decode lattice

[john at newington.f9.co.uk]

Andreas,

I changed our lattice files so that the words were not enclosed in double quotes. This fixed the initial problem and enabled me to get an output from lattice-tool. However, I then realised that I needed to scale the output from my classifier by subtracting the log prior probabilities for each class before building the lattice. Now, when I try the rescaling and decoding using lattice-tool it predicts the same (low frequency) label for almost every token.

Am I wrong to scale my 'accoustic' probabilities before building the lattice? Does lattice-tool do this for me when I call:

./lattice-tool -read-htk -in-lattice lattice.slf -write-htk \ -out-lattice lattice.out -lm DAgrammar -no-nulls

Hope you can shed some light on this.

Regards,

John Ferguson

  > > Dear Andreas,
 > >
 > > I am replying on behalf of my colleague who emailed you earlier
 > regarding
 > > correct use of the SRILM lattice-tool.
 > >
 > > Based on your previous advice I have tried to decode our
 > lattice using our
 > > bigram model. All files seem to be in the correct format, so
 > far as I can
 > > tell. However, when lattice-tool rescores the lattice, all the
 > newly added
 > > LM probabilities "l=..." come out as "-inf". I tried 1-best
 > decoding using
 > > viterbi on the rescored lattice and the output is simply:
 > >
 > > lattice.out </s>
 > >
 > > where lattice.out is the utterance name inserted by lattice-tool.
 > >
 > > Do you have any idea why we're experiencing behaviour like this? Can you
 > > suggest any alterations?
 >
 > John,
 >
 > the problem is that your lattices use double-quotes around the
 > word strings,
 > but the released version of SRILM does't yet implement the HTK quoting
 > mechanism (an oversight on my part).
 >
 > You can replace the file lattice/src/HTKLattice.cc with the
 > attached version
 > and rebuild lattice-tool to make it work. Or, you can just strip the
 > double quotes in your lattice files and keep using the old software.
 >