【kaldi】提取二階差分MFCC特徵

在kaldi裏面，提取MFCC特徵的工具compute-mfcc-feats 沒有選定提取二階MFCC的參數，只能提取一階。如果想要得到二階的MFCC特徵，用add-deltas 這個工具就能實現，例子如下

  $cmd JOB=1:$nj $logdir/make_mfcc_${name}.JOB.log \
    compute-mfcc-feats $vtln_opts $write_utt2dur_opt --verbose=2 \
      --config=$mfcc_config scp,p:$logdir/wav_${name}.JOB.scp ark:- \| \
    add-deltas ark:- 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;