Abstract:
A digital broadcast receiving apparatus and a method thereof are disclosed. The digital broadcast receiving apparatus includes a demultiplexer for separating a multichannel transport stream into a plurality of broadcasting channel data and outputting the broadcasting channel data, a buffer unit, including a plurality of buffers having different capacities that correspond to data bit rates, for storing the broadcasting channel data in the buffers having the corresponding capacities, respectively, according to the data bit rates, a user interface for outputting channel identification information corresponding to the broadcasting channel selected by a user, and a switching device for selecting one of outputs of the plurality of buffers according to the channel identification information.

Description:
PRIORITY  
       [0001]     This application claims priority to an application entitled “Digital Broadcast Receiving Apparatus and Method Thereof” filed in the Korean Industrial Property Office on Sep. 10, 2004 and assigned Serial No. 2004-72577, the contents of which are hereby incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a digital broadcast receiving apparatus and a method thereof.  
         [0004]     2. Description of the Related Art  
         [0005]     With the development of digital broadcasting technology and mobile communication technology, the provision of digital broadcasts to a mobile user has become an increasing matter of concern. Digital multimedia broadcasting (hereinafter referred to as a “DMB”) is a broadcasting service that enables a user to view diverse multimedia broadcasts on multiple channels using a personal portable receiver or a mobile vehicle receiver. Particularly, the satellite DMB adopted in Korea selects a CDM (Code Division Multiplexing) technology that is similar to a CDMA mobile phone as the Standard Rec. BO.1130-4: System-E of ITU (International Telecommunication Union).  
         [0006]     In existing digital broadcast receiving apparatuses, a buffer is filled with broadcasting program data before providing the program to the user through a speaker and a display unit. The time it takes to actually view a selected program includes the time it takes to respond to user input, via a keypress, plus the time it takes to buffer the program. In effect, the time required for selecting the broadcasting channel in the digital broadcasting corresponds to the size of the buffer.  
         [0007]     In such a DMB system, a plurality of broadcasting channels having different bit rates may be allocated to one transmission channel. For example, in the case of an audio broadcasting, four broadcasting channels of 64 Kbps, 48 Kbps, 48 Kbps and 32 Kbps are allocated to a certain transmission channel, and four broadcasting channels of 48 Kbps, 40 Kbps, 32 Kbps and 32 Kbps are allocated to another transmission channel. The minimum bit rate of the broadcasting channel is 24 Kbps.  
         [0008]     For practical applications, the digital broadcast receiving apparatus should include a buffer sufficient for the largest bit rate. For example, a buffer having a size corresponding to the buffering of the 64 Kbps broadcasting channel data for two seconds requires a 5.33-second buffering time in buffering the 24 Kbps broadcasting channel data. If the time required to fill half of this buffer with the 64 Kbps broadcasting channel data is one second, the time required to fill half of this buffer with the 24 Kbps broadcasting channel data is 2.67 seconds.  
         [0009]     As described above, in the digital broadcast receiving apparatus, the buffer-filling times are different from one another according to selected broadcasting channels, and this causes the waiting time (time to output the broadcasting channel data) to be different according to the selected broadcasting channel. Where the audio broadcasting channel buffer for the maximum bit rate is also used for the minimum bit rate, it increases the waiting time for broadcasting channel selection and output.  
       SUMMARY OF THE INVENTION  
       [0010]     Accordingly, the present invention has been designed to solve the above and other problems occurring in the prior art, and provides a digital broadcast receiving apparatus and a method thereof that can reduce the time required for broadcasting channel selection in receiving a digital broadcast.  
         [0011]     The present invention also provides a digital broadcast receiving apparatus and a method thereof that can select a broadcasting channel at high speed in a digital broadcasting.  
