FFmpeg stack two videos and merge audios

FFmpeg -i rtmp://192.168.137.1:1935/live/xyz -i rtmp://192.168.137.1:1935/live/abc -filter_complex "[0:v][1:v]vstack=inputs=2[v];[0:a][1:a]amerge=inputs=2[a]" -map "[v]" -map "[a]" -an -f flv rtmp://192.168.137.1:1935/live/qwe

The above command stacks video from two streams and merges audios into one.

I tried following commands before I came up with above. 

ffmpeg -i rtmp://192.168.137.1:1935/live/xyz -i rtmp://192.168.137.1:1935/live/abc -filter_complex "[0:a][1:a]amix[a]" -map 0:v -map "[a]" -c:v copy -f flv rtmp://192.168.137.1:1935/live/qwe

ffmpeg -i rtmp://192.168.137.1:1935/live/xyz -i rtmp://192.168.137.1:1935/live/abc -filter_complex "[0v][1v]xstack=inputs=2:layout=0_0|1920_0[stacked]" -map "[stacked]" -preset ultrafast -vcodec libx264 -tune zerolatency -an -f flv rtmp://192.168.137.1:1935/live/qwe

ffmpeg -i rtmp://192.168.137.1:1935/live/xyz -i rtmp://192.168.137.1:1935/live/abc -filter_complex "[0v][1v]xstack=inputs=2:layout=0_0|1920_0[stacked];[0:a][1:a]amix[a]" -map "[stacked]" -map 0:v -map "[a]" -preset ultrafast -vcodec libx264 -tune zerolatency -an -f flv rtmp://192.168.137.1:1935/live/qwe

How to test?

Use Node Media ServerNode Media Server to start a local server that takes in rtmp streams and publishes.

Create two rtmp streams using OBS StudioOBS Studio stream them to Node Media Server and use the rtmp streams url in the FFmpeg command above to create a third rtmp stream which you can use anywhere you want.