1. A method of controlling video data transmitted to a sink device from a source device, the method comprising: outputting video data received from the source device to a display unit; recognizing a text from a screen corresponding to the video data outputted to the display unit; saving the recognized text to a memory to correspond to location information on the screen corresponding to the video data; receiving, at the sink device, a voice signal from the source device wherein the source device corresponds to a remote controller that is wirelessly connected to the sink device; converting the received voice signal into a text using a speech-to-text (STT) function at the sink device; and if a specific text including at least one portion of the converted text exists in the recognized text, sending a message corresponding to a user input of selecting the specific text from the screen corresponding to the video data to the source device via user input back channel (UIBC), wherein the sink device comprises the display unit configured to display video data received from the source device, and wherein the UIBC is not configured to transmit the voice signal.
2. The method of claim 1 , wherein recognizing the text from the screen corresponding to the video data outputted to the display unit comprises: receiving a signal indicating a change of a screen of the source device from the source device; capturing the screen corresponding to the video data outputted to the display unit in response to the received signal; and recognizing the text from the captured screen.