Using CGI to Create Pages

↑ Introduction

CGI and other server-side technologies such as PHP can be used to dynamically generate references to streaming movies. Generating references via server-side technologies provides these advantages:

• The primary benefit: References to streams can be generated without knowing the URL in advance. Pages can be authored and the URL can be "filled in" when the page is viewed. The actual URL could be passed in via JavaScript or by another server-side technology. For example, the Streaming Server Directory listing scripts on this site dynamically generate URL links to movies using Perl cgi.
• Databases and web forms: Server side technologies provide ways to apply the use of web-forms to access the server and databases to access streaming content. Values entered in a web form or returned from a database can be passed to the server-side script to generate pages with streaming links. See this example of a php/mysql script (search on "bird").
• Redirection: Clients can be redirected to specific servers based on their platform, IP address, etc. Any of the user-agent attributes can be used by a server-side script to redirect clients to specific servers and/or content. Redirection can also form the basis of a load-balancing system by checking server load and redirecting a client to the least loaded server.
• Automatic sdp generation. Unicast to Multicast relays can be configured as described here. Part of this process involves copying an sdp file and editing some values. The resulting sdp file will be delivered for clients connecting to the multicast stream. The generation of the multicast sdp file can be automated via a server-side script.
• Server-side generation also provides a method to link to streams with HREF tags. Because parameters can be passed to the server-side scripts, standard HREF tags can be used to link to streaming content.

↑ Useful text formats for scripting

Since server-side technologies are excellent at returning text, the following QuickTime supported text formats are common for the applications outlined above. Note: The PHP examples shown directly below assume that the web server is running on the same system as the streaming server. The Perl example could be used on any web server as it accepts an absolute url to the streaming movie.

• ↑ RTSPtext is the simplest of all. The text returned is "RTSPtext" followed by the rtsp url. This data needs to be returned with the mime type video/quicktime. For example, the following PHP script accepts one parameter (the relative path to the movie on the server) and returns RTSPtext for the stream. This script could be accessed directly from QuickTime Player by opening a URL or as the href attribute in a Object/Embed tag.
  <?php
  

  // get the relative URL path to the movie
  $url_path = $_GET['url'];
  $server_name = $_SERVER['SERVER_NAME'];
  header("Content-type: video/quicktime\n\n");
  echo ("RTSPtextRTSP://$server_name/$url_path");
  

  ?>
  
• ↑ QTL is next simplest. The text returned is QTL XML with the QuickTime embed tag inside. A subset of the embed tag attributes are supported, providing more flexibility than RTSPtext. QTL needs to be returned with the mime type application/x-quicktime-media-link. For example, the following PHP script accepts two parameters: the relative path to the movie and the fullscreen mode. This script could be accessed directly from QuickTime Player by opening a URL or as the href attribute in a Object/Embed tag.
  <?php
  

  // get the relative URL path to the movie and the fullscreen mode
  $fullscreen = "";
  $url_path = $_GET['url'];
  $fullscreen = $_GET['fs'];
  $server_name = $_SERVER['SERVER_NAME'];
  $url = "rtsp://$server_name/$url_path";
  header("Content-type: application/x-quicktime-reference\n\n");
  print '<?xml version="1.0"?>';
  print '<?quicktime type="application/x-quicktime-media-link"?>';
  if (($fullscreen == "false") || ($fullscreen == "")) {
  

  # if fullscreen parameter is false use this embed statement
  print "<embed src=\"$url\" autoplay=\"true\" />";
  

  } else {
  

  # if fullscreen parameter is set use this embed statement
  print "<embed src=\"$url\" autoplay=\"true\" fullscreen=\"$fullscreen\" />";
  

  }
  

  ?>
• ↑ SMIL is the a sophisticated text format supported by QuickTime. It is a W3C XML format for describing multimedia presentations. QuickTime currently supports 1.0 of the specification. SMIL allows multiple media references to be combined into a "presentation." The following Perl script accepts the absolute url to the streaming movie and it's width and height.
  #!/usr/bin/perl --
  # Make an smil document with and embedded movie
  #
  # This cgi accepts a url to a movie and creates a smil file.
  # comma separated parameters include the url, width and height of the movie
  require 5;
  use strict;
  use CGI;
  $CGI::DISABLE_UPLOADS = 1; #disable any attempt to upload file via this cgi
  $CGI::POST_MAX = 512; #set the maximum input for post to 512 bytes
  my ($url, $w, $h);
  ($url, $w, $h) = split /,/,$ENV{'QUERY_STRING'};
  print "Content-type: application/smil\n\n";
  print <<XMLHEAD;
  <smil>
  <head>
  <<layout>
  <<root-layout width="$w" height="$h" />
  <<region id="1" top="0" left="0" width="$w" height="$h" />
  <</layout>
  </head>
  <body>
  XMLHEAD
  print <<EMBED;
  <video src="$url" region="1" />
  </body>
  </smil>
  EMBED
  exit;
  

↑ Redirection Scripts