TOOLS/subedit.pl

   1 #!/usr/bin/perl -w
   2
   3 # A script for pipelined editing of subtitle files.
   4 # Copyright (C) 2004 Michael Klepikov <mike72@mail.ru>
   5 #
   6 # Version 1.0  initial release  28-Mar-04
   7 #
   8 # Comments, suggestions -- send me an mail, but the recommended way is
   9 # to enhance/fix on your own and submit to the distribution;)
  10 # If you like, I can review the fixes.
  11 #
  12 # This script is free software; you can redistribute it and/or
  13 # modify it under the terms of the GNU Lesser General Public
  14 # License as published by the Free Software Foundation; either
  15 # version 2 of the License, or (at your option) any later version.
  16 # Retain original credits when modifying.
  17 #
  18 # This script is distributed in the hope that it will be useful,
  19 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  20 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  21 # Lesser General Public License for more details.
  22 #
  23 # You should have received a copy of the GNU Lesser General Public
  24 # License along with this library; if not, write to the Free Software
  25 # Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  26 #
  27
  28 use Math::BigInt;
  29
  30 # Constants
  31 my $FMT_UNKNOWN = 0;
  32 my $FMT_SRT = 1;
  33
  34 # Argument values
  35 my $DEBUG = 0;
  36 my $inFormat;
  37 my $outFormat;
  38 my $shiftMilli;
  39 my $scaleMilli;
  40 my $splitFromMilli;
  41 my $splitToMilli;
  42
  43 ## Process command line
  44 while (defined ($argVal = shift)) {
  45   if ($argVal eq "-d" || $argVal eq "--debug") {
  46     $DEBUG = 1;
  47   } elsif ($argVal eq "-if" || $argVal eq "--input-format") {
  48     $inFormat = shift;
  49     usage ("Must specify input format") if ! $inFormat;
  50     if ($inFormat =~ /^srt/i) {
  51       $inFormat = $FMT_SRT;
  52     } else {
  53       usage ("Invalid input format");
  54     }
  55   } elsif ($argVal eq "-of" || $argVal eq "--output-format") {
  56     $outFormat = shift;
  57     usage ("Must specify input format") if ! $outFormat;
  58     if ($outFormat =~ /^srt/i) {
  59       $outFormat = $FMT_SRT;
  60     } else {
  61       usage ("Invalid output format");
  62     }
  63   } elsif ($argVal eq "-s" || $argVal eq "--shift") {
  64     my $argTime = shift;
  65     if (! defined $argTime ||
  66         ! defined ($shiftMilli = getTimeMillis ($argTime))) {
  67       usage ("Invalid shift time value");
  68     }
  69   } elsif ($argVal eq "-c" || $argVal eq "--scale") {
  70     my $argTime = shift;
  71     if (! defined $argTime ||
  72         ! defined ($scaleMilli = getTimeMillis ($argTime))) {
  73       usage ("Invalid scale time value");
  74     }
  75   } elsif ($argVal eq "-f" || $argVal eq "--split-from") {
  76     my $argTime = shift;
  77     if (! defined $argTime ||
  78         ! defined ($splitFromMilli = getTimeMillis ($argTime))) {
  79       usage ("Invalid split start time value");
  80     }
  81   } elsif ($argVal eq "-t" || $argVal eq "--split-to") {
  82     my $argTime = shift;
  83     if (! defined $argTime ||
  84         ! defined ($splitToMilli = getTimeMillis ($argTime))) {
  85       usage ("Invalid split end time value");
  86     }
  87   } elsif ($argVal eq "-h" || $argVal eq "--help") {
  88     usage ();
  89   } else {
  90     usage ("Unrecognized argument $argVal");
  91   }
  92 }
  93
  94 # Input format defaults to SRT
  95 $inFormat = $FMT_SRT if (! defined $inFormat);
  96 # Output format defaults to the same as input
  97 $outFormat = $inFormat if (! defined $outFormat);
  98
  99 ## Read
 100
 101 my $subs;
 102 if ($inFormat == $FMT_SRT) {
 103   $subs = readSRT (*STDIN);
