Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1998-06-04
2001-08-14
Le, Vu (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C348S423100, C348S512000
Reexamination Certificate
active
06275537
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an audio and video multiplexed transmission system, and more particularly, to a multiplexed transmitter and/or receiver for transmitting and/or receiving audio and video information by effectively coding and/or decoding the audio and video information and performing a multiplexing and/or demultiplexing according to the transmission rate of a communication channel which is a limited transmission medium.
2. Background Art
Recently, an apparatus for simultaneously transmitting audio and video information for communication, such as a video conference system and a videophone, has been developed. In the multiplexed transmission system, a technique is required for coding/decoding information with high efficiency while maintaining balance of the audio and video information. In detail, coded video information occupies a greater amount of data compared to coded audio information. Thus, when transmitting audio and video information at the same time, the transmission rate at a communication channel is limited, and coding and decoding times become different, so that it is difficult to synchronize the audio and video information.
To solve this problem, a method using two transmission channels is used: one for video information, and the other for audio information. However, two transmission channels are required. Also, there is a method using one transmission channel. However, according to the method using one transmission channel, extra logic is required in a transmitter for calculating the delay time of the video information, and logic is required in a receiver for delaying the audio information by as much as the delay time of the video information. Also, there is a method for simultaneously transmitting lip-sync information, based on the MPEG-2 standard for the synchronization of the video and audio information. However, it is difficult to implement hardware for the method for transmitting the lip-sync information, and impossible if the transmission speed of a transmission medium is slow. MPEG is a compressed audio/video signal protocol established by the Moving Pictures Experts Group of the International Standardization Organization. An example of a MPEG coding system is provided in U.S. Pat. No. 5,751,356 to Hiroshi Suzuki entitled Video/Audio Signal Coding System. Additionally, an example of a MPEG decoding system is provided in U.S. Pat. No. 5,621,772 to Greg Maturi et al. entitled Hysteretic Synchronization System ForMPEGAudio Frame Decoder.
A further example of the prior art, which is related to the present invention, is U.S. Pat. No. 5,231,492 to Ryoichi Dangi et al. and entitled Video And Audio Multiplex Transmission System. The U.S. Pat. No. 5,231,492 patent discloses a multiplexed transmission system for audio and video information which is capable ofproviding optimum quality video and audio information. However, extra coding/ decoding of the video and audio information is performed under the control of a controller, so that it is difficult to overcome a time delay between the video and audio information. Thus, it is difficult to achieve exact synchronization between the video and audio information. Also, due to the difference in transmission rates between the video and audio information, it is also difficult to achieve an effective transmission while conforming to a channel transmission rate.
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to provide an audio and video multiplexed transmitter capable of providing exact synchronization between video and audio information by coding the video and audio information periodically according to a predetermined clock frequency.
It is another object of the present invention to provide an audio and video multiplexed receiver capable of providing exact synchronization between video and audio information by decoding the video and audio information periodically according to a predetermined clock frequency.
It is still another object of the present invention to provide an audio and video multiplexed transceiver capable of providing exact synchronization between video and audio information, by coding the video and audio information periodically according to a predetermined clock frequency for transmission, and decoding the transmitted video and audio information periodically according to a predetermined clock frequency for reception.
To achieve the first object, there is provided an audio and video multiplexed transmitter for coding and then transmitting audio and video information, comprising: an audio analog-to-digital (A/D) converter for converting an audio signal into a digital audio signal periodically according to a predetermined clock frequency; an audio encoder for coding the digital audio signal; a video A/D converter for converting a video signal into a digital video signal periodically according to a predetermined clock frequency; a video encoder for coding the digital video signal; a coding controller for providing control data corresponding to the predetermined clock frequency to the audio encoder and the video encoder; a timer for outputting time data representing the predetermined clock frequency to the audio A/D converter, the video A/D converter and the coding controller; and a multiplexer for multiplexing the coded audio and video signals, according to the control data of the coding controller, to output a data stream.
Preferably, the audio and video multiplexed transmitter further comprises an encapsulator for converting the data stream continuously output by the multiplexer into a data frame, according to the characteristics of a transmission medium.
To achieve the second object, there is provided an audio and video multiplexed receiver for receiving coded audio and video information for demultiplexing and decoding, comprising: a demultiplexer for demultiplexing a received data stream to separate digital audio and video signals; an audio decoder for decoding the digital audio signal; a video decoder for decoding the digital video signal; an audio digital-to-analog (D/A) converter for converting the decoded digital audio signal into an analog audio signal periodically according to a predetermined clock frequency; a video D/A converter for converting the decoded digital video signal into an analog video signal periodically according to a predetermined clock frequency; a decoding controller for providing control data, corresponding to the predetermined clock frequency, to the audio decoder and the video decoder; and a timer for outputting time data representing the predetermined clock frequency to the audio D/A converter, the video DIA converter and the decoding controller.
Preferably, the audio and video multiplexed receiver further comprises a decapsulator for converting a data frame, transmitted from an encapsulator of a transmitter or a transmission medium, into a data stream, according to the characteristics of the transmission medium.
To achieve the third object, there is provided an audio and video multiplexed transmission system for coding then transmitting audio and video information through a coding, and receiving the coded audio and video information for decoding, comprising: a transmitter; and a receiver, wherein the transmitter includes: an audio analog-to-digital (A/D) converter for converting an audio signal into a digital audio signal periodically according to a predetermined clock frequency; an audio encoder for coding the digital audio signal; a video A/D converter for converting a video signal into a digital video signal periodically according to a predetermined clock frequency; a video encoder for coding the digital video signal; a coding controller for providing control data corresponding to the predetermined clock frequency to the audio encoder and the video encoder; a timer for providing time data representing the predetermined clock frequency to the audio A/D converter, the video A/D converter and the coding controller; and a multiplexer for multiplexing the coded audio
Bushnell , Esq. Robert E.
Le Vu
Samsung Electronics Co,. Ltd.
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