certain exemplary embodiments will now be described in greater detail with reference to the accompanying drawings . in the following description , the same drawing reference numerals are used for the same elements even in different drawings . the matters defined in the description , such as detailed construction and elements , are provided to assist in a comprehensive understanding of exemplary embodiments . thus , it is apparent that exemplary embodiments can be carried out without those specifically defined matters . also , well - known functions or constructions are not described in detail since they would obscure the exemplary embodiments with unnecessary detail . fig1 illustrates a home network to which exemplary embodiments are applicable . the home network in fig1 comprises 1 ) a blu - ray disk player ( bdp ) 100 and a dtv - 1 210 located in a room - 1 10 , 2 ) a dtv - 2 220 located in a room - 2 20 , and 3 ) a dtv - 3 230 located in a room - 3 30 . the bdp 100 is a kind of source device which provides contents recorded in a blu - ray ( bd ). the dtvs 210 , 220 , 230 are kinds of sink devices which output contents provided by the bdp 100 working as a source device and provide the contents for a user . the dtvs 210 , 220 , 230 are connected to the bdp 100 to communicate with each other . accordingly , contents and a control command / request can be transmittable between the dtvs 210 , 220 , 230 and the bdp 100 . in detail , the bdp 100 can send contents generated by playing a bd to the dtvs 210 , 220 230 . moreover , the bdp 100 can generate a command / request to control the dtvs 210 , 220 , 230 and send it to the dtvs 210 , 220 , 230 . moreover , a control command on the bdp 100 can be input into the dtvs 210 , 220 , 230 by a user and can be sent to the bdp 100 . fig2 is a detailed block diagram of the bdp 100 illustrated in fig1 . as illustrated in fig2 , the bdp 100 comprises a bd playing unit 110 , an audio / video ( av ) processing unit 120 , a communication interface 130 , a control unit 140 , and a user - input unit 150 . the bd playing unit 110 reads content data recorded on the bd and sends it to the av processing unit 120 . the av processing unit 120 performs necessary signal processing on the content data sent from the bd playing unit 110 . in detail , the av processing unit 120 decompresses the content data sent from the bd playing unit 110 . moreover , the av processing unit 120 can also separate the decompressed content into a video signal and an audio signal . the communication interface 130 is connected to the previously - mentioned dtvs 210 , 220 , 230 to communicate with each other . a content control command / request is exchanged between the bdp 100 and the dtvs 210 , 220 , 230 through the communication interface 130 . the control unit 140 controls the functions of the bdp 100 in general based on 1 ) a control command input from the user - input unit 150 , or 2 ) a control command received from the dtvs 210 , 220 , 230 through the communication interface unit 130 . the control command ‘ 1 )’ refers to a control command directly input by a user into the bdp 100 unit to control the bdp unit 100 . the control command ‘ 2 )’ refers to a control command indirectly input by a user through the dtvs 210 , 220 , 230 , to control the bdp unit 100 . particularly , the control unit 140 controls the bdp 100 and the dtvs 210 , 220 , 230 to ensure that one dtv , which is a sink device where the contents read by the bd playing unit 110 and signal processed by the av processing unit 120 are output , can be changed to a different dtv where contents can be output . in detail , the control unit 140 controls a sink device which outputs contents , wherein the sink device can be changed , or converted among the dtvs 210 , 220 , 230 . sink device conversion is performed based on the command of a user . a process where the control unit 140 controls a sink device conversion , if a user commands a sink device to be converted from the dtv - 1 210 to the dtv - 2 220 , will be explained in detail with reference to fig3 . fig3 is a flow chart provided to explain a sink device conversion method according to an exemplary embodiment . a sink device conversion command is input by a user through the sink device dtv - 1 210 where contents are being output , and is sent to the bdp 100 . as illustrated in fig3 , if a sink device conversion command ( from the dtv - 1 to the dtv - 2 ) is received from dtv - 1 ( 210 ) ( s 320 — y ) while contents are being transmitted to the dtv - 1 210 ( s 310 ), the control unit 140 suspends the ongoing content transmission which has been going on in operation s 310 . ( s 330 ) in operation s 330 , content playing / transmission is suspended automatically in the bdp 100 , and outputting is suspended automatically in the dtv - 1 210 . to resume the content playing / transmitting and outputting , the user needs to move from room - 1 to room - 2 and input a sink device conversion approval into the dtv - 2 220 . the dtv - 2 220 sends the sink device conversion approval input by the user , to the bdp 100 . when the sink device conversion approval is received from the dtv - 2 220 ( s 340 — y ), the control unit 140 controls the bd playing unit 110 and the av processing unit 120 to resume the playing of contents . the control unit 140 controls the communication interface unit 130 to transmit the played contents to the dtv - 2 220 ( s 350 .) if a sink device conversion approval is received from the dtv - 2 220 ( s 340 — y ), it means that the user is ready to watch the contents through the dtv - 2 220 . content transmission in operation s 350 takes place after the moment when the transmission is suspended in operation s 330 ; i . e ., to enable a user to watch the contents seamlessly . since then , the control unit 140 transfers a bdp control authority from the dtv - 1 210 to dtv - 2 220 ( s 360 .) the dtv , which has the control authority , is a dtv where a user command on the bdp unit 100 such as commands to play , pause , fast forward and rewind a content in the bdp 100 are input . the control authority is transferred from the dtv - 1 210 to dtv - 2 220 . therefore , a user can input a command about the bdp unit 100 through the dtv - 2 220 , not through the dtv - 1 210 . accordingly , the bdp unit 100 receives a command related to the performance of its functions from the dtv - 2 220 , not from the dtv - 1 210 . thus far , a case has been described where a user inputs a sink device conversion approval into the dtv which is commanded to be converted into a sink device . in other words , the case has been described that , 1 ) after a user commands to convert a sink device from the dtv - 1 210 to the dtv - 2 220 , 2 ) a user inputs a sink device conversion approval into the dtv - 2 220 after moving to the room - 2 . however , a case can occur where a user inputs a sink device conversion approval into another dtv , not the dtv which is commanded by a user to convert a sink device , because of ignorance or misunderstanding of the user . for example , 1 ) a user commands to covert a sink device from the dtv - 1 210 to the dtv - 2 220 , 2 ) but the user misidentifies the dtv - 3 230 located in the room - 3 as the dtv - 2 220 , thus moving to the room - 3 and inputting a sink device conversion approval into the dtv - 3 230 . in this case , the control unit 140 receives a sink device conversion approval from the dtv - 3 230 , not from the dtv - 2 220 . in such a case , a process of sink device conversion approval will be explained below in detail . detailed explanation on operation s 410 or operation s 430 in fig4 can be inferred from the explanation on operation s 310 or s 330 illustrated in fig3 , and is omitted . a sink device conversion approval is received from the dtv - 3 230 , not from the dtv - 2 220 , the control unit 140 transmits a request for confirmation on , whether to convert a sink device to the dtv - 3 230 not to the dtv - 2 220 , to the dtv - 3 230 ( s 450 ). the dtv - 3 330 , which receives the conversion confirm request transmitted in operation s 450 , displays a text message on a display to ask whether to ‘ convert a sink device to the dtv - 3 230 , not to the dtv - 2 220 .’ the dtv - 3 330 receives a response from a user about the message and sends it in response to the confirm request from the bdp 100 . if a “ positive ” confirm response is received from the dtv - 3 230 ( s 460 — y ), the control unit 140 controls the bd playing unit 110 and the av processing unit 120 to resume the playing of contents , and controls the communication interface unit 130 to send the played contents to the dtv - 3 230 ( s 470 ). if a confirm response is received from the dtv - 3 230 , a user confirms that a sink device has been converted to the dtv - 3 230 , not to the dtv - 2 220 . thus , the contents are transmitted to the dtv - 3 230 in operation s 470 . afterwards , the control unit 140 transfers a control authority on the bdp 100 from the dtv - 1 210 to the dtv - 3 230 ( s 480 ). accordingly , the bdp 100 receives a command related to its functions from the dtv - 3 230 , not from the dtv - 1 210 . if a “ negative ” confirm response is received from the dtv - 3 230 ( s 460 — n ), the control unit 140 performs operation s 340 in fig3 . accordingly , if a sink device conversion approval is received from the dtv - 2 220 ( s 340 — y ), the control unit 140 performs operations s 350 and s 360 . after operation s 330 in fig3 and operation s 430 in fig4 , the control unit 140 can transmit a ‘ power turn - off ’ command to the dtv - 1 310 . that is to automatically turn off the power of the dtv - 1 310 where contents will not be output , because the content output is suspended now . after operation s 330 in fig3 or operation s 430 in fig4 , the control unit 140 can transmit a ‘ power turn - on ’ command to the dtv - 2 320 . that is to automatically turn on the power of the dtv - 1 310 where the contents will be output . in the above examples , contents are output through one dtv . however , that is just an example . accordingly , it is possible to realize that the contents can be transmitted to more than two sink devices and be output . for example , the contents , which were output from the dtv - 1 210 , can be transmitted to both of dtv - 2 220 and dtv - 3 230 and be output . moreover , a video signal and a audio signal contained in the contents can be transmitted to respective sink devices and be output . for example , as illustrated in fig5 , under the home network , the bdp 100 can separate the contents into a video signal and an audio signal , 1 ) send the video signal to the dtv - 220 , and 2 ) the audio signal to a hts ( home theater system ) 240 . in this case , a user can watch a video through the dtv - 2 220 in the room - 2 , and listen to an audio through the hts 240 . the home networks in fig1 and fig5 are examples of networks to which exemplary embodiments are applicable . exemplary embodiments are not limited to the illustrated home network and can also be applicable to a different network from the illustrated one . the devices mentioned in the home network assumed can be connected by a physical connection , but that is just an example for a better explanation . they can also be connected in a wireless manner . the bdp mentioned in the above examples is a kind of source device and can be replaced with other kinds of devices other than the bdp . dtv and hts are kinds of sink devices , therefore they can also be replaced with other kinds of devices . as explained thus far , according to exemplary embodiments , a user can suspend the contents being transmitted to a sink device , transmit the contents to another sink device which the user wants , and change the sink device that outputs the contents . accordingly , the user can convert the sink device to be provided with the contents , freely , so that the user enjoys more convenience . the foregoing exemplary embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention . the present teaching can be readily applied to other types of apparatuses . also , the description of the exemplary embodiments is intended to be illustrative , and not to limit the scope of the claims , and many alternatives , modifications , and variations will be apparent to those skilled in the art .