 104   printf STDERR ("Read %d SRT subs\n", scalar @{$subs}) if $DEBUG;
 105   # Sort by start time
 106   @{$subs} = sort {$a -> {srtStartTime} <=> $b -> {srtEndTime}} @{$subs};
 107 }
 108
 109 ## Transform
 110
 111 if (defined $shiftMilli && 0 != $shiftMilli) {
 112   printf STDERR ("Shift: %d milliseconds\n", $shiftMilli) if $DEBUG;
 113   shiftSRT ($subs, $shiftMilli);
 114 }
 115
 116 if (defined $splitFromMilli || defined $splitToMilli) {
 117   if ($DEBUG) {
 118     my $printFrom = (defined $splitFromMilli) ? $splitFromMilli : "-";
 119     my $printTo = (defined $splitToMilli) ? $splitToMilli : "-";
 120     printf STDERR ("Split: from $printFrom to $printTo\n");
 121   }
 122   splitSRT ($subs, $splitFromMilli, $splitToMilli);
 123 }
 124
 125 if (defined $scaleMilli && 0 != $scaleMilli) {
 126   my $lastSubIdx = scalar @{$subs} - 1;
 127   if ($lastSubIdx >= 0) {
 128     my $lastTimeOrig = $subs -> [$lastSubIdx] -> {srtEndTime};
 129     if ($lastTimeOrig == 0) {
 130       die "Cannot scale when last subtitle ends at 00:00:00,000";
 131     }
 132     my $lastTimeScaled = $lastTimeOrig + $scaleMilli;
 133     printf STDERR ("Scale: %d/%d\n", $lastTimeScaled, $lastTimeOrig) if $DEBUG;
 134     scaleSRT ($subs, $lastTimeScaled, $lastTimeOrig);
 135   }
 136 }
 137
 138 ## Write
 139 if ($outFormat == $FMT_SRT) {
 140   writeSRT (*STDOUT, $subs);
 141 }
 142
 143 # Close STDOUT, as recommended by Perl manual
 144 # (allows diagnostics on disc overflow, etc.)
 145 close (STDOUT) || die "Cannot close output stream: $!";
 146
 147 exit 0;
 148
 149 ## Subroutines
 150
 151 # Convert string time format to milliseconds
 152 # SRT style: "01:20:03.251", and "," is allowed instead of "."
 153 # Return undef in case of format error
 154 sub getTimeMillis
 155 {
 156   $_ = shift;
 157   my $millis = 0;
 158
 159   if (/\s*(.*)[\.,]([0-9]+)?\s*$/) { # Fraction; strip surrounding spaces
 160     #print STDERR "frac: \$1=$1 \$2=$2\n" if $DEBUG;
 161     $_ = $1;
 162     $millis += ("0." . $2) * 1000 if $2;
 163   }
 164   if (/(.*?)([0-9]+)$/) { # Seconds
 165     #print STDERR "secs: \$1=$1 \$2=$2\n" if $DEBUG;
 166     $_ = $1;
 167     $millis += $2 * 1000 if $2;
 168   }
 169   if (/(.*?)([0-9]+):$/) { # Minutes
 170     #print STDERR "mins: \$1=$1 \$2=$2\n" if $DEBUG;
 171     $_ = $1;
 172     $millis += $2 * 60000 if $2;
 173   }
 174   if (/(.*?)([0-9]+):$/) { # Hours
 175     #print STDERR "mins: \$1=$1 \$2=$2\n" if $DEBUG;
 176     $_ = $1;
 177     $millis += $2 * 3600000 if $2;
 178   }
 179   if (/(.*?)\-$/) { # Minus sign
 180     $_ = $1;
 181     $millis *= -1;
 182   }
 183   $millis = undef if (! /^$/); # Make sure we ate everything up
 184   if ($DEBUG) {
 185     if (defined $millis) {
 186       #print STDERR "time value match: $millis ms\n";
 187     } else {
 188       #print STDERR "time mismatch\n";
 189     }
 190   }
 191   return $millis;
 192 }
 193
 194 # Convert milliseconds to SRT formatted string
 195 sub getTimeSRT
 196 {
 197   my $t = shift;
 198   my $tMinus = "";
 199   if ($t < 0) {
 200     $t = -$t;
 201     $tMinus = "-";
 202   }
 203   my $tMilli = $t % 1000;
 204   $t /= 1000;
 205   my $tSec = $t % 60;
 206   $t /= 60;
 207   my $tMin = $t % 60;
 208   $t /= 60;
 209   my $tHr = $t;
 210   return sprintf ("%s%02d:%02d:%02d,%03d",
 211                   $tMinus, $tHr, $tMin, $tSec, $tMilli);
 212 }
 213
 214 # Read SRT subtitles
 215 sub readSRT
 216 {
 217   local *IN = shift;
 218   my $subs = [];
 219
 220   $_ = <IN>;
 221   print STDERR "Undefined first line\n" if ! defined $_ && $DEBUG;
 222   my $lineNo = 1;
 223   READ_SUBS:
 224   while (defined $_) {
 225     # Each loop iteration reads one subtitle from <IN>
 226     my $sub = {};
 227
