Television – Synchronization – Locking of video or audio to reference timebase
Reexamination Certificate
2000-04-19
2001-10-23
Lee, Michael (Department: 2614)
Television
Synchronization
Locking of video or audio to reference timebase
C348S513000, C348S516000, C348S521000
Reexamination Certificate
active
06307594
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for processing coded signals and a method of synchronizing coded signals. More particularly, the present invention relates to a coded signal processing device and a coded signal synchronizing method advantageously applicable to the processing of coded signals not synchronized to transmit or store the processed coded signals.
2. Description of the Background Art
It is a common practice to transmit a TV (television) or similar moving picture signal or store it in a desired recording medium by efficiently compressing it by use of an MPEG (Moving Picture Experts Group) or similar coding system. On the other hand, to combine two television signals not synchronized with each other or to switch from one to the other, it has been customary to synchronize them with, e.g., frame synchronizers and then combine or switch the resulting signals frame by frame or field by field. The frame synchronizers each separate a vertical and a horizontal synchronizing signal from the respective TV signal and write the TV signal in a buffer memory in accordance with the above two synchronizing signals. The TV signals are read out of the individual buffer memories in synchronization with each other in accordance with a vertical and a horizontal synchronizing signal derived from a reference synchronizing signal generated in local. The TV signals are then subjected to preselected processing.
A coded signal processing device of the type using the above frame synchronizers is conventional as a device for processing two different coded video signals and transmitting or storing the processed coded signals. This type of device, however, needs two decoders each for decoding a particular coded signal, e.g., an MPEG coded signal, two encoders for reproducing the original TV signals or composite signals from decoded component signals made up of a luminance signal (Y) and chrominance signals (C), the two frame synchronizers, a signal processor for executing combination, switching or similar signal processing, a decoder for converting the composite signals to component signals, and an encoder for again coding the component signals with a preselected coding system.
The two decoders each decode a particular coded signal input to the device and thereby output a digital component signal made up of a Y signal and C signals. The two encoders respectively transform the component signals output from the two decoders to composite signals on which the Y and C signals are superposed. The composite signals are converted to the original analog TV signals and then input to the frame synchronizers. At this instant, frame-by-frame or field-by-field horizontal and vertical synchronizing signals are separated from the TV signals and also input to the frame synchronizers.
Each frame synchronizer digitizes the TV signal input thereto and writes the resulting digital picture data in the respective buffer memory in accordance with a horizontal and a vertical synchronizing signal fed from the encoder. Such TV signals are read out of the buffer memories in accordance with a horizontal and a vertical synchronizing signal common to them and fed to the signal processor.
The signal processor combines the two synchronous video signals or switches them scene by scene to thereby output a single video signal. The video signal output from the signal processor is again converted to an analog signal and then transformed to Y and C component signals by the decoder. The encoder codes the component signals with, e.g., the MPEG coding scheme. The resulting coded signals are transmitted or written to a desired recording medium as efficiently compressed coded signals.
However, the problem with the conventional coded signal processing device must execute a sequence of steps of decoding coded video signals input thereto, converting the decoded signals to preselected signals , transforming the converted signals to analog signals, digitizing the resulting analog signals, and then processing the resulting digital signals, again transforming the processed digital signals to analog signals, again converting the analog signals to preselected signals, again digitizing the converted signals, and then coding the resulting digital signals. Image quality is deteriorated every time the signals are subjected to a signal conversion step.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a coded signal processing device and a coded signal synchronizing method capable of executing a signal processing with a coded signal while synchronizing it to a preselected synchronizing signal in the form of a coded signal, and therefore allowing deterioration in image quality to be minimized.
In accordance with the present invention, a coded signal processing device for executing preselected processing with a coded signal representative of a moving picture and coded by a preselected coding system and outputting a processed coded signal includes a code storage for sequentially storing an input coded signal. A decoder decodes the input coded signal to thereby produce an original moving picture signal. An encoder again codes the moving picture signal output from the decoder by the preselected coding system. A selector selectively outputs a coded signal output from the encoder or the coded signal read out of the code storage. A signal controller controls the reading of the coded signal out of the code storage, the output of the coded signal from the encoder, and the switching of the selector. The signal controller causes the code storage or the encoder to output the coded signal based on a preselected reference synchronizing signal which is a reference for a frame synchronizing signal included in the moving picture signal while synchronizing the coded signal frame by frame, and causes the selector to select the coded signal. A coded signal processor executes the preselected processing with the coded signal selected by the selector to thereby process the moving picture, and outputs the coded signal in the form of a coded signal.
Also, in accordance with the present invention, a method of processing a coded signal representative of a moving picture coded by a preselected coding system while synchronizing the coded signals includes the steps of (a) decoding the coded signal to thereby detect a synchronizing signal picture by picture, (b) comparing the synchronizing signal with a preselected reference synchronizing signal to thereby detect a phase difference, (c) temporarily storing the coded signal and reading out the coded signal in accordance with the reference synchronizing signal, (d) again coding one by one moving picture signals produced by decoding the coded signal, (e) selecting and then processing either one of the coded signal read out in step (c) and a coded signal output by step (d), (f) repeatedly reading out, when the phase difference detected in step (b) is smaller than a first preselected value, an intra-coded frame two times for synchronization in step (c), (g) omitting, when the phase difference detected in step (b) is greater than a second preselected value, any one of inter-coded frames of the moving picture signal decoded in step (d) and appearing between two consecutive intra-coded frames, while re-encoding the moving picture signal of the other frames to thereby synchronize the coded signal to the reference synchronizing signal.
REFERENCES:
patent: 5629740 (1997-05-01), Tanaka et al.
patent: 5913190 (1999-06-01), Fielder et al.
patent: 98024/1999 (1999-04-01), None
Frank Robert J.
Lee Michael
OKI Electric Industry Co., Ltd.
Sartori Michael A.
Venable
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