Help setting up RSTP

[OMEN44]

Question

I am using MediaMTX to relay video from a linux machine to a webapp. I have tested it with the builtin rpiCamera source and that works fine on my raspberry pi but I want to be able to use this on devices other than raspberry pi. When I try the gstreamer pipline that is in the README for a RSTP stream to MediaMTX:

gst-launch-1.0 filesrc location=file.mp4 ! qtdemux name=d d.video_0 ! rtspclientsink location=rtsp://localhost:8554/mystream

I get this error output:

Setting pipeline to PAUSED ...
Progress: (open) Opening Stream
Progress: (connect) Connecting to rtsp://192.168.10.10:8554/mystream
Pipeline is PREROLLED ...
Prerolled, waiting for progress to finish...
Progress: (open) Retrieving server options
Progress: (open) Opened Stream
Setting pipeline to PLAYING ...
New clock: GstSystemClock
Progress: (request) Sending RECORD request
Progress: (record) Sending server stream info
ERROR: from element /GstPipeline:pipeline0/GstRTSPClientSink:rtspclientsink0: Could not read from resource.
Additional debug info:
../gst/rtsp-sink/gstrtspclientsink.c(3157): gst_rtsp_client_sink_send (): /GstPipeline:pipeline0/GstRTSPClientSink:rtspclientsink0:
Got error response: 400 (Bad Request).
Execution ended after 0:00:00.009542362
Setting pipeline to NULL ...
Freeing pipeline ...

and in the MediaMTX terminal:

2025/01/24 12:05:26 INF [RTSP] [session c331be7f] created by 192.168.10.10:56514
2025/01/24 12:05:26 INF [RTSP] [conn 192.168.10.10:56514] closed: can't publish to path 'mystream' since 'source' is not 'publisher'
2025/01/24 12:05:26 INF [RTSP] [session c331be7f] destroyed: not in use
2025/01/24 12:05:26 INF [RTSP] [conn 192.168.10.10:56518] opened
2025/01/24 12:05:26 INF [RTSP] [conn 192.168.10.10:56518] closed: EOF
2025/01/24 12:05:29 INF [RTSP] [conn 192.168.10.10:53650] opened
2025/01/24 12:05:29 INF [RTSP] [conn 192.168.10.10:53650] closed: no one is publishing to path 'mystream'
2025/01/24 12:05:29 ERR [path mystream] [RTSP source] bad status code: 404 (Not Found)

MediaMTX v1.11.1 config is default except:

paths:
  mystream:
    source: rtsp://192.168.10.10:8554/mystream
    rtspTransport: tcp

Gstreamer version is 1.22