Re: [Kaldi-users] kaldi lattice

[Hao T. <lar...@gm...>]

I am confused. Maybe I misunderstood something in the following paper.

https://wiki.inf.ed.ac.uk/twiki/pub/CSTR/ListenSemester1_2007_8/povey_mpe.pdf

Won't you need to know the start and end of frame indices for each arc
in the lattice in order to run forward-backward on each phone arc?

Hao

On Wed, Oct 23, 2013 at 7:32 PM, Daniel Povey <dp...@gm...> wrote:
> 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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