Video synchronization pixel clock generating circuit

Abstract

The invention provides a video synchronization pixel clock generating circuit. The circuit performs low-pass filtering on an ADC-quantized CVBS or S-video signal, filters high-frequency information of over 1MHz to obtain line blanking edge information of the video signal, performs phase discrimination, performs error detection and error filtering to obtain an error value, obtains output of a 6-bit lookup table and finally performs double frequency multiplication or quadruple frequency multiplication on the signal through PLL so as to generate the pixel clock of 13.5MHz and a working clock of 27MHz of a chip.

Description

technical field [0001] The present invention relates to a synchronous pixel clock generation circuit for video, in particular to a technique for internally generating an adapted pixel clock based on an externally input video signal. The present invention can be used for non-standard video sources such as standard video sources and VCR. Standard video source. Background technique [0002] In the video signal, there are NTSC, PAL and other formats, 50Hz or 60Hz and other field frequencies, ideal standard video signals of different specifications, such as figure 1 As shown, it is mainly composed of "front porch", "sync head", "back porch", "rising / falling edge" and effective video signal during the line blanking period, and the line sync head represents the start of each line of video signal The position also represents that the decoded video data is at the leftmost end of each row of the monitor. Generally, the circuit can simply control the phase-locked loop PLL to regenerat...

AI Technical Summary

Problems solved by technology

However, the video signal usually sent to the decoder, whether it is generated by a camera, DVD or other types of video signal sources, even if the signal is relatively stable, there is a certain deviation from the ideal standard signal, that is, the line length jitters within a certain range

In addition, for non-standard video signals outside the specifications, such as analog video signals recorded on video tapes, etc., due to the long-term deterioration of the tape or the difference between the recording device and the playback device, it cannot be reproduced under the same conditions as when recorded. , the total line number and line length of each frame may change drastically, especially during the field blanking period, and the change range may even be as high as ±10%, which usually causes horizontal or vertical jitter in the decoded video data, making the image Unable to display stably and effectively

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