[Kaldi] 特征提取--MFCC(一)

20180629 qzd

一 准备工程目录文件

---

建立在thch30上进行的。

• s5
  ├─── conf
  ├─── local
  ├─── step
  ├─── utils
  └─── data/data_thchs30/(数据)
      ├─── train / *.wav
      ├─── dev / *.wav
      └─── test / *.wav

二 数据准备

---

在data内新建train文件夹，这个文件夹内需要三个文件：wav.scp、utt2spk、spk2utt。

• • data/
    ├───train
    │ ├───wav.scp (发音id 发音文件)
    │ ├───utt2spk (发音id 发音人)
    │ └───spk2utt (发音人 发音id)
    └───dev、test(同上)

local/thchs-30_data_prep.sh $H $thchs/data_thchs30 || exit 1;

格式分别如下：

• wav.scp:
  test1 data/test/test1.wav
  test2 data/test/test2.wav
  test3 data/test/test3.wav

• utt2spk:
  test1 global
  test2 global
  test3 global

• spk2utt:
  global test1 test2 test3

至此，都准备好了。

三 特征提取

---

rm -rf data/mfcc && mkdir -p data/mfcc &&  cp -R data/{train,dev,test,test_phone} data/mfcc || exit 1;
#produce MFCC features
for x in train dev test; do
  #make  mfcc
  steps/make_mfcc.sh --nj $n --cmd "$train_cmd" data/mfcc/$x exp/make_mfcc/$x mfcc/$x || exit 1;
  ##compute cmvn 计算每条wav文件的均值方差
  #steps/compute_cmvn_stats.sh data/mfcc/$x exp/mfcc_cmvn/$x mfcc/$x || exit 1;
done

可视化特征数据：

/wd/qzd/kaldi-master/src/bin/copy-matrix ark:raw_mfcc_train.1.ark ark,t:- | less

或者：

/wd/qzd/kaldi-master/src/featbin/copy-feats ark:raw_mfcc_train.1.ark ark,t:- | head

四 ark-->txt

---

如何将kaldi中的特征数据读取出来，将ark二进制文件转化成.txt格式的文件

/wd/qzd/kaldi-master/src/featbin/copy-feats --binary=false ark:raw_mfcc_train.1.ark ark,t:1.txt

ark:（二进制文件位置） ark,t:（你需要存放文件的位置）；
至此，在项目跟目录下即可看到已经转换好的文件1.txt，内容如下

image.png

附：特征提取代码

---

通过上面的过程，可以知道，对于一段语音，首先对其进行分帧（如，每10ms取25ms的窗口作为一帧），对每一帧进行平滑（加窗，如汉明窗），之后进行FFT（快速傅里叶变化）将连续信号转化为数字信号， 再进行离散余弦变换（DCT）得到一个多维向量，最后取前13维作为最后的MFCC。重复该过程，得到一段语音每个帧的特征向量。

steps/make_mfcc.sh --nj train_cmd" data/mfcc/x mfcc/$x || exit 1;

• step/make_mfcc.sh代码如下：

#!/bin/bash

# Copyright 2012-2016  Johns Hopkins University (Author: Daniel Povey)
# Apache 2.0
# To be run from .. (one directory up from here)
# see ../run.sh for example

# Begin configuration section.
nj=4
cmd=run.pl
mfcc_config=conf/mfcc.conf
compress=true
write_utt2num_frames=false  # if true writes utt2num_frames
# End configuration section.

echo "$0 $@"  # Print the command line for logging

if [ -f path.sh ]; then . ./path.sh; fi
. parse_options.sh || exit 1;

if [ $# -lt 1 ] || [ $# -gt 3 ]; then
   echo "Usage: $0 [options]  [ [] ]";
   echo "e.g.: $0 data/train exp/make_mfcc/train mfcc"
   echo "Note:  defaults to /log, and  defaults to /data"
   echo "Options: "
   echo "  --mfcc-config                       # config passed to compute-mfcc-feats "
   echo "  --nj                                         # number of parallel jobs"
   echo "  --cmd (utils/run.pl|utils/queue.pl ) # how to run jobs."
   echo "  --write-utt2num-frames      # If true, write utt2num_frames file."
   exit 1;
fi

data=$1
if [ $# -ge 2 ]; then
  logdir=$2
else
  logdir=$data/log
fi
if [ $# -ge 3 ]; then
  mfccdir=$3
else
  mfccdir=$data/data
fi

# make $mfccdir an absolute pathname.
mfccdir=`perl -e '($dir,$pwd)= @ARGV; if($dir!~m:^/:) { $dir = "$pwd/$dir"; } print $dir; ' $mfccdir ${PWD}`