 228     # print STDERR "Reading line $lineNo\n" if $DEBUG;
 229
 230     # Skip empty lines
 231     while (/^\s*$/) {
 232       last READ_SUBS if ! ($_ = <IN>);
 233       ++$lineNo;
 234     }
 235
 236     # Subtitle number
 237     if (/^\s*([0-9]+)\s*$/) {
 238       $sub -> {srtNumber} = $1;
 239       # print "SRT num: $1\n" if $DEBUG;
 240     } else {
 241       die "Invalid SRT format at line $lineNo";
 242     }
 243
 244     # Timing
 245     if ($_ = <IN>) {
 246       ++$lineNo;
 247     } else {
 248       die "Unexpected end of SRT stream at line $lineNo";
 249     }
 250     # print STDERR "LINE: $_\n" if $DEBUG;
 251     if (/^\s*(\S+)\s*--\>\s*(\S+)\s*$/) {
 252       my $startMillis = getTimeMillis ($1);
 253       my $endMillis = getTimeMillis ($2);
 254       die "Invalid SRT timing format at line $lineNo: $_"
 255         if ! defined $startMillis || ! defined $endMillis;
 256       $sub -> {srtStartTime} = $startMillis;
 257       $sub -> {srtEndTime} = $endMillis;
 258     } else {
 259       die "Invalid SRT timing format at line $lineNo: $_";
 260     }
 261
 262     # Text lines
 263     my $subLines = [];
 264     while (1) {
 265       last if ! ($_ = <IN>); # EOF ends subtitle
 266       ++$lineNo;
 267       last if /^\s*$/; # Empty line ends subtitle
 268       ($_ = $_) =~ s/\s+$//; # Strip trailing spaces
 269       push @{$subLines}, $_;
 270     }
 271     die "No text in SRT subtitle at line $lineNo" if 0 == scalar @{$subLines};
 272     $sub -> {lines} = $subLines;
 273
 274     # Append subtitle to the list
 275     push @{$subs}, $sub;
 276   }
 277   print STDERR "SRT read ok, $lineNo lines\n" if $DEBUG;
 278
 279   return $subs;
 280 }
 281
 282 # Write SRT subtitles
 283 sub writeSRT
 284 {
 285   use integer; # For integer division
 286   local *OUT = shift;
 287   my $subs = shift;
 288
 289   my $subNum = 0;
 290   foreach (@{$subs}) {
 291     ++$subNum;
 292
 293     my $sub = $_;
 294     my $sTimeSRT = getTimeSRT ($sub -> {srtStartTime});
 295     my $eTimeSRT = getTimeSRT ($sub -> {srtEndTime});
 296     printf OUT ("%d\n%s --> %s\n", $subNum, $sTimeSRT, $eTimeSRT);
 297     foreach (@{$sub -> {lines}}) {
 298       printf OUT ("%s\n", $_);
 299     }
 300     printf OUT "\n";
 301   }
 302   printf STDERR ("Wrote %d SRT subs\n", $subNum) if $DEBUG;
 303 }
 304
 305 # Shift SRT subtitles by a given number of seconds.
 306 # The number may be negative and fractional.
 307 sub shiftSRT
 308 {
 309   use integer; # $shiftMilli could be passed as float
 310   my $subs = shift;
 311   my $shiftMilli = shift;
 312
 313   foreach (@{$subs}) {
 314     $_ -> {srtStartTime} += $shiftMilli;
 315     $_ -> {srtEndTime} += $shiftMilli;
 316   }
 317 }
 318
 319 # Multiply each subtitle timing by a divident and divide by divisor.
 320 # The idea is that the divident is usually the new total number of
 321 # milliseconds in the subtitle file, and the divisor is the old
 322 # total number of milliseconds in the subtitle file.
 323 # We could simply use a double precision real coefficient instead of
 324 # integer divident and divisor, and that could be good enough, but
 325 # using integer arithmetics *guarantees* precision up to the last
 326 # digit, so why settle for good enough when we can have a guarantee.
 327 #
 328 # Uses Math::BigInt arithmetics, because it works with numbers
 329 # up to (total number of milliseconds for a subtitle timing)^2,
 330 # which could be on the order of approximately 1e+13, which is
 331 # larger than maximum 32-bit integer.
 332 # There is a performance loss when using BigInt vs. regular floating
 333 # point arithmetics, but the actual performance is quite acceptable
 334 # on files with a few thousand subtitles.
