Patent Publication Number: US-2006013308-A1

Title: Method and apparatus for scalably encoding and decoding color video

Description:
BACKGROUND OF THE INVENTION  
      This application claims priority from Korean Patent Application No. 10-2004-0055081, filed on Jul. 15, 2004 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.  
      1. Field of the Invention  
      Apparatuses and methods consistent with the present invention relate to scalable encoding and decoding of moving pictures, and more particularly, to scalable encoding and decoding based on color information of moving pictures.  
      2. Description of the Related Art  
      When a moving picture is encoded, a color format of the moving picture is presented using a ratio of luminance to chrominance of pixels included in a pixel line which extends in a horizontal direction of the moving picture. Hereinafter, the luminance will be represented by Y, and the chrominance will be represented by Cb/Cr. The luminance represents the brightness of an image, and in an ITU-R standard, luminance of one pixel is expressed with eight bits. The chrominance represents the color of an image, and expresses the color of a pixel with two eight-bit values (Cb/Cr). A coordinate system representing a color is called a color space, and in the Moving Picture Encoding Group (MPEG) standard, the color format of the moving picture is presented using three eight-bit pieces of information, i.e., Y, Cb, and Cr.  
      When a moving picture is presented using Y, Cb, and Cr, a plurality of color formats can exist according to the ratios between Y, Cb, and Cr. However, since Y, i.e., the luminance, is equal in all of the color formats, it is inefficient to repeatedly encode the luminance Y when moving pictures are encoded in different color formats.  
      In conventional moving picture encoding technologies suggested by standards such as MPEG-2, MPEG-4, and Joint Video Team (JVT) standards, since the luminance Y is repeatedly encoded when a moving picture is encoded in a 4:4:4 color format, a 4:2:2 color format, and a 4:2:0 color format, an amount of data becomes unnecessarily large when the moving pictures encoded in a plurality color formats are stored or transmitted, and the encoding is inefficient.  
      Also, in the conventional moving picture encoding technologies, a method of scalably encoding or decoding a color image format has not been developed.  
       FIG. 1  illustrates an operation of performing loss encoding by reducing a color space resolution.  
      As described above, a pixel value is generally presented by allocating 24 bits, i.e., eight bits for each of Y, Cb, and Cr. In the loss encoding method, considering that the eyesight of a person is more insensible to chrominance than luminance, an image is loss-encoded by reducing space resolutions of the chrominance values Cb/Cr. A 4:4:4 color format image, a space resolution of which is not reduced, maintains high quality color information in which chrominance values corresponding to luminance values exist for each pixel. In this case, N×N pixel luminance values and N×N pixel chrominance values are used in an N×N pixel image.  
      A 4:2:2 color format image is obtained by maintaining the 4:4:4 format chrominance values in a vertical direction and ½ horizontally downsampling the 4:4:4 format chrominance values. Therefore, if there are N×N 4:4:4 format chrominance values, then there are N×N/2 4:2:2 format chrominance values. A 4:2:0 color format image is obtained by ½ downsampling the 4:4:4 format chrominance values in a horizontal direction and a vertical direction. Therefore, if the number of 4:4:4 format chrominance values is N×N, then there are N/2×N/2 the size of a 4:2:0 format chrominance values.  
       FIG. 2  is a block diagram of a conventional color video encoding apparatus.  
      If a 4:4:4 format YCrCb image is input to the color video encoding apparatus, an encoded 4:4:4 format bitstream is output, if a 4:2:2 format YCrCb image is input to the color video encoding apparatus, an encoded 4:2:2 format bitstream is output, and if a 4:2:0 format YCrCb image is input to the color video encoding apparatus, an encoded 4:2:0 format bitstream is output.  
