paper on lattice tool

[Andreas Stolcke]

In message <WuCUZvMQ.1184791247.2874780.jpinto at idiap.ch>you wrote:
> I am talking about the option compute posteriors. E.g. my options are
> 
>  $lattice_tool -compute-posteriors \
>                   -read-htk -in-lattice $path \
>                   -write-htk -out-lattice ${tmp_lattice_dir}/${file} \
>                   -htk-lmscale 8.3 \
>                   -htk-acscale 1.0 \
>                   -htk-wdpenalty -4.3429 \
>                   -htk-logbase 2.718 \
>                   -posterior-scale 8.3 \

lattice-tool -compute-posteriors computes NODE posterior probabilities,
not WORD posterior probabilities.  In other words, posteriors of the 
same word appearing on different nodes are not summed over.
Therefore, the algorithm is the basic FB known from HMMs, which is explained
in many text books, as well as the popular tutorial

L. R. Rabiner and B. H. Juang, An Introduction to Hidden {Markov} Models,
IEEE Signal Processing Magazine, 3(1), 4-16, Jan. 1986.

The Wessel et al. paper talks about how to sum over multiple hypotheses
containing the same word in the same "position".
That is something lattice-tool can do also, using word confusion networks
(see the -write-mesh option).

Andreas 

> 
> 
> Thanks,
> Joel.
> 
> On 7/18/2007, "Andreas Stolcke" <stolcke at speech.sri.com> wrote:
> 
> >jpinto at idiap.ch wrote:
> >> Dear SRILM user,
> >>
> >> Is there any publication or write up on how exactly the forward-backward
> >> alogirthm (for estimation of word posterior probability from a word
> >> lattice) is implemented in lattice-tool ?
> >>
> >What lattice-tool options specifically are you talking about ?
> >
> >Andreas
> >
> >> How similar or different is it from the algorithm described in
> >> "Confidence Measures for Large Vocabulary Continuous Speech
> >> Recognition" by Frank Wessel et. al.
> >>
> >> Many thanks,
> >> Joel.
> >>
> >>
> >
>