[SRILM User List] Posterior Probability : HTK

Andreas Stolcke stolcke at icsi.berkeley.edu
Fri Mar 9 16:02:07 PST 2012

The first step is to compute posterior probabilities for arcs and nodes 
in your lattice, using the forward-backward algorithm.
The posterior probability is the sum of the scores of all paths going 
through an arc/node, normalized by the sum over all paths through the 
This is implemented by the lattice-tool -write-posteriors option (the 
output format is different from HTK format though).
It is important to scale the combined acoustic/language model scores, 
check the -posterior-scale option.

Often one wants posterior probabilities at the word level, and combine 
all word hypotheses that occur at the same "position" in the lattice.
For this you can build a word confusion network or "word mesh".  This is 
done by the lattice-tool -write-mesh option.

For an introduction to these concepts you might want to check the 
but note that the confusion network algorithm in SRILM is not the same 
as described in there.


On 3/8/2012 10:39 PM, Vinay Shashidhar wrote:
> Hi Guys,
> I have a read a lot of papers regarding posterior probability being a
> more robust and speaker independent features, but how does one
> calculate it?
> I am using HTK and am doing forced alignment. All i get is the
> likelihood scores.
> Thanks. Looking forward for your help.!
> regards
> Vinay
> _______________________________________________
> SRILM-User site list
> SRILM-User at speech.sri.com
> http://www.speech.sri.com/mailman/listinfo/srilm-user

More information about the SRILM-User mailing list