OpenSL ES

OpenSL ES (Open Sound Library for Embedded Systems) is a royalty-free, cross-platform, hardware-accelerated, C-language audio API for 2D and 3D audio. It provides access to features such as 3D positional audio and MIDI playback. It is made for developers in the mobile and gaming industry and is working toward allowing for easy porting of applications across multiple platforms.

For the graphics API, see OpenGL ES.
OpenSL ES
Developer(s)Khronos Group, Inc.
Stable release
1.1 / January 18, 2011 (2011-01-18)
Operating systemCross-platform
TypeAPI
LicenseRoyalty free
Websitewww.khronos.org/opensles/

Overview

The OpenSL ES API has five major features:

  • Basic audio playback and recording
  • 3D audio effects including 3D positional audio
  • Music experience enhancing effects including bass boost and environmental reverb
  • Interactive music and ringtones using SP-MIDI, Mobile DLS, Mobile XMF
  • Buffer Queues[1]

The features of Audio Playback and Recording and Basic MIDI are common with OpenMAX AL.

Design

OpenSL ES utilizes an object oriented design to give application developers access to the audio functionality. The object model is shared with OpenMAX AL, and a device manufacturer can choose to implement one or both of the APIs. Together the two APIs give access to a wide range of functionality of the device's multimedia engine.

The design goal of OpenSL ES is to give application developers access to advanced audio features such as 3D positional audio and MIDI playback while striving for easy application porting between manufacturers and platforms. It is developed primarily for application developers in the mobile and gaming industry.

Profiles

To avoid fragmentation, OpenSL ES is divided up into three profiles:

  • Phone
  • Music
  • Game

Each profile is designed for the respective device needs with a specific set of audio functionalities. A vendor can choose to be conformant with only one or with any combination of profiles.

An application can query the OpenSL ES implementation to find out which profiles are supported. The application developer can then design their application to either work with only the common parts of the profiles, or adapt to the available functionality as given by the profiles in the device it is running on. An application developer can also specify both the minimum and the optimal profile requirements.

Development

OpenSL ES is managed by the non-profit technology consortium Khronos Group. The current chair of the OpenSL ES working group is Erik Noreke.

Specification versions

Implementations
  • Android 2.3 exposes OpenSL ES 1.0 as part of their NDK.[4][5] The latency of the implementation has improved in later releases.[6][7][8]
  • A full implementation of OpenSL ES 1.1 is available from SRS Labs.[9]

See also

References
  1. "Intel Developer Zone".
  2. Khronos Group Releases OpenSL ES 1.0 Specification for Portable Mobile and Embedded Audio Processing Archived 7 April 2009 at the Wayback Machine, Khronos press release
  3. Khronos Group Releases OpenSL ES 1.1 Specification For Stereo and 3D Audio on Any Mobile Platform and OS Archived 17 March 2011 at the Wayback Machine, Khronos press release
  4. Ionut Arghire (7 December 2010). "Android 2.3 Brings Changes for Developers too, New SDK Available". softpedia.
  5. "Native Audio: OpenSL ES™ for Android".
  6. "Audio Latency Measurements".
  7. Rudi Villing (3 December 2015). "APPROACHES FOR CONSTANT AUDIO LATENCY ON ANDROID". Proc. of the 18th Int. Conference on Digital Audio Effects.
  8. "Rebooting Android's 10 Millisecond Problem: Audio Latency Improvements in Android 6.0 Marshmallow". Superpowered Audio for iOS, OSX and Android. 25 August 2016.
  9. "SRS Labs Launches Industry's First Khronos OpenSL ES 1.1 Audio Solution for Android Mobile Devices at Mobile World Congress".
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