      The color video encoding apparatus includes a luminance encoder  210 , a chrominance encoder  220 , and a multiplexer  230 . A chrominance component input to the chrominance encoder  220  is varied according to a color format of an input image, and a luminance component input to the luminance encoder  210  is fixed since the luminance component is the same for each of the 4:4:4, 4:2:2, and 4:2:0 format images, as described with reference to  FIG. 1 . The luminance encoder  210  compensates for motion of an input image by predicting a motion vector from an input luminance component signal Y and outputs Y component texture information obtained by discrete cosine transforming, quantizing, and entropy coding the compensated image. The chrominance encoder  220  outputs Cb/Cr component texture information obtained by compensating for the motion of the input image based on the motion vector of the luminance component signal Y. The multiplexer  230  generates an encoded 4:4:4, 4:2:2, or 4:2:0 video bitstream by multiplexing the motion vector, the Y component texture information, and the Cb/Cr component texture information.  
      The operation of the luminance encoder  210  will now be described in detail. A motion estimation unit  201  determines a motion prediction value of a macro block of a current frame with reference to a reference frame and outputs a motion difference as a motion vector. That is, the motion estimation unit  201  finds the macro block to be motion-predicted in a predetermined search range of the reference frame, determines a most similar macro block, and outputs the difference between the macro blocks as the motion vector. A motion compensator  202  obtains a prediction macro block corresponding to the motion vector from the reference frame.  
      A difference obtained by subtracting the motion-compensated prediction macro block of the reference frame from the macro block of the current frame is discrete cosine transformed by a discrete cosine transformer  203 , quantized by a quantizer  204 , entropy-coded by an entropy coder  205 , and output as texture information. The multiplexer  230  generates an encoded bitstream by multiplexing the texture information with the motion vector.  
      The difference obtained by subtracting the motion-compensated prediction macro block of the reference frame from the macro block of the current frame is called a residual value. This residual value is encoded to reduce an amount of data when encoding. Since errors are generated in a quantizing process, errors generated in discrete cosine transforming (DCT) and quantizing processes are included in video data represented as a bitstream.  
      To generate a reference image, the quantized residual signal is processed by an inverse quantizer  206  and an inverse discrete cosine transformer  207 , added to the motion-predicted and compensated image, and stored in a decoded Y component storage unit  208 . Therefore, the reference image stored in the decoded Y component storage unit  208  is an image obtained by adding encoding errors in the DCT and quantizing processes to the current image. The chrominance encoder  220  performs the same encoding operation as the luminance encoder  210  on the Cb/Cr component.  
      When one moving picture is separately encoded in the 4:4:4, 4:2:2, and 4:2:0 formats, since the chrominance encoder  220  encodes 4:4:4, 4:2:2, and 4:2:0 format Cb/Cr components and multiplexes them with a Y component, the Y component is repeatedly encoded.  
     SUMMARY OF THE INVENTION  
      The present invention provides a scalable video encoding and decoding methods and apparatuses for scalably encoding and decoding a moving picture in various color format.  
      According to an aspect of the present invention, there is provided a color video encoding method comprising: generating an encoded luminance bitstream by encoding a luminance component using a motion prediction based encoding method; and generating at least one encoded chrominance bitstream by encoding at least one color format chrominance component using a motion vector generated by the motion prediction based encoding method.  
      The generating at least one encoded chrominance bitstream may comprise: independently receiving and encoding 4:2:0, 4:2:2, and 4:4:4 color format chrominance components.  
      According to another aspect of the present invention, there is provided a color video encoding method comprising: generating an encoded base layer bitstream by downsampling a chrominance component of an original image and encoding the downsampled chrominance component and a luminance component which is not downsampled using a motion prediction based encoding method; and generating an encoded enhancement layer bitstream by encoding a residual chrominance component, which is a difference between a value obtained by upsampling a chrominance component obtained by decoding the encoded base layer bitstream and a chrominance component of an original image which has not been downsampled.  
      According to another aspect of the present invention, there is provided a color video decoding method comprising: generating a decoded luminance component by decoding a luminance bitstream encoded by using a motion prediction based encoding method using only a luminance component of an image; generating at least one decoded chrominance component by decoding at least one encoded chrominance bitstream; and generating at least one color format image by adding the decoded luminance component and the at least one decoded chrominance component.  