 335 sub scaleSRT
 336 {
 337   use integer; # Divident and divisor could be passed as floats, truncate
 338   my $subs = shift;
 339   my $scaleDividend = shift;
 340   my $scaleDivisor = shift;
 341
 342   foreach (@{$subs}) {
 343     my $ss = Math::BigInt -> new ($_ -> {srtStartTime});
 344     $ss = $ss -> bmul ($scaleDividend);
 345     $_ -> {srtStartTime} = $ss -> bdiv ($scaleDivisor) -> bsstr ();
 346     my $se = Math::BigInt -> new ($_ -> {srtEndTime});
 347     $se = $se -> bmul ($scaleDividend);
 348     $_ -> {srtEndTime} = $se -> bdiv ($scaleDivisor) -> bsstr ();
 349   }
 350 }
 351
 352 # Extract a fragment within a given time interval
 353 # Either "from" or "to" may be undefined
 354 sub splitSRT
 355 {
 356   use integer; # fromMilli and toMilli could be passed as floats, truncate
 357   my $subs = shift;
 358   my $fromMilli = shift;
 359   my $toMilli = shift;
 360
 361   my $iSub = 0;
 362   while ($iSub < scalar @{$subs}) {
 363     $_ = $subs -> [$iSub];
 364     my $keep = 0;
 365     if (! defined $fromMilli || $_ -> {srtEndTime} >= $fromMilli) {
 366       # The subtitle ends later than the start boundary
 367
 368       # Fix overlapping start timing,
 369       # but only of the start boundary is not infinite (undef)
 370       if (defined $fromMilli && $_ -> {srtStartTime} < $fromMilli) {
 371         $_ -> {srtStartTime} = $fromMilli;
 372       }
 373       if (! defined $toMilli || $_ -> {srtStartTime} <= $toMilli) {
 374         # The subtitle begins earlier than the end boundary
 375
 376         # Fix overlapping end timing,
 377         # but only of the end boundary is not infinite (undef)
 378         if (defined $toMilli && $_ -> {srtEndTime} > $toMilli) {
 379           $_ -> {srtEndTime} = $toMilli;
 380         }
 381
 382         # All conditions met, all fixes done
 383         $keep = 1;
 384       }
 385     }
 386     if ($keep) {
 387       ++$iSub;
 388     } else {
 389       splice @{$subs}, $iSub, 1;
 390     }
 391   }
 392 }
 393
 394 # Print brief usage help
 395 # Accepts an optional error message, e.g. for errors parsing command line
 396 sub usage
 397 {
 398   my $msg = shift;
 399   my $exitCode = 0;
 400
 401   if (defined $msg) {
 402     $exitCode = 2;
 403     print STDERR "$msg\n";
 404   }
 405
 406   print STDERR <<USAGE;
 407 Usage: $0 [switches]
 408   -if,--input-format <fmt>  input format; supported: SRT
 409                             default is SRT
 410   -of,--output-format <fmt> output format; supported: SRT
 411                             default is same as input format
 412   -s,--shift <time>         shift all subtitles by <time>
 413                             (format: [-]hh:mm:ss,fraction)
 414   -c,--scale <time>         scale by adding <time> to overall duration
 415   -f,--split-from <time>    Drop subtitles that end before <time>
 416   -t,--split-to <time>      Drop subtitles that start after <time>
 417                             (will truncate timing if it overlaps a boundary)
 418   -r,--renumber             renumber SRT subtitles in output
 419   -d,--debug                enable debug output
 420   -h,--help                 this help message
 421
 422 All times could be negative. Input/output may also contain negative timings,
 423 which is sometimes useful for intermediate results.
 424 SRT subtitles are always renumbered on output.
 425
 426 EXAMPLES
 427
 428 Split subtitle file into two disks at a boundary of one hour 15 minutes:
 429
 430   subedit.pl --split-to 1:15:0 < all.srt > p1.srt
 431   subedit.pl -f 1:15:0 < all.srt | subedit.pl --shift -1:15:0 > p2.srt
 432
 433 Join the previous two disks back into one file:
 434
 435   subedit.pl -s 1:15:00 < p2.srt | cat p1.srt - | subedit.pl > all.srt
 436
 437 Correct a situation where the first subtitle starts in sync with the video,
 438 but the last one starts 3.5 seconds earlier than the speech in the video,
 439 assuming the first subtitle timing is 00:01:05.030:
 440
 441   subedit.pl -s -1:5.03 | subedit.pl -c 3.5 | subedit.pl -s 1:5.03
 442 USAGE
 443
 444   exit $exitCode;
 445 }