# use "name" as part of name of the archive.
name=`basename $data`

mkdir -p $mfccdir || exit 1;
mkdir -p $logdir || exit 1;

if [ -f $data/feats.scp ]; then
  mkdir -p $data/.backup
  echo "$0: moving $data/feats.scp to $data/.backup"
  mv $data/feats.scp $data/.backup
fi

scp=$data/wav.scp

required="$scp $mfcc_config"

for f in $required; do
  if [ ! -f $f ]; then
    echo "make_mfcc.sh: no such file $f"
    exit 1;
  fi
done
utils/validate_data_dir.sh --no-text --no-feats $data || exit 1;

if [ -f $data/spk2warp ]; then
  echo "$0 [info]: using VTLN warp factors from $data/spk2warp"
  vtln_opts="--vtln-map=ark:$data/spk2warp --utt2spk=ark:$data/utt2spk"
elif [ -f $data/utt2warp ]; then
  echo "$0 [info]: using VTLN warp factors from $data/utt2warp"
  vtln_opts="--vtln-map=ark:$data/utt2warp"
fi

for n in $(seq $nj); do
  # the next command does nothing unless $mfccdir/storage/ exists, see
  # utils/create_data_link.pl for more info.
  utils/create_data_link.pl $mfccdir/raw_mfcc_$name.$n.ark
done


if $write_utt2num_frames; then
  write_num_frames_opt="--write-num-frames=ark,t:$logdir/utt2num_frames.JOB"
else
  write_num_frames_opt=
fi


if [ -f $data/segments ]; then
  echo "$0 [info]: segments file exists: using that."

  split_segments=""
  for n in $(seq $nj); do
    split_segments="$split_segments $logdir/segments.$n"
  done

  utils/split_scp.pl $data/segments $split_segments || exit 1;
  rm $logdir/.error 2>/dev/null

  $cmd JOB=1:$nj $logdir/make_mfcc_${name}.JOB.log \
    extract-segments scp,p:$scp $logdir/segments.JOB ark:- \| \
    compute-mfcc-feats $vtln_opts --verbose=2 --config=$mfcc_config ark:- ark:- \| \
    copy-feats --compress=$compress $write_num_frames_opt ark:- \
      ark,scp:$mfccdir/raw_mfcc_$name.JOB.ark,$mfccdir/raw_mfcc_$name.JOB.scp \
     || exit 1;

else
  echo "$0: [info]: no segments file exists: assuming wav.scp indexed by utterance."
  split_scps=""
  for n in $(seq $nj); do
    split_scps="$split_scps $logdir/wav_${name}.$n.scp"
  done

  utils/split_scp.pl $scp $split_scps || exit 1;


  # add ,p to the input rspecifier so that we can just skip over
  # utterances that have bad wave data.

  $cmd JOB=1:$nj $logdir/make_mfcc_${name}.JOB.log \
    compute-mfcc-feats  $vtln_opts --verbose=2 --config=$mfcc_config \
     scp,p:$logdir/wav_${name}.JOB.scp ark:- \| \
      copy-feats $write_num_frames_opt --compress=$compress ark:- \
      ark,scp:$mfccdir/raw_mfcc_$name.JOB.ark,$mfccdir/raw_mfcc_$name.JOB.scp \
      || exit 1;
fi


if [ -f $logdir/.error.$name ]; then
  echo "Error producing mfcc features for $name:"
  tail $logdir/make_mfcc_${name}.1.log
  exit 1;
fi

# concatenate the .scp files together.
for n in $(seq $nj); do
  cat $mfccdir/raw_mfcc_$name.$n.scp || exit 1;
done > $data/feats.scp || exit 1

if $write_utt2num_frames; then
  for n in $(seq $nj); do
    cat $logdir/utt2num_frames.$n || exit 1;
  done > $data/utt2num_frames || exit 1
  rm $logdir/utt2num_frames.*
fi

rm $logdir/wav_${name}.*.scp  $logdir/segments.* 2>/dev/null

nf=`cat $data/feats.scp | wc -l`
nu=`cat $data/utt2spk | wc -l`
if [ $nf -ne $nu ]; then
  echo "It seems not all of the feature files were successfully processed ($nf != $nu);"
  echo "consider using utils/fix_data_dir.sh $data"
fi

if [ $nf -lt $[$nu - ($nu/20)] ]; then
  echo "Less than 95% the features were successfully generated.  Probably a serious error."
  exit 1;
fi

echo "Succeeded creating MFCC features for $name"

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