Television – Synchronization – Sync generation
Patent
1996-12-19
1998-09-08
Grant, Chris
Television
Synchronization
Sync generation
348536, H04N 506
Patent
active
058052313
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to phase synchronizing method and circuit for use in synchronizing phases of video signals, for example, and particularly to phase synchronizing method and circuit used to form a desired signal synchronized with a phase of an inputted signal by digital signal processing.
BACKGROUND ART
When a plurality of video signals are synthesized, phases of synchronizing signals of a plurality of video signals to be synthesized should be synchronized. As phase synchronizing method and circuit used to synchronize phases of video signals, for example, techniques disclosed in Japanese laid-open patent publication No. 64-1147 and Japanese laid-open patent publication No. 1-190176 have hitherto been proposed.
Specifically, according to Japanese laid-open patent publication No. 64-11477, for example, a first video signal is converted into digital data and sequentially stored in three memory means. Then, these memory means are read in synchronism with a second video signal, whereby the first video signal stored in these memory means are synchronized with the second video signal. Therefore, the first and second video signals can be synthesized.
However, according to Japanese laid-open patent publication No. 64-11477, although the first and second video signals are synchronized in synchronizing signal level, a color subcarrier signal with a higher frequency cannot be synchronized at all so that color signals cannot be synthesized. Color signals can be synthesized only when the first video signal, for example, is a luminance signal (black and white signal).
On the other hand, according to Japanese laid-open patent publication No. 1-190176, RGB signals are decoded from the first and second video signals and stored in the first and second frame memories in accordance with respective synchronizing signals. These frame memories are read in synchronism with any one of the video signals, the first and second video signals thus read are synthesized in the state of the RGB signals, and the composite video signals are encoded again from the synthesized RGB signals.
According to the above-mentioned arrangement, since the video signals are synthesized in the form of RGB signals, a problem of synchronization of color subcarrier signal does not occur. However, according to this arrangement, three systems for RGB should be provided in the circuit arrangement from the A/D converters 61c, 62c to the D/A converter 72 so that the circuit arrangement becomes extremely large.
When the composite video signal are synthesized, phase-synchronization of color subcarrier signal should be made. In that case, although a so-called PLL based on analog processing is used in the prior art, this requires complex circuit elements such as oscillator. Moreover, there were problems of fluctuation of characteristics and unstableness due to the analog processing.
Video signals are more and more digitized in recent digital television broadcasting or the like. Therefore, in the digital signal processing, it is requested to realize the phase-synchronization based on the digital signal processing.
In view of the aforesaid aspect, it is an object of this application to provide a phase synchronizing method and circuit in which a desired signal synchronized with the phase of the inputted signal can be formed with a simple arrangement by digital signal processing.
DISCLOSURE OF INVENTION
According to the present invention, there is provided a method which comprises the steps of having memory means in which a desired signal waveform is stored, reading out the desired signal waveform from the memory means, phase-comparing an inputted signal with an arbitrary frequency and a signal with the desired signal waveform read out from the memory means and synchronizing a phase of the signal with the desired signal waveform read out from the memory means with a phase of the inputted signal with the arbitrary frequency by controlling a read address signal of the memory means based on a phase error signal detected by the phase-compari
REFERENCES:
patent: 4122488 (1978-10-01), Mikado
patent: 5181116 (1993-01-01), Nakagaki et al.
Mogi Yasuhide
Yamauchi Etsuro
Frommer William S.
Grant Chris
Sony Corporation
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