         [0012]     In one aspect of the present invention, there is provided a digital broadcast receiving apparatus which includes a demultiplexer for separating a multichannel transport stream into a plurality of broadcasting channel data and outputting the broadcasting channel data, a buffer unit, including a plurality of buffers having different capacities that correspond to data bit rates, for storing the broadcasting channel data in the buffers having the corresponding capacities, respectively, according to the data bit rates, a user interface for outputting channel identification information corresponding to the broadcasting channel selected by a user, and a switching device for selecting one of outputs of the plurality of buffers according to the channel identification information. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:  
         [0014]      FIG. 1  is a block diagram illustrating the construction of a digital broadcast receiving apparatus according to a preferred embodiment of the present invention;  
         [0015]      FIG. 2  is a block diagram illustrating the construction of an MPEG decoder according to an embodiment of the present invention;  
         [0016]      FIG. 3  is a view illustrating the structure of a database according to an embodiment of the present invention;  
         [0017]      FIG. 4  is a flowchart illustrating an operation of a PID detection unit according to an embodiment of the present invention; and  
         [0018]      FIG. 5  is a flowchart illustrating a control flow during an audio broadcasting channel selection in a digital broadcast receiving apparatus according to an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     Preferred embodiments of the present invention will be described in detail hereinafter with reference to the accompanying drawings. In the following description of the present invention, only the parts for understanding the operation of the present invention will be explained, but a detailed description of known functions and configurations incorporated herein will be omitted when it may obscure the subject matter of the present invention.  
         [0020]      FIG. 1  is a block diagram illustrating the construction of a digital broadcast receiving apparatus according to a preferred embodiment of the present invention. In the following description of the present invention, it is assumed that a digital audio broadcast from among digital multimedia broadcasts is received. Referring to  FIG. 1 , the digital broadcast receiving apparatus  100  according to the preferred embodiment of the present invention includes a CDM (Code Division Multiplexing) channel processing unit  110  for deinterleaving and outputting CDM channel data received through at least one CDM channel CDM 0  to CDMN, a merge unit  120  for merging the CDM channel data and generating a transport stream, an MPEG decoder  130  for MPEG-decoding the transport stream from the merge unit  120  and outputting specified broadcasting channel data, and a codec  140  for converting a digital signal that is the broadcasting channel data provided from the MPEG decoder  130  into audio and video signals.  
         [0021]     The CDM channel processing unit  110  is constructed to receive and process about five CDM channels. Essentially, the CDM channel processing unit  110  receives a channel for transmitting pilot information, a channel for transmitting EPG (Electronic Program Guide) information and a channel for transmitting CAS (Conditional Access System) information. Additionally, the CDM channel processing unit  110  can actually receive at least one CDM transmission channel for transmitting broadcasting channel data.  
         [0022]     In this case, the number of CDM channels that can be decoded by the digital broadcast receiving apparatus is generally smaller than the number of CDM channels provided from the DMB system. For example, according to the transmission/reception standard of a satellite DMB of, such as the ARIB STD B41—a collection of satellite DMS transmitting standards suggested by the Association of Radio Industries and Businesses (ARIB) in Japan—the DMB system uses thirty channels in a manner that it transmits data through twenty-nine channels and transmits a control signal through one channel. Data of 512 Kbps is transmitted through each of the twenty-nine channels for transmitting data. Since the data of 512 Kbps becomes the data of 256 Kbps through a ½-convolution coding and then becomes the data of about 236 (=188/204) Kbps through an R-S coding, effective data of about 236 Kbps can be transmitted through each channel. Accordingly, the satellite DMB system can transmit data of about 6.844 Mbps in all, since twenty-nine channels exist. In the future, the digital broadcast receiving apparatus may be constructed to process five or more CDM transmission channels, and the present invention can be applied to this digital broadcast receiving apparatus as well.  
         [0023]     The DMB system can transmit an AV (Audio/Video) broadcasting channel data through two CMD transmission channels instead of one CMD transmission channel. In the case of an audio broadcasting channel, multiple audio broadcasting channel data can be served through one transmission channel. The audio broadcasting channel data capacity is of about 48 Kbps, and thus a transmission channel (i.e., CDM channel) can carry about 5 (=236/48) audio broadcasting channel data. Several broadcasting channel data are mixed and carried in the transmission channel through multiplexing equipment.  
         [0024]     The CDM channel processing unit  110  can receive at least one CDM transmission channel for transmitting the broadcasting channel data stream. The deinterleaved CDM channel data output from the CDM channel processing unit  110  is output to the merge unit  120 . The merge unit  120  generates a transport stream by merging the CDM channel data. As described above, since the broadcasting channel data are multiplexed through various transmission channels, the merge unit  120  generates the transport stream from the received CDM channels, and provides the transport stream to the MPEG decoder  130 . The transport stream may include one or more broadcasting channel data since the merge unit  120  merges the broadcasting channel data and generates the transport stream, which includes various broadcasting channel data.  
