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Copyright (C) 2015-2020 Dennis Sheirer

jmbe - Java Multi-Band Excitation library

Audio conversion library for decoding MBE encoded audio frames.

Decodes IMBE 144-bit and AMBE 72-bit encoded 20 millisecond audio frames to 8 kHz 16-bit mono PCM encoded audio.

PATENT NOTICE

This source code is provided for educational purposes only. It is a written description of how certain voice encoding/decoding algorithms could be implemented. Executable objects compiled or derived from this package may be covered by one or more patents. Readers are strongly advised to check for any patent restrictions or licensing requirements before compiling or using this source code.

Note: this patent notice is verbatim from the mbelib library README at (https://github.com/szechyjs/mbelib)

End Users: Creating the JMBE Library (Version 1.0.7+)

YOU DO NOT HAVE TO INSTALL THE JAVA JDK. The instructions for creating the JMBE library have changed starting with version 1.0.7.

  1. Download the latest JMBE Creator for your operating system from the Releases page.
  2. Unzip the JMBE Creator
  3. Open a command/console window and run the JMBE Creator application
  • Windows: (unzip directory)/bin/creator.bat
  • Linux/OSX: (unzip directory)/bin/creator
  1. When the program finishes, it will display the location of your JMBE library.
  2. Move the library to a permanent location

Note: for sdrtrunk use the menu item View > Preferences and then use the JMBE Audio Library section to tell sdrtrunk where your compiled JMBE library is located.

Software Developers - Using the JMBE audio conversion library in your own java program

  • Follow the same instructions for downloading the source code above. Use the following command to build the API:

WINDOWS:

gradlew.bat api

LINUX:

./gradlew api

  • Add the API library jar to your project.

  • Add the following code to your program

      IAudioCodecLibrary audioCodecLibrary = null;
  
  try
  {
              URLClassLoader childClassLoader = new URLClassLoader(new URL[]{path.toUri().toURL()},
                  this.getClass().getClassLoader());

              Class classToLoad = Class.forName("jmbe.JMBEAudioLibrary", true, childClassLoader);

              Object instance = classToLoad.getDeclaredConstructor().newInstance();

              if(instance instanceof IAudioCodecLibrary)
              {
                  audioCodecLibrary = (IAudioCodecLibrary)instance;
  	    } 
  catch (Exception e)
  {
      //error handling
  }

  • To convert 18-byte IMBE audio frames:

      IAudioCodec audioCodec = library.getAudioConverter("IMBE");
  float[] convertedAudio = audioCodec.getAudio(byte[] imbeFrameData);

  • To convert 9-byte AMBE audio and tone frames:

      IAudioCodec audioCodec = library.getAudioConverter("AMBE");
  float[] convertedAudio = audioCodec.getAudio(byte[] ambeFrameData);

  • To convert 9-byte AMBE audio frames and tone frames along with tone frame metadata:

      IAudioCodec audioCodec = library.getAudioConverter("AMBE");
  IAudioWithMetadata convertedAudio = audioCodec.getAudioWithMetadata(byte[] ambeFrameData);

Creating Legacy JMBE Library (Versions prior to 1.0.7)

Preparing to Compile the Library From Source Code

WINDOWS: Compiling the Library from Source Code

This should respond with the directory where you have installed the JDK.

  • Verify that your computer is using the correct version of the Java compiler. At a command prompt type:

    • > javac -version

This should respond with the java version.

  • Unzip the source code file with a tool like 7-Zip or using the Windows File Manager (right-click on file)

  • Using the command prompt, change to the directory where you downloaded and unzipped the source code (jmbe-master.zip in this example):

    • > cd C:\Users\Denny\Downloads\jmbe-1.0.6

  • Run the build script

    • > gradlew.bat build

  • The build script will compile the source code and create the library. The first time that you run the build script, it may download some additional files needed for installing the gradle build tool and some java libraries needed for compiling the jmbe library code.

  • The compiled JMBE library will be located in a sub-folder named '\codec\build\libs', for example:

    • > C:\Users\Denny\Downloads\jmbe-master\codec\build\libs\jmbe-1.0.6.jar

  • Follow the instructions for the application that will use the JMBE library.

Note: for sdrtrunk use the menu item View > Preferences and then use the JMBE Audio Library section to tell sdrtrunk where your compiled JMBE library is located.

LINUX: Compiling the Library from Source Code

  • Setup the JAVA_HOME and PATH environment variables

(https://askubuntu.com/questions/175514/how-to-set-java-home-for-java)

  • Verify that JAVA_HOME points to the Java Development Kit (JDK) version 8 or higher. Open a terminal and type:

    • > echo $JAVA_HOME$

This should respond with the directory where you have installed the JDK.

  • Verify that your computer is using the correct version of the Java compiler. At a command prompt type:

    • > javac -version

This should respond with the java version.

  • Unzip the source code file with a tool like 7-Zip or ark using the File Manager (right-click on file)

  • In the terminal window, change to the directory where you downloaded and unzipped the source code (jmbe-master.zip in this example):

    • > denny@denny-desktop:~$ cd Downloads\jmbe-1.0.6

  • Run the build script

    • > ./gradlew build

  • The build script will compile the source code and create the library. The first time that you run the build script, it may download some additional files needed for installing the gradle build tool and some java libraries needed for compiling the jmbe library code.

  • The compiled JMBE library will be located at:

    • > ~\Downloads\jmbe-master\codec\build\libs\jmbe-1.0.6.jar

  • Follow the instructions for the application that will use the JMBE library.