[SRILM User List] Nbest list to lattice

[Alfonso MHC]

Hello,

I'm trying to build a lattice in HTK format from a N-best list also in 
HTK format.I have run a simple example where I start with this Nbest 
list in the file ex2.nbest:

    NBestList2.0
    (0) c1 ( st: 0 et: 4 g: 0 a: 0 ) c2 ( st: 5 et: 10 g: 0 a: 0 )
    (0) c3 ( st: 0 et: 1 g: 0 a: 0 ) c4 ( st: 1.01 et: 2  g: 0 a: 0 ) c5
    ( st: 2.1 et: 3  g: 0 a: 0 ) c6 ( st: 3.1 et: 4  g: 0 a: 0 ) c7 (
    st: 4.1 et: 10  g: 0 a: 0 )


Given the time information, c1 happens at the same time as c3 c4 c5 c6, 
and c2 happens at the same time as c7. Then I hope to obtain a lattice 
that allows only four combinations:

    c1 c2
    c3 c4 c5 c6 c2
    c1 c7
    c3 c4 c5 c6 c7

However, the lattice I obtained allowed other paths and then I wonder if 
I have missunderstood something. This is what I did:


To build the lattice I run:

    ./nbest-lattice -nbest ex2.nbest -use-mesh -write out2.lat


And get this lattice in out2.lat:

    name ex2.nbest
    numaligns 5
    posterior 1
    align 0 *DELETE* 0.5 c3 0.5
    align 1 *DELETE* 0.5 c4 0.5
    align 2 *DELETE* 0.5 c5 0.5
    align 3 c1 0.5 c6 0.5
    align 4 c2 0.5 c7 0.5


Then I build the HTK lattice with:

    ./lattice-tool -read-mesh -in-lattice out2.lat -out-lattice
    out_htk_2.lat -write-htk

And get (I copy only the Links part...):

    # Links
    J=0    S=0    E=1    W=!NULL    x1=-0.30103    a=-0.30103
    J=1    S=0    E=1    W=c3    x1=-0.30103    a=-0.30103
    J=2    S=1    E=2    W=!NULL    x1=-0.30103    a=-0.30103
    J=3    S=1    E=2    W=c4    x1=-0.30103    a=-0.30103
    J=4    S=2    E=3    W=!NULL    x1=-0.30103    a=-0.30103
    J=5    S=2    E=3    W=c5    x1=-0.30103    a=-0.30103
    J=6    S=3    E=4    W=c1    x1=-0.30103    a=-0.30103
    J=7    S=3    E=4    W=c6    x1=-0.30103    a=-0.30103
    J=8    S=4    E=5    W=c2    x1=-0.30103    a=-0.30103
    J=9    S=4    E=5    W=c7    x1=-0.30103    a=-0.30103

It seems that this lattice allows other paths than the ones I expected, 
e.g. c4 c1 c7. Then I think that the time information is not used how I 
was expecting. Maybe I have not used the tools correctly or I have 
missunderstod something. Could anyone let me know where the problem is?

Thanks in advance,

Alfonso