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Media Streaming over Websockets

Requesting streaming using Dial Command​

The requesting dial command can be extended in the following way to request streaming using WebSockets:

curl -X POST \
  --header "Content-Type: application/json" \
  --header "Accept: application/json" \
  --header "Authorization: Bearer YOUR_API_KEY" \
  --data '{"connection_id": "uuid", "to": "+18005550199", "from": "+18005550100", "stream_url": "wss://yourdomain.com", “stream_track”:”inbound_track|outbound_track|both_tracks”}' \
  https://api.telnyx.com/v2/calls

The following additional attributes need to be added to the request:

  • stream_url - the destination address when the stream is going to be delivered
  • stream_track - specifies which track should be streamed, with possible options:
  • inbound_track (default)
  • outbound_track
  • both_tracks

As a response, a regular confirmation is sent:

{
  "data": {
    "call_control_id": "v2:T02llQxIyaRkhfRKxgAP8nY511EhFLizdvdUKJiSw8d6A9BborherQ",
    "call_leg_id": "2dc6fc34-f9e0-11ea-b68e-02420a0f7768",
    "call_session_id": "2dc1b3c8-f9e0-11ea-bc5a-02420a0f7768",
    "is_alive": false,
    "record_type": "call"
  }
}

Requesting streaming using Answer Command​

Using the same attributes as above, streaming can be requested while answering the call:

curl -X POST \
  --header "Content-Type: application/json" \
  --header "Accept: application/json" \
  --header "Authorization: Bearer YOUR_API_KEY" \
  --data '{"client_state":"aGF2ZSBhIG5pY2UgZGF5ID1d","command_id":"891510ac-f3e4-11e8-af5b-de00688a4901","stream_url": "wss://yourdomain.com", “stream_track”:”inbound_track|outbound_track|both_tracks”}' \
  https://api.telnyx.com/v2/calls/{call_control_id}/actions/answer

In this case, confirmation that the call has been answered includes streaming details:

{
  "data": {
    "event_type": "call.answered",
    "id": "0ccc7b54-4df3-4bca-a65a-3da1ecc777f0",
    "occurred_at": "2018-02-02T22:25:27.521992Z",
    "payload": {
      "call_control_id":     "v2:T02llQxIyaRkhfRKxgAP8nY511EhFLizdvdUKJiSw8d6A9BborherQ",
      "call_leg_id": "428c31b6-7af4-4bcb-b7f5-5013ef9657c1",
      "call_session_id": "428c31b6-abf3-3bc1-b7f4-5013ef9657c1",
      "client_state": "aGF2ZSBhIG5pY2UgZGF5ID1d",
      "connection_id": "7267xxxxxxxxxxxxxx",
      "from": "+35319605860",
      "state": "answered",
      "stream_url": "wss://yourdomain.com",
      "stream_track”:”inbound_track|outbound_track|both_tracks",
      "to": "+13129457420"
    },
    "record_type": "event"
  }
}

Streaming process flow​

When the WebSocket connection is established, the following event is being sent:

{ 
  "event": "connected", 
  "version": "1.0.0"
}

Before the stream begins, the streaming.started webhook is sent:

{
  "data": {
   "event_type": "streaming.started",
   "id": "0ccc7b54-4df3-4bca-a65a-3da1ecc777f0",
   "occurred_at": "2018-02-02T22:25:27.521992Z",
   "payload": {
     "call_control_id": "v2:T02llQxIyaRkhfRKxgAP8nY511EhFLizdvdUKJiSw8d6A9BborherQ",
     "stream_url": "wss://yourdomain.com"
    },
  "record_type": "event"
  }
}

An event over WebSockets which contains information about the encoding mediaFormat section and stream_id that identifies a particular stream:

