marath007 / avs-device-sdk

An SDK for commercial device makers to integrate Alexa directly into connected products.

IMPORTANT NOTE

Significant changes have been made to the authorization process and the AlexaClientSDKConfig.json configuration file in v1.7 of the AVS Device SDK. Click here for update instructions.

See release notes for a complete list of updates, enhancements, bug fixes, and known issues for this release.

What is the Alexa Voice Service (AVS)?

The Alexa Voice Service (AVS) enables developers to integrate Alexa directly into their products, bringing the convenience of voice control to any connected device. AVS provides developers with access to a suite of resources to quickly and easily build Alexa-enabled products, including APIs, hardware development kits, software development kits, and documentation.

Learn more »

Overview of the AVS Device SDK

The AVS Device SDK provides C++-based (11 or later) libraries that leverage the AVS API to create device software for Alexa-enabled products. It is modular and abstracted, providing components for handling discrete functions such as speech capture, audio processing, and communications, with each component exposing the APIs that you can use and customize for your integration. It also includes a sample app, which demonstrates the interactions with AVS.

Get Started

You can set up the SDK on the following platforms:

• Ubuntu Linux
• Raspberry Pi (Raspbian Stretch)
• macOS
• Windows 64-bit
• Generic Linux

You can also prototype with a third party development kit:

• XMOS VocalFusion 4-Mic Kit - Learn More Here
• Synaptics AudioSmart 2-Mic Dev Kit for Amazon AVS with NXP SoC - Learn More Here
• Intel Speech Enabling Developer Kit - Learn More Here
• Amlogic A113X1 Far-Field Dev Kit for Amazon AVS - Learn More Here
• Allwinner SoC-Only 3-Mic Far-Field Dev Kit for Amazon AVS - Learn More Here

Or if you prefer, you can start with our SDK API Documentation.

Learn More About The AVS Device SDK

Watch this tutorial to learn about the how this SDK works and the set up process.

SDK Architecture

This diagram illustrates the data flows between components that comprise the AVS Device SDK for C++.

Audio Signal Processor (ASP) - Third-party software that applies signal processing algorithms to both input and output audio channels. The applied algorithms are designed to produce clean audio data and include, but are not limited to acoustic echo cancellation (AEC), beam forming (fixed or adaptive), voice activity detection (VAD), and dynamic range compression (DRC). If a multi-microphone array is present, the ASP constructs and outputs a single audio stream for the array.

Shared Data Stream (SDS) - A single producer, multi-consumer buffer that allows for the transport of any type of data between a single writer and one or more readers. SDS performs two key tasks:

1. It passes audio data between the audio front end (or Audio Signal Processor), the wake word engine, and the Alexa Communications Library (ACL) before sending to AVS
2. It passes data attachments sent by AVS to specific capability agents via the ACL

SDS is implemented atop a ring buffer on a product-specific memory segment (or user-specified), which allows it to be used for in-process or interprocess communication. Keep in mind, the writer and reader(s) may be in different threads or processes.

Wake Word Engine (WWE) - Software that spots wake words in an input stream. It is comprised of two binary interfaces. The first handles wake word spotting (or detection), and the second handles specific wake word models (in this case "Alexa"). Depending on your implementation, the WWE may run on the system on a chip (SOC) or dedicated chip, like a digital signal processor (DSP).

Audio Input Processor (AIP) - Handles audio input that is sent to AVS via the ACL. These include on-device microphones, remote microphones, an other audio input sources.

The AIP also includes the logic to switch between different audio input sources. Only one audio input source can be sent to AVS at a given time.

Alexa Communications Library (ACL) - Serves as the main communications channel between a client and AVS. The ACL performs two key functions:

1. Establishes and maintains long-lived persistent connections with AVS. ACL adheres to the messaging specification detailed in Managing an HTTP/2 Connection with AVS.
2. Provides message sending and receiving capabilities, which includes support JSON-formatted text, and binary audio content. For additional information, see Structuring an HTTP/2 Request to AVS.

Alexa Directive Sequencer Library (ADSL): Manages the order and sequence of directives from AVS, as detailed in the AVS Interaction Model. This component manages the lifecycle of each directive, and informs the Directive Handler (which may or may not be a Capability Agent) to handle the message.

Activity Focus Manager Library (AFML): Provides centralized management of audiovisual focus for the device. Focus is based on channels, as detailed in the AVS Interaction Model, which are used to govern the prioritization of audiovisual inputs and outputs.

Channels can either be in the foreground or background. At any given time, only one channel can be in the foreground and have focus. If multiple channels are active, you need to respect the following priority order: Dialog > Alerts > Content. When a channel that is in the foreground becomes inactive, the next active channel in the priority order moves into the foreground.

Focus management is not specific to Capability Agents or Directive Handlers, and can be used by non-Alexa related agents as well. This allows all agents using the AFML to have a consistent focus across a device.

