Abstract:
An image storing and/or replaying apparatus and a method therefor capable of storing a transient image and replaying the stored image at a desired time, the apparatus receives a broadcast stream including a plurality of still image frames and replays the images on a screen. The apparatus includes an image unit, which extracts and stores at least a portion of the plurality of the still image frames and replays the stored still image frames; and a control unit, which controls the extracting, storing, and replaying operations. The apparatus can be adapted to digital and analog broadcasts. In addition, in case of the digital broadcast, an I-frame may be extracted from a compressed image frame and stored. In particular, only some portion of the I-frame, that is, a lower slice of the I-frame, may be stored.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of Korean Patent Application No. 2003-87941, filed on Dec. 5, 2003 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an apparatus receiving and processing a broadcast image and a method therefor, and more particularly, to an image storing and/or replaying apparatus and a method therefor capable of conveniently viewing a past caption by storing a predetermined portion of an image including a caption and replaying the stored image at a desired time.  
         [0004]     2. Description of the Related Art  
         [0005]      FIG. 1A  illustrates a block diagram of a conventional digital broadcast receiver. The conventional digital broadcast receiver includes a tuner unit  10 , a transport stream parsing unit  11 , an A/V decoder  12 , a TV screen  13 , and a speaker  14 . If a broadcast channel is selected by the tuner unit  10 , a broadcast stream is received. The transport stream parsing unit  11  separates image transfer packets and voice transfer packets from 188-byte transfer packets constituting the broadcast stream of the selected broadcast channel. The A/V decoder  12  decodes and outputs the image and voice transfer packets to the TV screen  13  and the speaker  14 , respectively.  
         [0006]     The broadcast stream is an image signal compressed in accordance with a compression scheme such as an MPEG-2 scheme. The compressed image signal includes I-frames, P-frames, and B-frames. The I-frame is a frame capable of randomly accessing data without referring to the other frames. The I-frame is a frame including entire information upon which the reproducing apparatus can reproduce an image of a frame without any information of another frame. The I-frame is compressed using a JPEG compression scheme, that is, a still image compression scheme. The P-frame is a frame compressed by encoding a minute change of a current frame from preceding I-frame or P-frame. The B-frame is a frame compressed by referring to the foregoing and following I-frame and P-frame. Therefore, the B-frame and I-frame have the highest and lowest compression rates, respectively.  
         [0007]      FIG. 2  is a conceptual view explaining compression and decompression of an original image including 8 frames F 1  to F 8 . When the original image is compressed, the P-frame refers to the preceding I-frame or P-frame, and the B-frame refers to the preceding and following I-frame or P-frame. Therefore, the original image is encoded in a sequence of F 1 , F 2 , F 5 , F 3 , F 4 , F 8 , F 6 , and F 7 . On the other hand, in order to obtain a decompressed image, the encoded, compressed image is decoded in the same sequence.  
         [0008]     On the other hand, the digital broadcast receiver may further include a storage medium such as a hard disk drive storing the broadcast stream in order to function as a personal video recorder (PVR). In addition, the digital broadcast receiver may be implemented in a form of a set-top box separate from a TV set. Otherwise, the digital broadcast receiver may be built in the TV set.  
         [0009]      FIG. 1B  illustrates a block diagram of a conventional digital broadcast receiver. The conventional analog broadcast receiver includes a tuner unit  20 , a broadcast signal processing unit  21 , an amplifier unit  22 , a TV screen  23 , and a speaker  24 . If the tuner unit  20  selects a broadcast channel, a broadcast signal is received. The broadcast signal processing unit  21  performs intermediate frequency amplification on an image and voice of an output signal of the tuner unit  20  to separate the image signal from the voice signal. The amplifier unit  22  amplifies and outputs the separated image and voice signals to the TV screen  23  and the speaker  24 , respectively.  
         [0010]     The conventional digital and analog broadcast receivers have a problem in that the images broadcasted in real time cannot be stored. In particular, as the scene changes, the text displayed as a caption is erased. Therefore, a viewer must memorize or write down the text if desired.  
         [0011]     In addition, if text transiently displayed on the caption has a large amount of information, it is difficult for the viewer to completely memorize or write down the information.  
       SUMMARY OF THE INVENTION  
       [0012]     According to an aspect of the present invention, there is provided an image storing and/or replaying apparatus and a method therefor capable of conveniently viewing a past image by storing a broadcast image and replaying the stored image at a desired time.  
         [0013]     According to an aspect of the present invention, there is provided an image storing and/or replaying apparatus and a method therefor capable of conveniently viewing a past caption by storing a predetermined portion of an image including a caption and replaying the stored image at a desired time.  
