RTSP error

[JIA-HONG-CHU]

i'm are trying to create an RTSP stream using the following command:

video-viewer /dev/video0 rtsp://0.0.0.0:1234/my_output --width=640 --height=480 --input-codec=mjpeg --input-decoder=v4l2 --output-codec=mjpeg --output-encoder=v4l2

Then, when attempting to view it in another terminal using:
ffplay -loglevel debug rtsp://127.0.0.1:1234/my_output

I encounter a 503 error. How can this issue be resolved?

Initialized opengl renderer.
[tcp @ 0xffff48003ac0] No default whitelist set
[tcp @ 0xffff48003ac0] Original list of addresses:
[tcp @ 0xffff48003ac0] Address 127.0.0.1 port 1234
[tcp @ 0xffff48003ac0] Interleaved list of addresses:
[tcp @ 0xffff48003ac0] Address 127.0.0.1 port 1234
[tcp @ 0xffff48003ac0] Starting connection attempt to 127.0.0.1 port 1234
[tcp @ 0xffff48003ac0] Successfully connected to 127.0.0.1 port 1234
[rtsp @ 0xffff48000c10] method DESCRIBE failed: 503 Service Unavailable
[rtsp @ 0xffff48000c10] CSeq: 2
Server: GStreamer RTSP server
Date: Wed, 20 Nov 2024 07:57:52 GMT

rtsp://127.0.0.1:1234/my_output: Server returned 5XX Server Error reply