#!/usr/bin/perl
# Author: Alan J. Pippin
# Description: Extract the given chapter(s) from an mkv file into separate video files
# Requires: Newer version of ffmpeg to be installed that supports MKV chapters

# Howto compile the latest FFMPEG from src under Linux
# FFMPEG - http://ubuntuforums.org/showthread.php?t=786095

# Howto eliminate the non-monotonically increasing dts to muxer error
# Comment out the error message in ffmpeg src tree in libavformat/utils.c
# http://ffmpeg.zeranoe.com/forum/viewtopic.php?f=7&t=49

# MOV:
# major_brand : qt
# Video: h264 (avc1 / 0x31637661) 
# Audio: pcm_s16le

# MTS:
# Video: h264 (High) (HDMV / 0x564D4448)
# Audio: ac3 (AC-3 / 0x332D4341)

# MP4:
# Video: h264 (Baseline) (avc1 / 0x31637661)
# Audio: aac (mp4a / 0x6134706D)

# 3GP:
# Video: h264 (Baseline) (avc1 / 0x31637661)
# Audio: aac (mp4a / 0x6134706D)

# FFMPEG EXAMPLE CMD:
#ffmpeg -ss 00:00:00.000 -t 00:00:38.299 -i 2010-12-04.000.mkv -map 0 -vcodec copy -acodec copy test.mov

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# Includes
use File::Copy;
use File::Basename;
use Getopt::Std;

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# Configuration parameters - CHANGE THESE TO SUITE YOUR NEEDS
my $ffmpeg=`which ffmpeg`; chomp($ffmpeg);
my $tmpfile = `mktemp`; chomp($tmpfile);
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# Command Line Options
getopts("c:i:o:kse:");

if(! -x $ffmpeg) { die "-E- Unable to find required program: ffmpeg\n"; }
if(! defined $opt_i) { &usage(); die "-E- Missing required argument input video name: -i <input.mkv>\n"; }
if(! defined $opt_c) { &usage(); die "-E- Missing required chapter: -c <all|1,2,...>"; }
if(! -r $opt_i) { &usage(); die "-E- Unable to open/find the input mkv file: $opt_i\n"; }
if(! defined $opt_o) {
    if($opt_i =~ /^(\d+-\d+-\d+)/) { $opt_o = $1; }
    elsif($opt_i =~ /^(.*?)\./) { $opt_o = $1; }
}

sub usage {
    print "usage: $0 -i <input.mkv> -o <output_base_name> -c <chapter,chapter,...>\n";
    print "  -c <chapter,chapter,...>  Specify which chapter from the mkv file to extract (all or 1,2,3, ...)\n";
    print "  -i <input.mkv>            Specify the name of the input mkv file\n";
    print "  -o <output_base_name>     Sets the base name to use when naming the output videos extracted from the chapters\n";
    print "                            If not specified, the base name will be taken from the name of your input video\n";
    print "  -e <ext>                  Specify the extension that should be used on the output files.\n";
    print "                            This is automatically determined. You only need to specify it if autodetection fails.\n";
    print "  -s                        Simulate mode. Don't actually make the video, but tell us what you will do\n";
    print "  -k                        Keep intermediate mkv file created during the extraction/conversion of mp4 clips\n";
    print "\n";
    return 1;
}

####################################################################################################
# SUBROUTINES

sub detect_ext {
    my ($ffmpeg_info, $progressive) = @_;

    my $h264 = 0;
    my $h264_high = 0;
    my $ac3 = 0;
    my $aac = 0;
    my $pcm_s16le = 0;
    
    foreach $line (@{$ffmpeg_info}) {
	if($line =~ /Stream/) {
	    if($line =~ /h264/i) { $h264 = 1; }
	    if($line =~ /h264.*High/i) { $h264_high = 1; }
	    if($line =~ /ac3/i) { $ac3 = 1; }
	    if($line =~ /aac/i) { $aac = 1; }
	    if($line =~ /pcm_s16le/i) { $pcm_s16le = 1; }
	}
    }

    # Quicktime/MOV
    if($h264 && $pcm_s16le) { return "mov"; }
    # MTS
    if($h264_high && $ac3) { if(!$progressive) { return "mkv"; } else { return "mp4"; } }
    # 3GP/MP4
    if($h264 && $aac) { if(!$progressive) { return "mkv"; } else { return "mp4"; } }

    return "UNKNOWN";
}

sub export_chapter {
    my ($chapters, $chapter) = @_;
    foreach $ch (@{$chapters}) {
	if($ch == $chapter) { return 1; }
    }
    return 0;
}

####################################################################################################
# MAIN

# Turn our list of chapters into an ordered array
my @chapters = sort(split(/,/, $opt_c));
my $all_chapters = 0;
if($opt_c =~ /all/) { $all_chapters = 1; }
print "-> Extracting the following chapters from $opt_i: @chapters\n";

my $progressive = system('ffmpeg -i "$opt_i" 2>&1 | grep -q "frame rate differs"');
if(!$progressive) {
    print "   Detected interlaced video content\n";
} else {
    print "   Detected progressive video content\n";
}

# Use ffmpeg to extract the list of chapters available to rip
# For each chapter specified on the command line, use ffmpeg to extract a video clip from that chapter
my @ffmpeg_info = `$ffmpeg -i $opt_i 2>&1`;
foreach $line (@ffmpeg_info) {
    if($line =~ /Chapter #\d+\:(\d+): start (\S+), end (\S+)/) {
	$chapter = $1;
	$start = $2;
        if($start > 0) { $start += 1; } # Add some margin to prevent taking a piece of the previous clip
	$end = $3;
	$duration = $end - $start;
	if($duration < 0) { die "-E- Unexpected negative duration detected for chapter $chapter\n"; }
	if($all_chapters || &export_chapter(\@chapters,$chapter)) {
	    $ext = "UNKNOWN"; 
	    if(defined $opt_e) { $ext = $opt_e; }
	    else { $ext = &detect_ext(\@ffmpeg_info, $progressive); } 
	    if($ext =~ /UNKNOWN/) { die "-E- Unable to determine the file type/extension to use for the output videos. Specify it with the -e <ext> option.\n"; }
	    $dstfile = $opt_o . ".c" . sprintf("%03d",$chapter) . "." . $ext;
	    print "-> Exporting $chapter to $dstfile:\n";
	    $cmd = "ffmpeg -ss $start -t $duration -i $opt_i -map 0 -vcodec copy -acodec copy $dstfile 2>&1";
	    if(defined $opt_s) {
		print "$cmd\n";
	    } else {
		print "\n";
		print "$cmd\n";
		$errno = system("$cmd");
		$errno = $errno >> 8;
		if($errno > 0) { die "-E- ffmpeg encountered some errors with exit code $errno\n"; }
	    }
	    if(!$progressive && $ext =~ /mkv/i) {
		$ext = "mp4";
		$srcfile = $dstfile;
		$dstfile = $dstfile = $opt_o . ".c" . sprintf("%03d",$chapter) . "." . $ext;
		$cmd = "mencoder -oac copy -ovc copy -of lavf -lavfopts format=mp4 -o $dstfile $srcfile";
		if(defined $opt_s) {
		    print "$cmd\n";
		} else {
		    print "\n";
		    print "$cmd\n";
		    $errno = system("$cmd");
		    $errno = $errno >> 8;
		    if(! defined $opt_k) { unlink "$srcfile"; }
		    if($errno > 0) { die "-E- mencoder encountered some errors with exit code $errno\n"; }
		}
	    }
	}
    }
}

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