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• Subtitling Sierra RBT Files

  2 juin 2016, par Multimedia Mike — Game Hacking

  This is part 2 of the adventure started in my Subtitling Sierra VMD Files post. After I completed the VMD subtitling, The Translator discovered a wealth of animation files in a format called RBT (this apparently stands for “Robot” but I think “Ribbit” format could be more fun). What are we going to do ? We had come so far by solving the VMD subtitling problem for Phantasmagoria. It would be a shame if the effort ground to a halt due to this.

  Fortunately, the folks behind the ScummVM project already figured out enough of the format to be able to decode the RBT files in Phantasmagoria.

  In the end, I was successful in creating a completely standalone tool that can take a Robot file and a subtitle file and create a new Robot file with subtitles. The source code is here (subtitle-rbt.c). Here’s what the final result looks like :

  
  
  “What’s in the refrigerator ?” I should note at this juncture that I am not sure if this particular Robot file even has sound or dialogue since I was conducting these experiments on a computer with non-working audio.
  

  The RBT Format
  I have created a new MultimediaWiki page describing the Robot Animation format based on the ScummVM source code. I have not worked with a format quite like this before. These are paletted animations which consist of a sequence of independent frames that are designed to be overlaid on top of static background. Because of these characteristics, each frame encodes its own unique dimensions and origin coordinate within the frame. While the Phantasmagoria VMD files are usually 288×144 (which are usually double-sized for the benefit of a 640×400 Super VGA canvas), these frames are meant to be plotted on a game field that was roughly 576×288 (288×144 doublesized).
  

  For example, 2 minimalist animation frames from a desk investigation Robot file :

  
  
  100×147

  
  101×149
  

  As for compression, my first impression was that the algorithm was the same as VMD. This is wrong. It evidently uses an unmodified version of a standard algorithm called Lempel-Ziv-Stac (LZS). It shows up in several RFCs and was apparently used in MS-DOS’s transparent disk compression scheme.

  Approach
  Thankfully, many of the lessons I learned from the previous project are applicable to this project, including : subtitle library interfacing, subtitling in the paletted colorspace, and replacing encoded frames from the original file instead of trying to create a new file.

  Here is the pitch for this project :

  • Create a C program that can traverse through an input file, piece by piece, and generate an output file. The result of this should be a bitwise identical file.
  • Adapt the LZS compression decoding algorithm from ScummVM into the new tool. Make the tool dump raw Portable NetMap (PNM) files of varying dimensions and ensure that they look correct.
  • Compress using LZS.
  • Stretch the frames and draw subtitles.
  • More compression. Find the minimum window for each frame.

  Compression
  Normally, my first goal is to decompress the video and store the data in a raw form. However, this turned out to be mathematically intractable. While the format does support both compressed and uncompressed frames (even though ScummVM indicates that the uncompressed path is yet unexercised), the goal of this project requires making the frames so large that they overflow certain parameters of the file.

  A Robot file has a sequence of frames and 2 tables describing the size of each frame. One table describes the entire frame size (audio + video) while the second table describes just the video frame size. Since these tables only use 16 bits to specify a size, the maximum frame size is 65536 bytes. Leaving space for the audio portion of the frame, this only leaves a per-frame byte budget of about 63000 bytes for the video. Expanding the frame to 576×288 (165,888 pixels) would overflow this limit.

  Anyway, the upshot is that I needed to compress the data up front.

  Fortunately, the LZS compressor is pretty straightforward, at least if you have experience writing VLC-oriented codecs. While the algorithm revolves around back references, my approach was to essentially write an RLE encoder. My compressor would search for runs of data (plentiful when I started to stretch the frame for subtitling purposes). When a run length of n=3 or more of the same pixel is found, encode the pixel by itself, and then store a back reference of offset -1 and length (n-1). It took a little while to iron out a few problems, but I eventually got it to work perfectly.

  I have to say, however, that the format is a little bit weird in how it codes very large numbers. The length encoding is somewhat Golomb-like, i.e., smaller values are encoded with fewer bits. However, when it gets to large numbers, it starts encoding counts of 15 as blocks of 1111. For example, 24 is bigger than 7. Thus, emit 1111 into the bitstream and subtract 8 from 23 -> 16. Still bigger than 15, so stuff another 1111 into the bitstream and subtract 15. Now we’re at 1, so stuff 0001. So 24 is 11111111 0001. 12 bits is not too horrible. But the total number of bytes (value / 30). So a value of 300 takes around 10 bytes (80 bits) to encode.

  Palette Slices
  As in the VMD subtitling project, I took the subtitle color offered in the subtitle spec file as a suggestion and used Euclidean distance to match to the closest available color in the palette. One problem, however, is that the palette is a lot smaller in these animations. According to my notes, for the set of animations I scanned, only about 80 colors were specified, starting at palette index 55. I hypothesize that different slices of the palette are reserved for different uses. E.g., animation, background, and user interface. Thus, there is a smaller number of colors to draw upon for subtitling purposes.

