SWF info and Frame Rate extraction

1. Purpose

To extract ***from PHP*** various SWF file information, in particular the difficult-to-obtain "Frame Rate":

2. Introduction

The first idea is of course not to reinvent the wheel and search for an already-made solution:

3. Third-party Tools

The tools I found and tried are usually:

Video Converters (SWF to AVI, etc) like Magic Swf2Avi 3.11.
SWF Decompilers, Decompressors or pure Extractors, like Action Script Viewer or SWF Decompiler or SWF Extractor Free or WinSWF Extractor, when you transform a SWF file in its collection of Resources in binary format.
SWF Editors, like SWF Editor or Flash Digger, when you perform manually some operations on SWF files.

The conclusion of this tools analysis is that I found them:

Sometimes clumsy
Usually too low-level (hexadecimal dump) or too bloated (Windows executable with GUI) to be really useable from PHP
Lacking a command-line mode (so that they could be called from PHP via exec() for instance) or to get output on the console (stdout)
Always platform-dependent, which is incompatible with my use of PHP scripts
Giving out too much or too few information
And moreover, NOT displaying efficiently the Frame Rate (in fps, frames per second)

So I had to find a really good way to extract information from a SWF file. I had two trivial ways to go : (a) find an already-made SWF Header Extractor, or (b) work at the binary level.

At first, of course, I turned to the PHP documentation (http://www.php.net/manual/en/) and found out the LibSWF and Ming libraries as candidates.

4. PHP common libraries - LibSWF

PHP has since long (PHP 4 RC2) "Shockwave Flash Functions" (see http://www.php.net/manual/en/ref.swf.php)
The two problems are that (a) it is not available on Windows, and I don't want to use a custom port or emulator (Cygwin...), (b) it can only CREATE SWF files. There is no GetFrameRate() function and no Getter at all.

5. PHP common libraries - Ming

Ming is now a standard library and was added in PHP 4.0.5. See http://www.php.net/manual/en/ref.ming.php.
The "only" problem is that the necessary SWFVideoStream object is only available in the CVS version of the current PHP ;-)

PHP code:


$video= new SWFVideoStream ($_GET['file']);
echo "number of frames is ".$video->getNumFrames().'<br>';

Results:


Fatal error: Cannot instantiate non-existent class: swfvideostream in analflash.php on line 15

6. My Solution

I finally found out the solution I wanted : a ready-made binary-level analyser written in PHP. All we're left to is write a correct instanciation of the new class and use the defined methods to get the frame rate. Or I could have extended the class to add a GetFrameRate() getter.

The Library Header:

This a well-written little-known PHP class of 6877 bytes and which deserves better visibility on the Web, even if it is known since 2004 ;-)
You can already find it at :

Main Repository : http://slainte.phpclasses.org/swfheader [linked page is blank at the time I write]
Main Author's Site : http://www.bisinteractive.net/ [link is broken at the time I write]
http://www.zend.com/codex.php?id=1382&single=1
http://phpclasses.linuxpourtous.com/browse/package/1653.html
Local Copy on this Server : swfheader.class.php.txt (remove .txt to use the File ; do Save Link As or Click and Save As the displayed text file)


<?php
//-----------------------------------------------------------------------------
// SWF HEADER - version 1.0
// Small utility class to determine basic data from a SWF file header
// Does not need any php-flash extension, based on raw binary data reading
//-----------------------------------------------------------------------------
//   SWFHEADER CLASS - PHP SWF header parser
//   Copyright (C) 2004  Carlos Falo Hervás
//   This library is free software; you can redistribute it and/or
//   modify it under the terms of the GNU Lesser General Public
//   License as published by the Free Software Foundation; either
//   version 2.1 of the License, or (at your option) any later version.
//-----------------------------------------------------------------------------

class swfheader {
  var $debug ;            // Output DEBUG info
  var $fname ;            // SWF file analyzed
  var $magic ;            // Magic in a SWF file (FWS or CWS)
  var $compressed ;      // Flag to indicate a compressed file (CWS)
  var $version ;         // Flash version
  var $size ;               // Uncompressed file size (in bytes)
  var $width ;            // Flash movie native width
  var $height ;            // Flash movie native height
  var $valid ;            // Valid SWF file
  var $fps ;               // Flash movie native frame-rate
  var $frames ;            // Flash movie total frames
  //---------------------------------------------------------------------------    
  // swfheader($debug) :    Constructor, basically does nothing but initilize
  //                                 debug and data fields
  //---------------------------------------------------------------------------
  function swfheader($debug = false) {}
  //---------------------------------------------------------------------------    
  // init() : initialize the data fields to "empty" values
  //---------------------------------------------------------------------------
  function init() {}
  //---------------------------------------------------------------------------
  // loadswf($filename) : loads $filename and stores data from it's header
  //---------------------------------------------------------------------------
  function getDimensions($filename) {} // returns String ; object has been updated
}
?>

My PHP code:

Local Copy on this Server : AnalFlash.php.txt (remove .txt to use the File ; do Save Link As or Click and Save As the displayed text file)


<?php
//
// AnalFlash.php : analyze of a Flash (SWF) file
//
//VGR09062006 Creation with Ming to get the fps of an SWF "video"
//
// TODO : Nil
//

if (!isset($_GET['file'])) { die("Please feed me a filename in 'file' parameter"); exit; }

if (strlen(trim($_GET['file']))==0) die("Empty filename");
else if (!file_exists($_GET['file'])) die("Could not open file '{$_GET['file']}'");
else { // let's go
  //$video= new SWFVideoStream ($_GET['file']); // type : SWFVideoStream (VGR REM : unavailable, CVS only)
  //echo "number of frames is ".$video->getNumFrames().'<br>';
  require('swfheader.class.php');
  $video=new swfheader();
  $thedim=str_replace('|','x',$video->getDimensions($_GET['file']));
  echo "AnalFlasp.php v 1.0 ©2006 <a href=mailto:vgr@europeanexperts.org?Subject=AnalFlash>VGR</a> for <a href='http://www.edainworks.com/'>Edaìn Works Ltd</a> - uses swfheader class
© 2004 Carlos Falo Hervás<hr>file {$_GET['file']} <br>dimensions $thedim px<br><pre>";
  print_r($video);
  echo '</pre>';
}
?>

You may see it in action at http://www.fecj.org/extra/AnalFlash/AnalFlash.php and one file available locally is monster_NL.swf.

Result:


AnalFlasp.php v 1.0 ©2006 VGR for Edaìn Works Ltd - uses swfheader class © 2004 Carlos Falo Hervás
file monster_NL.swf
dimensions 425x600 px

swfheader Object
(
    [debug] => 
    [fname] => monster_NL.swf
    [magic] => CWS
    [compressed] => 1
    [version] => 6
    [size] => 46871
    [width] => 425
    [height] => 600
    [valid] => 1
    [fps] => Array
        (
            [0] => 0
            [1] => 18
        )

    [frames] => 1
)

And the Frame Rate is ... 18 fps. CQFD.

8. Extending the technique

You can extract any kind of header field using the same script and looking at the print_r() results.

9. Conclusion

This technique is extremely simple and efficient and does the job well.
Many many thanks to the Author of the Library : Carlos Falo Hervás (SP) CarlosFaloHervas
Best regards,
for European Experts Exchange and Edaìn Works back to list of test scripts
Last update 2010-02-14 11:40:27

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