Sensor Stream Server
Sensor Stream Server grabs data from the frame source, encodes it, and sends it out to a destination using zmq
Sensor Stream Server is started with a path to a configuration yaml file as a command line argument
The configuration file defines:
Where the data should be streamed to (destination)
Frame Source (where the data is coming from - frame list/video/kinect/iphone)
What frame types will be streamed (color/depth/ir/confidence)
Encoders for each of the frame types ( null/libav/nvenc/zdepth)
IReader
is constructed with parameters defined in the configuration fileThe instantiated
IReader
's frame types are defined by a vector of integers returned byGetType()
method0 - if exists in vector then color is being sent (encoders available: null/libav/nvenc)
1 - if exists in vector then depth is being sent (encoders available: null/libav/nvenc/zdepth)
2 - if exists in vector then ir is being sent (encoders available: null/libav/nvenc)
3 - if exists in vector then confidence is being sent (encoders available: null)
IReader
will useGetCurrentFrame()
in Step #5 to grab data from the frame source and create aFrameStruct
for each defined frame type
Server creates a vector of
IEncoder
s for each frame type returned byIReader
'sGetType()
The
IEncoder
s will be used to encodeFrameStruct
s in Step #5NullEncoder
- passes raw data throughLibAvEncoder
- uses LibAv to encode video framesNvEncoder
- uses Nvidia Pipe to encode video framesZDepthEncoder
- uses Zdepth to encode depth frames
Server creates a vector of encoded
FrameStruct
sServer is paced to transmit frames only as fast as the fps allows
IReader
creates a vector ofFrameStruct
sOne for each frame type returned by
GetType()
IReader.GetCurrentFrame()
- FillsFrameStruct
if (
IReader.HasNextFrame()
) - Used to iterateIReader.NextFrame()
- Used to iterate
Server iterates over vector of
FrameStruct
s andIEncoder
which returns an encodedFrameStruct
IEncoder.AddFrameStruct()
- Attempts encodingFrameStruct
IEncoder.HasNextPacket()
- Checks if encoded frame availableIEncoder.CurrentFrameEncoded()
- Returns encoded frame
The vector of encoded
FrameStruct
s is sent to destination zmq socket as a zmq messageCall
CerealStructToString()
on vector of encoded frames to create string messageCreate zmq message out of the string message
Call
socket.send()
passing through the zmq messageLog timings
Currently the frame rate
The Sensor Stream Server can stream from 4 frame (data) sources:
Images: frames from images stored on the disk.
Video: encoded frames that have been captured using a color/depth camera, such as the Kinect. All video types supported by FFmpeg/Libav can be processed.
Kinect: Live Kinect DK frame data.
iPhone: Live iPhone RGBD data (must have lidar)
Each of these data sources have their own implementation of IReader
defined in image_reader.h
which is able to create read data and write to FrameStruct
s.
ImageReader: Can be used to stream public datasets and can be composed into MultiImageReader
VideoFileReader: Reads .mkv files like those created by Azure Kinect DK recorder
KinectReader: Reads Azure Kinect DK stream
IPhoneReader: Reads ARFrame data
For all four data sources, the data can be sent losslessly (very high bandwidth requirements), or compressed (20-50x lower bandwidth requirements), using Libav or NVCodec through the NVPipe.
As any compression will affect quality, we recommend first experimenting with the Sensor Stream Tester to figure out the optimal levels for your use case.
Server File: https://github.com/moetsi/Sensor-Stream-Pipe/blob/master/servers/ssp_server.cc
Building Sensor Stream Server
Building Sensor Stream Server also builds Sensor Stream Client and Sensor Stream Tester.
You can turn off Kinect, Bodytrack and NVPipe support by changing the following to the cmake ..
options to off:
Starting the Sensor Stream Server
The Sensor Stream Server will start streaming frame data by default, but it will not keep any frames if it is not connected to a client. This is a zmq setting. From ssp_server.cc:
When it connects to Sensor Stream Client, the packets in the buffer will be sent first. After the buffer has emptied, the Sensor Stream Server will resume reading frames from the selected input in order, ensuring that no frames are dropped.
The Sensor Stream Server configuration is stored in a YAML file. It includes Sensor Stream Client host and port, input data configuration and encoding configuration.
The format of the file (encoding Kinect DK frame data with the Nvidia encoder) is as follows:
The config/
folder includes a set of examples for all types of data using multiple encoders, codecs and parameters.
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