral 101 denotes a recording medium which stores an encoded image and other information. Reference numeral 102 denotes a file processing unit that reads the entire specified file or a specified portion of the files stored in the recording medium 101 and outputs the read information to the image decoding unit 103. Reference numeral 103 denotes an image decoding unit that decodes an input encoded image and outputs a decoded image.

  An image scaler 104 is a scaling unit that enlarges or reduces the decoded image at a specified magnification. The image scaler 104 specifies the magnification, and performs an enlargement or reduction process on the inputted decoded image at the magnification designated by the display switching unit 105 every time the decoded image is inputted from the image decoding unit 103. Output to the image display unit 107. A display switching unit 105 calculates a magnification for performing enlargement or reduction processing from the number of pixels of the decoded image and the number of pixels of the display device and the designated display method, and sets the magnification to the image scaler 104. To do.

An operation unit 106 is connected to an interface for a user to perform an operation such as a switch, detects whether the user has performed an operation and the type of operation, and determines the operation of the apparatus determined by the result. The operation of the block in the apparatus is changed by notifying each block of the operation of the block in the apparatus according to the type. For example, when full screen display is selected by the operation unit 106, the display switching unit 105 sets the image scaler from the number of pixels of the decoded image acquired from the image decoding unit 103 and the number of pixels of the display image determined by the display method. Calculate the magnification to be set, and set the image scaler. The magnification set for the image scaler is calculated from the number of pixels of the decoded image and the number of pixels of the display image. In the following, the calculation procedure will be described using the case of full screen display as an example. Note that full-screen display means that all the pixels of the decoded image are displayed and displayed with enlargement or reduction using a magnification that provides the maximum display area. This magnification can be calculated by the following method, for example. In the full screen display, the horizontal display pixel number is Wd, the vertical display pixel number is Hd, the horizontal pixel number of the encoded image is Wp, and the vertical pixel number is Hp (see FIG. 6). . When Wd / Hd and Wp / Hp, which are the respective aspect ratios, are compared, and Wd / Hd> Wp / Hp, the magnification Sa during full screen display is Hd / Hp. In other cases, the magnification Sa during full screen display is Wd / Wp.

  By setting the magnification calculated in the above procedure in the image scaler, the display 108 displays an image on the entire screen like the display image of FIG. 6B. For example, when the same size display is selected by the operation unit 106, the magnification is set to 1 in the image scaler. In this case, a part of the screen as shown in FIG. 6A is displayed with the same number of pixels as the decoded image. In addition to the full screen display and the same magnification display, a method of displaying the image by enlarging or reducing it to a predetermined screen size as shown in FIG. Reference numeral 107 denotes an image display unit that has a frame memory therein and outputs the contents of the frame memory to the display 108 at a constant cycle. The decoded image is enlarged or reduced by the image scaler 104 and written into the frame memory inside the image display unit 107.

  Further, the image scaler 104 skips writing to the outer portion of the image when writing to the frame memory when the image after scaling processing is less than the size of the display screen. As a result, the contents written from the original in the frame memory are displayed in the outer portion of the image after the scaling process, and the display is as shown in FIG. In addition, although (a) of FIG. 6 illustrated the case where it displayed on the center of a screen, it does not necessarily need to be a center. Reference numeral 108 denotes a display that displays an image based on an input time-series signal. Generally, devices such as CRT and LCD are used.

When an image compressed at a low resolution and a high compression rate is displayed on a full-resolution display on the above-mentioned apparatus, the decoded image is enlarged so that the number of pixels is the same as the number of pixels of the display unit. If this is done, the noise due to compression is also enlarged, so that there is a problem that deterioration that cannot be seen in the same magnification display is recognized.
In addition, when the display method is switched by the user's operation, an image with sufficient image quality for full-screen display is displayed in a display method other than full-screen display, or an image with noticeable image quality degradation in full-screen display. Is displayed on the full screen, the user needs to perform an operation of switching the display, which causes a problem that the operation becomes complicated.

  The present invention solves the above-described problems, and includes means for determining the image quality when the encoded image to be reproduced is displayed on the full screen, and can automatically switch to a display method in which the image quality deterioration due to encoding is not noticeable. An object of the present invention is to provide an image reproducing apparatus.

In order to solve the above-described problem, the present invention provides an image reproduction unit that includes an image decoding unit that decodes an encoded image as a decoded image, and an image display unit that displays the decoded image as a display image on a display screen. In the apparatus, based on the magnitude relationship between the number of pixels of the encoded image and the number of pixels of the display image, so that a decoded image of the encoded image is displayed on the display screen in a full screen . A display magnification determining unit that determines a magnification for displaying the enlarged or reduced decoded image; and an image scaler unit that enlarges or reduces the decoded image based on the magnification determined by the display magnification determining unit. The image scaler unit is determined by the display magnification determination unit when the magnification determined by the display magnification determination unit is equal to or less than a threshold magnification and the compression rate of the decoded image is equal to or less than a predetermined compression rate. The image is enlarged or reduced at a magnification, otherwise, enlarged or reduced at a predetermined magnification smaller than a threshold magnification, and the image display unit displays an image enlarged or reduced at the image scaler unit. It is characterized by that.