      According to another aspect of the present invention, there is provided a color video decoding method comprising: decoding a base layer bitstream generated by downsampling a chrominance component of an original image and encoding the downsampled chrominance component and a luminance component which is not downsampled using a motion prediction based encoding method; decoding an enhancement layer bitstream generated by encoding a residual chrominance component, which is a difference between a value obtained by upsampling a chrominance component obtained by decoding the generated base layer bitstream and a chrominance component of an original image, which has not been downsampled; and generating at least one enhancement layer color format image by adding a luminance component decoded from the base layer bitstream to a decoded chrominance component obtained by adding a chrominance component decoded from the base layer bitstream and a chrominance component obtained by decoding the enhancement layer bitstream.  
      According to another aspect of the present invention, there is provided a color video encoding apparatus comprising: a luminance encoder receiving a luminance component of an image, encoding the luminance component using a motion prediction based encoding method, and outputting an encoded luminance bitstream; and a chrominance encoder receiving at least one color format chrominance component, encoding the chrominance component using a motion vector generated by the motion prediction based encoding method, and outputting at least one encoded chrominance bitstream.  
      The chrominance encoder may comprise: a first chrominance encoder receiving and encoding a 4:2:0 color format chrominance component; a second chrominance encoder receiving and encoding a 4:2:2 color format chrominance component; and a third chrominance encoder receiving and encoding a 4:4:4 color format chrominance component.  
      According to another aspect of the present invention, there is provided a color video encoding apparatus comprising: a downsampler downsampling a chrominance component of an original image; a base layer encoder encoding the downsampled chrominance component and a luminance component, which is not downsampled, using a motion prediction based encoding method and outputting an encoded base layer bitstream; and an enhancement layer encoder encoding a residual chrominance component, which is a difference between a value obtained by upsampling a chrominance component obtained by decoding the encoded base layer bitstream and a chrominance component of an original image which has not been downsampled and outputting an encoded enhancement layer bitstream.  
      According to another aspect of the present invention, there is provided a color video decoding apparatus comprising: a luminance decoder receiving a luminance bitstream encoded by using a motion prediction based encoding method using only a luminance component of an image, decoding the luminance bitstream, and outputting a decoded luminance component; and a chrominance decoder receiving at least one encoded chrominance bitstream, decoding the at least one chrominance bitstream, generating at least one decoded chrominance component, and outputting at least one color format image obtained by adding the decoded luminance component and the at least one decoded chrominance component.  
      According to another aspect of the present invention, there is provided a color video decoding apparatus comprising: a base layer decoder receiving and decoding a base layer bitstream, which is generated by downsampling a chrominance component of an original image and encoding the downsampled chrominance component and a luminance component which is not downsampled using a motion prediction based encoding method; an enhancement layer decoder receiving and decoding an enhancement layer bitstream generated by encoding a residual chrominance component, which is a difference between a value obtained by upsampling a chrominance component obtained by decoding the generated base layer bitstream and a chrominance component of an original image which has not been downsampled; and an enhancement layer color image output unit outputting at least one enhancement layer color format image obtained by adding a luminance component decoded from the base layer bitstream to a decoded chrominance component obtained by adding a chrominance component decoded from the base layer bitstream and a chrominance component decoded from the enhancement layer bitstream.  
      According to another aspect of the present invention, there is provided an information storage medium having recorded thereon an encoded color image comprising: an encoded luminance bitstream generated by encoding a luminance component of an image using a motion prediction based encoding method; and at least one encoded chrominance bitstream generated by encoding at least one color format chrominance component using a motion vector generated by the motion prediction based encoding method.  
      The luminance bitstream may be generated by determining a motion vector, and multiplexing the motion vector and luminance texture information obtained by encoding the luminance component using a motion prediction based encoding method based on the motion vector.  
      Also, 4:2:0, 4:2:2, and 4:4:4 color format chrominance components may be independently encoded in the chrominance bitstream.  
