Method and apparatus for time-multiplexed processing of multiple digital video programs
View Patent ↗The present invention relates generally to the processing of multiple data streams with common resources. More particularly, this invention relates to a technique for time-multiplexed processing of, for example, multiple digital video programs. In one embodiment, an exemplary method provides for time-multiplexed processing of a set of digital streams includes storing each received packet in a random access memory. For each stream, the deadline for the arrival of the next packet at the receiver is determined and a priority based on the deadline is assigned. The stream with the highest assigned priority is identified as an identified stream. In some embodiments, the processing state of the identified stream is then restored. One or more packets of data corresponding to the identified stream are retrieved from random access memory to produce retrieved packets. The processing state is saved after the retrieved packets have been processed.
1. A method for processing a plurality of different digital video program streams, wherein each stream includes packets sequenced for continuous presentation, said method comprising:
receiving packets, each packet being associated with a respective one of said plurality of different digital video program streams;
assigning a priority for video processing of each different stream based on a delivery deadline for at least one packet in that stream;
monitoring the packets of each stream;
reassigning the video processing priorities of the plurality of different streams based on delivery deadlines of the monitored packets; and
performing video processing operations on packets from the plurality of different streams in order of the priorities assigned to the associated streams.
2. The method of claim 1 , wherein said video processing operations are performed by a video processor shared by said plurality of different digital video program streams.
3. The method of claim 1 , wherein said delivery deadline is derived from a Decoding Time Stamp (DTS) associated with said at least one packet.
4. The method of claim 3 , wherein said DTS is associated with the next packet of the associated stream.
5. The method of claim 1 , wherein the priority for video processing of each stream is based on the delivery deadline for the next packet in that stream.
6. The method of claim 1 , wherein:
said packets of each digital stream are arranged in sequences of packets.
7. The method of claim 6 , wherein:
each sequence of packets is a representation of a video frame.
8. The method of claim 1 , further comprising:
assigning a tag to each packet identifying a priority for the packet and an address of the packet in a buffer; and
storing each tag in memory corresponding to the digital stream associated with the packet to which the tag is assigned.
9. The method of claim 8 , wherein the packets are monitored during said monitoring step via the tags.
10. The method of claim 1 , further comprising:
determining when new packets commence after a gap in one of said streams; and
reassigning the video processing priority of that stream based on said new packets.
11. The method of claim 1 , further comprising:
maintaining a state associated with each of said plurality of different digital streams.
12. The method of claim 11 , wherein:
said state includes parameters for said processing the packets of each stream.
13. The method of claim 11 , wherein:
said state includes pixel data representing at least one frame of video.
14. The method of claim 11 , further comprising:
allocating memory for storing said state.
15. The method of claim 14 , wherein:
said memory allocation step includes recursively subdividing said memory into quadrants, where one of said quadrants cannot be further subdivided without at least one dimension becoming smaller than a corresponding dimension of a video or audio frame.
16. The method of claim 14 , wherein:
said memory is allocated in pages, where each of said pages is a contiguous memory unit of a fixed size.
17. The method of claim 16 , wherein:
unallocated pages are managed using a free list configured to manage unused pages of memory.
18. The method of claim 1 wherein said packets are continuously monitored.
19. Apparatus for processing a plurality of different digital video program streams, wherein each different stream includes packets sequenced for continuous presentation, said apparatus comprising:
a packet receiver adapted to receive packets that are each associated with a respective one of said plurality of different digital video program streams;
means for assigning a priority for video processing of each different stream based on a delivery deadline for at least one packet in that stream;
means for continuously monitoring the packets of each stream;
means for reassigning the video processing priorities of the plurality of different streams based on delivery deadlines of the continuously monitored packets; and
a video processor coupled to process packets from the plurality of different streams in order of the priorities assigned to the associated streams.
20. The apparatus of claim 19 , further comprising:
means for selecting said packets for video processing based on said priorities; and
means for retrieving said selected packets from a buffer.
21. The apparatus of claim 19 wherein the priority for video processing of each stream is based on the delivery deadline for the next packet in that stream.
22. The apparatus of claim 19 , further comprising means for extracting Decoding Time Stamps (DTS's) associated with said packets for use in deriving said delivery deadline.
23. The apparatus of claim 22 , further comprising:
means for assigning a tag to each packet identifying a priority for the packet and an address of the packet in a buffer; and
memory for storing each tag in association with the digital stream containing the packet to which the tag is assigned.
24. The apparatus of claim 19 , further comprising:
means for determining when new packets commence after a gap in one of said streams; and
means for reassigning the video processing priority of that stream based on the new packets.
25. The apparatus of claim 19 , further comprising:
means for maintaining a state associated with each of said plurality of different digital streams.
26. The apparatus of claim 25 , wherein:
said means for maintaining a state includes a memory for storing processing parameters.
27. The apparatus of claim 25 , wherein:
said means for maintaining said state includes memory for storing pixel data representing at least one frame of video.
28. The apparatus of claim 27 , further comprising:
means for recursively subdividing said memory into quadrants.
29. The apparatus of claim 27 , further comprising:
means for partitioning said memory into pages, where each of said pages is a contiguous memory unit of a fixed size.
30. The apparatus of claim 29 , further comprising:
a free list for managing unused pages of memory.
31. The apparatus of claim 29 , further comprising:
a translation look-aside buffer for mapping virtual addresses to physical page addresses.
32. The apparatus of claim 29 , further comprising:
means for retrieving pages from memory and merging data into blocks of a requested size.
33. The apparatus of claim 32 , further comprising:
a cache for storing one or more pages that have been retrieved from memory.