Tutorials for OpenSL ES for Android

Question

I've been trying to look into using the OpenSL ES library that is available for doing native audio with android 2.3, but it appears that the header files and the 600 page pdf of the spec are the only available documentation.

Where should I be looking for examples, tutorials, or a brief overview of the capabilities?

Solution 1

There's an example app that comes with the NDK called NativeAudio. It has examples of nearly anything you would ever want to implement: effects, streaming, synthesis, etc. If you look at its code, you'll get a good head start.

Solution 2

You could also check victor lazzarini's audio programming blog, it has an android section: http://audioprograming.wordpress.com/category/android/

There you will find working examples, they were extremely useful to me to get started with openSL and can be used as a base to develop audio applications with ndk.

And also, don't overlook the specifications document, it's not so long after all, the first part is no more than fifty pages and gives you the needed perspective to understand how everything works, the rest is for reference use. Be careful that some things in android openSL implementation differ from the specifications: see in your-ndk-directory/docs/opensles/index.html for more informations about this.

Solution 3

After a quite searching the more valuable information I've found:

• The NativeAudio project included in NDK is a good start.
• Also it's a great start point the chapter 7 "Playing Sound with OpenSL ES" of the book "Android NDK Beginner's Guide" by Sylvain Ratabouil (You can take a look in amazon using the "look inside" feature or buy it).
• This google code project for replace SoundPool with OpenSL is a great example too. All credits and thanks to their authors.

Solution 4

For those of you wanting just to play single soundfiles or record a short snapshot (in a single buffer), the NDK project will be enough. I had a look at the "Android NDK Beginner's Guide" and it really does not explain too much more than the sample NDK project.

But really, for these applications, you are probably better off with one of the Java APIs. Using OpenSL ES for them is a bit of an overkill IMHO. There will be much more code to write and no real gain.

The advantage of OpenSL is for those interested in lower latencies (when these become available) for audio synthesis and processing, and for this, you will probably want to stream audio, rather than play/record single buffers. The book chapter and the NDK example will not teach you about that. The blogposts in the audio programming blog are more informative for these purposes.

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Comments

[Amit]

and what are those blog posts ? Is your answer is really an answer ? it looks like a comment to me..

[Mike Ortiz]

I believe he's referring to this: audioprograming.wordpress.com, which is actually called "The Audio Programming Blog"

[Kevin Crain]

seems like I accidentally down voted this answer :/ will remove the down vote as soon as my vote is unlocked

[athos]

@Timo, the question is more than five years old, a lot of things have changed since then (there's even a new audio API that can be used instead of OpenSL on newer devices!). If you are still looking for examples, have a look at these google's github repos: github.com/googlesamples/android-ndk/tree/master/audio-echo and github.com/googlesamples/android-audio-high-performance . My advice regarding the OpenSL specs still stands. Another source of info is the ndk google group: groups.google.com/forum/#!forum/android-ndk , just search with the "audio" keyword.