      According to another aspect of the present invention, there is provided an information storage medium having recorded thereon an encoded color image comprising: an encoded base layer bitstream generated by downsampling a chrominance component of an original image and encoding the downsampled chrominance component and a luminance component which is not downsampled using a motion prediction based encoding method; and an encoded enhancement layer bitstream generated by encoding a residual chrominance component, which is a difference between a value obtained by upsampling a chrominance component obtained by decoding the encoded base layer bitstream and a chrominance component of an original image which has not been downsampled. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other aspects of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:  
       FIG. 1  illustrates an operation of performing loss encoding by reducing a color space resolution;  
       FIG. 2  is a block diagram of a conventional color video encoding apparatus;  
       FIG. 3  is a block diagram of a scalable encoding of color video apparatus according to an exemplary embodiment of the present invention;  
       FIG. 4  is a block diagram of a scalable decoding of color video apparatus according to an exemplary embodiment of the present invention;  
       FIG. 5  is a flowchart illustrating a scalable encoding of color video method according to an exemplary embodiment of the present invention;  
       FIG. 6  is a flowchart illustrating a scalable color video decoding method according to an exemplary embodiment of the present invention;  
       FIG. 7  is a block diagram of a scalable encoding of color video apparatus according to another exemplary embodiment of the present invention;  
       FIG. 8  is a block diagram of a scalable decoding of color video apparatus according to another exemplary embodiment of the present invention;  
       FIG. 9  is a flowchart illustrating a scalable encoding of color video method according to another exemplary embodiment of the present invention; and  
       FIG. 10  is a flowchart illustrating a scalable decoding of method according to another exemplary embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION  
      Hereinafter, the present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown.  
       FIG. 3  is a block diagram of a scalable encoding of color video apparatus according to an exemplary embodiment of the present invention.  
      The color video encoding apparatus includes a luminance encoder  310 , a chrominance encoder  320 , and a multiplexer  330 . The chrominance encoder  320  includes a first chrominance encoder  322 , a second chrominance encoder  324 , and a third chrominance encoder  326 .  
      The luminance encoder  310  receives a Y component, encodes the Y component using a motion prediction based encoding method, and outputs Y component texture information and a Y component motion vector. The encoding process is the same as described with reference to  FIG. 2 . The first chrominance encoder  322  receives a 4:2:0 format Cb/Cr component, encodes the 4:2:0 format Cb/Cr component by compensating it using the Y component motion vector, and outputs a 4:2:0 enhancement layer bitstream. The second chrominance encoder  324  receives a 4:2:2 format Cb/Cr component, encodes the 4:2:2 format Cb/Cr component by compensating it using the Y component motion vector, and outputs a 4:2:2 enhancement layer bitstream. The third chrominance encoder  326  receives a 4:4:4 format Cb/Cr component, encodes the 4:4:4 format Cb/Cr component by compensating it using the Y component motion vector, and outputs a 4:4:4 enhancement layer bitstream. Any conventional motion prediction based encoding method can be used by the color video encoding apparatus. The multiplexer  330  outputs a base layer bitstream by multiplexing the encoded Y component texture information and the motion vector.  
       FIG. 4  is a block diagram of a scalable decoding of color video apparatus according to an exemplary embodiment of the present invention.  
      The color video decoding apparatus includes a luminance decoder  410  and a chrominance decoder  420 . The chrominance decoder  420  includes a first chrominance decoder  422 , a second chrominance decoder  424 , and a third chrominance decoder  426 .  
      The luminance decoder  410  receives a base layer bitstream generated by the luminance encoder  310  and the multiplexer  330 , extracts a motion vector, outputs the Y component by entropy decoding, inverse quantizing, and inverse discrete cosine transforming (IDCT) the base layer bitstream using the motion vector.  
      The first chrominance decoder  422  receives a 4:2:0 color format enhancement layer bitstream, generates a 4:2:0 chrominance component using the motion vector extracted by the luminance decoder  410 , and outputs a 4:2:0 format color image obtained by adding the Y component output from the luminance decoder  410  to the 4:2:0 chrominance component.  