         [0014]     According to an aspect of the present invention, there is provided an image storing and/or replaying apparatus receiving a broadcast stream having a plurality of still image frames and replaying an image on a screen, the apparatus including: an image unit, which extracts and stores at least a portion of the plurality of the still image frames and replays the stored still image frames; and a control unit, which controls the extracting, storing, and replaying operations.  
         [0015]     According to an aspect of the present invention, in the image storing and/or replaying apparatus, the broadcast stream may be a digital broadcast stream, and the image unit may include: a still image extracting unit, which extracts at least a portion of the plurality of the still image frames; and a still image storing unit, which stores the extracted still image frames. The image storing and/or replaying apparatus may further include a codex unit, which encodes the extracted still image frames in accordance with a predetermined compression scheme, and the still image storing unit may store the encoded still image frames.  
         [0016]     In the image storing and/or replaying apparatus, the codex unit may decompress the encoded still image frames stored in the still image storing unit in response to an external input signal indicating replaying the stored still image frames.  
         [0017]     In the image storing and/or replaying apparatus, the broadcast stream may be an analog broadcast stream, and the image unit may include: an image extracting unit, which extracts at least a portion of the plurality of the still image frames; an A/D converter, which converts the extracted analog still image frames into digital still image frames; an encoder, which compresses the digital still image frames in accordance with a predetermined still image compression scheme; a memory, which stores the compressed digital still image frame; a decoder, which decompresses the digital still image frames stored in the memory; and a D/A converter, which converts the decompressed digital still image frames into analog still image frames.  
         [0018]     According to an aspect of the present invention, in the image storing and/or replaying apparatus, the image unit may extract a portion of data from at least a portion of frames of the plurality of the still image frames. In the image storing and/or replaying apparatus, the extracting operation may be performed at a predetermined time interval. In the image storing and/or replaying apparatus, the control unit may control the replayed still image frames to be scrolled and displayed on the screen.  
         [0019]     According to an aspect of the present invention, there is provided an image storing and/or replaying apparatus receiving a broadcast stream having a plurality of compressed image frames including I-frames, P-frames, and B-frames and replaying an image on a screen, the apparatus including: an I-frame extracting unit, which extracts at least a portion of I-frames of the compressed image frames; an I-frame storing unit, which stores the extracted I-frames; a decoding unit, which decodes the stored I-frames in accordance with a predetermined decoding scheme to replay the I-frame; and a control unit, which controls the extracting, storing, and replaying operations.  
         [0020]     According to an aspect of the present invention, in the image storing and/or replaying apparatus, the I-frame extracting unit may extract the at least a portion of the I-frames at a predetermined time interval. In the image storing and/or replaying apparatus, the I-frame extracting unit may extract a portion of data in the I-frames.  
         [0021]     Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
         [0023]      FIGS. 1A and 1B  illustrate block diagrams of conventional digital and analog broadcast receivers;  
         [0024]      FIG. 2  is a view explaining compression and decompression of a digital image signal;  
         [0025]      FIG. 3  illustrates a block diagram of a digital broadcast receiver according to an embodiment of the present invention;  
         [0026]      FIG. 4  illustrates a block diagram of an analog broadcast receiver according to an embodiment of the present invention;  
         [0027]      FIG. 5  illustrates a block diagram of a digital broadcast receiver according to another embodiment of the present invention;  
         [0028]      FIG. 6  illustrates flowcharts of a broadcast image storing and/or replaying method according to an embodiment of the present invention; and  
         [0029]      FIG. 7  illustrates flowcharts of a broadcast image storing and/or replaying method according to still another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0030]     Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the present invention by referring to the figures.  
         [0031]      FIG. 3  illustrates a block diagram of a digital broadcast receiver according to an embodiment of the present invention. The digital broadcast receiver includes a tuner unit  10 , a transport stream parsing unit  11 , an A/V decoder  12 , a TV screen  13 , a speaker  14 , a still image extracting unit  15 , a codex unit  16 , a still image storing unit  17 , and a control unit  18 . Since the tuner unit  10 , the transport stream parsing unit  11  and the A/V decoder  12  have the same structures and function as conventional ones, their description is omitted. The still image extracting unit  15 , the codex unit  16 , and the still image storing unit  17  constitute the image unit.  
