Re: [Kaldi-users] kaldi lattice

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

We implement something slightly different called MFPE which does not
require the start/end information.  Anyway most recipes use BMMI which
also does not require it.
Dan


On Wed, Oct 23, 2013 at 8:58 PM, Hao Tang <lar...@gm...> wrote:
> 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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