ros_rtsp/README.md

# ros_rtsp
ROS package to subscribe to an ROS Image topic (and as many other video sources as you want) and serve it up as a RTSP video feed with different mount points.
Should provide a real-time video feed (or as close as possible).

This is still very much a work in progress. Developing on Ubuntu 16.04 and 18.04 with ROS kinetic and melodic.


## Dependencies
- ROS

- gstreamer development libs:
```bash
sudo apt-get install libgstreamer-plugins-base1.0-dev libgstreamer-plugins-good1.0-dev libgstreamer-plugins-bad1.0-dev libgstrtspserver-1.0-dev 
```

## Stream Setup
Change the config/stream_setup.yaml to suit your required streams.

```yaml
# Set up your streams to rtsp here.
streams: # Cannot rename - must leave this as is.

  # Example v4l2 camera stream
  stream-x:                 # Can name this whatever you choose
    type: cam               # cam - Will not look in ROS for a image. The video src is set in the 'source' parameter.
    source: "v4l2src device=/dev/video0 ! videoconvert ! videoscale ! video/x-raw,framerate=15/1,width=1280,height=720"  # Should work with most valid gstreamer piplines (ending with raw video) 
    mountpoint: /front      # Choose the mountpoint for the rtsp stream. This will be able to be accessed from rtsp://<server_ip>/front
    bitrate: 800            # bitrate for the h264 encoding.

  # Example ROS Image topic stream
  this-is-stream-42:        # Can name this whatever you choose
    type: topic             # topic - Image is sourced from a sensor_msgs::Image topic
    source: /usb_cam0/image_raw  # The ROS topic to subscribe to
    mountpoint: /back      # Choose the mountpoint for the rtsp stream. This will be able to be accessed from rtsp://<server_ip>/back
    caps: video/x-raw,framerate=10/1,width=640,height=480  # Set the caps to be applied after getting the ROS Image and before the x265 encoder.
    bitrate: 500            # bitrate for the h264 encoding.
```
Notes:
- Add as many streams as you need. If too much latency is encounted with multiple streams running, the server computer may be maxing out its processor trying to encode all the streams. Try reducing the resolution of the source caps.
- The ROS Image topic stream may be buggy with framerates too fast for the Image publisher and the buffer writing. Stick with 10/1 fps unless you want to debug? :)
- If too many frames are being dropped, it is likely due to network bandwidth. Try dropping the bitrate.

## Checking the streams
### gstreamer
The best way to check a stream is working is to use `gst-launch-1.0`. You will need to install gstreamer for your client system. See https://gstreamer.freedesktop.org/documentation/installing/index.html
```bash
gst-launch-1.0 -v rtspsrc location=rtsp://<server_ip>:8554/<your_stream_mountpoint> drop-on-latency=true use-pipeline-clock=true do-retransmission=false latency=0 protocols=GST_RTSP_LOWER_TRANS_UDP ! rtph264depay ! h264parse ! avdec_h264 ! xvimagesink sync=true
```
If `xvimagesink` isn't available, try replacing with `autovideosink`.

### VLC
The command I've had the lowest latency with is:
```bash
vlc --no-audio --avcodec-hw=any --sout-rtp-proto=udp --network-caching=300 --sout-udp-caching=0 --clock-jitter=0 --rtp-max-misorder=0 rtsp://<server_ip>:8554/<your_stream_mountpoint> :udp-timeout=0
```