I am having an issue and am not sure if I am allowed to ask here. We are pushing an rtmp stream to our nginx+ffmpeg transcoder. Nginx forwards the stream and transcodes it to 2x lower quality streams. The origin stream play fine and stays in sync. The transcodes streams have audio drift. Basically the audio slowly goes out of sync. Anyone have any ideas?

My Nginx exec command:

exec_push /root/bin/ffmpeg -r 30 -i rtmp://127.0.0.1:1935/$app/$name -async 1 -vsync -1 -c:v libx264 -c:a aac -b:v 256k -b:a 32k -vf "scale=480:trunc(ow/a/2)*2" -tune zerolatency -preset veryfast -crf 23 -f flv rtmp://127.0.0.1:1935/show/$name_low -c:v libx264 -c:a aac -b:v 768k -b:a 64k -vf "scale=720:trunc(ow/a/2)*2" -tune zerolatency -preset veryfast -crf 23 -f flv rtmp://127.0.0.1:1935/show/$name_mid -c copy -f flv rtmp://127.0.0.1:1935/show/$name_src 2>>/var/log/ffmpeg.log