Re: [Kaldi-users] kaldi lattice

[Daniel P. <dp...@gm...>]

BTW, the time information does not matter at all for MMI training.

Dan


On Wed, Oct 23, 2013 at 8:30 PM, Daniel Povey <dp...@gm...> wrote:
> I just updated that paragraph to the below.
>
>  If you want the time information of the lattices explicitly (rather than having
>  to count transition-ids), there is a function LatticeStateTimes (for Lattice),
>  and CompactLatticeStateTimes (for CompactLattice), which will give you the time
>  where each state is located (a number from 0 to the number of frames in the
>  file).  Be careful that in general, the words are not synchronized with to the
>  transition-ids, meaning that the transition-ids on an arc won't necessarily all
>  belong to the word whose label is on that arc.  This means that the times you
>  get from the lattice will (as far as the word labels are concerned) be inexact.
>  The same is also true of the weights; these are also not synchronized with
>  either the words or the transition-ids on a particular arc.  If you want exact
>  times (e.g. for conversion to HTK lattices, or for sclite scoring), then you
>  should run the program lattice-align-words.  This program only works if you
>  built your system with word-position-dependent phones, and it requires certain
>  command-line options to tell it which phones are in which position in the word.
>  See egs/wsj/s3/run.sh for an example (search for align).  There is an
>  alternative program, lattice-align-words-lexicon, that you can use if your
>  system does not have word-position-dependent phones.
>
> Dan
>
>
>
>>
>> I'm trying to understand the last paragraph in the lattice page.
>>
>> http://kaldi.sourceforge.net/lattices.html
>>
>> What does it mean that the labels are pushed relative to the
>> transition-ids and why does Kaldi choose to do this?
>>
>> In addition, what is latbin/lattice-align-words.cc doing exactly?
>> After aligning, I see plenty of silence phones appear in the lattice,
>> and the weights seem to be pushed. I assume the weights after aligning
>> are not meaningful for individual edges anymore and are only
>> meaningful for the whole path?
>>
>> Thanks,
>> Hao
>>
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