Hdtv trellis decoder architecture
(19)AUSTRALIAN PATENT OFFICE (54) Title Hdtv trellis decoder architecture (51)6 International Patent Classification(s) H04L 005/12 (21) Application No: 2003226159 (22) Application Date: 2003 .04.01 (87) WIPO No: WO03/090451 (30) Priority Data (31) Number (32) Date (33) Country 60/372,971 2002 .04 .16 US (43) Publication Date : 2003.11.03 (43) Publication Journal Date : 2003 .12.11 (71) Applicant(s) THOMSON LICENSING S.A. (72) Inventor(s) Mai km an, Ivonctc (-1-1) Application NoAU2003226159 A8(19)AUSTRALIAN PATENT OFFICE (54) Title Hdtv trellis decoder architecture (51)6 International Patent Classification(s) H04L 005/12 (21) Application No: 2003226159 (22) Application Date: 2003 .04.01 (87) WIPO No: WO03/090451 (30) Priority Data (31) Number (32) Date (33) Country 60/372,971 2002 .04 .16 US (43) Publication Date : 2003.11.03 (43) Publication Journal Date : 2003 .12.11 (71) Applicant(s) THOMSON LICENSING S.A. (72) Inventor(s) Mai km an, Ivonctc-1- A trellis decoding system for use in processing a High Definition Television signal. The trellis decoding system includes a traceback unit that identifies a sequence of antecedent trellis states in accordance with a state transition trellis. A branch metric computer includes eight discrete subunits, one for each possible trellis state. Each subunit generates two output bits indicative of the two trellis branches exiting the trellis state represented by that particular subunit. An add-compare-select unit includes eight discrete subunits, each associated with a particular trellis state. Each subunit includes as an input two bits received from the branch metric computer and as an output two bits. Bit 31 is chosen from 28 and 29 . Bit 6 is chosen from the branch metric information input to each subunit. A traceback control memory unit includes an N to 1 multiplexer which receives as an input the output bits from the add-compare-select unit. The present system offers a hardware reduction from prior art. Apparatus for providing trellis decoded data in a system for processing video data comprising groups of interleaved trellis encoded data packets, the apparatus (1) comprising:
means (2) for generating decision data (28,29) associated with trellis state transitions in response to said video data, including a branch metric computer sub-unit comprising means for selecting an estimated value for a second information data bit from a pair of first and second data bits based on a signal indicative of a survivor path into a particular branch metric computer subunit trellis state for a previous trellis branch; a traceback network (33) responsive to said decision data including said estimated value for identifying a sequence of antecedent trellis states, as determined by a state transition trellis, wherein said antecedent states are identified for a sequence of collocated interleaved packets; means (3) for calculating for a current trellis branch a value (14) for a first data bit and the estimated value (15) for the second information data bit; means (41) for providing a plurality of trellis decoded data sequences; means (52) for identifying one of the plurality of trellis decoded data sequences with a pointer updated by identifying antecedent trellis states with said decision data; means (23) for concurrently selecting an output first data bit (6) and an output second data bit (31) among all trellis states in response to the selection of the minimum path metric among all trellis states; and means (50) responsive to said identified sequence of antecedent trellis states, for providing said trellis decoded data (51). The apparatus according to claim 1, further including means (8) for concurrently selecting an input first data bit (26) and an input second data bit (27) into a trellis state in response to the selection of the minimum path metric into the trellis state. The apparatus according to claim 1, wherein the traceback network (33) further comprises means (45) for storing the value of first data bit (6) and the estimated value of the second data bit (31). The apparatus according to claim 3, wherein the pointer selects one of the first data bits (6) and one of the second data bits (31) as correctly decoded data bits. A method of providing trellis decoded data in a system for processing video data comprising groups of interleaved trellis encoded data packets formed from information data pairs containing a first data bit and a second data bit, the method comprising the steps of:
generating decision data associated with trellis state transitions in response to said video data including selecting an estimated value for a second information data bit from a pair of first and second data bits based on a signal indicative of a survivor path into a particular branch metric computer subunit trellis state for a previous trellis branch; identifying a sequence of antecedent trellis states in accordance with a state transition trellis, wherein said antecedent states are identified for a sequence of collocated interleaved packets in response to said decision data; calculating for a current trellis branch the value of the first data bit and the estimated value of the second data bit; concurrently selecting an output first data bit and an output second data bit among all trellis states in response to selection of a minimum path metric among all trellis states; providing a plurality of trellis decoded data sequences and; identifying one of the plurality of trellis decoded data sequences with a pointer updated by identifying antecedent trellis states with said decision data; and providing said trellis decoded data in response to said identified sequence of antecedent trellis states. The method according to claim 5, further comprising the step of concurrently selecting an input first data bit and an input second data bit into a trellis state in response to selection of a minimum path metric into the trellis state. The method according to claim 5, further comprising the step of updating the pointer once for each epoch.