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Lattice quality metrics

2011-01-31
2012-09-22
  • Vassil Panayotov

    Hi,

    How can be the "goodness" of lattices or confusion networks(sausages)
    evaluated? Say I have two lattices (or sausages) generated from different
    recognizers or from the same recognizer but with different parameters/models.
    What metric I can use to test the quality of the WFSAs and prefer one over the
    other if I know the true transcription?
    Maybe the posterior probability of the "oracle" path through the lattice?
    What if the oracle path is not perfectly present in the lattices (sausage) due
    to insertions/deletions/substitutions of some of the words? Is there a metric
    that can be used in this case?

    Thanks!

     
  • Nickolay V. Shmyrev

    There are mulitple parameters - 1-best accuracy, n-best accuracy, oracle WER,
    entropy. For example you might want to use smaller entropy lattice even if it
    has a bit lower WER.

    I suggest you to look on "wlat-stats" script from SRILM.

    As for LWER, David said one day

    LWER calcuation is composition with a Levenshtein transducer then path
    search you can of course replace the Levenshtein transducer with any other
    error model.

    The code for this thing is available in
    Sphinxtrain/python/cmusphinx/lattice_error.py and lattice_error_fst.py

     
  • Vassil Panayotov

    Thank you Nickolay - you are a living SR encyclopedia :)

    There was a discussion about the lattices produced by S4 on the development ML
    some months ago. One of the problems was for example that the hypotheses
    produced were unballanced with more alternatives toward the end of the
    lattice. Did you find the reason for this?

     
  • Nickolay V. Shmyrev

    One of the problems was for example that the hypotheses produced were
    unballanced with more alternatives toward the end of the lattice. Did you find
    the reason for this?

    No, this is still pending, one should establish a public test set for the
    confidence quality first of all. Something like

    http://www.cs.cmu.edu/~rongz/eurospeech_2005.pdf

     

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