      The second chrominance decoder  424  receives a 4:2:2 color format enhancement layer bitstream, generates a 4:2:2 chrominance component using the motion vector extracted by the luminance decoder  410 , and outputs a 4:2:2 format color image obtained by adding the Y component output from the luminance decoder  410  to the 4:2:2 chrominance component.  
      The third chrominance decoder  426  receives a 4:4:4 color format enhancement layer bitstream, generates a 4:4:4 chrominance component using the motion vector extracted by the luminance decoder  410 , and outputs a 4:4:4 format color image obtained by adding the Y component output from the luminance decoder  410  to the 4:4:4 chrominance component.  
       FIG. 5  is a flowchart illustrating a scalable encoding of color video method according to an exemplary embodiment of the present invention.  
      A luminance component is encoded using one of the motion prediction based encoding methods described above in operation S 510 . Then, 4:2:0, 4:2:2, and 4:4:4 color format chrominance components are separately encoded using a motion vector extracted in the process of generating the luminance bitstream in operation S 520 . Accordingly, 4:2:0, 4:2:2, and 4:4:4 color format chrominance bitstreams are generated. Since the chrominance bitstreams are not transmitted when a network status is abnormal, scalable encoding is very useful considering network status.  
       FIG. 6  is a flowchart illustrating a scalable decoding of color video method according to an exemplary embodiment of the present invention.  
      An encoded luminance bitstream generated using the color video encoding method is decoded to generate a luminance image in operation S 610 . The luminance image is a black/white image classified by light and shade since a chrominance component is not included. Next, 4:2:0, 4:2:2, and 4:4:4 color format chrominance images are generated by decoding 4:2:0, 4:2:2, and 4:4:4 color format chrominance bitstreams in operation S 620 . Then, 4:2:0, 4:2:2, and 4:4:4 format color images are generated by adding the chrominance images to the luminance image in operation S 630 . When the chrominance bitstreams cannot be received since the network status is abnormal, or when an error exists in the received chrominance bitstreams, a moving picture including only the luminance image is output. Therefore, scalable decoding can be performed according to circumstances.  
       FIG. 7  is a block diagram of a scalable encoding of color video apparatus according to another exemplary embodiment of the present invention.  
      The color video encoding apparatus includes a downsampler  710 , a base layer encoder  720 , a first enhancement layer encoder  730 , and a second enhancement layer encoder  740 .  
      A first downsampler  712  generates a 4:2:0 format Cb/Cr image including (N/2)×(N/2) pixels by downsampling a 4:4:4 format Cb/Cr image including N×N pixels, and a second downsampler  714  generates a 4:2:2 format Cb/Cr image including N×(N/2) pixels by downsampling the 4:4:4 format Cb/Cr image. A Y component and the 4:2:0 format Cb/Cr component generated by the first downsampler  712  are input to the base layer encoder  720 , and a 4:2:0 format base layer bitstream is output from the base layer encoder  720 . In the base layer encoder  720 , a decoded 4:2:0 format Cb/Cr component stored in a decoded image storage unit  722  is input to a first upsampler  732  included in the first enhancement layer encoder  730 . The first upsampler  732  generates a decoded 4:2:2 format Cb/Cr image by upsampling the decoded 4:2:0 format Cb/Cr component. The upsampling performed by the first upsampler  732  may be performed using a color upsampling filter used in an MPEG standard.  
      The first enhancement layer encoder  730  generates a 4:2:2 format Cb/Cr bitstream by performing DCT on, quantizing, and entropy coding a residual 4:2:2 format Cb/Cr image, which is a difference between a 4:2:2 format Cb/Cr component downsampled by a second downsampler  714  and the decoded 4:2:2 format Cb/Cr component generated by the first upsampler  732 . In the generation of the 4:2:2 format Cb/Cr bitstream, a chrominance image obtained by inverse quantizing and performing IDCT on a chrominance component input to an entropy coder is added to the decoded 4:2:2 format Cb/Cr image generated by the first upsampler  732 , and the added image is stored in a decoded image storage unit  734 .  
