Re: [Kaldi-users] kaldi lattice

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

Thanks for the clarification. I am sorry it's getting a little bit off
topic. I just want to confirm it is safe to assume that the times
before aligning are not too off in the context of rescoring a dense
lattice.

I've looked at the MMI and MPE script. latbin/lattice-boost-ali.cc
boosts the not time-aligned denominator with the time-aligned
numerator, so I guess the answer to the above question is yes?

Hao

On Wed, Oct 23, 2013 at 8:13 PM, Daniel Povey <dp...@gm...> wrote:
> 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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