Double Agent is currently written entirely in C++ and exclusively for the Windows operating system.

• Animation and sound effects are rendered using Windows DirectShow technology.  There are several reasons for this choice.
  • Although using DirectShow introduces an intrinsic dependency on Windows, it also leverages the existing collection of DirectShow filters.
  • DirectShow is tightly integrated with other Windows components.  This allows very efficient media rendering without any noticeable effect on application performance.
  • The DirectShow filter graph implements a composite media stream with both visual and audio components.  It allows each component to be prepared independently while keeping rendering exactly synchronized.
  • Double Agent version 1.x includes a custom video rendering filter.  The DirectShow 9.0 Video Mixing Renderer (VMR) doesn't include support for transparent rendering of the base video stream, and it's overkill for Double Agent's animations.  However, as a future enhancement the VMR could easily be used to allow character animations to be overlaid on another video stream (for example) or even a DirectX-compatible game.
  • The Audio Compression Manager (ACM) filter is used to handle all of the different sound formats that can be found in existing character files.
  • The Direct Show Audio Renderer is used to handle all of the possible audio output devices (although version 1.x only uses the default audio device, allowing a choice of audio devices will be a very simple enhancement).

• Double Agent uses the Windows Speech API (SAPI) for text-to-speech and speech recognition.
  • The 32-bit build supports both SAPI4 and SAPI5 for text-to-speech.  For speech recognition, it uses SAPI5 only.
  • The 64-bit build uses SAPI5 only.  SAPI4 is a 32-bit-only runtime.
  • SAPI5 is pre-installed with Windows.  SAPI4 (and its associated voices) can be downloaded and installed separately.  If, for some reason, SAPI is not available, Double Agent will still function, but the text-to-speech and speech recognition won't be available.
  • Although version 1.x uses only the default input and output devices, allowing a choice of devices will be a very simple enhancement.

• The speech balloon is implemented as a Windows ToolTip control.
  • This isn't strictly required.  However, because of its text-to-speech features, Agent is often used by the visually impaired.  The native ToolTip control is recognized and properly handled by screen reader software, thus keeping Double Agent accessible.

Double Agent has no runtime dependencies other than Windows itself.  Although it was designed for Windows 7, it's been kept compatible with Windows XP and Windows Vista.  This allows application developers to develop and distribute Double Agent applications on those Windows platforms as well as Windows 7.

In development, Double Agent has as few dependencies as possible.  Here's a summary of the build environment for Double Agent 1.x.

• Microsoft Visual C++ 2008
  • The compiler version was 15.00.21022.08
  • The resource compiler version was 6.1.7600.16385
  • The linker version was 9.00.21022.08

• Microsoft Windows SDK version 7.0
  • For backward compatibility, DirectShow version 9.0 is used.
  • For backward compatibility, the old Windows XP thread pooling API is used rather than the newer Windows Vista thread pooling.

• Microsoft Foundation Classes (MFC) version 9.0
  • MFC is statically linked to avoid any runtime dependencies.
  • MFC is the only dependency that isn't available with Visual C++ Express Edition.

The Double Agent installation is packaged as a set of Windows Installer Package (.msi) files and associated Cabinet (.cab) files.  The installer packages contain the basic runtime components, and the cabinets contain optional development components.  Thus, end-users require only the installer packages while developers can download and install the development components as required.

When the installation is run, the installer package will check for the optional cabinet files (in the same directory as the installer package) and will enable or disable the optional components accordingly.

There are three separate installations, depending on the target environment:

• DoubleAgent_x86.msi (with DoubleAgentSymbols_x86.cab and DoubleAgentSamples_x86.cab)
  • This is the 32-bit build for the 32-bit versions of Windows 7, Windows Vista, and Windows XP.
  • The samples cabinet includes all of the sample programs.

• DoubleAgent_x64x86.msi (with DoubleAgentSymbols_x64x86.cab and DoubleAgentSamples_x64x86.cab)
  • This is the combined 64-bit and 32-bit builds for 64-bit versions of Windows 7 and Windows Vista.
  • 64-bit runtimes (and debugging symbols) are installed in Program Files, while 32-bit runtimes (and debugging symbols) are installed in Program Files (x86).
  • The sample programs that are compatible with 64-bit development are installed in Program Files, and those that are only compatible with 32-bit development (such as VB6) are installed in Program Files (x86).

• DoubleAgent_x64.msi (with DoubleAgentSymbols_x64.cab and DoubleAgentSamples_x64.cab)
  • This is the 64-bit build for the 64-bit versions of Windows 7 and Windows Vista.
  • The samples cabinet includes only those samples that are compatible with 64-bit development.
  • Since end-users will likely run a combination of 32-bit and 64-bit applications, this installation is not recommended for them.