      The decoded 4:2:2 format Cb/Cr component stored in the decoded image storage unit  734  is input to a second upsampler  742  included in the second enhancement layer encoder  740 . The second upsampler  742  generates a 4:4:4 format Cb/Cr image by upsampling the decoded 4:2:2 format Cb/Cr component. The upsampling performed by the second upsampler  742  may be performed using a color upsampling filter used in the MPEG standard. The second enhancement layer encoder  740  generates a 4:4:4 format Cb/Cr bitstream by performing DCT, quantizing, and entropy coding a residual 4:4:4 format Cb/Cr image, which is a difference between a 4:4:4 format Cb/Cr component and the decoded 4:4:4 format Cb/Cr component generated by the second upsampler  742 .  
      The encoding method performed in the base layer encoder  720 , the first enhancement layer encoder  730 , and the second enhancement layer encoder  740  may be any conventional motion prediction based encoding method.  
       FIG. 8  is a block diagram of a scalable decoding of color video apparatus according to another exemplary embodiment of the present invention.  
      The scalable color video decoding apparatus includes a base layer decoder  810 , a first enhancement layer decoder  820 , a second enhancement layer decoder  830  and an enhancement layer color video output unit  840 .  
      The base layer decoder  810  receives a 4:2:0 format base layer bitstream and outputs a 4:2:0 format color image by decoding the 4:2:0 format base layer bitstream. A Y component and a 4:2:0 format Cb/Cr component of the 4:2:0 format color image are stored in a decoded image storage unit  812  included in the base layer decoder  810 . The 4:2:0 format Cb/Cr component is input to the first enhancement layer decoder  820 . A first upsampler  822  receives the 4:2:0 format Cb/Cr component and generates a 4:2:2 format Cb/Cr component. The first enhancement layer decoder  820  receives a 4:2:2 format Cb/Cr bitstream, generates a 4:2:2 format Cb/Cr component by entropy decoding, inverse quantizing, and performing IDCT on the 4:2:2 format Cb/Cr bitstream, generates a decoded 4:2:2 format Cb/Cr image by adding the generated 4:2:2 format Cb/Cr component and the upsampled 4:2:2 format Cb/Cr component, and stores the decoded 4:2:2 format Cb/Cr image in a decoded Cb/Cr component storage unit  824 . The enhancement layer color video output unit  840  receives the stored 4:2:2 format Cb/Cr component and outputs a 4:2:2 format color image by adding the 4:2:2 format Cb/Cr component to the Y component output from the decoded image storage unit  812  included in the base layer decoder  810 .  
      A second upsampler  832  included in the second enhancement layer decoder  830  receives the decoded 4:2:2 format Cb/Cr component from the decoded Cb/Cr component storage unit  824  included in the first enhancement layer decoder  820  and generates a 4:4:4 format Cb/Cr component. The second enhancement layer decoder  830  receives a 4:4:4 format Cb/Cr bitstream, generates a 4:4:4 format Cb/Cr component by entropy decoding, inverse quantizing, and performing IDCT on the 4:4:4 format Cb/Cr bitstream, generates a decoded 4:4:4 format Cb/Cr image by adding the generated 4:4:4 format Cb/Cr component and the upsampled 4:4:4 format Cb/Cr component, and stores the decoded 4:4:4 format Cb/Cr image in a decoded Cb/Cr component storage unit  834 . The enhancement layer color video output unit  840  receives the stored 4:4:4 format Cb/Cr component and outputs a 4:4:4 format color image by adding the 4:4:4 format Cb/Cr component to the Y component output from the decoded image storage unit  812  included in the base layer decoder  810 .  
       FIG. 9  is a flowchart illustrating a scalable encoding of color video method according to another exemplary embodiment of the present invention.  
