#!/usr/bin/perl
 
###
### this is a lesson recording utility
### uses scrot to get screenshots of the screen while I'm teaching
### the screenshots are taken at a given interval of seconds
### and saved in consecutively numbered files
###
 
use Getopt::Std;
getopts("so:ht:f:k");
 
$DFLT_DT = 10;
$DFLT_FN = "screenshot";
$DFLT_VC = "out.mp4";
 
###
### prepares a video out of the jpgs
###
sub makevideo {
  my @args = @_; 
  ### close audio track, if present
  if($opt_s) {
    print RECORD "stop\n";
    close RECORD;
  }
  ### prepare video out of the snapshots 
  $cmd = "avconv -f image2 -r 1/$delta -i $froot\%05d.jpg $video";
  print "$cmd\n";
  system($cmd);
  ### join audio and video if present
  if($opt_s) {
    $cmd = "avconv -i $video -i $audio -acodec copy -vcodec copy av_$video";
    print "$cmd\n";
    system($cmd);
  }
  exit;
}
 
use sigtrap 'handler' => \&makevideo, 'INT';
 
### 
### option handling 
###
if($opt_h) {
  print "Usage is:\nlesson.pl [-h] [-s] [-t secs] [-f filenameroot] [-o videofile.xxx] [-k]\n"; 
  print "-h:\thelp\n";
  print "-k:\tkeep existing images (default: remove)\n";
  print "-s:\trecord audio as well\n";
  exit;
}
if($opt_t) {
  $delta = $opt_t; 
} else {
  $delta = $DFLT_DT;
}
if($opt_f) {
  $froot = $opt_f; 
} else {
  $froot = $DFLT_FN;
}
$froot = $froot."_";
if($opt_o) {
    $video = $opt_o; 
} else {
  $video = $froot.".mp4";
}
 
###
### inizialization
###
 
print "lesson.pl: capturing screen images every $delta secs in files named $froot"; 
print "NNN\n";
 
### removing old jpg files
if(!($opt_k)) {
  print "Removing old files $froot*.jpg\n";
  $cmd = "rm -f $froot*.jpg";
  print "--> $cmd\n";
  system($cmd);
  print "Done!\n";
}
 
### sound processing
if($opt_s) {
  $audio = $froot.".mp3";
  open RECORD, "|ecasound -i alsa -o $audio -c" or die "cannot open ecasound\n";
}
 
###
### start looping
###
$fcount = 0; 
while(1==1) {  ### terminate upon ^C
  if($opt_s) {
    print RECORD "start\n";
  }
  $cmd = sprintf("scrot %s%05d.jpg", $froot, $fcount);
  print "$cmd\n";
  system($cmd);
  $fcount++;
  sleep $delta; ### wait delta seconds
}
exit;