In the present invention, the number of pixels of the display image is the number of pixels of the display screen.

Further, the present invention relates to an image reproduction method for decoding an encoded image as a decoded image and displaying the image on a display screen after being enlarged or reduced, and the decoded image of the encoded image is displayed on the display screen in full screen. Determining the magnification for displaying the decoded image in an enlarged or reduced manner based on the magnitude relationship between the number of pixels of the encoded image and the number of pixels of the display screen; and If the determined magnification is less than or equal to a predetermined threshold and the compression rate of the decoded image is less than or equal to the predetermined compression rate, the image is enlarged or reduced at the determined magnification, and otherwise Has a step of enlarging or reducing at a predetermined magnification smaller than a threshold magnification.

  According to the present invention, an image reproduction apparatus capable of determining an image quality when an encoded image to be reproduced is enlarged and displayed before reproduction, and automatically selecting an enlargement factor that is not conspicuously deteriorated based on the determination result. Can be realized.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a block diagram showing an embodiment of a moving image recording / playback apparatus according to the present invention. The blocks given the same numbers as in FIG. 7 have the same functions as in the conventional example. Therefore, detailed description of the blocks with the same numbers is omitted.

  In the figure, reference numeral 109 denotes a display magnification determination unit, which acquires a part of encoded data to be displayed and file information from the file processing unit 102, and obtains a numerical value highly correlated with image quality based on the acquired information. To calculate. Based on a numerical value highly correlated with the image quality, the image quality of the display image at a plurality of magnifications is evaluated and selected for output.

  Numerical values that have a high correlation with the image quality after scaling, for example, when enlarging the image, noise included in the decoded image and encoding distortion caused by encoding are also enlarged, so that it was difficult to see at the same magnification. Deterioration of is visually recognized. Moreover, since blur etc. arise, this is also recognized as deterioration. Since the larger the magnification is, the easier it is to be visually recognized, the magnification of the enlargement has a correlation with the image quality after scaling. In encoding, the larger the compression rate, which is the ratio of the data amount of the original image to the data amount of the compressed image, the greater the encoding distortion caused by the code. The image quality of the display image is determined using a numerical value highly correlated with the image quality after scaling, and the magnification is determined.

  Based on the number of pixels of the decoded image and the number of pixels of the display unit, it is possible to calculate the magnification necessary for full screen display. Here, the full screen display means that all the pixels of the decoded image are displayed and enlarged and reduced using a magnification that provides the maximum display area. This magnification can be calculated by the following method, for example. In the full screen display, the horizontal display pixel number is Wd, the vertical display pixel number is Hd, the horizontal pixel number of the encoded image is Wp, and the vertical pixel number is Hp (see FIG. 6). . The aspect ratios Wd / Hd and Wp / Hp are compared. If Wd / Hd> Wp / Hp, the magnification Sa during full screen display is set to Hd / Hp. In other cases, the magnification Sa during full screen display is Wd / Wp.

  The display magnification determination unit 109 may determine deterioration when full screen display is performed by comparing the magnification Sa obtained above with a predetermined threshold value St. Hereinafter, the operation of the display magnification determination unit 109 will be described with reference to the flowchart shown in FIG.

  The display magnification determination unit 109 compares the magnification Sa with a predetermined threshold value St, and determines whether Sa ≦ St (S4). If Sa> St, the magnification S set in the image scaler is set to a predetermined value Sc smaller than St (S5). For this value, for example, 1 may be specified. A numerical value selected and set by the user in advance may be used. If Sa ≦ St, the magnification S set for the image scaler is set to Sa (S6). This means full screen display.

The determination equivalent to the above may be performed as follows.
It is assumed that Wt = Wd / St and Ht = Hd / St. Since Wt, Ht are values necessary for calculation, Wd, St, and Hd are known, it is possible to calculate in advance. Therefore, the determination can be made simply by comparing with the pixel numbers Wp and Hp. At this time, if Wp ≧ Wt or Hp ≧ Ht, full screen display is performed. Otherwise, the same operation is performed by selecting the same size display or the display method set by the user. . The magnification S determined by the display magnification determination unit 109 is input to the display switching unit 105, and is set in the image scaler 104 by the display switching unit 105.

  By determining the magnification to be set for the image scaler 104 according to the procedure described above, the apparatus operates so as not to perform full-screen display when the magnification necessary for full-screen display exceeds a predetermined value. As a result, it is possible to suppress a phenomenon in which image quality deterioration due to full screen display is conspicuous. In addition, it is possible to automatically switch to full screen display for an image that is determined to have no noticeable image quality degradation due to full screen display. Thereby, a simple operation can be provided to the user.

  In the determination method shown in FIG. 2 described above, determination is performed only with a magnification necessary for full-screen display. However, image degradation is correlated with the compression rate, and it is insufficient to determine with only the magnification. There is a case. Therefore, a determination procedure as described below may be used. The compression rate R is obtained by dividing the data amount of the image before compression by the data amount of the encoded image after compression. In addition, in a moving image etc., you may determine using the bit rate which is the information amount per time. However, when the bit rate is used, since the bit rate and the compression rate R are in an inversely proportional relationship, all determinations with respect to the threshold value described below must be reversed.

