Large Vocabulary Continuous Speech Recognition - Berlin Chen

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WC: Pruning of Path Hypotheses (2/5)• Pruning Techniques1. Standard Beam Pruning (Acoustic-level Pruning)• Retain only hypotheses with a score close to the best hypothesis⎡⎤ThrAC() t = ⎢ max Q n −1( t , s;arc ) × fn −1AC( v s arc )v⎥1⎣ 1 , ,⎦Q t,s;arc < Thr t ⇒v1n ⎡⎤LM() t = ⎢ max Q n −1( t , S ; arcB) × fn −1LM( v S arc )v0 ⎥⎣ , 0 , B 11⎦( ) ( ) pruned!2. Language Model Pruning (Word-level Pruning)• Applied to word-end or tree start-up hypothesesThr−1( ) ( ) pruned!ACQ− 1v1nt, S0; arcB
WC: Pruning of Path Hypotheses (3/5)• Pruning Techniques (cont.)– Stricter pruning applied at word ends• The threshold is tightly compared to the acoustic-level onePose severerequirements onthe system memory• Reasons– A single path hypothesis is propagated into multiple wordends (words with the same pronunciation)– A large number of arcs (models) of the new generatedtree copies are about to be activatedSpeech – Berlin Chen 23
Page 1 and 2: Large Vocabulary ContinuousSpeech R
Page 3 and 4: Why LVCSR Difficult ? (2/2)• Maxi
Page 5 and 6: Classification of Approaches to LVC
Page 7 and 8: Word-conditioned vs. Time-condition
Page 9 and 10: Word-Conditioned Tree-Copy Search (
Page 11 and 12: Lexical/Phonetic Tree (2/2)• Reas
Page 13 and 14: Context-Dependent Phonetic Constrai
Page 15 and 16: Word-Conditioned Search (1/3)• Wo
Page 17 and 18: Word-Conditioned Search (3/3)Backtr
Page 19 and 20: WC: Implementation Issues (2/3)•
Page 21: WC: Pruning of Path Hypotheses (1/5
Page 25 and 26: WC: Pruning of Path Hypotheses (5/5
Page 27 and 28: WC: Language Model Look-ahead (2/2)
Page 29 and 30: WC: Acoustic Look-ahead (2/3)• Po
Page 31 and 32: More Details on Time-Conditioned Se
Page 33 and 34: TC: Decomposition of Search History
Page 35 and 36: TC vs. WC: Conflicting Expectations
Page 37 and 38: TC vs. A* search (2/2)- Operations
Page 39 and 40: Word Graph Rescoring (1/6)• Tree-
Page 41 and 42: Word Graph Rescoring (3/6)• If bi
Page 43 and 44: Word Graph Rescoring (5/6)• “Wo
Page 45: • Feature ExtractionConfiguration

Large Vocabulary Continuous Speech Recognition - Berlin Chen

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