         [0032]     The still image extracting unit  15  extracts frames from an image decoded by the A/V decoder  12  and outputs the extracted frames to the codex unit  16 . The codex unit  16  compresses the extracted frames in accordance with a predetermined still image compression scheme such as the JPEG scheme. The still image storing unit  17  stores the compressed image frames. The control unit  18  controls the extracting, storing, and replying operations on the still image. On the other hand, the codex unit  16  is needed to store a great amount of all decoded frames of the original image output from the decoder  12 . Therefore, if there is a sufficient storage space, the codex unit  16  may be omitted.  
         [0033]     Now, the operation of the digital broadcast receiver according to the embodiment of the present invention will be described. The control unit  18  operates in response to commands input via an external input unit (not show) such as a function button panel and a remote control input device by a user. When the user inputs a still image storing command, the control unit  18  controls the still image extracting unit  15  to extract the still image frames output from the A/V decoder  12 .  
         [0034]     The user may input time information such as a storing time period, a storing starting time, and a storing ending time in addition to the still image storing command. The control unit  18  controls the extracting interval of the still image extracting unit  15  based on the time information. If the user does not input the time information, the time period may be set to a default value. In most cases, captions are displayed at a lower portion of a TV screen  13 . Therefore, only the lower portion of the frames output from A/V decoder  12  may be extracted. In some cases, another portion of the frames may be extracted in response to an external input.  
         [0035]     In response to a command of the control unit  18 , the still image extracting unit  15  extracts still image frames from the original image and outputs the extracted still image frames to the codex unit  16 . The codex unit  16  compresses the extracted still image frames in accordance with a predetermined still image compression scheme and stores the compressed still image frames in the still image storing unit  17 . On the other hand, if the to-be-stored still image frames exceed the storage capacity of the still image storing unit  17 , some of the stored still image frames are removed in a “first store first remove” manner.  
         [0036]     When the user inputs a replay command to the control unit  18 , the control unit  18  controls the still image storing unit  17  to output the stored still image frames to the codex unit  16 . The codex unit  16  decodes the compressed still image frame and outputs the decoded still image frame to the TV screen  13 . The control unit  18  controls the replayed still image frames to be scrolled on the TV screen  13 , so that the user can easily view the stored still image frames.  
         [0037]      FIG. 4  illustrates a block diagram of an analog broadcast receiver according to an embodiment of the present invention. The analog broadcast receiver includes a tuner unit  20 , a broadcast signal processing unit  21 , an amplifier unit  22 , a TV screen  23 , a speaker  24 , an image extracting unit  25 , an A/D converter  26 , an encoder  27 , a memory  28 , a D/A converter  29 , a decoder  30 , and a control unit  31 . Since the tuner unit  20 , the broadcast signal processing unit  21 , and the amplifier unit  22  in the embodiment have the same structures and function as conventional ones, their description is omitted. The image extracting unit  25 , the A/D converter  26 , the encoder  27 , the memory  28 , the D/A converter  29 , and the decoder  30  constitute still image storing means or the image unit.  
         [0038]     The analog broadcast receiver according to the embodiment of the present invention basically has the same structure as the digital broadcast receiver of  FIG. 3 . When time information such as an extracting time interval is input to the control unit  31 , the image extracting unit  25  detects image signals to extract an image with a predetermined time interval in response to a command of the control unit  31 . Similar to the digital broadcast image, the analog broadcast image includes a plurality of still images. In the below description, a frame refers to a still image as a unit of the analog broadcast image as well as the digital broadcast image.  
         [0039]     The extracted image is constituted with analog signals. The A/D converter  26  converts the analog signals to digital signals constituting the digital image. The converted still image frame is encoded in a predetermined compression scheme by the encoder  27  and stored in the memory  28 . Even in this case, the control unit  31  may control the image extracting unit  25  to extract some portion of the still image frame. On the other hand, in response to a replay command for replaying the still images stored in the memory  28 , the control unit  31  controls the memory  28  to output the still image. The output still images are decoded by the decoder  30  and converted to analog signals by the D/A converter  29 . The analog signals are output to the amplifier  22 .  
         [0040]     In addition, the image extracting scheme and the replaying scheme applied to the digital broadcast receiver of  FIG. 3  can be applied to the analog broadcast receiver of  FIG. 4 .  
         [0041]      FIG. 5  illustrates a block diagram of a digital broadcast receiver according to another embodiment of the present invention. The digital broadcast receiver includes a tuner unit  10 , a transport stream parsing unit  11 , an A/V decoder  12 , a TV screen  13 , a speaker  14 , an I-frame extracting unit  35 , an I-frame storing unit  36 , a control unit  37 , and a decoder  38 .  
