Iterate over list of YouTube/RTSP streams, add text overlays, and expose as a fixed RTSP endpoint

Question

My goal is a shell script or Python utility that cycles through list (.csv, .yaml, or .json) of YouTube/RSTP source streams in a format similar to the following (.csv) example below:

url,overlay_text,delay_ms
rtsp://admin:[email protected]:554/Streaming/Channels/101,THIS IS OVERLAY TEXT,5000
https://www.youtube.com/watch?v=dQw4w9WgXcQ,THIS IS MORE OVERLAY TEXT,5000
.
.
.
rtsp://admin:[email protected]:554/Streaming/Channels/101,THIS IS OVERLAY TEXT,5000
https://www.youtube.com/watch?v=dQw4w9WgXcQ,THIS IS MORE OVERLAY TEXT,5000

For each record in the text file, the utility will:

• Capture the stream from the specified source URL
• Add the overlay_text for that record to the stream
• Proxy or otherwise expose it as a fixed/unchanging RTSP endpoint
• Wait delay_ms for that record
• Kill that stream, go on to the next one, and repeat...exposing the next stream using the same RTSP endpoint. So, to a consumer of that RTSP stream, it just seems like a stream that switched to a different source.
• When it reaches the last record in the text file, go back to the beginning

It could be as simple as a Bash shell script that reads the input text file and iterates through it, running a Gstreamer gst-launch-1.0 command w the appropriate pipeline arguments.

I can handle the reading of the text file and the iteration in either Bash or Python. I just need to know the proper way to invoke (and kill) gstreamer to add the text overlay and expose as an RTSP endpoint.

Answer 1

The best way to solve your problem would be to write an application in either C or Python using gstreamer. However, for what wou want to accomplish, a simple pipeline created with gst-launch-1.0 can be enought. I am no expert with bash scripting so I will not comment on how to implement that. I can write you a simple pipeline that, given an rtsp source adds a text overlay and than forwards it to another device. The pipeline would be something like:

gst-launch-1.0 rtspsrc location=rtsp://your_rtsp_source/path ! rtph264depay ! avdec_h264 ! autovideoconvert ! textoverlay text="Your text" valignment=top halignment=left ! autovideoconvert ! x264enc ! rtph264pay ! udpsink host=192.168.1.2 port=12444

(host is the receiving device IP, port is the port used on the device forwarding the stream)

More customization options is available, use gst-inspect-1.0 textoverlay to see what is available, e.g., text size, fonts...

Keep in mind that specific elements for both decoding and encoding h264 (or h265 if is the case) exist, using

gst-inspect-1.0 | grep h264

or

gst-inspect-1.0 | grep h265

will list the elements available on your device, alternatively you can search on the gstreamer website the list of available elments. The above pipeline works only for the case of streaming to 1 device, if you want multicast use multiudpsink in a similar manner.

Using udp sink requires your receiving device to have minimal informations regarding the incoming stream. A simple .sdp file configured as follows will be sufficient:

c=IN IP4 192.168.1.56
m=video 12444 RTP/AVP 96
a=rtpmap:96 H264/90000

Where 192.168.1.56 is the IP of the device streaming, 12444 is the port it is pushing the stream to and H264 is how the stream is encoded. The file then just has to be saved as name.sdp.

Using the above .sdp configuration file and using the machine with 192.168.1.2 with VLC I can see the stream from 192.168.1.56:12444:

Additionally you might also look into gstreamer's gst-rtsp-server (Link) which is slightly different but has the advantage of being capable of handling .sdp file transmission automatically so that the receiving side would only require the rtsp url.

---

For completeness the pipeline I used on 192.168.1.56 to test is the following:

gst-launch-1.0 videotestsrc ! video/x-raw, width=1920, height=1080 ! autovideoconvert ! textoverlay text="Your text" valignment=top halignment=left ! autovideoconvert ! x264enc ! rtph264pay ! udpsink host=192.168.1.2 port=12444