android-opus-codec

An android wrapper around libopus 1.3.1 written on C++ and Kotlin.

Supported features:

1. Encoding PCM audio into Opus.
2. Decoding Opus audio into PCM.
3. Sample rate of input audio from 8000Hz to 48000Hz.
4. Different frame sizes.
5. Mono or stereo input audio.
6. Input in bytes or shorts.
7. Output in bytes or shorts.
8. Convert from bytes to shorts and vice versa.
9. Bitrate setting.
10. Complexity setting.

Supported ABIs:

armeabi-v7a, arm64-v8a, x86, x86_64

How to use

Init encoder and decoder:

val SAMPLE_RATE = Constants.SampleRate._48000()       // samlpe rate of the input audio
val CHANNELS = Constants.Channels.stereo()            // type of the input audio mono or stereo 
val APPLICATION = Constants.Application.audio()       // coding mode of the encoder
var FRAME_SIZE = Constants.FrameSize._120()           // default frame size for 48000Hz

val codec = Opus()                                    // getting an instance of Codec
codec.encoderInit(SAMPLE_RATE, CHANNELS, APPLICATION) // init encoder
codec.decoderInit(SAMPLE_RATE, CHANNELS)              // init decoder

Setup the encoder:

/* this step is optional because the encoder can use default values */
val COMPLEXITY = Constants.Complexity.instance(10)    // encoder's algorithmic complexity 
val BITRATE = Constants.Bitrate.max()                 // encoder's bitrate
codec.encoderSetComplexity(COMPLEXITY)                // set the complexity
codec.encoderSetBitrate(BITRATE)                      // set the bitrate

Encoding:

val frame = ...                                       // gets a chunk of audio from some source as an array of bytes or shorts
val encoded = codec.encode(frame, FRAME_SIZE)         // encode a chunk of audio into Opus
if (encoded != null) Log.d("Opus", "encoded chunk size: ${encoded.size}")

Decoding:

val decoded = codec.decode(encoded, FRAME_SIZE)       // decode a chunk of audio into PCM
if (decoded != null) Log.d("Opus", "decoded chunk size: ${decoded.size}")

Freeing resources when closing the app:

codec.encoderRelease()
codec.decoderRelease()

Project structure

The project consists of two modules:

• app - here you can find a sample app that demonsrates ecoding, decoding and converting procedures by capturing an audio from device's mic and play it from a loud speaker. I recommend to check this app using a headphones, otherwise there may be echo in a hight levels of volume.
• opus - here you can find a C++ class that interacts with libopus 1.3.1 and a JNI wrapper for interacting with it from Java/Kotlin layer.

Compiled library:

• opus.aar - it's a compiled library of opus module that mentioned above, it placed in a root directory of the project, you can easily add it to your project using gradle dependencies. First you should place opus.aar in the libs folder of your project and then add to your build.gradle:

dependencies {
    api fileTree(dir: 'libs', include: '*.jar')       // this line is necessary in order to gradle took opus.aar from "libs" dir
    api files('libs/opus.aar')                        // dependency for opus.aar library
    ...                                               // other dependencies
}