AudioStream API

Version: 1.0.0

Status:

AudioStream interface for Thunder framework.

(Defined with IAudioStream in IAudioStream.h)

Introduction

Scope

This document describes purpose and functionality of the AudioStream interface (version 1.0.0). It includes detailed specification about its methods and properties as well as sent notifications.

Case Sensitivity

All identifiers of the interfaces described in this document are case-sensitive. Thus, unless stated otherwise, all keywords, entities, properties, relations and actions should be treated as such.

Acronyms, Abbreviations and Terms

The table below provides and overview of acronyms used in this document and their definitions.

Acronym	Description
API	Application Programming Interface
HTTP	Hypertext Transfer Protocol
JSON	JavaScript Object Notation; a data interchange format
JSON-RPC	A remote procedure call protocol encoded in JSON

The table below provides and overview of terms and abbreviations used in this document and their definitions.

Term	Description
callsign	The name given to an instance of a plugin. One plugin can be instantiated multiple times, but each instance the instance name, callsign, must be unique.

References

Ref ID	Description
HTTP	HTTP specification
JSON-RPC	JSON-RPC 2.0 specification
JSON	JSON specification
Thunder	Thunder API Reference

Description

AudioStream JSON-RPC interface.

This interface uses legacy lowercase naming convention. With the next major release the naming convention will change to camelCase.

Methods

The following methods are provided by the AudioStream interface:

Built-in methods:

Method	Description
exists	Checks if a JSON-RPC method or property exists
register	Registers for an asynchronous JSON-RPC notification
unregister	Unregisters from an asynchronous JSON-RPC notification

exists ^method

Checks if a JSON-RPC method or property exists.

Description

This method will return True for the following methods/properties: name, state, capabilities, audioprofile, time, speed, exists, register, unregister.

Parameters

Name	Type	M/O	Description
params	object	mandatory	...
params.method	string	mandatory	Name of the method or property to look up

Result

Name	Type	M/O	Description
result	boolean	mandatory	Denotes if the method exists or not

Example

Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.exists",
  "params": {
    "method": "methodName"
  }
}

Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": false
}

register ^method

Registers for an asynchronous JSON-RPC notification.

Description

This method supports the following event names: audiotransmission, audioframe.

Parameters

Name	Type	M/O	Description
params	object	mandatory	...
params.event	string	mandatory	Name of the notification to register for
params.id	string	mandatory	Client identifier

Result

Name	Type	M/O	Description
result	null	mandatory	Always null

Errors

Message	Description
`ERROR_FAILED_REGISTERED`	Failed to register for the notification (e.g. already registered)

Example

Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.register",
  "params": {
    "event": "eventName",
    "id": "myapp"
  }
}

Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": null
}

unregister ^method

Unregisters from an asynchronous JSON-RPC notification.

Description

This method supports the following event names: audiotransmission, audioframe.

Parameters

Name	Type	M/O	Description
params	object	mandatory	...
params.event	string	mandatory	Name of the notification to register for
params.id	string	mandatory	Client identifier

Result

Name	Type	M/O	Description
result	null	mandatory	Always null

Errors

Message	Description
`ERROR_FAILED_UNREGISTERED`	Failed to unregister from the notification (e.g. not yet registered)

Example

Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.unregister",
  "params": {
    "event": "eventName",
    "id": "myapp"
  }
}

Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": null
}

Properties

The following properties are provided by the AudioStream interface:

AudioStream interface properties:

Property	R/W	Description
name	read-only	Name of the stream
state	read-only	Current state of the stream
capabilities	read-only	List of codecs supported by the stream
audioprofile	read/write	Preferred profile of the stream
time	read-only	Stream position
speed	read/write	Stream speed

name ^property

Provides access to the name of the stream.

This property is read-only.

Value

Name	Type	M/O	Description
(property)	string	mandatory	Name of the stream

Errors

Message	Description
`ERROR_ILLEGAL_STATE`	The stream is not ready for this operation

Example

Get Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.name"
}

Get Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": "..."
}

state ^property

Provides access to the current state of the stream.

This property is read-only.

Value

Name	Type	M/O	Description
(property)	string	mandatory	Current state of the stream (must be one of the following: Idle, Started, Unavailable)

Example

Get Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.state"
}

Get Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": "Idle"
}

capabilities ^property

Provides access to the list of codecs supported by the stream.

This property is read-only.

Value

Name	Type	M/O	Description
(property)	array	mandatory	List of codecs supported by the stream
(property)[#]	string	mandatory	... (must be one of the following: IMA-ADPCM, PCM)

Errors

Message	Description
`ERROR_ILLEGAL_STATE`	The stream is not ready for this operation

Example

Get Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.capabilities"
}

Get Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": [
    "IMA-ADPCM"
  ]
}

audioprofile ^property

Provides access to the preferred profile of the stream.

Value

Name	Type	M/O	Description
(property)	object	mandatory	Preferred profile of the stream
(property).value	object	mandatory	...
(property).value.codec	string	mandatory	Compression method (PCM: uncompressed) (must be one of the following: IMA-ADPCM, PCM)
(property).value?.codecparams	opaque object	optional	Additional parameters for codec
(property).value.channels	integer	mandatory	Number of audio channels
(property).value.resolution	integer	mandatory	Sample resultion in bits
(property).value.samplerate	integer	mandatory	Sample rate in hertz
(property).value?.bitrate	integer	optional	Data rate of the compressed stream in bits per second

Name	Type	M/O	Description
(property)	object	mandatory	Preferred profile of the stream
(property).codec	string	mandatory	Compression method (PCM: uncompressed) (must be one of the following: IMA-ADPCM, PCM)
(property)?.codecparams	opaque object	optional	Additional parameters for codec
(property).channels	integer	mandatory	Number of audio channels
(property).resolution	integer	mandatory	Sample resultion in bits
(property).samplerate	integer	mandatory	Sample rate in hertz
(property)?.bitrate	integer	optional	Data rate of the compressed stream in bits per second