  Scaling
  One bit of residual weirdness in this format is the presence of a per-frame scale factor. While most frames set this to 100 (100% scale), I have observed 70%, 80%, and 90%. ScummVM is a bit unsure about how to handle these, so I am as well. However, I eventually realized I didn’t really need to care, at least not when decoding and re-encoding the frame. Just preserve the scale factor. I intend to modify the tool further to take scale factor into account when creating the subtitle.

  The Final Resolution
  Right around the time that I was composing this post, The Translator emailed me and notified me that he had found a better way to subtitle the Robot files by modifying the scripts, rendering my entire approach moot. The result is much cleaner :

  
  
  Turns out that the engine supported subtitles all along
  

  It’s a good thing that I enjoyed the challenge or I might be annoyed at this point.

  See Also

  • Subtitling Sierra VMD Files : My effort to subtitle the main FMV files found in Sierra games.

• Subtitling Sierra RBT Files

  2 juin 2016, par Multimedia Mike — Game Hacking

  This is part 2 of the adventure started in my Subtitling Sierra VMD Files post. After I completed the VMD subtitling, The Translator discovered a wealth of animation files in a format called RBT (this apparently stands for “Robot” but I think “Ribbit” format could be more fun). What are we going to do ? We had come so far by solving the VMD subtitling problem for Phantasmagoria. It would be a shame if the effort ground to a halt due to this.

  Fortunately, the folks behind the ScummVM project already figured out enough of the format to be able to decode the RBT files in Phantasmagoria.

  In the end, I was successful in creating a completely standalone tool that can take a Robot file and a subtitle file and create a new Robot file with subtitles. The source code is here (subtitle-rbt.c). Here’s what the final result looks like :

  
  
  “What’s in the refrigerator ?” I should note at this juncture that I am not sure if this particular Robot file even has sound or dialogue since I was conducting these experiments on a computer with non-working audio.
  

  The RBT Format
  I have created a new MultimediaWiki page describing the Robot Animation format based on the ScummVM source code. I have not worked with a format quite like this before. These are paletted animations which consist of a sequence of independent frames that are designed to be overlaid on top of static background. Because of these characteristics, each frame encodes its own unique dimensions and origin coordinate within the frame. While the Phantasmagoria VMD files are usually 288×144 (which are usually double-sized for the benefit of a 640×400 Super VGA canvas), these frames are meant to be plotted on a game field that was roughly 576×288 (288×144 doublesized).
  

  For example, 2 minimalist animation frames from a desk investigation Robot file :

  
  
  100×147

  
  101×149
  

  As for compression, my first impression was that the algorithm was the same as VMD. This is wrong. It evidently uses an unmodified version of a standard algorithm called Lempel-Ziv-Stac (LZS). It shows up in several RFCs and was apparently used in MS-DOS’s transparent disk compression scheme.

  Approach
  Thankfully, many of the lessons I learned from the previous project are applicable to this project, including : subtitle library interfacing, subtitling in the paletted colorspace, and replacing encoded frames from the original file instead of trying to create a new file.

  Here is the pitch for this project :

  • Create a C program that can traverse through an input file, piece by piece, and generate an output file. The result of this should be a bitwise identical file.
  • Adapt the LZS compression decoding algorithm from ScummVM into the new tool. Make the tool dump raw Portable NetMap (PNM) files of varying dimensions and ensure that they look correct.
  • Compress using LZS.
  • Stretch the frames and draw subtitles.
  • More compression. Find the minimum window for each frame.

  Compression
  Normally, my first goal is to decompress the video and store the data in a raw form. However, this turned out to be mathematically intractable. While the format does support both compressed and uncompressed frames (even though ScummVM indicates that the uncompressed path is yet unexercised), the goal of this project requires making the frames so large that they overflow certain parameters of the file.

  A Robot file has a sequence of frames and 2 tables describing the size of each frame. One table describes the entire frame size (audio + video) while the second table describes just the video frame size. Since these tables only use 16 bits to specify a size, the maximum frame size is 65536 bytes. Leaving space for the audio portion of the frame, this only leaves a per-frame byte budget of about 63000 bytes for the video. Expanding the frame to 576×288 (165,888 pixels) would overflow this limit.

  Anyway, the upshot is that I needed to compress the data up front.

  Fortunately, the LZS compressor is pretty straightforward, at least if you have experience writing VLC-oriented codecs. While the algorithm revolves around back references, my approach was to essentially write an RLE encoder. My compressor would search for runs of data (plentiful when I started to stretch the frame for subtitling purposes). When a run length of n=3 or more of the same pixel is found, encode the pixel by itself, and then store a back reference of offset -1 and length (n-1). It took a little while to iron out a few problems, but I eventually got it to work perfectly.

