gistfile1.txt

#!/usr/bin/env perl

use strict;
use warnings;

open(my $fh, "<", $ARGV[0]) or die $!;

parse_mp4($fh, -s $fh);

exit 0;

sub parse_mp4 {
    my ($fh, $len, $line) = @_;

    $line = "$line  ";

    my $so_far = 0;

    while ($so_far < $len) {
        my $offset = sysseek($fh, 0, 1);
        sysread($fh, my $size, 4)==4 or die $!;
        sysread($fh, my $type, 4)==4 or die $!;

          
        $size = unpack("N", $size);
        print "$line Type: $type, size = $size, offset=$offset, offset mod 8=".($offset % 8)."\n";

        if ($type =~ /^(?:moov|udta|trak|mdia|minf|stbl)$/) {
            parse_mp4($fh, $size-8, $line);
        }
        else {
            seek($fh, $size-8, 1) or die $!;
        }
        $so_far+=$size;
    }
    die "flown off eof" unless $so_far == $len;
    
}