MPEG decoding system including tag list for associating presentation time stamps with encoded data units
First Claim
1. A decoding system for decoding a data stream:
- the data stream comprising;
an encoded data unit;
a header corresponding to said encoded data unit; and
a time stamp included in said header for indicating a requested decoding time for said encoded data unit;
the system comprising;
a header memory;
a data memory;
a list memory;
parsing means for parsing said data stream, storing said header in the header memory, storing said encoded data unit in the data memory beginning at a starting address and capturing said time stamp;
computing means responsive to said parsing by the parsing means for storing said time stamp and said starting address as a list entry in said list memory; and
decoding means for reading and decoding said encoded data unit from the data memory at an actual decoding time which can differ from said requested decoding time to produce a decoded data unit;
the computing means being further responsive to said reading and decoding by the decoding means for accessing said list entry in the list memory using said starting address to obtain said time stamp;
wherein the relationship between said requested decoding time and said actual decoding time can be utilized to synchronize subsequent presentation of said decoded data unit.
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Accused Products
Abstract
A Motion Picture Experts Group (MPEG) multiplexed data bitstream includes encoded video and audio data units, which are prefixed with headers including Presentation Time Stamps (PTS) indicating desired presentation times for the respective data units. The data units are decoded, and presented at a fixed time after decoding, such that the fixed time can be subtracted from the PTS to provide a desired decoding time. The bitstream is parsed, the video and audio headers are stored in video and audio header memories, and the associated video and audio data units are stored in video and audio channel memories respectively. A first interrupt is generated each time a header is stored, and a host microcontroller responds by storing the PTS from the header and the starting address of the corresponding data unit in the channel memory as an entry in a list. A second interrupt is generated each time a data unit is decoded, and the host microcontroller responds by accessing the list using the starting address of the data unit to obtain the corresponding PTS and thereby the desired decoding time. Decoding and presentation are synchronized by comparing the desired decoding time with a system clock time. If the desired decoding time is later than the system clock time by more than one presentation (frame) time period for the data unit, presentation of the data unit is skipped. If the desired decoding time is earlier than the system clock time by more than the presentation time period, presentation of the data unit is repeated.
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Citations
26 Claims
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1. A decoding system for decoding a data stream:
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the data stream comprising; an encoded data unit; a header corresponding to said encoded data unit; and a time stamp included in said header for indicating a requested decoding time for said encoded data unit; the system comprising; a header memory; a data memory; a list memory; parsing means for parsing said data stream, storing said header in the header memory, storing said encoded data unit in the data memory beginning at a starting address and capturing said time stamp; computing means responsive to said parsing by the parsing means for storing said time stamp and said starting address as a list entry in said list memory; and decoding means for reading and decoding said encoded data unit from the data memory at an actual decoding time which can differ from said requested decoding time to produce a decoded data unit; the computing means being further responsive to said reading and decoding by the decoding means for accessing said list entry in the list memory using said starting address to obtain said time stamp; wherein the relationship between said requested decoding time and said actual decoding time can be utilized to synchronize subsequent presentation of said decoded data unit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A decoding system for decoding a data stream:
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the data stream comprising; an encoded data unit; a header corresponding to said encoded data unit; and a time stamp included in said header for indicating a decoding time for said encoded data unit; the system comprising; a header memory; a data memory; a list memory; parsing means for parsing said data stream, storing said header in the header memory, storing said encoded data unit in the data memory beginning at a starting address and capturing said time stamp; computing means responsive to said .parsing by the parsing means for storing said time stamp and said starting address as a list entry in said list memory; decoding means for reading and decoding said encoded data unit from the data memory to produce a decoded data unit; the computing means being further responsive to said reading and decoding by the decoding means for accessing said list entry in the list memory using said starting address to obtain said time stamp; system timer means for maintaining a system clock time; comparator means for comparing said time stamp with a current value of said system clock time from the system timer means when the decoder means begins to read and decode said encoded data unit; presentation means for presenting said decoded data unit; and synchronization means for controlling the presentation means to repeat presentation of said decoded data unit if said time stamp exceeds said current value of said system clock time by more than a first predetermined value; and