         [0025]     The MPEG decoder  130  extracts the broadcasting channel data from the transport stream output from the merge unit  120  according to the user&#39;s selection. If the user selects a broadcasting channel, a PID (Packet ID) corresponding to the selected broadcasting channel is provided to the MPEG decoder  130 . The MPEG decoder  130  outputs the desired broadcasting channel data among the transport stream according to the selected PID. The codec  140  converts the digital signal that is the broadcasting channel data provided from the MPEG decoder  130  into an audio signal or a video signal.  
         [0026]      FIG. 2  is a block diagram illustrating the construction of an MPEG decoder according to an embodiment of the present invention. Referring to  FIG. 2 , the MPEG decoder  130  includes a transport stream (TS) demultiplexer  210 , a buffer unit  220 , a multi-buffer switching unit  230 , a database  240  and a PID detection unit  260 . When receiving the digital broadcast, a transport stream in which a plurality of broadcasting channels are multiplexed is applied to the transport stream demultiplexer  210 .  
         [0027]     As described above, in the case of a satellite DMB or a digital audio broadcast that uses the transport stream, a plurality of audio broadcasting channel data are carried on one transmission channel. For example, in the case of the satellite DMB, a CDM channel has a transmission capacity of 256 Kbps, whereas the channel data rate of one audio broadcasting station is in the range of about 24 Kbps to 64 Kbps. Typically, four to six audio broadcasting channel data can be carried on a CDM channel.  
         [0028]     In the case of receiving two multiplexed CDM channels, for example, it corresponds to the reception of 10 or more audio broadcasting channels. In effect, as described above, all the received broadcasting channel data are merged into the same transport stream by the merge unit  120 , and the transport stream is transferred to the TS demultiplexer  210 .  
         [0029]     In order for the TS demultiplexer  210  to demultiplex the same transport stream into the plurality of broadcasting channel data, information about the PID allocated by broadcasting channels should be recognized. For this, the MPEG decoder  130  includes a database  240  with broadcasting channel data and corresponding information of CDM transmission channels. The structure of the database  240  is illustrated in  FIG. 3 .  
         [0030]     Referring to  FIG. 3 , the database  240  has information about a service ID  310 , a PMT (Program Map Table) PID  320 , an AUD (Audio) PID  330 , a CDM channel number  340 , a broadcasting channel capacity  350 , etc. The service ID  310  refers to information for identifying a program selected by the user. The PMT PID  320  and the AUD PID  330  refer to PSI (Program Specific Information) transmitted through the EPG channel and so on for transmitting the EPG. An EPG engine (not illustrated) may collect the PSI information and construct the database  240 .  
         [0031]     The PID detection unit  260  detects the PID from the database  240  according to the broadcasting channel selected by the user through the user interface  250 . Specifically, the PID detection unit  260  receives an input of a broadcasting channel from the user interface  250 . Additionally, the PID detection unit  260  can recognize the PID values related to the CDM channel presently received through the database  240 . Accordingly, the PID detection unit  260  can recognize the number of all broadcasting channels existing in the present transport stream and the corresponding PID values. The PID detection unit  260  selectively arranges the PID values existing in the present transport stream and the related information on a table, and provides the table to the TS demultiplexer  210  and the multi-buffer switching unit  230 . The operation of the PID detection unit  260  will now be explained in detail with reference to  FIG. 4 .  
         [0032]      FIG. 4  is a flowchart illustrating an operation of a PID detection unit according to an embodiment of the present invention. Referring to  FIG. 4 , the PID detection unit  260  receives the PID corresponding to the broadcasting channel from the user interface at step  410 . The user interface  250 , if the user selects a specified broadcasting channel, provides the corresponding PID to the PID detection unit  260 . Then, the PID detection unit  260  searches for the presently received CDM channel with reference to the database  240  at step  420 . The PID detection unit  260  obtains all the PIDs of the present transport stream using the search results of the CDM channel information at step  430 . In addition, the PID detection unit  260  determines whether the PID of the broadcasting channel selected by the user exists among the PIDs of the present transport stream. If the PID of the broadcasting channel selected by the user is one of the PIDs of the present transport stream, the PID detection unit  260  provides the corresponding PID information to the multi-buffer switching unit  230  at step  440 , to make the multi-buffer switching unit  230  switch the buffer for the corresponding broadcasting channel data to the codec  140 .  
         [0033]     If the PID of the broadcasting channel selected by the user does not exist in the present transport stream, the digital broadcast receiving apparatus receives a new CDM channel. Accordingly, the PID detection unit  260  selectively arranges the PID values corresponding to the new CDM channel and the related information on a table, and provides the table to the TS demultiplexer  210  and the multi-buffer switching unit  230 .  