{ 
 "event": "start",  
 "sequence_number": "1", 
 "start": {
   "user_id": "3E6F995F-85F7-4705-9741-53B116D28237", 
   "call_control_id": "v2:T02llQxIyaRkhfRKxgAP8nY511EhFLizdvdUKJiSw8d6A9BborherQ", 
   "media_format": { 
     "encoding": "PCMU",
     "sample_rate": 8000, 
     "channels": 1 
   } 
 },
 "stream_id": "32DE0DEA-53CB-4B21-89A4-9E1819C043BC"
}

The start event is followed by the following media events:

{ 
 "event": "media",
 "sequence_number": "4",
 "media": { 
   "track": "inbound/outbound", 
   "chunk": "2",
   "timestamp": "5",
   "payload": "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"                        
 },
 "stream_id": "32DE0DEA-53CB-4B21-89A4-9E1819C043BC" 
}

The payload contains a base64-encoded RTP payload (no headers).

Please note that the order of events is not guaranteed and the chunk number can be used to reorder the events.

When the call ends, the streaming.stopped webhook is sent:

{
  "data": {
    "event_type": "streaming.stopped",
    "id": "0ccc7b54-4df3-4bca-a65a-3da1ecc777f0",
    "occurred_at": "2018-02-02T22:25:27.521992Z",
    "payload": {
      "call_control_id": "v2:T02llQxIyaRkhfRKxgAP8nY511EhFLizdvdUKJiSw8d6A9BborherQ",
      "stream_url": "wss://yourdomain.com"
    },
    "record_type": "event"
  }
}

And the stop event over WebSockets connection is sent:

{ 
 "event": "stop",
 "sequence_number": "5",
 "stop": {
  "user_id": "3E6F995F-85F7-4705-9741-53B116D28237",
  "call_control_id": "v2:T02llQxIyaRkhfRKxgAP8nY511EhFLizdvdUKJiSw8d6A9BborherQ"
  },
  "stream_id": "32DE0DEA-53CB-4B21-89A4-9E1819C043BC" 
}

Please note that at the moment only one streaming/fork operation is supported per call. In case of requesting media forking the WebSocket stream will be stopped and replaced by an RTP connection.

Bidirectional media streaming​

Sending media​

Media can also be sent back to the call through the websocket. This is done in a similar way to the playback_start command, when using a base64 encoded mp3 file in the payload. Simply send a packet to the websocket connection as follows:

{
  "event": "media",
  "media": {
    "payload" : "your base64 encoded mp3 file"
  }
}

The payload, which is a base64-encoded mp3 file, will be played on the call. Multiple media messages will be queued and played in the order they were submitted.

Some limitations to be aware of:

  • Media payloads can only be submitted once per second.
  • Media must be base64 encoded mp3.

Clear message​

Sending a clear message will immediately stop the media playing on the stream and clear the media queue.

{
  "event": "clear"
}

Mark message​

Mark messages can be used to keep track of media ending on the stream:

  • You can send a mark message to the stream after a media message.
  • When the media immediately preceding the mark finishes you'll receive the same mark back.

Example mark message sent to the stream:

{
  "event": "mark",
  "mark": {
    "name": "some_mark_name"
  }
}

Example mark message received from the stream:

{
  "event": "mark",
  "stream_id": "32DE0DEA-53CB-4B21-89A4-9E1819C043BC",
  "sequence_number": "5",
  "mark": {
    "name": "some_mark_name"
  }
}

Submitting marks when no audio is played or queued will result in them being immediately sent back. Similarly, the clear message will also result in all queued marks being sent back.

Error message​

In case of any case of error during media streaming, an error frame in the following format is sent:

{
  "event": "error",
  "payload": {
    "code": integer,
    "title": string,
    "detail": string
  },
  "stream_id": uuid
}

The list of the potential errors:

CodeTitleDescription
100002unknown_errorAn unknown error occurred on the stream
100003malformed_frameReceived frame was not formed correctly
100004invalid_mediaMedia provided was not base64 encoded
100005rate_limit_reachedToo many requests

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