  I have to say, however, that the format is a little bit weird in how it codes very large numbers. The length encoding is somewhat Golomb-like, i.e., smaller values are encoded with fewer bits. However, when it gets to large numbers, it starts encoding counts of 15 as blocks of 1111. For example, 24 is bigger than 7. Thus, emit 1111 into the bitstream and subtract 8 from 23 -> 16. Still bigger than 15, so stuff another 1111 into the bitstream and subtract 15. Now we’re at 1, so stuff 0001. So 24 is 11111111 0001. 12 bits is not too horrible. But the total number of bytes (value / 30). So a value of 300 takes around 10 bytes (80 bits) to encode.

  Palette Slices
  As in the VMD subtitling project, I took the subtitle color offered in the subtitle spec file as a suggestion and used Euclidean distance to match to the closest available color in the palette. One problem, however, is that the palette is a lot smaller in these animations. According to my notes, for the set of animations I scanned, only about 80 colors were specified, starting at palette index 55. I hypothesize that different slices of the palette are reserved for different uses. E.g., animation, background, and user interface. Thus, there is a smaller number of colors to draw upon for subtitling purposes.

  Scaling
  One bit of residual weirdness in this format is the presence of a per-frame scale factor. While most frames set this to 100 (100% scale), I have observed 70%, 80%, and 90%. ScummVM is a bit unsure about how to handle these, so I am as well. However, I eventually realized I didn’t really need to care, at least not when decoding and re-encoding the frame. Just preserve the scale factor. I intend to modify the tool further to take scale factor into account when creating the subtitle.

  The Final Resolution
  Right around the time that I was composing this post, The Translator emailed me and notified me that he had found a better way to subtitle the Robot files by modifying the scripts, rendering my entire approach moot. The result is much cleaner :

  
  
  Turns out that the engine supported subtitles all along
  

  It’s a good thing that I enjoyed the challenge or I might be annoyed at this point.

  See Also

  • Subtitling Sierra VMD Files : My effort to subtitle the main FMV files found in Sierra games.

  The post Subtitling Sierra RBT Files first appeared on Breaking Eggs And Making Omelettes.

• How to add new pages and menu items to Piwik – Introducing the Piwik Platform

  11 septembre 2014, par Thomas Steur — Development

  This is the next post of our blog series where we introduce the capabilities of the Piwik platform (our previous post was How to create a widget). This time you’ll learn how to extend Piwik by adding new pages and menu items. For this tutorial you will need to have basic knowledge of PHP and optionally of Twig which is the template engine we use.

  What can be displayed in a page ?

  To make it short : You can display any corporate related content, key metrics, news, help pages, custom reports, contact details, information about your server, forms to manage any data and anything else.

  Getting started

  In this series of posts, we assume that you have already set up your development environment. If not, visit the Piwik Developer Zone where you’ll find the tutorial Setting up Piwik.

  To summarize the things you have to do to get setup :

  • Install Piwik (for instance via git).
  • Activate the developer mode : ./console development:enable --full.
  • Generate a plugin : ./console generate:plugin --name="MyControllerPlugin". There should now be a folder plugins/MyControllerPlugin.
  • And activate the created plugin under Settings => Plugins.

  Let’s start creating a page

  We start by using the Piwik Console to create a new page :

  ./console generate:controller

  The command will ask you to enter the name of the plugin the controller should belong to. I will simply use the above chosen plugin name “MyControllerPlugin”. There should now be two files plugins/MyControllerPlugin/Controller.php and plugins/MyControllerPlugin/templates/index.twig which both already contain an example to get you started easily :

  Controller.php

  class Controller extends \Piwik\Plugin\Controller
  {
      public function index()
      {
          return $this->renderTemplate('index', array(
               'answerToLife' => 42
          ));
      }
  }
  Télécharger

  and templates/index.twig

  {% extends 'dashboard.twig' %}
   
  {% block content %}
      <strong>Hello world!</strong>
      <br/>
   
      The answer to life is {{ answerToLife }}
  {% endblock %}
  Télécharger

  Note : If you are generating the Controller before Piwik 2.7.0 the example will look slightly different.

  The controller action index assigns the view variable answerToLife to the view and renders the Twig template templates/index.twig. Any variable assigned this way can then be used in the view using for example {{ answerToLife }}.

  Using a Twig template to generate the content of your page is actually optional : instead feel free to generate any content as desired and return a string in your controller action.

  As the above template index.twig is extending the dashboard template the Logo as well as the top menu will automatically appear on top of your content which is defined within the block content.

