Video::Info::RIFF - Probe DivX and AVI files for attributes

 -video codec
 -audio codec
 -frame height
 -frame width
 -frame count

  use Video::Info::RIFF;

  my $video;

  $video = Video::Info::RIFF->new(-file=>$filename);                          #like this
  $video = Video::Info::RIFF->new(-file=>$filename,-headersize=>$headersize); #or this

  $video->vcodec;                         #video codec
  $video->acodec;                         #audio codec
  ...

 method              returns
 ---------------------------------------------------
 achans()            number of audio channels
 acodec()            audio codec
 acodecraw()         audio codec numeric ID
 arate()             audio bitrate
 afrequency()        sampling rate of audio streams, in Hertz
 astreams()          number of audio streams
 filename()          path file used to create object
 filesize()          size in bytes of filename()
 expectedsize()      expected size in bytes of filename(),
                     according to the RIFF header
 fourcc()            RIFF Four Character Code
 fps()               frames/second
 height()            frame height in pixels
 probe()             try to determine filetype
 scale()             video bitrate
 type()              type of file data.  RIFF or AVI
 vcodec()            video codec
 vframes()           number of frames
 vrate()             video bitrate
 vstreams()          number of video streams
 width()             frame width in pixels

 Copyright (c) 2002
 Aladdin Free Public License (see LICENSE for details)
 Allen Day <allenday@ucla.edu>

package Video::Info::RIFF;

use strict;
our $VERSION = '1.07';

use base qw(Video::Info);

#is this reasonable?  big fudge factor here.
use constant MAX_HEADER_BYTES => 10240;

use Class::MakeMethods::Emulator::MethodMaker
  get_set => [qw( fourcc )],
;

sub init {
  my $self = shift;
  my %param = @_;
  $self->init_attributes(@_);
  $self->header_size($param{-headersize} || MAX_HEADER_BYTES);
  return $self;
}

##------------------------------------------------------------------------
## header_size()
##
## Set the header size.  Hrm, should this be in the accessor method
## closures above?
##------------------------------------------------------------------------
sub header_size {
  my($self,$arg) = @_;
  return $self->{header_size} unless defined $arg;
  $self->{header_size} = $arg;
}

sub expectedsize {
  my($self,$arg) = @_;
  return $self->{expectedsize} unless defined $arg;
  $self->{expectedsize} = $arg;
}

##------------------------------------------------------------------------
## probe()
##
## Obtain the filehandle from Video::Info and extract the properties from
## the RIFF structure.
##------------------------------------------------------------------------
sub probe {
  my $self = shift;

  my $fh = $self->handle; ## inherited from Video::Info

  my $type;
  sysread($fh,$type,12) or die "probe(): can't read 12 bytes: $!\n";

  (warn "probe(): doesn't look like RIFF data" and return 0)
    if( ($type !~ /^(RIFF)/) && ($type !~ /^(AVI) /) );
  $self->type( $1 );

  $self->expectedsize(unpack("V",substr($type,4,4)));

  #onward
  my $hdrl_data = undef;

  while ( !$hdrl_data ) {
      my $byte;
      sysread($fh,$byte,8) or die "probe(): can't read 8 bytes: $!";
      if ( substr( $byte, 0, 4 ) eq 'LIST' ) {
	  sysread( $fh, $byte, 4 ) or die "probe() can't read 4 bytes: $!\n";
	  
	  if ( substr( $byte, 0, 4 ) eq 'hdrl' ) {
	      sysread( $fh, $hdrl_data, $self->header_size );
	  } elsif ( $byte eq 'movi' ) {
	      ### noop
	  }
      } elsif ( $byte eq 'idx1' ) {
	  ### noop
      }
  }
  
  my $last_tag = 0;
  for ( my $i=0; $i < length($hdrl_data); $i++ ) {
      
      my $t = $i;
      my $window = substr( $hdrl_data, $t, 4 );
 
     if ( $window eq 'strh' ) {

	  $t += 8;
	  $window = substr( $hdrl_data, $t, 4 );
	  
	  if ( $window eq 'vids' ) {
	      $self->fourcc(substr($hdrl_data,$t+4,4));
	      $self->scale(unpack("V",substr($hdrl_data,$t+20,4)));
	      $self->vrate(unpack("V",substr($hdrl_data,$t+24,4)));
	      $self->fps($self->vrate / $self->scale);
	      $self->vframes(unpack("V",substr($hdrl_data,$t+32,4)));
	      $self->vstreams( ($self->vstreams || 0) + 1 );;
	      
              $self->duration($self->vframes / $self->fps) if $self->fps;

              $last_tag = 1;
	      
	  } elsif($window eq 'auds') {
	      $self->astreams( ($self->astreams || 0) + 1);
	      $last_tag = 2;
   
	  }
      } 
      elsif ( $window eq 'strf' ) {
	  
	  $t += 8;
	  $window = substr( $hdrl_data, $t, 4 );
	  
	  if ( $last_tag == 1 ) {
	      $self->width(unpack("V",substr($hdrl_data,$t+4,4)));
	      $self->height(unpack("V",substr($hdrl_data,$t+8,4)));
	      $self->vcodec(substr($hdrl_data,$t+16,4));
	      
	  } elsif( $last_tag == 2 ) {
	      $self->acodecraw(unpack("v",substr($hdrl_data,$t,2)));
	      $self->achans(unpack("v",substr($hdrl_data,$t+2,2)));
	      $self->afrequency(unpack("v",substr($hdrl_data,$t+4,2)));
	      $self->arate(
                           8 * unpack("V",substr($hdrl_data,$t+8,4))
                          );
	      
	  }
	  
	  $last_tag = 0;
      }
  }
  return 1;
}

1;

__END__
# Below is stub documentation for your module. You better edit it!