Errors

Message	Description
`ERROR_NOT_SUPPORTED`	Profile change is not supported by this stream
`ERROR_ILLEGAL_STATE`	The stream is not ready for this operation
`ERROR_BAD_REQUEST`	The profile specified is invalid
`ERROR_INPROGRESS`	Stream is started, profile will be changed for the next streaming

Example

Get Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.audioprofile"
}

Get Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": {
    "codec": "IMA-ADPCM",
    "codecparams": {},
    "channels": 1,
    "resolution": 16,
    "samplerate": 16000,
    "bitrate": 64000
  }
}

Set Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.audioprofile",
  "params": {
    "value": {
      "codec": "IMA-ADPCM",
      "codecparams": {},
      "channels": 1,
      "resolution": 16,
      "samplerate": 16000,
      "bitrate": 64000
    }
  }
}

Set Response

{
    "jsonrpc": "2.0",
    "id": 42,
    "result": "null"
}

time ^property

Provides access to the stream position.

This property is read-only.

Value

Name	Type	M/O	Description
(property)	integer	mandatory	Stream position

Errors

Message	Description
`ERROR_NOT_SUPPORTED`	Time reporting is not supported by this stream
`ERROR_ILLEGAL_STATE`	The stream is not ready for this operation

Example

Get Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.time"
}

Get Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": 0
}

speed ^property

Provides access to the stream speed.

Value

Name	Type	M/O	Description
(property)	object	mandatory	Stream speed
(property).value	integer	mandatory	...

Name	Type	M/O	Description
(property)	integer	mandatory	Stream speed

Errors

Message	Description
`ERROR_NOT_SUPPORTED`	Speed setting is not supported by this stream
`ERROR_ILLEGAL_STATE`	The stream is not ready for this operation

Example

Get Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.speed"
}

Get Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": 0
}

Set Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.speed",
  "params": {
    "value": 0
  }
}

Set Response

{
    "jsonrpc": "2.0",
    "id": 42,
    "result": "null"
}

Notifications

Notifications are autonomous events triggered by the internals of the implementation and broadcasted via JSON-RPC to all registered observers. Refer to [Thunder] for information on how to register for a notification.

The following events are provided by the AudioStream interface:

AudioStream interface events:

Notification	Description
audiotransmission	Signals state of the stream
audioframe	Provides audio data

audiotransmission ^notification

Signals state of the stream.

This notification may also be triggered by client registration.

Notification Parameters

Name	Type	M/O	Description
params	object	mandatory	...
params.state	string	mandatory	New state of the stream (must be one of the following: Idle, Started, Unavailable)
params?.profile	object	optional	Details on the format used in the stream
params?.profile.codec	string	mandatory	Compression method (PCM: uncompressed) (must be one of the following: IMA-ADPCM, PCM)
params?.profile?.codecparams	opaque object	optional	Additional parameters for codec
params?.profile.channels	integer	mandatory	Number of audio channels
params?.profile.resolution	integer	mandatory	Sample resultion in bits
params?.profile.samplerate	integer	mandatory	Sample rate in hertz
params?.profile?.bitrate	integer	optional	Data rate of the compressed stream in bits per second

Example

Registration

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.register",
  "params": {
    "event": "audiotransmission",
    "id": "myid"
  }
}

Notification

{
  "jsonrpc": "2.0",
  "method": "myid.audiotransmission",
  "params": {
    "state": "Idle",
    "profile": {
      "codec": "IMA-ADPCM",
      "codecparams": {},
      "channels": 1,
      "resolution": 16,
      "samplerate": 16000,
      "bitrate": 64000
    }
  }
}

The client ID parameter is passed within the notification designator, i.e. <client-id>.audiotransmission.

audioframe ^notification

Provides audio data.

Notification Parameters

Name	Type	M/O	Description
params	object	mandatory	...
params?.seq	integer	optional	Frame number in current transmission
params?.timestamp	integer	optional	Timestamp of the frame
params.length	integer	mandatory	Size of the raw data frame in bytes
params.data	string (base64)	mandatory	Raw audio data, the format of the data is specified in the most recent audiotransmission notification

Example

Registration

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.register",
  "params": {
    "event": "audioframe",
    "id": "myid"
  }
}

Notification

{
  "jsonrpc": "2.0",
  "method": "myid.audioframe",
  "params": {
    "seq": 1,
    "timestamp": 0,
    "length": 400,
    "data": "..."
  }
}

The client ID parameter is passed within the notification designator, i.e. <client-id>.audioframe.

AudioStream API

Table of Contents

Introduction

Scope

Case Sensitivity

Acronyms, Abbreviations and Terms

References

Description

Methods

exists method

Description

Parameters

Result

Example

Request

Response

register method

Description

Parameters

Result

Errors

Example

Request

Response

unregister method

Description

Parameters

Result

Errors

Example

Request

Response

Properties

name property

Value

Errors

Example

Get Request

Get Response

state property

Value

Example

Get Request

Get Response

capabilities property

Value

Errors

Example

Get Request

Get Response

audioprofile property

Value

Errors

Example

Get Request

Get Response

Set Request

Set Response

time property

Value

Errors

Example

Get Request

Get Response

speed property

Value

Errors

Example

Get Request

Get Response

Set Request

Set Response

Notifications

audiotransmission notification

Notification Parameters

Example

Registration

Notification

audioframe notification

Notification Parameters

exists ^method

register ^method

unregister ^method

name ^property

state ^property

capabilities ^property

audioprofile ^property

time ^property

speed ^property

audiotransmission ^notification

audioframe ^notification