Add a script to extract frames from the UCF-101 dataset.

diff --git a/extract-ucf101.sh b/extract-ucf101.sh
new file mode 100755 (executable)
index 0000000..23a83ee
--- /dev/null
+++ b/extract-ucf101.sh
@@ -0,0 +1,70 @@
+#! /bin/bash
+set -e
+
+# Extract frame triplets from the UCF-101 dataset
+# (http://crcv.ucf.edu/data/UCF101.php). Run as follows:
+#
+#   ./extract-ucf101.sh dir/file.avi
+#
+# Or, with parallel from moreutils, you can do it for all videos
+# over many cores:
+#
+#   parallel -j 12 ./extract-ucf101.sh -- $( find -name \*.avi )
+#
+# but do note that this will produce ~250 GB of PNGs, probably many
+# more frames than you actually would get to use for training
+# and likely straining the file system with ~5M files.
+#
+# The script will create a set of frame files that you can easily combine
+# and use for training:
+#
+#  for N in 1 2 3; do echo $N; cat $( find -name \*_frame$N.txt | sort -u )  > ../frame$N.txt; done
+
+FILE=$1
+PREFIX=$( dirname $FILE )/$( basename $FILE | tr -c "a-zA-Z0-9_-" "_" )
+
+echo $FILE
+
+rm -f ${PREFIX}_frame[123].tmp.txt ${PREFIX}_delayed1_*.png ${PREFIX}_delayed2_*.png
+
+ffmpeg -loglevel error -i $FILE -vf scale=256:256 ${PREFIX}_%04d.png
+NUM_FRAMES=$( ls -1 ${PREFIX}_*.png | sed 's/.*\([0-9]\{4\}\)\.png$/\1/' | tail -n 1 | sed 's/^0*//' )
+
+# Verify that the frames contain some sort of motion (we use PSNR <35 dB as a proxy).
+# Note that we need to check the entire triplet, since many of the videos seem to have
+# been through some sort of pull-up, so there could be differences between n and n+2,
+# but n and n+1 would essentially be identical. See v_BoxingPunchingBag_g09_c02.avi
+# for an example.
+for X in `seq 1 $(( NUM_FRAMES - 2 ))`; do
+       ln -s $( basename $( printf "%s_%04d.png" $PREFIX $(( X + 1 )) ) ) $( printf "%s_delayed1_%04d.png" $PREFIX $X )
+       ln -s $( basename $( printf "%s_%04d.png" $PREFIX $(( X + 2 )) ) ) $( printf "%s_delayed2_%04d.png" $PREFIX $X )
+done   
+
+ffmpeg -loglevel error -i ${PREFIX}_%04d.png -i ${PREFIX}_delayed1_%04d.png -filter_complex "psnr=stats_file=${PREFIX}.d1.psnr" -f null /dev/null
+ffmpeg -loglevel error -i ${PREFIX}_%04d.png -i ${PREFIX}_delayed2_%04d.png -filter_complex "psnr=stats_file=${PREFIX}.d2.psnr" -f null /dev/null
+
+cut -d" " -f1,6 < ${PREFIX}.d1.psnr > ${PREFIX}.d1.cut.psnr
+cut -d" " -f1,6 < ${PREFIX}.d2.psnr > ${PREFIX}.d2.cut.psnr
+
+join ${PREFIX}.d1.cut.psnr ${PREFIX}.d2.cut.psnr | sed 's/psnr_avg://g;s/n://;s/\.[0-9]*//g' | while read FRAMENO PSNR1 PSNR2; do
+       #echo FRAMENO=$FRAMENO PSNR1=$PSNR1 PSNR2=$PSNR2
+       if [ "$FRAMENO" -le $(( NUM_FRAMES - 2 )) ] && [ "$PSNR1" != "inf" ] && [ "$PSNR1" -lt 35 ] && [ "$PSNR2" != "inf" ] && [ "$PSNR2" -lt 35 ]; then
+                printf "%s_%04d.png\n" $PREFIX $(( FRAMENO + 0 )) >> ${PREFIX}_frame1.tmp.txt
+                printf "%s_%04d.png\n" $PREFIX $(( FRAMENO + 1 )) >> ${PREFIX}_frame2.tmp.txt
+                printf "%s_%04d.png\n" $PREFIX $(( FRAMENO + 2 )) >> ${PREFIX}_frame3.tmp.txt
+       fi
+done
+
+for X in `seq 1 $(( NUM_FRAMES - 2 ))`; do
+       rm $( printf "%s_delayed1_%04d.png" $PREFIX $X )
+       rm $( printf "%s_delayed2_%04d.png" $PREFIX $X )
+done   
+
+mv ${PREFIX}_frame1.tmp.txt ${PREFIX}_frame1.txt
+mv ${PREFIX}_frame2.tmp.txt ${PREFIX}_frame2.txt
+mv ${PREFIX}_frame3.tmp.txt ${PREFIX}_frame3.txt
+rm -f ${PREFIX}.d1.psnr
+rm -f ${PREFIX}.d2.psnr
+rm -f ${PREFIX}.d1.cut.psnr
+rm -f ${PREFIX}.d2.cut.psnr
+