         [0034]     Referring again to  FIG. 2 , the TS demultiplexer  210  separates the transport stream into the respective broadcasting channel data with reference to the PID values provided from the PID detection unit  260 , and provides the broadcasting channel data to the buffer unit  220 . In this case, the TS demultiplexer  210  can allocate the respective broadcasting channel data to a plurality of ring buffers  222 ,  224 , . . . ,  226  provided in the buffer unit  220  to match their buffering capacities with reference to the bit rate information by broadcasting channels provided from the PID detection unit  260 .  
         [0035]     Specifically, the respective ring buffers  222 ,  224 , . . . ,  226  buffer the broadcasting channel data received from the TS demultiplexer. In this case, since the bit rates of the plurality of broadcasting channel data are different, the ring buffers each have unique capacities different from one anther. The capacities of the ring buffers are determined based on the bit rates. The TS demultiplexer  210  provides the respective broadcasting channel data to the plurality of ring buffers  222 ,  224 , . . . ,  226  according to the broadcasting channel bit rates.  
         [0036]     For example, if about 10 audio broadcasting channel data have the data rate of about 512 Kbps and the respective ring buffers buffer the input broadcasting channel data for two seconds, the whole size of the buffer unit  220  becomes about 1028 Kbit (i.e., 128 Kbyte). Memory size of this scale does not impose a great burden on the digital broadcast receiving apparatus.  
         [0037]     The respective ring buffers  222 ,  224 , . . . ,  226  output the buffered channel data to the multi-buffer switching unit  230 . If the user selects a broadcasting channel, the multi-buffer switching unit  230  receives the PID information that corresponds to the broadcasting channel selected by the user from the user interface  250 . The multi-buffer switching unit  230  switches one of the outputs of the plurality of ring buffers  222 ,  224 , . . . ,  226  in the buffer unit  220  to the codec  240  according to the PID information provided from the user interface  250 .  
         [0038]     As described above, according to the present invention, by simultaneously storing a plurality of broadcasting streams in the multiple ring buffers and directly switching the corresponding audio ring buffer to the codec using the pre-allocated broadcasting stream and buffer information when a broadcasting channel selection command is input, a high-speed broadcasting channel selection can be achieved.  
         [0039]      FIG. 5  is a flowchart illustrating the control flow when the audio broadcasting channel is selected in the digital broadcast receiving apparatus according to an embodiment of the present invention where audio broadcasting channel is received. However, it is apparent that the present invention can also be applied to AV broadcast reception.  
         [0040]     Referring to  FIG. 5 , the MPEG decoder  130  waits for the multichannel audio stream from the merge unit  120  at step  510 . Once received, the MPEG decoder  130  proceeds to step  520 , and inputs the received audio stream to the TS demultiplexer  210 . The TS demultiplexer  210  separates the multichannel audio stream into a plurality of broadcasting channel data. Then, the MPEG decoder  130  proceeds to step  530 , and provides the separated broadcasting channel data to the buffer unit  220 . The respective ring buffer  222 ,  224 , . . . ,  226  of the buffer unit  220  buffers the broadcasting channel data received from the TS demultiplexer  210 .  
         [0041]     Then, the MPEG decoder  130  judges whether the user selects the broadcasting channel at step  540 . If the user selects a broadcasting channel, the MPEG decoder  130  receives the PID information that corresponds to the broadcasting channel selected by the user through the user interface  250 . Accordingly, the MPEG decoder  130  controls the multi-buffer switching unit  230  to switch to one of the outputs of the plurality of ring buffers  222 ,  224 , . . . ,  226  according to the PID information provided from the user interface  250  at step  550 . Then, the digital broadcast receiving apparatus determines whether the reception of the digital broadcast is terminated at step  560 . The digital broadcast reception may be terminated by the user at any time. In addition, the digital broadcast reception may be terminated if the digital broadcast receiving apparatus moves to a place where the digital broadcast is not received any more, or due to the discharge of a battery. If the digital broadcast reception is not terminated, the digital broadcast receiving apparatus returns to step  540 .  
         [0042]     As described above, according to the present invention, the waiting time required for broadcasting channel selection can greatly be reduced by removing the time for filling the buffer with data. Additionally, even if the buffer size is increased, it does not affect the waiting time for the broadcasting channel selection, and thus the stability of the receiving apparatus can be increased.  
         [0043]     While the present invention has been shown and described with reference to certain preferred 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 present invention as defined by the appended claims.