      Referring to  FIG. 9 , a 4:4:4 format current video data is received in operation S 910 . A 4:2:2 format Cb/Cr component and a 4:2:0 format Cb/Cr component are generated by receiving and downsampling a 4:4:4 format Cb/Cr component of the 4:4:4 format current video data in operation S 920 . A base layer bitstream is generated by encoding the 4:2:0 format Cb/Cr component and a Y component of the 4:4:4 format current video data together using a motion prediction based encoding method in operation S 930 . A 4:2:2 format first enhancement layer Cb/Cr bitstream is generated by generating and encoding a residual 4:2:2 format Cb/Cr component, which is a difference between the 4:2:2 format Cb/Cr component generated by downsampling the 4:4:4 format Cb/Cr component and a 4:2:2 format Cb/Cr component generated by upsampling a decoded 4:2:0 format Cb/Cr component generated when the base layer bitstream is generated in operation S 940 .  
      A decoded 4:2:2 format Cb/Cr component is generated by adding a 4:2:2 format Cb/Cr component generated by decoding the 4:2:2 format first enhancement layer Cb/Cr bitstream and a 4:2:2 format Cb/Cr component generated by upsampling a decoded 4:2:0 format Cb/Cr component generated when the base layer bitstream is generated in operation S 950 . A 4:4:4 format second enhancement layer Cb/Cr bitstream is generated by generating and encoding a residual 4:4:4 format Cb/Cr component, which is a difference between the 4:4:4 format Cb/Cr component of the 4:4:4 format current video data and a 4:4:4 format Cb/Cr component generated by upsampling the decoded 4:2:2 format Cb/Cr component in operation S 950 .  
       FIG. 10  is a flowchart illustrating a scalable decoding of color video method according to another exemplary embodiment of the present invention.  
      Referring to  FIG. 10 , in operation S 1010 , a decoded 4:2:0 format color image is generated by decoding a 4:2:0 format base layer bitstream using a motion prediction based decoding method. In operation S 1020 , a 4:2:2 format Cb/Cr component is generated by upsampling the decoded 4:2:0 format Cb/Cr component generated in operation S 1010 . In operation S 1030 , another 4:2:2 format Cb/Cr component is generated by decoding a first enhancement layer bitstream. In operation S 1040 , a decoded 4:2:2 format Cb/Cr component is generated by adding the 4:2:2 format Cb/Cr component generated in operation S 1020  and the 4:2:2 format Cb/Cr component generated in operation S 1030 . In operation S 1050 , a 4:2:2 format color image is output by adding a Y component generated in operation S 1020  and the decoded 4:2:2 format Cb/Cr component generated in operation S 1040 .  
      In operation S 1060 , a 4:4:4 format Cb/Cr component is generated by upsampling the decoded 4:2:2 format Cb/Cr component generated in operation S 1040 . In operation S 1070 , another 4:4:4 format Cb/Cr component is generated by receiving and decoding a second enhancement layer bitstream. In operation S 1080 , a decoded 4:4:4 format Cb/Cr component is generated by adding the 4:4:4 format Cb/Cr component generated in operation S 1060  and the 4:4:4 format Cb/Cr component generated in operation S 1070 . In operation S 1090 , a 4:4:4 format color image is output by adding the Y component generated in operation S 1020  and the decoded 4:4:4 format Cb/Cr component generated in operation S 1080 .  
      The present invention may be embodied in a general-purpose computer by running a program from a computer-readable medium, including but not limited to storage media such as magnetic storage media (ROMs, RAMs, floppy disks, magnetic tapes, etc.), optically readable media (CD-ROMs, DVDs, etc.), and carrier waves (transmission over the internet). The present invention may be embodied as a computer-readable medium having a computer-readable program code unit embodied therein for causing a number of computer systems connected via a network to effect distributed processing. And the functional programs, codes and code segments for embodying the present invention may be easily deducted by programmers in the art which the present invention belongs to.  
      As described above, according to an exemplary embodiment of the present invention, storage, transmission, and reproduction of a moving picture can be efficiently performed by scalably encoding the moving picture according to a color format in which the moving picture is encoded.  
      While this invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The above-described exemplary embodiments should be considered in a descriptive sense only and are not for purposes of limitation. Therefore, the scope of the invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being included in the present invention.