DirectX 9 SDK

As an example of a class that you may create with DirectSound, using such a utility library, look at the drumpad below. The drumpad class can be integrated in your 3D program, using DirectInput, to create your own musical instrument. The header of the class, which is, with some syntactical modifications, taken from the SDK samples section, looks as follows:

  class  drumpad {
  public:
      drumpad()
      ~drumpad();
      bool    initialize( DWORD dwNumElements, HWND hwnd );
      bool    load( DWORD dwID, const TCHAR* tcszFilename );
      bool    play( DWORD dwID );
  protected:
      void    CleanUp();
      CSoundManager* m_lpSoundManager;
      CSound **      m_lpSamples;
  };
  

The play function is surprisingly simple.

  bool drumpad::play( DWORD id ) {
      m_lpSamples[id] -> Stop();
      m_lpSamples[id] -> Reset();
      m_lpSamples[id] -> Play( 0, 0 );
      return true;
  }
  

As we have seen in chapter 3, working with multimedia presents some major challenges:

multimedia challenges

• volume -- multimedia streams contain large amounts of data, which must be processed very quickly.
• synchronization -- audio and video must be synchronized so that it starts and stops at the same time, and plays at the same rate.
• delivery -- data can come from many sources, including local files, computer networks, television broadcasts, and video cameras.
• formats -- data comes in a variety of formats, such as Audio-Video Interleaved (AVI), Advanced Streaming Format (ASF), Motion Picture Experts Group (MPEG), and Digital Video (DV).
• devices -- the programmer does not know in advance what hardware devices will be present on the end-user's system.

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2

The diagram above, taken from the DirectX 9 SDK online documentation, shows the relations between an application, the DirectShow components, and some of the hardware and software components that DirectShow supports.

An interesting and convenient feature of the filter-based dataflow architecture of DirectShow is SmartConnect, which allows the developer to combine filters by indicating constraints on media properties such as format. The actual connections then, which involves linking input pins to output pins, is done automatically by searching for the right order of filters, and possibly the introduction of auxiliary filters to make things match.

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DepthCube, see example(s) -- 3D vision

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3

DirectX application development

The examples that come with the DirectX`9 SDK use an application utility library, which includes a general application class that takes care of most of the details of creating an application and rendering window, initialization and event handling. For each of the SDK components there are numerous examples, ranging in difficulty from beginners to expert level. There are also a number of examples that illustrate how to mix the functionality of different SDK components, as for example the projection of video on 3D, which we will discuss in more detail in the next section.

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3D vision	Perspectra	DepthCube

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4

example(s) -- 3D vision

Have you ever wondered how it would feel to be in Star Trek's holodeck, or experience your game in a truly spatial way, instead of on a flat LCD-display. In  [DEEP], an overview is given of technology that is being developed to enable volumetric display of 3D data, in particular the Perspecta swept-volume display (middle) and LightSpace DepthCube (right), that uses a projector behind a stack of 20 liquid-crystal screens.

The first approach of displaying volumetric data, taken by the Perspecta swept-volume display, is to project a sequence of images on a rotating sheet of reflective material to create the illusion of real volume. The psychological mechanism that enables us to see volumes in this way is the same as the mechanism that forces us to see motion in frame-based animation, at 24 frames per second, namely persistence of vision.

LightSpace DepthCube uses a stack of 20 transparent screens and alternates between these screens in a rapid way, thus creating the illusion of depth in a similar way. In comparison with other approaches of creating depth illusion, the solutions sketched above require no special eyewear and do not impose any strain on the spectator due to unnatural focussing as for example with autostereoscopic displays.

For rendering 3D images on either the Perspecta or DepthCube traditional rendering with for example OpenGL suffices, where the z-coordinate is taken as an indication for selecting a screen or depth position on the display. Rendering with depth, however, comes at a price. Where traditional rendering has to deal with, say 1024x748 pixels, the DepthCube for example needs to be able to display 1024x748x20, that is 15.3 million, voxels (the volumetric equivalent of a pixel) at a comparable framerate.

research directions -- the next generation multimedia platform

Factors that may influence your choice of multimedia development platform include:

• platform-dependence -- both hardware and OS
• programming language -- C/C++, Java, .NET languages
• functionality -- graphics, streaming media
• deployment -- PC/PDA, local or networked, web deployment

A first dividing line is whether you prefer to develop on/for Linux or Microsoft windows. Another dividing line, indeed, is your choice of programming language, C/C++, Java or .NET languages. Another factor that may influence your choice is the functionality you strive for. For example, Managed DirectX, for the .NET languages, provides only limited support for DirectShow and does not allow for capturing live video from a DV camera. And finally, it matters what deployment you wish to target for, mobile phone, PDAs or PCs, and whether you plan to make stand-alone applications or applications that must run in a web browser.

Apart from the hard-core programming environments such as the Microsoft DirectX 9 SDK, the Java Media Framework, OpenGL with OpenML extensions for streaming media, or the various open source (game development) toolkits, there are also high-level tools/environments, such as Macromedia Director MX, that allow you to create similar functionality with generally less effort, but also less control. In appendix E, a number of resources are listed that may assist you in determining your choice.

Given the range of possible options it is futile to speculate on what the future will offer. Nevertheless, whatever your choice is, it is good to keep in mind, quoting Bill Gates:

Software will be the single most important force in digital entertainment over the next decade.

It should not come as a surprise that this statement is meant to promote a new initiative, XNA, which as the announcement says is targeted to help contain the skyrocketing development costs and allow developers to concentrate on the unique content that differentiates their games.

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[] readme course(s) preface I 1 2 II 3 4 III 5 6 7 IV 8 9 10 V 11 12 afterthought(s) appendix reference(s) example(s) resource(s) _

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(C) Æliens 04/09/2009

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