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2. XAudio2: Audio Building Blocks for the Future
4/1/2017 4:16 PM
XAudio2: Audio Building Blocks for the Future
Brian Schmidt
Program Manager
XNA Professional Game Platform Microsoft

3. Game Audio Pipelines

4. Game Audio Pipelines

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Game Audio Pipelines

6. XAudio2

7. XAudio2 XAudio2 Xbox 360 Game Windows Game (XACT 3) (XACT 3)
WASAPI (Vista)/DirectSound (XP)
XMA Decoder
Xbox 360 Audio Output Hardware
Drivers/Audio Output Hardware

8. Bit of History… 1995: DirectSound released “Bleeding Edge” CPU:
Pentium, 133 MHz (no MMX)
DirectSound3D API introduced (1997)
ISA sound cards w/ on-board memory
“wave file is a sound”

9. Fast Forward to 2008 Multicore, 3+ GHz CPUs HD motherboard audio
Surround Sound
High fidelity
SIMD floating-point architectures
High-level audio tools
Complex sounds and processing

10. XAudio2 is…
A new API for code-driven, low-level audio processing for games
Replacement for DirectSound for gaming applications for Windows XP and Windows Vista
Replacement for XAudio for Xbox 360 games
Based on Xbox 360 XAudio architecture
XAudio2 API will be familiar to XAudio developer, but not just a recompile
Incorporates feedback on XAudio API

11. XAudio2 Design Goals Focus exclusively on game scenarios
Simple – Just a few methods cover basic scenarios
Greater emphasis on digital signal processing (DSP FX)
Write and integrate your own DSP FX easily
Submixing
Allow more flexibility for 3D
Support Microsoft gaming platforms

12. XAudio2 Features Programmable voices
Separation of sound data from “voice”
Point XAudio2 at some sound data and Play()
Submixing
Multirate processing
Arbitrary loop point
Per-voice filtering
Programmable voices
Effects processing, SRC
Software DSP
Enhanced Surround Sound support
Native Compressed Data Support
XMA on Xbox 360
xWMA on Windows and Xbox 360
ADPCM on Windows
Extensible

13. XAudio2 Components Source Voice
Reads data from XMA decoder /ADPCM or PCM xWMA
Sample Rate Conversion, Volume, loop, N-way Pan
Can insert arbitrary FX
Multichannel support
Submix Voice(s)
Input from one or more voices & submixes them together
N-way Pan
Can send to additional submix voices
Mastering Voice
Takes final N channel mix as input
Can insert arbitrary FX (compression, etc.)
Outputs data to system

14. XAudio2 Overall Architecture

15. XAudio2 Source Voice
XAudio2 Submix Voice

16. Submix Voices
Useful for summing sounds and applying single DSP and/or 3D panning on the aggregate mix
Also used for shared “send to” effects
Reverb, etc.
Can be used to reduce CPU usage by creating a “low rate submix”

17. Example: Submixing Voices

18. Example: Reverb Sends Source Voice Submix Voice Source Voice
Mastering Voice
Source Voice
Submix Voice with
Global Reverb

19. Example: Low Rate Submix

20. 3D/Surround Sound 3D Audio handled differently from DirectSound3D
XAudio2 provides enhanced Surround support
Explicit multichannel panning/mapping
3D handled as a separate, replaceable library
XAudio2 takes multichannel speaker volumes
X3DAudio library transforms source/listener coordinates into speaker volumes and other synthesis parameters

21. Game Engine X3DAudio XAudio2 Game Object Geometry Data
-5.1 Speaker Volumes
-DSP Data
-Intermediate calculations
-5.1 Speaker Volumes
-DSP Data
XAudio2

22. DSP Audio Effects
XAudio2 uses new cross-platform DSP model, xAPO (Audio Processing Object)
Simplification of APO model used for Windows Vista system effects
Can use supplied xAPOs or write your own

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XAudio 2 Demo

24. Additional Enhancements Beyond Xbox 360 XAudio API
Built-in filter per voice
Can set overall sampling rate
Submixes can have their own sampling rate
Reduce CPU usage
Non-blocking API
Deferred commands
Not limited to 6-channel source data
Improved DSP architecture

25. Libraries Built on XAudio2
Several libraries are built on top of XAudio2
These are updated as well
Follow same Beta/RTM schedule
XACT 3
XACT running on XAudio2
Windows and Xbox
XMedia2 (XMV)
Xbox 360 movie player running on XAudio2
XHV2
Xbox 360 voice library running on XAudio2

26. Release Schedule XAudio2 is available now RTM/Approved in March 2008
Beta/Unapproved in November SDK/XDK
RTM/Approved in March 2008
Update in June 2008 SDK/XDK

27. Summary
XAudio2 provides all-software audio pipeline for Windows and Xbox 360
Provides consistent experience across hardware configurations
Based on Xbox 360 XAudio API, with enhancements
Addresses long-standing issues with DirectSound
Buffer/Data/Allocations
Flexible DSP, submixing, signal processing
Cross-pollination of Xbox 360 and Windows Technologies

28. Call to action Windows Games Xbox 360 Games Everybody!
Move your DirectSound game to XAudio2
Xbox 360 Games
Move your XAudio game to XAudio2
Everybody!
Please give us feedback
Use connect.microsoft.com for status, newsgroups, etc.

29. © 2008 Microsoft Corporation. All rights reserved.
4/1/2017 4:16 PM
© 2008 Microsoft Corporation. All rights reserved.
This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.