  

  How to display the page within the admin

  If you would like to add the admin menu on the left you have to modify the following parts :

  • Extend \Piwik\Plugin\ControllerAdmin instead of \Piwik\Plugin\Controller in the file Controller.php. In a future version of Piwik this step will be no longer neccessary, see #6151
  • Extend the template admin.twig instead of dashboard.twig
  • Define a headline using an H2-element

  {% extends 'admin.twig' %}
   
  {% block content %}
      <h2>Hello world!</h2>
      <br/>
   
      The answer to life is {{ answerToLife }}
  {% endblock %}
  Télécharger

  Note : Often one needs to add a page to the admin to make a plugin configurable. We have a unified solution for this using the Settings API.

  

  How to display a blank page

  If you would like to generate a blank page that shows only your content the template should contain only your markup as follows :

  <strong>Hello world!</strong>
  <br/>
   
  The answer to life is {{ answerToLife }}
  Télécharger

  Predefined variables, UI components, security and accessing query parameters

  In this blog post we only cover the basics to get you started. We highly recommend to read the MVC guide on our developer pages which covers some of those advanced topics. For instance you might be wondering how to securely access $_GET or $_POST parameters, you might want to restrict the content of your page depending on a user role, and much more.

  If you would like to know how to make use of JavaScript, CSS and Less have a look at our Working with Piwik’s UI guide.

  Note : How to include existing UI components such as a site selector or a date selector will be covered in a future blog post. Also, there are default variables assigned to the view depending on the context. A list of those variables that may or may not be defined is unfortunately not available yet but we will catch up on this.

  Let’s add a menu item to make the page accessible

  So far you have created a page but you can still not access it. Therefore we need to add a menu item to one of the Piwik menus. We start by using the Piwik Console to create a menu template :

  ./console generate:menu

  The command will ask you to enter the name of the plugin the menu should belong to. I will use again the above chosen plugin name “MyControllerPlugin”. There should now be a file plugins/MyControllerPlugin/Menu.php which contains an example to get you started easily :

  Menu.php

  class Menu extends \Piwik\Plugin\Menu
  {
      public function configureUserMenu(MenuUser $menu)
      {
          // reuse an existing category. 
          $menu->addManageItem('My User Item', $this->urlForAction('showList'));
   
          // or create a custom category
          $menu->addItem('My Custom Category', 'My User Item', $this->urlForDefaultAction());
      }
  }
  Télécharger

  This is only a part of the generated template since all the examples of the different menus are similar. You can add items to four menus :

  • configureReportingMenu To add a new item to the reporting menu which includes all the reports like “Actions” and “Visitors”.
  • configureAdminMenu To add a new item to the admin menu which includes items like “User settings” and “Websites”.
  • configureTopMenu To add a new item to the top menu which includes items like “All Websites” and “Logout”.
  • configureUserMenu To add a new item to the user menu which is accessible when clicking on the username on the top right.

  In this blog post we will add a new item to the user menu and to do so we adjust the generated template like this :

  class Menu extends \Piwik\Plugin\Menu
  {
      public function configureUserMenu(MenuUser $menu)
      {
          $menu->addManageItem('My User Item', $this->urlForAction($method = 'index'), $orderId = 30);
      }
  }
  Télécharger

  That’s it. This will add a menu item named “My User Item” to the “Manage” section of the user menu. When a user chooses the menu item, the “index” method of your controller will be executed and your previously created page will be first rendered and then displayed. Optionally, you can define an order to influence the position of the menu item within the manage section. Following this example you can add an item to any menu for any action. I think you get the point !

  

  Note : In Piwik 2.6.0 and before the above example would look like this :

  class Menu extends \Piwik\Plugin\Menu
  {
      public function configureUserMenu(MenuUser $menu)
      {
          $menu->addManageItem('My User Item', array($module = 'MyControllerPlugin', $action = 'index'), $orderId = 30);
      }
  }
  Télécharger

  How to test a page

  After you have created your page you are surely wondering how to test it. A controller should be usually very simple as it is only the connector between model and view. Therefore, we do usually not create unit or integration test for controllers and for the view less than ever. Instead we would create a UI test that takes a screenshot of your page and compares it with an expected screenshot. Luckily, there is already a section UI tests in our Automated tests guide.

  Publishing your Plugin on the Marketplace

  In case you want to share your page with other Piwik users you can do this by pushing your plugin to a public GitHub repository and creating a tag. Easy as that. Read more about how to distribute a plugin.

  Advanced features

  Isn’t it easy to create a page ? We never even created a file ! Of course, based on our API design principle “The complexity of our API should never exceed the complexity of your use case.” you can accomplish more if you want : You can make use of Vanilla JavaScript, jQuery, AngularJS, Less and CSS, you can reuse UI components, you can access query parameters and much more.

  Would you like to know more about this ? Go to our MVC (Model-View-Controller) and Working with Piwik’s UI guides in the Piwik Developer Zone.

  If you have any feedback regarding our APIs or our guides in the Developer Zone feel free to send it to us.