Re: [Kaldi-developers] Phonetic decoding

[Xavier A. <xan...@gm...>]

Dan, all,
while yesterday's solution worked perfectly for my needs, I later found a
"simpler" way to obtain the time codes of a phoneme decoding that seems to
also work, but is giving me a slightly different output.
I your proposal the set of steps is: steps/decode_si.sh -> lattice-1best
-> nbest-to-linear -> ali-to-phones
This generates lattices that then converts into a 1-best decoding. Instead,
I found the following to avoid outputing lattices, but just the alignments:
steps/decode_nolats.sh -> ali-to-phones

While this second solution is faster (less steps) it is not returning the
exact same output.. I see that internally it is based on gmm-decode-faster
instead of gmm-latgen-faster. Should I worry? which one is the best
solution (if any)

thanks,

X. Anguera

On Tue, Jan 6, 2015 at 12:41 AM, Xavier Anguera <xan...@gm...> wrote:

> Thanks Dan,
> it worked perfectly!
>
> X.
>
>
> On Mon, Jan 5, 2015 at 9:21 PM, Daniel Povey <dp...@gm...> wrote:
>
>> Your whole pipeline is based on using the words in the lattices, not
>> the phones.  In your case the words *are* the phones, because you're
>> using a phone bigram LM.  So you need to do lattice-align-words, not
>> lattice-align-phones.  The confidence algorithm only works on words so
>> you need to use words.
>> Alternatively, if you don't need the confidences, a more efficient way
>> to do it without lattice-align-words is to simply do lattice-1best |
>> nbest-to-linear [only keeping the alignment output] | ali-to-phones
>> (--write-lengths=true).  You'll have to write a script to convert the
>> output of ali-to-phones to ctm format.
>>
>> Wei, if you have time, could you please work on adding a boolean
>> option --ctm-output to the program ali-to-phones (and an option
>> --frame-shift, default 0.01, to control the times of the ctm output)?
>> The confidences can just be 1.  This issue seems to come up
>> repeatedly.
>>
>>
>> Dan
>>
>>
>> On Mon, Jan 5, 2015 at 12:10 PM, Xavier Anguera <xan...@gm...>
>> wrote:
>> > Hi,
>> > I am trying to perform phonetic decoding in Kaldi where I would like to
>> > obtain a final ctm file with a time-aligned 1-best phone sequence given
>> my
>> > input audio. I must be missing something, as the decoded phones look
>> good
>> > but their timings are not accurate at all. Here is what I am doing:
>> >
>> > 1) I create a phone bigram LM with utils/make_phone_bigram_lang.sh
>> > 2) I combine LM and acoustic models into a recognition graph with
>> > utils/mkgraph.sh
>> > 3) I perform the decoding of the input audio with steps/decode_si.sh
>> > 4) Obtain the 1-best CTM using the following command:
>> >     lattice-align-phones --output-error-lats=true $hmm/final.mdl
>> "ark:gunzip
>> > -c $decodedir/lat.*.gz |" ark:- | \
>> >      lattice-to-ctm-conf --decode-mbr=true --acoustic-scale=$acwt ark:-
>> - |
>> > \
>> >      utils/int2sym.pl -f 5 $graph_or_lang/words.txt > $odir/$name.ctm
>> ||
>> > exit 1;
>> >
>> > Note that when using the same acoustic models for word decoding I get
>> very
>> > good word-starting times. In this case I am using, in step 4,
>> > lattice-align-words instead, could this be the problem?
>> >
>> > Thanks,
>> >
>> > X. Anguera
>> >
>> >
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