AVS Device SDK Optional Features
This page provides extra information to help you implement optional AVS features with the Alexa Voice Service (AVS) Device SDK. For code samples and full implementation details, see the AVS Device SDK on GitHub or the AVS Device SDK API references.
To enable Alerts, you must follow these instructions.
- Install SQLite.
- Set your device system clock to UTC time. To set UTC time, use Network Time Protocol (NTP).
- Install a file system.
SQLITE_THREADSAFE value of 0.
Building with Bluetooth is optional and is supported on Linux or Raspberry Pi.
- To build with Bluetooth on a Raspberry Pi, see the Raspberry Pi Quick-start Guide
- To build with Bluetooth on Ubuntu, see the Ubuntu Quick-start Guide
The Alexa Voice Service (AVS) Device SDK 1.17.0 adds support for captions.
In the SDK, it's disabled by default. You enable through the CMake build option
CAPTIONS=ON. You must also install a new dependency – the libwebvtt parsing library. Webvtt is a C/C++ library for interpreting and authoring WebVTT content. WebVTT is a caption and subtitle format designed for use with HTML5 audio and video elements.
By default, captions works with the
en-US locale. If you want to support another locale, you must modify the line break logic in the
CaptionManager::onParsed() method and use a locale-safe method for determining the break points between words. For example, you can use the ICU BreakIterator to handle the task. The exact method of this implementation is determined by you.
MediaPlayerInterface::SourceId value being unique across all instances.
To enable captions to your device
- Download and install libwebvtt to a directory of your choice. If there are any additional instructions provided for your OS on the libwebvtt page, make sure you follow them.
Build the AVS Device SDK and configure your CMake command with the following flags
-DCAPTIONS=ON \ -DLIBWEBVTT_LIB_PATH=$HOME/captions/webvtt-master/build/src/webvtt/libwebvtt.a \ -DLIBWEBVTT_INCLUDE_DIR=$HOME/captions/webvtt-master/include
Custom media player
For more details about enabling a custom media player, see Media Players.
For more details about enabling endpoints, see Smart Home Endpoints.
SAMPLE-AES decryption is optional.
To enable SAMPLE-AES decryption for audio streamed to your device
- Install the FFMPEG library.
Enable SAMPLE-AES decryption with the following CMake command.
cmake [absolute path to source] -DENABLE_SAMPLE_AES[ON|OFF] -DFFMPEG_LIB_PATH=[absolute path to ffmpeg library] -DFFMPEG_INCLUDE_DIR=[absolute path to ffmpeg include directory]
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Last updated: Sep 28, 2021