Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1998-06-01
2001-02-13
Britton, Howard (Department: 2713)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C348S632000, C455S194100
Reexamination Certificate
active
06188731
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and method for synchronizing audio/video signal and, more particularly, to an apparatus and method for detecting motion of picture when timing difference between audio signal and video signal transmitted occurs and subsequently adjusting a threshold in association with the detected motion of picture, thereby controlling the mute audio signal.
2. Description of the Prior Art
MPEG is a compressed audio/video signal protocol established by the Moving Pictures Experts Group of the International Standardization Organization. One description of MPEG is provided in U.S. Pat. No. 5,621,772 to Greg Maturi et al. entitled Hysteretic Synchronization System For MPEG Audio Frame Decoder.
In general, an audio/video signal is compressed according to an MPEG protocol. According the MPEG protocol, the compressed audio/video signal is segmented into packets for transmission and subsequently the compressed audio signal is time division multiplexed with the compressed video signal.
The associated compressed audio/video signal is not only asynchronous, but their mutual timing relationship or synchronism is nonexistent in transmission.
Accordingly, when an audio/video signal compressed according to an MPEG protocol is decompressed to display on screen, the audio signal must be synchronized with the video signal so that a voice is coincident with a corresponding picture.
A timing difference between the audio and video signals, however, may sometimes occur when the compressed audio/video signal is decompressed. When the timing difference between the audio and video signals occurs, the audio signal should be muted to be in synchronization with video signal so that a voice is coincident with a corresponding picture.
However, decompression in the art is problematic in that it cannot determine the degree of motion of a picture since the mute of the audio signal for synchronization is based on comparison between a previous or subsequent frames to picture, thereby frequently muting the audio signal unnecessarily.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an apparatus and method for synchronizing an audio/video signal wherein a variable associated with the motion of a picture is utilized to determine a threshold according to which the mute of audio signal is adjusted.
To achieve the above-mentioned object, an apparatus for synchronizing audio/video signal according to the present invention comprises an inverse transport processor for outputting compressed audio/video signal and further detecting a motion of picture to output a variable associated with the motion of picture, a video decompressor for decompressing the compressed video signal from the inverse transport processor, an audio decompressor for decompressing the compressed audio signal from the inverse transport processor, a microprocessor for processing the audio/video signal outputted from the audio decompressor and the video decompressor respectively to generate a synchronization error signal, and a threshold detector for generating audio muting signal, responsive to the variable from the inverse transport processor and the synchronization error signal from the microprocessor. The microprocessor comprises a first latch, a second latch, a first subtracter, a second subtracter and a third subtracter.
Further objects, features and other aspects will be understood from the following detailed description of preferred embodiments of the present invention referring to the accompanying drawings.
REFERENCES:
patent: 4641190 (1987-02-01), Testin et al.
patent: 5276714 (1994-01-01), Hori et al.
patent: 5381186 (1995-01-01), Lee
patent: 5621772 (1997-04-01), Maturi et al.
Britton Howard
Bushnell , Esq. Robert E.
Samsung Electronics Co,. Ltd.
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