controlling the presentation means to skip presentation of said decoded data unit if said current value of said system clock time exceeds said time stamp by more than a second predetermined value. - View Dependent Claims (10, 11, 12, 13)
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14. A decoder for decoding a data stream:
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the data stream comprising; an encoded data unit; and a header corresponding to said encoded data unit; the decoder comprising; a header memory; a data memory; parsing means for parsing said data stream, storing said header in the header memory, storing said encoded data unit in the data memory, and generating a first interrupt upon storing said header in the header memory; and decoding means for reading and decoding said encoded data unit from the data memory to produce a decoded data unit, and generating a second interrupt upon beginning of reading and decoding said encoded data unit;
in whichthe data stream further comprises a time stamp included in said header for indicating a requested decoding time for said encoded data unit; the parsing means further captures and stores said time stamp; and the decoder further comprises; system timer means for maintaining a system clock time; and comparator means for reading and comparing said time stamp with a current value of said system clock time which constitutes an actual decoding time from the system timer means when the decoder means begins to read and decode said encoded data unit. - View Dependent Claims (15, 16, 17)
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18. A decoder for decoding a data stream:
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the data stream comprising; an encoded data unit; and a header corresponding to said encoded data unit;
..the decoder comprising; a header memory; a data memory; parsing means for parsing said data stream, storing said header in the header memory, storing said encoded data unit in the data memory, and generating a first interrupt upon storing said header in the header memory; and decoding means for reading and decoding said encoded data unit from the data memory to produce a decoded data unit, and generating a second interrupt upon beginning of reading and decoding said encoded data unit; the data stream further comprising a time stamp included in said header for indicating a decoding time for said encoded data unit; the parsing means further capturing said time stamp; system timer means for maintaining a system clock time; comparator means for comparing said time stamp with a current value of said system clock time from the system timer means when the decoder means begins to read and decode said encoded data unit; presentation means for presenting said decoded data unit; and synchronization means for controlling the presentation means to repeat presentation of said decoded data unit if said time stamp exceeds said current value of said system clock time by more than a first predetermined value; and
controlling the presentation means to skip presentation of said decoded data unit if said current value of said system clock time exceeds said time stamp by more than a second predetermined value. - View Dependent Claims (19, 20, 21, 22)
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23. A method of decoding a data stream:
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the data stream comprising; an encoded data unit; a header corresponding to said encoded data unit; and a time stamp included in said header for indicating a requested decoding time for said encoded data unit; the method comprising the steps of; (a) parsing said data stream; (b) storing said header in a header memory; (c) storing said encoded data unit in a data memory beginning at a starting address; (d) capturing said time stamp; (e) storing said time stamp and said starting address as a list entry in a list memory; (f) reading and decoding said encoded data unit from the data memory at an actual decoding time which can differ from said requested decoding time to produce a decoded data unit; and (g) accessing said list entry in the list memory using said starting address to obtain said time stamp; wherein the relationship between said requested decoding time and said actual decoding time can be utilized to synchronize subsequent presentation of said decoded data unit. - View Dependent Claims (24, 25)
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26. A method of decoding a data stream:
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the data stream comprising; an encoded data unit; a header corresponding to said encoded data unit; and a time stamp included in said header for indicating a decoding time for said encoded data unit; the method comprising the steps of; (a) parsing said data stream; (b) storing said header in a header memory; (c) storing said encoded data unit in a data memory beginning at a starting address; (d) capturing said time stamp; (e) storing said time stamp and said starting address as a list entry in a list memory; (f) reading and decoding said encoded data unit from the data memory to produce a decoded data unit; and (g) accessing said list entry in the list memory using said starting address to obtain said time stamp; (h) maintaining a system time; (i) comparing said time stamp with a current value of said system clock time from the system timer means upon performing step (f); (j) repeating presentation of said decoded data unit if said time stamp exceeds said current value of said system clock time by more than a first predetermined value; and (k) skipping presentation of said decoded data unit if said current value of said system clock time exceeds said time stamp by more than a second predetermined value.
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Specification