Add sample_video and documentation

Author: Atcold

data/README.md

@@ -7,6 +7,7 @@ This folder contains the following scripts:
  - [`objectify.sh*`](objectify.sh): convert sampled-data from video-indexed to object-indexed;
  - [`resize_and_split.sh*`](resize_and_split.sh): see [below](#matchnet-mode);
  - [`resize_and_sample.sh*`](resize_and_sample.sh): see [below](#temponet-mode);
+ - [`sample_video.sh*`](sample_video.sh): sample the `<src video>` into `k` time-subsampled `<dst prefix>-` videos;
  - [`VideoFolder.py`](VideoFolder.py): *PyTorch* `data.Dataset`'s sub-class for video data loading.
 
 ## Remove white spaces from file names

data/sample_video.sh

@@ -0,0 +1,43 @@
+################################################################################
+# Video sampler: y_i[n] = x[n_i + N * n], i < N
+################################################################################
+# Alfredo Canziani, Mar 17
+################################################################################
+# Run as
+# ./sample_video.sh src_video dst_prefix
+################################################################################
+
+src="small_data_set/cup/sfsdfs-nb.mp4"
+dst="sampled/sfsdfs-nb"
+src="data_set/barcode/20160613_140057.mp4"
+dst="sampled/20160613_140057"
+src="data_set/floor/VID_20160605_094332.mp4"
+dst="sampled/VID_20160605_094332"
+src="/home/atcold/Videos/20170416_184611.mp4"
+dst="bme-car/20170416_184611"
+src="/home/atcold/Videos/20170418_113638.mp4"
+dst="bme-chair/20170418_113638"
+src="/home/atcold/Videos/20160603_133515.mp4"
+dst="abhi-car/20160603_133515"
+src="/home/atcold/Videos/20170419_125021.mp4"
+dst="bme-chair/20170419_125021"
+
+src=$1
+dst=$2
+
+k=5
+kk=$(awk "BEGIN{print 1/$k}")
+ffmpeg \
+    -i $src \
+    -an \
+    -loglevel error \
+    -filter_complex \
+        "setpts=$kk*PTS, \
+        scale=w=2*trunc(128*max(1\, iw/ih)):h=2*trunc(128*max(1\, ih/iw))[m]; \
+        [m]select=n=$k:e=(mod(n\, $k)+1)*lt(n\, 564) \
+        $(for ((i=1; i<=$k; i++)); do
+            echo -n "[a$i]"
+        done)" \
+    $(for ((i=1; i<=$k; i++)); do
+        echo -n "-r 31230000/1042111 -map [a$i] $dst-$i.mp4 "
+    done)