NCO based timebase recovery system and method for A/V decoder
View Patent ↗Systems and methods are disclosed for recovering a clock or time reference for A/V systems. One method comprises receiving at least one input time reference generated using a first clock and generating, using a second clock asynchronous to the first clock, at least one time reference value representative of the at least one input time reference. The method further comprises outputting the generated time reference value used by the A/V system.
1. A method for recovering a time reference in an A/V system comprising:
(a) receiving at least one input time stamp based on an input clock rate;
(b) generating one or more NCO stepsize offset signals;
(c) generating at least one time reference value representative of said at least one input time stamp using an NCO, wherein said one or more NCO stepsize offset signals are a function of the difference between the at least one input time stamp and the at least one time reference value, wherein the one or more NCO stepsize signals comprise at least one filtered difference between the at least one input time stamp and the at least one time reference value; and
(d) outputting said at least one generated time reference value.
2. The method of claim 1 , comprising repeating steps (a) through (d).
3. The method of claim 1 , wherein said time reference value is generated using said NCO and a digital PLL.
4. The method of claim 1 , wherein said time reference value is a system time reference value.
5. The method of claim 4 comprising comparing said system time reference value to said time stamp.
6. The method of claim 4 comprising locking said system time reference value to said time stamp, forming at least one recovered system time reference value.
7. The method of claim 1 , wherein the time stamp comprises a program clock reference value.
8. The method of claim 1 , wherein the time stamp comprises a presentation time stamp.
9. The method of claim 1 , wherein generating at least one time reference value representative of said at least one input time stamp using an NCO, said one or more NCO stepsize offset signals being not synchronized with said input clock rate, further comprises generating at least one time reference value representative of said at least one input time stamp using an NCO, said one or more NCO stepsize offset signal being based on an HSYNC signal.
10. A method of processing data in a data stream using an A/V decoder comprising:
(a) receiving at least one input time stamp from the data;
(b) generating one or more NCO stepsize offset values;
(c) generating at least one system time reference value using an NCO device and said one or more NCO stepsize offset values, wherein the NCO stepsize values are a function of the difference between the at least one input time stamp and the at least one system time reference value, wherein the one or more NCO stepsize signals comprise at least one filtered difference between the at least one input time stamp and the at least one time reference value;
(d) comparing said system time reference value to said input time stamp;
(e) locking said system time reference value to said input time stamp, forming at least one recovered system time reference value;
(f) outputting said recovered system time reference value; and
(g) processing the data using at least one clock not synchronized with said recovered system time reference value.
11. The method of claim 10 , comprising repeating at least steps (a) through (f).
12. A method of processing data in a data stream using an A/V decoder comprising:
(a) receiving at least one input time stamp from the data;
(b) generating at least one system time reference value;
(c) comparing said system time reference value to said input time stamp;
(d) locking said system time reference value to said input time reference value, forming at least one recovered system time reference value, wherein the NCO stepsize values are a function of the difference between the at least one input time stamp and the at least one system time reference value, wherein the one or more NCO stepsize signals comprise at least one filtered difference between the at least one input time stamp and the at least one time reference value;
(e) processing the data using a clock not synchronized with said recovered system time reference value; and
(f) outputting said recovered system time reference value.
13. The method of claim 12 , comprising repeating steps (a) through (e).
14. The method of claim 12 , wherein said system time reference value is generated using an NCO device.
15. The method of claim 12 , further comprising generating one or more offset values.
16. The method of claim 15 , wherein an NCO device uses said offset values to generate said system time reference values.
17. The method of claim 12 , further comprising providing the processed data using the clock not synchronized with said recovered system time reference value to a digital to analog converter.