RTMP proxy to crop original video and send it to another RTMP server

Question

I need to crop the video from an RTMP stream and send it to another RTMP server which always change. My understanding is that I should use nginx-proxy and ffmpeg, can anybody help me on how to set it up?

I suppose that i need to send the stream to an endpoint like /stream/:stream-key/:next-server-ip process the stream with ffmpeg and then send it to the :next-server-ip, what language should I use in the backend for this?

Answer 1

There are 2 strategies for processing such task:

1. "Pull"

You have some published rtmp stream and use ffmpeg to pull it, convert and send result to another server:

ffmpeg -i rtmp://source-server/stream -filter:v "crop=out_w:out_h:x:y" -vcodec h264 -acodec copy -f flv rtmp://next-server/stream

2. "Push"

RTMP stream is pushed to your server which processes it and sends result to another server. For such task you can use nginx-rtmp module for nginx and setup ffmpeg command using exec_push directive:

application src {
    live on;
    exec_push ffmpeg -i rtmp://localhost/src/$name -filter:v "crop=out_w:out_h:x:y" -vcodec h264 -acodec copy -f flv rtmp://next-server/stream 2>>/var/log/ffmpeg-$name.log;
}

When someone start to stream to rtmp://your-server/src/stream_name this ffmpeg command will be executed and the processing will begin

For additional information about video cropping and related ffmpeg parameters see https://video.stackexchange.com/a/4571