opencore-amr-android

An opencore amr codec JNI wrapper with explanation, And one solution for packaging amr audio files.

!!!AMR-WB support wanted, welcome PR.!!!

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Background

• opencore is the multimedia framework of android, which is a originallly contributed by PacketVideo.
• amr is abbreviation for Adaptive Multi-Rate audio codec, which is an audio compression format optimized for speech coding.
• opencore-amr is extracted from opencore as an codec for amr<->pcm encode/decode

What Is This

• opencore-amr-dndroid is a wrapper for handy usage. You can usage wrapped api in Android Application without any troubles of writing c++ wrapper or ndk mk file.
• amr project offer a solution for packaging amr audio files, in elegant code structure.

Setup

Android Studio

• Add jcenter as your repository in project's build.gradle:

  allprojects {
        repositories {
            jcenter()//this is the default setting
        }
      }
  

• Add dependency in your module's build.gradle:

  dependencies {
        compile fileTree(dir: 'libs', include: ['*.jar'])
        compile 'io.kvh:amr:1.1.1'//this is the lib
  }
  

  OR: Copy the content if Codec/amr to your module, as follows:

ADT(Eclipse)

Copy the content if Codec/amr to your project:

Copy content of libs and src to the corresponding folder

Quick Start Up

• encode

AmrEncoder.init(0);

int mode = AmrEncoder.Mode.MR122.ordinal();
short[] in = new short[160];//short array read from AudioRecorder, length 160
byte[] out = new byte[32];//output amr frame, length 32
int byteEncoded = AmrEncoder.encode(mode, in, out);

AmrEncoder.exit();        

Arm-2-File

• decode

long state = AmrDecoder.init();

byte[] amrframe = new byte[32];//amr frame 32 bytes
short[] pcmframs = new short[160];//pcm frame 160 shorts
AmrDecoder.decode(state, amrframe, pcmframs);

AmrDecoder.exit(state);

AmrFileDecoder.java

Prerequisite Knowledge

• Amr file has 6 bytes of header "23 21 41 4D 52 0A" => "#!amr.", please remember to remove the header before decoding frames, thanks to AAccount's explaination.

Packaging amr audio to file system

record->encode->package amr file->upload(not implemented)

Audio steam is packaged to file in slices, the slice last a few seconds(customizable). This policy is suitable for this scenario: client is under unstable mobile network, client records amr file, sends slice by slice, server re-assembles the slices.

If you are interested in this solution, please refer to Codec/app

Milestone

v1.2.0 April-15-2015

• format converter for amr/wav
• test cases

Changelog

v1.1.1 2020-04-23

• add docs for framesize

v1.1.1 2016-04-05

• fix decoding bug of 32bit

v1.1.0 2016-04-02

• add prebuilds for all archs
• rename package

FAQ

Please edit the FAQ files to help others, thanks! (赠人玫瑰，手留余香)

FAQ_CN

FAQ