Video telephony apparatus and signal transmitting/receiving method for mobile terminal

1. A signal transmitting method for a transmitting mobile terminal, comprising:

establishing a video call connection to a receiving mobile terminal;

setting a captioned video mode according to a user selection;

collecting both an image signal carrying a photographed image and an audio signal including a voice signal;

generating a text caption signal using the voice signal;

combining the text caption signal and image signal into a video signal without the voice signal;

encoding and compressing the video signal; and

multiplexing the compressed video signal and the audio signal into a multiplex signal, and transmitting the multiplex signal to the receiving mobile terminal.

2. The signal transmitting method of claim 1 , wherein the generating the text caption signal step comprises:

analyzing the voice signal to recognize phonemes, morphemes, and syllables;

generating a sequence of words using the recognized syllables; and

converting the generated sequence of words into the text caption signal.

3. The signal transmitting method of claim 1 , wherein the multiplex signal further includes a control signal for audio/video synchronization.

4. The signal transmitting method of claim 1 , wherein a text caption corresponding to the text caption signal is displayed at an edge region of a display unit of the other mobile terminal, and a display size of the displayed text caption is adjustable.

5. A signal receiving method for a receiving mobile terminal, comprising:

establishing a video call connection to a transmitting mobile terminal;

receiving a multiplex signal through the video call connection from the transmitting mobile terminal;

demultiplexing the received multiplex signal into an audio signal, a compressed video signal without a voice signal being compressed thereon, and a control signal;

reproducing the audio signal through a speaker;

separating the compressed video signal into a text caption signal and an image signal;

displaying the text caption signal and the image signal in a manner synchronized with the audio signal.

6. The signal receiving method of claim 5 , wherein audio reproduction and video display are performed independently from each other.

7. The signal receiving method of claim 5 , wherein the displaying step comprises:

displaying the image signal on a full screen of a display unit; and

displaying the text caption signal in a display area allocated on the screen or in a manner overlapped with displayed images on the screen.

8. The signal receiving method of claim 5 , wherein the control signal carries synchronization data for audio/video synchronization.

9. The signal receiving method of claim 5 , wherein a text caption corresponding to the text caption signal is displayed at an edge region of a screen of a display unit, and a display size of the displayed text caption is adjustable.

10. A signal transmitting/receiving method for mobile terminals, comprising:

establishing a video call connection between a transmitting mobile terminal and a receiving mobile terminal;

converting a voice signal in a collected audio signal into a text caption signal;

combining the text caption signal and image signal into a video signal without the voice signal;

encoding and compressing the video signal;

multiplexing the audio signal and a compressed video signal into a multiplex signal;

transmitting the multiplex signal through the video call connection;

receiving the multiplex signal through the video call connection; and

demultiplexing the received multiplex signal into the compressed video signal and audio data, and outputting the audio data.

11. The signal transmitting/receiving method of claim 10 , further comprising

combining the compressed video signal and the audio signal.

12. The signal transmitting/receiving method of claim 10 , wherein the demultiplexing step comprises:

reproducing the audio data through a speaker; and

displaying text caption data and image data from the compressed video signal.

13. The signal transmitting/receiving method of claim 10 , wherein the multiplex signal further includes a control signal for audio/video synchronization.

14. The signal transmitting/receiving method of claim 12 , wherein a text caption corresponding to the text caption data is displayed at an edge region of a screen of a display unit in the receiving mobile terminal, and a display size of the displayed text caption is adjustable.

15. A video telephony apparatus for a mobile terminal, comprising:

a radio frequency unit for establishing a video call connection with another mobile terminal;

an audio processor for collecting and reproducing an audio signal including a voice signal;

a caption generator for converting the voice signal into a text caption signal;

a camera module for photographing a target object to generate an image signal carrying photographed images;

a video processor for combining the text caption signal and image signal into a video signal without the voice signal;

a display unit for displaying visual image data; and

a control unit for controlling the radio frequency unit to transmit the video signal; wherein the control unit comprises: a video coder/decoder for encoding and compressing the video signal; and a multiplexer/demultiplexer for multiplexing the compressed video signal and the audio signal into a multiplex signal, and for demultiplexing a received multiplex signal.

16. The video telephony apparatus of claim 15 , wherein the caption generator comprises:

a speech analyzer for analyzing the voice signal to recognize phonemes, morphemes and syllables; and

a text synthesizer for generating a sequence of words using the recognized syllables and converting the sequence of words into a text caption signal.

17. The video telephony apparatus of claim 15 , wherein the multiplex signal further includes a control signal for audio/video synchronization.

18. The video telephony apparatus of claim 15 , wherein the display unit displays video data of the received multiplex signal on a full screen, and displays text caption data of the received multiplex signal in a display area allocated on the screen or in a manner overlapped with the displayed video data.

19. The video telephony apparatus of claim 18 , wherein a text caption corresponding to the text caption data is displayed at an edge region of the screen, and a display size of the displayed text caption is adjustable.