Method and system for synchronizing video information derived from an asynchronously sampled video signal

A circuit for synchronizing video data sampled by a fixed-frequency sampling clock, comprising:

• a video data input for receiving said video data;
• a local timebase;
• a phase detector coupled to said video data input and said local timebase for comparing a video source clock derived from said video data to said local timebase, wherein a phase and a frequency of the video source clock are independent of changes in the output of the phase detector;
• a loop filter for filtering an output of said phase detector and providing an input to said local timebase, whereby said local timebase is phase-locked to said video source clock;
• and
• a ratio generator coupled to said loop filter for generating a first ratio of a frequency of said sampling clock to the frequency of said video source clock, whereby said video data can be synchronized to a reference generated in conformity with said ratio without changing the phase or the frequency of the video source clock.

A circuit for synchronizing video data sampled by a fixed-frequency sampling clock, comprising:

• a video data input for receiving said video data;
• a digital filter for generating a representation of a video source clock of said video data;
• a first numeric oscillator for providing a local timebase;
• a phase detector coupled to said digital filter for receiving said video source clock representation and further coupled to an output of said first numeric oscillator, wherein a phase and a frequency of the video source clock representation are independent of any output of the phase detector;
• a loop filter for filtering an output of said phase detector;
• a ratio generator coupled to an output of said loop filter for generating a ratio of a frequency of said sampling clock to a frequency of said video source clock;
• a video clock generator for generating a video clock synchronized with a video source clock of said video data;
• a numeric inverter for computing a numeric inverse of said ratio;
• a second numeric oscillator having a frequency control input coupled to an output of said numeric inverter;
• and
• a sample rate converter having a data input coupled to said video data input, a clock input coupled to an output of said video clock generator and a synchronization input coupled to an output of said second numeric oscillator, wherein the sample rate converter synchronizes the video data to a rate specified by the output of the second numeric oscillator without changing a phase or the frequency of the video source clock.