         [0042]     Although the digital broadcast receiver of  FIG. 3  extracts the image processed by the A/V decoder  12 , the digital broadcast receiver according to the embodiment extracts only the I-frame from the compressed image which is not processed by the A/V decoder  12 . In principle, two or more compressed images are contained in the I-frames per second, and the caption resides on a screen for one or more seconds. The digital broadcast receiver according to the embodiment is implemented as follows.  
         [0043]     In addition, since the P-frame or B-frame refers to other I-frames and/or P-frames in order to decompress the still image, it is of no use to extract the P-frame or B-frame which is not processed by the A/V decoder  12 .  
         [0044]     In response to a command of the control unit  37 , the I-frame extracting unit  35  extracts only the I-frame from the compressed image separated by the transport stream parsing unit  11  within a predetermined extracting time interval. In this case, an external input signal may include a still image extracting command and information about the extracting time interval, etc. In addition, at the set time, if the frame output from the transport stream parsing unit  11  is not an I-frame, the I-frame extracting unit  35  extracts an I-frame output at the nearest time.  
         [0045]     The I-frame storing unit  36  stores the I-frame output from the I-frame extracting unit  35 , and outputs the stored I-frame to the decoder  38  in response to the replay command of the control unit  37 . The decoder  38  decodes the compressed I-frame in accordance with the same compression scheme as the predetermined compression scheme such as the JPEG compression scheme, and outputs the decoded I-frame on the TV screen.  
         [0046]     Now, operations of a digital broadcast receiver according to another embodiment of the present invention will be described. When a user inputs a still image storing command and a storing time interval, etc., using an external input unit (not shown), the control unit  37  controls an extracting operation for extracting I-frame output from a transport stream parsing unit  11  with a predetermined extracting time interval. The controller  37  may control an extracting operation for extracting some portion of the I-frame, for example, a lower slice of the I-frame. As a result, it is possible to view not the entire image but the caption thereof, if desired.  
         [0047]     The I-frames extracted by the I-frame extracting unit  35  are stored in the I-frame storing unit  36 . In response to a command from the control unit  37 , the stored I-frames are output to the decoder  38 , and the stored I-frame is displayed on the TV screen  13 . The control unit  37  controls the I-frame to be scrolled on the TV screen  13 , so that the user can conveniently view the still image or the caption.  
         [0048]      FIGS. 6A and 6B  illustrate flowcharts of a broadcast image storing and/or replaying method according to an embodiment of the present invention Firstly,  FIG. 6A  is a flowchart illustrating operations of extracting and storing a still image frame. In operation S 610 , it is determined that an external extracting start signal is input. If the signal is input, the procedure proceeds to operation S 620  of extracting the still image frame with a predetermined extracting time interval which is input together with the extracting start signal. In operation  630 , the extracted still image frame is compressed in accordance with a predetermined still image compression scheme such as a JPEG compression scheme. In operation  640 , the compressed still image frame is stored.  
         [0049]      FIG. 6B  is a flowchart illustrating operations of decompressing and replaying the stored still image frame. In operation S 650 , it is determined whether an external replay signal is input. If the signal is input, the procedure proceeds to operation S 660  of decompressing the compressed still image frame in accordance with the same scheme as the still image compression scheme. In operation  670 , the decompressed still image frame is displayed on the TV screen  13 .  
         [0050]      FIGS. 7A and 7B  illustrate flowcharts of an I-frame storing and/or replaying method in a digital broadcast receiver according to another embodiment of the present invention.  
         [0051]      FIG. 7A  is a flowchart illustrating operations of extracting and storing the I-frame. In operation S 710 , it is determined whether an external extracting start signal is input. If the signal is input, the procedure proceeds to operation S 720  of determining whether or not it is the set time input together with the extracting start signal. If it is the set time, the procedure proceeds to operation  730 . In operation  730 , it is determined whether or not the compressed image frame output from the transport stream parsing unit  11  at the set time is an I-frame. If the compressed image frame is the I-frame, the I-frame is extracted in operation  740 . If not, in operation  750 , the I-frame occurring at the nearest time is extracted.  
         [0052]      FIG. 7B  is a flowchart illustrating operations of replaying the stored I-frame. In operation S 760 , it is determined whether an external replay signal is input. If the signal is input, the procedure proceeds to operation S 770  of decoding the stored I-frame. The decoded I-frame is replayed in operation  780 .  
         [0053]     According to the present invention, since a broadcast image is stored and the stored image is replayed at a desired time, it is possible to conveniently view a past image.  
         [0054]     In addition, according to the present invention, since a predetermined portion of an image including a caption is stored and the stored image is replayed at a desired time, it is possible to conveniently view a past caption.  
         [0055]     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.