Built-in nodes

Source

audio_rtp

This node consumes a remote RTP audio stream, and makes it available to its destinations as chunks of a configurable length.

Internally, audio_rtp spawns a local ffmpeg thread that will receive the stream on a port picked at runtime and make it available to the standard output. Received samples will be collected and transmitted

This approach allows to demand all the decode-encode heavy lifting to ffmpeg.

argument	type	description
rec_host	str	the host from which the stream will be received
rec_port	int | str	the port the stream will be received on
audio_rate	int	rate of the receiving audio
block_size	int	length (in seconds) of the audio chunks to generate
channels	int	number of channels of the receiving audio
payload_type	dict	payload type as specified in the incoming stream

During the warmup phase, this node will write in its node folder the sdp file with all the relevant information about the local stream.

Nodes:

• the node automatically selects a receiving port if rec_port is set to auto in the configuration, otherwise will use the provided port; the same applies to the local transmitting port

• this node accumulates audio samples until the temporal length of all the samples reach block_size, computed in seconds; this length is computed using audio_rate, so make sure it matches the sources’

audio_file

This node loads an audio file, and makes it available to any destinations node in chunks of a coinfigurable length.

argument	type	description
file_source	str	path of the source audio file
audio_rate	int	rate of the audio file
block_size	int	length (in seconds) of the audio chunks to generate

video_rtp

This node consumes a remote RTP video stream, and makes it available to its destinations as either individual frames or collections of frames, depending on its working mode. Internally, it works in a similar fashion to the audio_rtp node.

argument	type	description
rec_host	str	the host from which the stream will be received
rec_port	int | str	the port on which the stream will be received
width	int	width of the received video stream
height	int	height of the received video stream
codec	int	the codec of the source stream
payload_type	dict	payload type as specified in the incoming stream

Notes:

• the node automatically selects a receiving port if rec_port is set to auto in the configuration, otherwise will use the provided port

Sink

notifier_http

A simple notifier that transmits data to a HTTP endpoint.

argument	type	description
endpoint	str	destination endpoint
timeout	int	transmission timeout in seconds
content_type	str	type of data to transmit

Notes:

• the node currently supports transmission of json and text data, for which the content_type values are application/json and application/text respectively

• the node will transmit the faw data contained in the payload of the update messages it receives, so that should match the transmission data type

notifier_websocket

A transmission node that transmits data to a websocket endpoint.

argument	type	description
endpoint	str	destination endpoint

Notes:

• the node sends to its endpoint the serialised content of the update message payload, retrieved using json.dumps(message.payload)

• currently, the node reconnects to the destination endpoint every time there is a message to transmit, so the connection is not persistent

videostream_ffmpeg

A transmission node that receives update messages containing frames, and transmits them over a destination endpoint. Internally, the node creates a ffmpeg process and whenever an update message is available, writes its content to the process standard output.

argument	type	description
dst_host	str	destination host
dst_port	int	destination port
in_width	int	width of the received frame
in_height	int	height of the received frame

Notes:

• this node is still experimental, as many of the options provided to the underlying ffmpeg process are still not included in the configuration

notifier_udp

A transmission node that receives messages containing dictionaries, and sends them on a simple UDP endpoint. The node fragments the data to send into smaller chunks, calculating the number of required chunks based on the maximum payload size available. The sent chunks are encoded using the encoding specified in the configuration file. If encode_b64 is set to true, the data chunks will be encoded in base64.

argument	type	description
endpoint	str	destination host
port	int	destination port
payload_size	int	size in bytes of the message payload
max_sequence	int	maximum message sequence number
max_chunks	int	maximum frame sequence number
encoding	int	data encoding format
encode_b64	int	whether to encode the payload in base64

Each transmitted chunk will have the following format:

{
  "seq": 1,
  "frag": 1,
  "tot": 99,
  "data": ...,
}

• seq is the sequence number of the message being transmitted

• frag is the fragment number of the transmitted chunk

• tot is the total number of expected chunks for the message

• data is the chunk data content