mix.sh

#! /bin/bash

if [ -z "$2" ]; then
	echo  usage: $0 cam pres
	exit 2
fi

ffmpeg -y -loglevel verbose \
  -i  "$1" -map '0:v0' \
  -i  "$2" -map '0:v1' \
  -loop 1 -i './bg.png' \
-filter_complex "[1:1] asetpts=PTS-STARTPTS, channelmap=map=FL|FL [maina];
[v0:0] setpts=PTS-STARTPTS, scale=1024:576 [pres];
[v1:0] setpts=PTS-STARTPTS, scale=320:180 [cam];
[0:0] setsar=1/1, setpts=PTS-STARTPTS [bg];
[bg_c][pres] overlay=x=12:y=8:eof_action=endall [bg_pc];
[bg][cam] overlay=x=948:y=532:eof_action=endall [bg_c];
[bg_pc][maina] concat=n=1:v=1:a=1 [outv][outa]" \
 -map '[outv]:v' -map '[outa]:a' \
 -pix_fmt yuv420p \
 -vcodec libx264 -threads 4 -preset veryfast -b:v 1000k -acodec aac -aq 80 -strict -2 \
 -f flv rtmp://strm.ludost.net/st/test