Method of timebase management for MPEG decoding with personal video recording functionality
Systems and methods that provide time-based management for MPEG decoding are provided. In one example, a method for live decoding in a personal video recorder system includes the steps of receiving at least one data packet; determining at least one program clock reference (PCR) using the at least one data packet; and locking a timing mechanism to the at least one determined PCR.
1. A method for handling a program clock reference (PCR) discontinuity during a live decode in a personal video recorder (PVR) system, comprising:
receiving a PCR from an incoming transport packet;
checking whether a discontinuity bit of the incoming transport packet has been set;
if the discontinuity bit has been set, then:
updating at least a video system time clock (STC) with the received PCR, and
after updating the at least a video STC with the received PCR, decoding remaining pictures after the PCR discontinuity based at least in part on an old timebase prior to the PCR discontinuity; and
if the discontinuity bit has not been set, then:
capturing an STC,
comparing the captured STC with the received PCR, and
determining whether an error between the captured STC and the received PCR is within a programmable threshold.
2. The method according to claim 1 , wherein receiving the PCR from the incoming transport packet comprises monitoring the incoming transport packet via a timing recovery circuit.
3. The method according to claim 1 , wherein the discontinuity bit of the incoming transport packet is in a transport packet header.
4. The method according to claim 1 , wherein updating the at least a video STC with the received PCR comprises updating via a timing recovery circuit the video STC and one or both of an audio STC and a timing recovery circuit STC.
5. The method according to claim 1 , wherein the captured STC is at least one of a video STC, an audio STC, or a timing recovery circuit STC.
6. The method according to claim 1 , wherein the error between the STC and the received PCR is an absolute difference between the STC and the received PCR.
7. The method according to claim 1 , wherein the programmable threshold is related to a programmable frequency range of a voltage controlled crystal oscillator (VCXO).
8. The method according to claim 1 , wherein if the discontinuity bit has not been set:
if it is determined that the error is within the programmable threshold, then filtering the error, and
updating a frequency of a voltage controlled crystal oscillator (VCXO).
9. The method according to claim 8 , wherein updating a frequency of a VCXO comprises updating the frequency of the VCXO as a function of the received PCR.
10. The method according to claim 8 , wherein updating a frequency of a VCXO comprises updating the frequency of the VCXO as a function of the error.
11. The method according to claim 1 , wherein if the discontinuity bit has not been set: if it is determined that the error is not within the programmable threshold, then:
updating the at least the video STC with the received PCR, and
after updating the at least a video STC with the received PCR, decoding remaining pictures after the PCR discontinuity based at least in part on an old timebase prior to the PCR discontinuity.
12. A personal video recorder (PVR) system for handling a program clock reference (PCR) discontinuity during a live decode in a PVR system, the system comprising:
at least one module adapted to, at least:
receive a PCR from an incoming transport packet;
check whether a discontinuity bit of the incoming transport packet has been set;
if the discontinuity bit has been set, then
update at least a video system time clock (STC) with the received PCR, and
after updating the at least a video STC with the received PCR, decode remaining pictures after the PCR discontinuity based at least in part on a timebase prior to the PCR discontinuity; and
if the discontinuity bit has not been set, then:
capture an STC,
compare the captured STC with the received PCR, and
determine whether an error between the captured STC and the received PCR is within a programmable threshold.
13. The PVR system of claim 12 , wherein the programmable threshold is related to a programmable frequency range of a voltage controlled crystal oscillator (VCXO).
14. The PVR system of claim 12 , wherein receiving the PCR from the incoming transport packet comprises monitoring the incoming transport packet via a timing recovery circuit.
15. The PVR system of claim 12 , wherein the discontinuity bit of the incoming transport packet is in a transport packet header.
16. The PVR system of claim 12 , wherein updating the at least a video STC with the received PCR comprises updating via a timing recovery circuit the video STC and one or both of an audio STC and a timing recovery circuit STC.
17. The PVR system of claim 12 , wherein the captured STC is at least one of a video STC, an audio STC, or a timing recovery circuit STC.
18. The PVR system of claim 12 , wherein the error between the STC and the received PCR is an absolute difference between the STC and the received PCR.
19. The PVR system of claim 12 , wherein if the discontinuity bit has not been set and if it is determined that the error is within the programmable threshold, then the at least one module is further adapted to, at least:
filter the error, and
update a frequency of a voltage controlled crystal oscillator (VCXO).
20. The PVR system of claim 19 , wherein updating a frequency of a VCXO comprises updating the frequency of the VCXO as a function of the received PCR.