trunk: add previously missing script get_num_frames.sh

git-svn-id: https://svn.code.sf.net/p/kaldi/code/trunk@4324 5e6a8d80-dfce-4ca6-a32a-6e07a63d50c8

egs/wsj/s5/steps/nnet2/get_num_frames.sh

+#!/bin/bash
+
+# This script works out the approximate number of frames in a training directory
+# this is sometimes needed by higher-level scripts
+
+num_samples=1000
+
+
+if [ -f path.sh ]; then . ./path.sh; fi
+. parse_options.sh || exit 1;
+
+if [ $# -ne 1 ]; then
+  echo "Usage: $0 <data-dir>"
+  echo "Prints the number of frames of data in the data-dir, via sampling rather"
+  echo "than trying to access all the data."
+fi
+
+data=$1
+
+if [ ! -f $data/feats.scp ]; then
+  echo "$0: expected $data/feats.scp to exist"
+  exit 1;
+fi
+
+
+sample_frames=$(utils/shuffle_list.pl $data/feats.scp | head -n $num_samples | sort | feat-to-len --print-args=false scp:-)
+
+num_files_orig=$(wc -l <$data/feats.scp)
+if [ $num_samples -lt $num_files_orig ]; then
+  num_files_sampled=$num_samples
+else
+  num_files_sampled=$num_files_orig
+fi
+
+perl -e "\$n = int(($sample_frames * 1.0 * $num_files_orig) / (1.0 * $num_files_sampled)); print \"\$n\n\";";