Capability Agents: Handle Alexa-driven interactions; specifically directives and events. Each capability agent corresponds to a specific interface exposed by the AVS API. These interfaces include:

• SpeechRecognizer - The interface for speech capture.
• SpeechSynthesizer - The interface for Alexa speech output.
• Alerts - The interface for setting, stopping, and deleting timers and alarms.
• AudioPlayer - The interface for managing and controlling audio playback.
• Notifications - The interface for displaying notifications indicators.
• PlaybackController - The interface for navigating a playback queue via GUI or buttons.
• Speaker - The interface for volume control, including mute and unmute.
• System - The interface for communicating product status/state to AVS.
• TemplateRuntime - The interface for rendering visual metadata.

Security Best Practices

In addition to adopting the Security Best Practices for Alexa[https://developer.amazon.com/docs/alexa-voice-service/security-best-practices.html], when building the SDK:

• Protect configuration parameters, such as those found in the AlexaClientSDKCOnfig.json file, from tampering and inspection.
• Protect executable files and processes from tampering and inspection.
• Protect storage of the SDK's persistent states from tampering and inspection.
• Your C++ implementation of AVS Device SDK interfaces must not retain locks, crash, hang, or throw exceptions.
• Use exploit mitigation flags and memory randomization techniques when you compile your source code, in order to prevent vulnerabilities from exploiting buffer overflows and memory corruptions.

Important Considerations

• Review the AVS Terms & Agreements.
• The earcons associated with the sample project are for prototyping purposes only. For implementation and design guidance for commercial products, please see Designing for AVS and AVS UX Guidelines.
• Please use the contact information below to-
  • Contact Sensory for information on TrulyHandsFree licensing.
  • Contact KITT.AI for information on SnowBoy licensing.
• IMPORTANT: The Sensory wake word engine referenced in this document is time-limited: code linked against it will stop working when the library expires. The library included in this repository will, at all times, have an expiration date that is at least 120 days in the future. See Sensory's GitHub page for more information.

Release Notes and Known Issues

Note: Feature enhancements, updates, and resolved issues from previous releases are available to view in CHANGELOG.md.

v1.7.0 released 04/18/2018:

Enhancements

• AuthDelegate and AuthServer.py have been replaced by CBLAUthDelegate, which uses Code Based Linking for authorization.
• Added new properties to AlexaClientSDKConfig:
  • cblAuthDelegate - This object specifies parameters for CBLAuthDelegate.
  • miscDatabase - A generic key/value database to be used by various components.
  • dcfDelegate - This object specifies parameters for DCFDelegate. Within this object, values were added for endpoint and overridenDcfPublishMessageBody. endpoint is the endpoint for the Capabilities API. overridenDcfPublishMessageBodyis the message that is sent to the Capabilities API. Note: Values in the dcfDelegate object will only work in DEBUG builds.
  • deviceInfo - Specifies device-identifying information for use by the Capabilities API and CBLAuthDelegate.
• Updated Directive Sequencer to support wildcard directive handlers. This allows a handler for a given AVS interface to register at the namespace level, rather than specifying the names of all directives within a given namespace.
• Updated the Raspberry Pi installation script to include alsasink in AlexaClientSDKConfig.
• Added audioSink as a configuration option. This allows users to override the audio sink element used in Gstreamer.
• Added an interface for monitoring internet connection status: InternetConnectionMonitorInterface.h.
• The Alexa Communications Library (ACL) is no longer required to wait until authorization has succeeded before attempting to connect to AVS. Instead, HTTP2Transport handles waiting for authorization to complete.
• Device capabilities can now be sent for each capability interface using the Capabilities API.
• The sample app has been updated to send Capabilities API messages, which are automatically sent when the sample app starts. Note: A successful call to the Capabilities API must occur before a connection with AVS is established.
• The SDK now supports HTTP PUT messages.
• Added support for opt-arg style arguments and multiple configuration files. Now, the sample app can be invoked by either of these commands: SampleApp <configfile> <debuglevel> OR SampleApp -C file1 -C file2 ... -L loglevel.

Bug Fixes

• Fixed Issues 447 and 553.
• Fixed the AttachmentRenderSource's handling of BLOCKING AttachmentReaders.
• Updated the Logger implementation to be more resilient to nullptr string inputs.
• Fixed a TimeUtils utility-related compile issue.
• Fixed a bug in which alerts failed to activate if the system was restarted without network connection.
• Fixed Android 64-bit build failure issue.

Known Issues

• The ACL may encounter issues if audio attachments are received but not consumed.
• SpeechSynthesizerState currently uses GAINING_FOCUS and LOSING_FOCUS as a workaround for handling intermediate state. These states may be removed in a future release.
• Some ERROR messages may be printed during start-up event if initialization proceeds normally and successfully.
• If an unrecoverable authorization error is encountered the sample app may crash on shutdown.
• If a non-CBL clientId is included in the deviceInfo section of AlexaClientSDKConfig.json, the error will be reported as an unrecoverable authorization error, rather than a more specific error.