Hereinafter, it will be explained according to a flowchart shown in FIG.
R is compared with a predetermined threshold value Rt (S5). If Sa ≦ St and R ≦ Rt, S = Sa is set (S7). Otherwise, Sa> St in the above determination method. Similarly to S, S is set to a predetermined constant Sc (S6). As a result, even when the image sizes are the same, the determination is made in consideration of the deterioration due to the compression, and therefore the deterioration is less likely to be visually recognized. Further, in the above description, the case where there is one threshold value is described for the sake of simplification. However, the compression rate R is determined by a plurality of threshold values, a region is determined, and a magnification is set with a different threshold value for each region. May be determined.

The procedure of the case determination is described according to the flow diagram of FIG.
N−1 threshold values Rtn (n is an integer from 1 to N−1) for determining the compression rate R are provided. In this example, Rtn is pre-sorted in ascending order. From n = 1 to N−1, the threshold value Rtn is sequentially compared, and the maximum n that satisfies R ≦ Rtn is obtained (S2 to S4). When n is obtained, the threshold values Stn and Sa are compared, and if Sa <Stn, the magnification is set to Sa (S7), and if Sa> Stn, the magnification S is set to Scn (S6). In this way, the magnification S is determined.

  In some apparatuses, a combination of the size and compression rate of an image to be recorded is defined as a mode, and the mode is associated with encoded data and recorded in a file. In such an apparatus, the display magnification determination unit 109 requests the file processing unit 102 to read the mode information recorded as a file on the recording medium 101, and acquires the recorded mode of the file. If the mode is known, the corresponding image size and compression rate are determined, so the magnification for the mode can be determined in advance.

Therefore, the display magnification determination unit 109 can make the magnification S correspond to the mode information on a one-to-one basis. In order to obtain the magnification S from the mode information, for example, a table as shown in FIG. 5 is prepared, and the magnification S is directly obtained from the mode by referring to the table. According to the selection of the user, by performing the rewriting of magnification in the table, it is possible to reflect the user's selection.

  In the embodiment described above, the case where there are two display methods has been described, but there may be three or more display methods. In this case, a predetermined priority order is provided for each display method, and a determination equivalent to the above is performed in order from the higher priority order. That is, first, a determination equivalent to that in the above embodiment is performed between the display method 1 having the first priority and the display method 2 having the second priority. When a display method with a high priority is selected, the display method is used. When a display method with a low priority is selected, the same determination is performed as the selected display method and the display method with the next highest priority. The display method is determined by repeating the same determination until the display method to be used is determined or the lowest priority is reached.

It is a block diagram which shows the image reproduction apparatus of embodiment of this invention. It is a flowchart which shows operation | movement of the 1st display magnification determination means in this invention. It is a flowchart which shows operation | movement of the 2nd display magnification determination means in this invention. It is a flowchart which shows operation | movement of the 3rd display magnification determination means in this invention. It is a figure which shows the table used with the 4th display magnification determination means in this invention. It is a figure which shows the example of the relationship between the decoding image in the prior art and embodiment of this invention, and the display method of an image. It is a block diagram which shows the form of the conventional image reproduction apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Recording medium 102 File processing part 103 Image decoding part 104 Image scaler 105 Display switching part 106 Operation part 107 Display controller 108 Display 109 Display magnification determination part

Claims (3)

In an image reproduction device comprising: an image decoding unit that decodes an encoded image as a decoded image; and an image display unit that displays the decoded image as a display image on a display screen;
Based on the magnitude relationship between the number of pixels of the encoded image and the number of pixels of the display image, the decoded image is converted so that the decoded image of the encoded image is displayed on the display screen in full screen. A display magnification determination unit for determining a magnification for displaying in an enlarged or reduced manner,
An image scaler unit that enlarges or reduces the decoded image based on the magnification determined by the display magnification determination unit;
Further comprising
The image scaler unit is determined by the display magnification determination unit when the magnification determined by the display magnification determination unit is equal to or less than a threshold magnification and the compression rate of the decoded image is equal to or less than a predetermined compression rate. Enlarge or reduce at a magnification, otherwise, enlarge or reduce at a predetermined magnification smaller than the threshold magnification,
The image display device, wherein the image display unit displays an image enlarged or reduced by the image scaler unit.   The image reproduction device according to claim 1, wherein the number of pixels of the display image is the number of pixels of the display screen. In an image reproduction method for decoding an encoded image as a decoded image and displaying the image on a display screen after being enlarged or reduced,
Based on the magnitude relationship between the number of pixels of the encoded image and the number of pixels of the display screen, the decoded image is displayed so that the decoded image of the encoded image is displayed on the display screen in full screen. Determining a magnification for displaying in an enlarged or reduced manner;
When the determined magnification is equal to or smaller than a predetermined threshold and when the decoded image compression rate is equal to or lower than the predetermined compression rate, the image is enlarged or reduced at the determined magnification, and otherwise Includes enlarging or reducing at a predetermined magnification smaller than a threshold magnification, and
An image reproduction method comprising:

Images