Re: [Kaldi-developers] align reverse

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

There is actually some stuff in Kaldi that uses this type of backward
decoding already, I think there is an example script like
local/run_fwdbwd.sh in one of the example setups.
But I doubt very much that this is something you really want to do or would
be useful to you for alignment purposes.
Dan


On Tue, Oct 14, 2014 at 5:41 AM, Tony Robinson <to...@ca...>
wrote:

> On 10/14/2014 07:00 AM, Saman Mousazadeh wrote:
> > I have trained two models for alignment one mono and the other is tri.
> > now I want to use these models to align data in reverse (i.e. from the
> > end of utterance to the beginning). I have changed the L fst and the
> > mono models works pretty well but the tri model does not work at all
> > (as expected!! ). Is there any way (except new training ) to use these
> > tri model for reverse alignment?
>
> This is an interesting theoretical problem.   There are two things to
> reverse, the WFSTs and the features.
>
> The WFSTs either all need to be reversed (i.e. each of H C L G), or you
> need to reverse the composition.
>
> You may also need to reverse the features, that is if you view your
> frames as t+1, t, t-1 then the first order differences will have the
> opposite sign to the normal window of frames, t-1, t, t+1.     Here by
> far the easiest is to compute all the higher order features (e.g. to
> third order differences) in the forward time order then reverse these.
> Perhaps it works to flip the sign of even differences, but I wouldn't
> trust this.
>
> I'm finding it hard to resist the temptation to ask why you want to do
> this!
>
>
> Tony
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