Various tweaks to make it work on Linux (Debian)

README.md

@@ -1,6 +1,6 @@
 # pmcam - poor man's video capture with motion detection in Bash
 
-This simple Bash script can be used to capture images from a webcam, and will provide motion detection support. There's Yawcam on Windows which is good, but I couldn't find anything free on OS X. So I put together this quick and dirty solution, which does the job surprisingly well.
+This simple Bash script captures images from a webcam with motion detection support. I wanted to find out what my dog was up to when I'm not at home, but couldn't find any free video capture software on OS X. I put together this quick and dirty solution, which does the job surprisingly well.
 
 Frames are captured at regular intervals using `ffmpeg`. Then ImageMagick's `compare` tool is used to check if this frame is similar to the previous one. If the frames are different enough, they are kept, otherwise they are deleted. This provide very simple motion detection and avoids filling up the hard drive with duplicate frames.
 
@@ -14,17 +14,15 @@ Frames are captured at regular intervals using `ffmpeg`. Then ImageMagick's `com
 
 ### Linux
 
-	apt-get install ffmpeg
-	apt-get install imagemagick
+	sudo apt-get install ffmpeg
+	# or: sudo apt-get install libav-tools
+	sudo apt-get install imagemagick
 	curl -O https://raw.github.com/laurent22/pmcam/master/pmcam.sh
 
-I could not test on Linux (feedback would be welcome) but according to the [ffmpeg documentation](https://trac.ffmpeg.org/wiki/Capture/Webcam) the ffmpeg command might need to be changed as follow:
-
-- Set `-f v4l2`
-- Set `-i /dev/video0`
-
 ### Windows
 
+(Not tested)
+
 * Install [Cygwin](https://www.cygwin.com/) or [MinGW](http://www.mingw.org/)
 * Install [ffmpeg](http://ffmpeg.zeranoe.com/builds/)
 * Install [ImageMagick](http://www.imagemagick.org/script/binary-releases.php)
@@ -37,13 +35,14 @@ The script will use the default webcam to capture frames. To capture using a dif
 
 A frame will then be saved approximately every 1 second to the "images" folder next to the Bash script. Both delay and target folder can be changed in the script.
 
-To stop the script, type Ctrl + C.
+To stop the script, press Ctrl + C.
 
 ## TODO
 
-* Check if the script is working on Linux. If necessary, provide alternative ffmpeg command depending on the OS - https://trac.ffmpeg.org/wiki/Capture/Webcam
+* Allow specifying the video capture source and format (curently hardcoded)
 * Command line argument to change frame directory.
 * Command line argument to change interval between frame captures.
+* Command line argument to specify the threshold for a frame to be kept.
 
 ## License
 

pmcam.sh

@@ -2,9 +2,18 @@
 
 SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 OUTPUT_DIR="$SCRIPT_DIR/images"
+
 CAPTURE_INTERVAL="1" # in seconds
+FFMPEG=ffmpeg
+command -v $FFMPEG >/dev/null 2>&1 || { FFMPEG=avconv ; }
+DIFF_RESULT_FILE=$OUTPUT_DIR/diff_results.txt
+
+fn_cleanup() {
+	rm -f diff.png $DIFF_RESULT_FILE
+}
 
 fn_terminate_script() {
+	fn_cleanup
 	echo "SIGINT caught."
 	exit 0
 }
@@ -16,16 +25,20 @@ while true ; do
 	FILENAME="$OUTPUT_DIR/$(date +"%Y%m%dT%H%M%S").jpg"
 	echo "-----------------------------------------"
 	echo "Capturing $FILENAME"
-	ffmpeg -loglevel fatal -f avfoundation -i "" -r 1 -t 0.0001 $FILENAME
+	if [[ "$OSTYPE" == "linux-gnu" ]]; then
+		$FFMPEG -loglevel fatal -f video4linux2 -i /dev/video0 -r 1 -t 0.0001 $FILENAME
+	elif [[ "$OSTYPE" == "darwin"* ]]; then
+		# Mac OSX
+		$FFMPEG -loglevel fatal -f avfoundation -i "" -r 1 -t 0.0001 $FILENAME
+	fi
 
 	if [[ "$PREVIOUS_FILENAME" != "" ]]; then
 		# For some reason, `compare` outputs the result to stderr so
 		# it's not possibly to directly get the result. It needs to be
 		# redirected to a temp file first.
-		OUT_FILE=$(mktemp -t diff)
-		compare -fuzz 20% -metric ae $PREVIOUS_FILENAME $FILENAME diff.png 2> $OUT_FILE
-		DIFF="$(cat $OUT_FILE)"
-		rm -f diff.png $OUT_FILE
+		compare -fuzz 20% -metric ae $PREVIOUS_FILENAME $FILENAME diff.png 2> $DIFF_RESULT_FILE
+		DIFF="$(cat $DIFF_RESULT_FILE)"
+		fn_cleanup
 		if [ "$DIFF" -lt 20 ]; then
 			echo "Same as previous image: delete (Diff = $DIFF)"
 			rm -f $FILENAME