Leveraging Cross-Utterance Context For ASR Decoding
Robert Flynn Anton Ragni
While external language models (LMs) are often incorporated into the decoding
stage of automated speech recognition systems, these models usually operate
with limited context. Cross utterance information has been shown to be
beneficial during second pass re-scoring, however this limits the hypothesis
space based on the local information available to the first pass LM. In this
work, we investigate the incorporation of long-context transformer LMs for
cross-utterance decoding of acoustic models via beam search, and compare
against results from n-best rescoring. Results demonstrate that beam search
allows for an improved use of cross-utterance context. When evaluating on the
long-format dataset AMI, results show a 0.7\% and 0.3\% absolute reduction on
dev and test sets compared to the single-utterance setting, with improvements
when including up to 500 tokens of prior context. Evaluations are also provided
for Tedlium-1 with less significant improvements of around 0.1\% absolute.