nginx push rtmp stream to ffmpeg - nginx

Question

On my Raspberry Pi with camera module, I try to setup a web-based streaming platform. I want to preview the stream in my browser and use CGI scripts to start/stop broadcasting to youtube (,...).
This is how I did the streaming setup so far:
Nginx puts up an RTMP application webcam. This is where I'll send the camera and audio stream usig ffmpeg. It publishes the stream as HLS for the web preview. It's also pushing the stream to another application source. That's where I want to (occasionally) hook up another ffmpeg process for broadcasting to youtube (,...) RTMP end points.
I initiate the stream using ffmpeg like this:
ffmpeg -loglevel debug -f v4l2 -framerate 15 -video_size 1280x720 -input_format h264 -i /dev/video0 -f alsa -i hw:2 -codec:v copy -g 15 -codec:a aac -b:a 128k -ar 44100 -strict experimental -f flv "rtmp://localhost:1935/webcam/hhart"
So far everything works fine. I can preview the HLS stream using a video.js viewer on my website (also served by nginx).
Now I want to start another ffmpeg process for broadcasting to my youtube channel, hooked up to the source application like this:
ffmpeg -loglevel debug -f flv -listen 1 -i rtmp://localhost:1935/source/hhart -c copy 'rtmp://a.rtmp.youtube.com/live2/<KEY>'
(in the final setup, launching and killing this process will be done via CGI scripts)
This is what ffmpeg returns:
Opening an input file: rtmp://localhost:1935/source/hhart.
[flv # 0x2032480] Opening 'rtmp://localhost:1935/source/hhart' for reading
[rtmp # 0x2032a10] No default whitelist set
[tcp # 0x20330f0] No default whitelist set
and then... nothing happens. There's no stream coming in at Youtube studio, but there are no error messages either.
Some other tests I did:
from the webcam application, push directly to the Youtube RTMP => that works! (but it's not what I want, because I want the HLS stream to be online always, but the broadcasting only when I'm going live.)
from VLC display the stream at rtmp://localhost:1935/source/hhart => similar to ffmpeg, there's no error message, the progress bar keeps loading.
So I have the impression that there is something going on, but there's no actual data transmitted.
RTMP section in nginx.conf:
rtmp {
server {
listen 1935;
chunk_size 4000;
application webcam {
live on;
hls on;
hls_path /Services/Webcam/HLSStream;
hls_fragment 3;
hls_playlist_length 60;
#deny play all;
push rtmp://localhost:1935/source/;
#push rtmp://a.rtmp.youtube.com/live2/<KEY>;
}
application source {
live on;
record off;
}
}
}
Of course, I may be totally on the wrong track, so any suggestions how I can realize my requirements in a better way, are welcome!

Answer 1

OK, I recompiled nginx with --with-debug and that got me to a solution.
Rather than pushing the stream to another application, I have to push the stream to an RTMP address on another port, and there the second ffmpeg process can pick it up. And it seems to be better to use 127.0.0.1 instead of localhost.
Like this:
rtmp {
server {
listen 1935;
chunk_size 4000;
application webcam {
live on;
hls on;
hls_path /Services/Webcam/HLSStream;
hls_fragment 3;
hls_playlist_length 60;
#deny play all;
push rtmp://127.0.0.1:1936/test/; # ADDED
record off;
}
}
}
Launching the broadcast to youtube:
ffmpeg -loglevel debug -f flv -listen 1 -i rtmp://127.0.0.1:1936/test/ -c copy -f flv 'rtmp://a.rtmp.youtube.com/live2/<KEY>'
Now my HLS stream is always online, and I can control broadcasting to youtube by launching/killing the second ffmpeg process.