DeepSpeech/native_client/java/README.md

DeepSpeech Java / Android bindings

This is still preliminary work. Please refer to native_client/README.md for building libdeepspeech.so and deepspeech binary for Android on ARMv7 and ARM64 arch.

Android Java / JNI bindings: libdeepspeech

Java / JNI bindings are available under the libdeepspeech subdirectory. Building depends on prebuilt shared object. Please ensure to place libdeepspeech.so into the libdeepspeech/libs/{arm64-v8a,armeabi-v7a}/ matching subdirectories.

Building the bindings is managed by gradle and should be limited to issuing ./gradlew libdeepspeech:build, producing an AAR package in ./libdeepspeech/build/outputs/aar/. This can later be used by other Gradle-based build with the following configuration:

implementation 'deepspeech.mozilla.org:libdeepspeech:VERSION@aar'

Please note that you might have to copy the file to a local Maven repository and adapt file naming (when missing, the error message should states what filename it expects and where).

Android demo APK

Provided is a very simple Android demo app that allows you to test the library. You can build it with make apk and install the resulting APK file. Please refer to Gradle documentation for more details.

The APK should be produced in /app/build/outputs/apk/. This demo app might require external storage permissions. You can then push models files to your device, set the path to the file in the UI and try to run on an audio file. When running, it should first play the audio file and then run the decoding. At the end of the decoding, you should be presented with the decoded text as well as time elapsed to decode in miliseconds.

Running deepspeech via adb

You should use adb push to send data to device, please refer to Android documentation on how to use that.

Please push DeepSpeech data to /sdcard/deepspeech/, including:

• output_graph.tflite which is the TF Lite model
• alphabet.txt
• lm.binary and trie files, if you want to use the language model ; please be aware that too big language model will make the device run out of memory

Then, push binaries from native_client.tar.xz to /data/local/tmp/ds:

• deepspeech
• libdeepspeech.so
• libc++_shared.so

You should then be able to run as usual, using a shell from adb shell:

user@device$ cd /data/local/tmp/ds/
user@device$ LD_LIBRARY_PATH=$(pwd)/ ./deepspeech [...]

Please note that Android linker does not support rpath so you have to set LD_LIBRARY_PATH. Properly wrapped / packaged bindings does embed the library at a place the linker knows where to search, so Android apps will be fine.