Memory management for an MPEG2 compliant decoder
AssigneeInternational Business Machines Corporation
InventorsDennis Phillip Cheney, Mark Louis Ciacelli, Steven Bradford Herndon, John David Myers, Chuck Hong Ngai
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Abstract
Disclosed is a digital signal decoder system for receiving compressed encoded digitized video signals and transmitting decompressed decoded digital video signals. This is accomplished with a minimum of DRAM demand through the use of a Spill Buffer.
Claims12
A digital video decoder comprising an input data buffer, a variable length decoder, a dequantizer, an inverse discrete cosine transform decoder, a motion compensator, and a frame memory, said frame memory having at least a past reference frame buffer, a future reference frame buffer, a frame buffer for a frame currently being decoded, and a Spill Buffer, said Spill Buffer being dynamically allocable within said frame memory as frames are decoded, and where said three frame buffers are accessed on a rotating basis according to the following algorithm:
- C=D*NBF+ NBF*(T*(PREV =B)+P*(PREV=B*PRES =B));
- P=C*NBF+ NBF*F*(PRES =B);
- F=T*(PREV =B*PRES= B)+P*(PREV=B*PRES =B);
- D=C*NBF+ NBF*(F*(PRES =B)+T*(PREV =B*PRES=B));
- and
- T=D;
- where
- C=Current picture pointer;
- P=Past picture pointer;
- F=Future picture pointer;
- D=Display picture pointer;
- T=Temporary pointer;
- PRES=Present picture type;
- PREV=Previous picture type;
- and
- NBF=No B frame mode.
A method of decoding a digital video datastream in a digital video decoder comprising an input data buffer, a variable length decoder, a dequantizer, an inverse discrete cosine transform decoder, a motion compensator, and a frame memory, said frame memory having at least a past reference frame buffer, a future reference frame buffer, a frame buffer for a frame currently being decoded, and a Spill Buffer, said Spill Buffer being dynamically allocable within said frame memory as frames are decoded, and where said three frame buffers are accessed on a rotating basis according to the following algorithm:
- C=D*NBF+ NBF*(T*(PREV =B)+P*(PREV=B*PRES =B));
- P=C*NBF+ NBF*F*(PRES =B);
- F=T*(PREV =B*PRES= B)+P*(PREV=B*PRES =B);
- D=C*NBF+ NBF*(F*(PRES =B)+T*(PREV =B*PRES=B));
- and
- T=D;
- where
- C=Current picture pointer;
- P=Past picture pointer;
- F=Future picture pointer;
- D=Display picture pointer;
- T=Temporary pointer;
- PRES=Present picture type;
- PREV=Previous picture type;
- and
- NBF=No B frame mode;
- which method comprises:
- a. storing a frame currently being decoded in the current frame buffer;
- b. storing a past reference frame in the past reference frame buffer;
- and
- c. storing a future reference frame in the future reference frame buffer.
Dependencies are inferred from the claim text.