Streaming more than two audio tracks

I have a 8ch channel and I want to have a stream of all my audio tracks, because I have files with 8 tracks.
I did some tests with something like
ADD 1 STREAM rtmp:// -acodec libvo_aacenc -vcodec libx264 -pix_fmt yuv420p -crf 18 -tune zerolatency -preset ultrafast -maxrate 5M -bufsize 1M -format flv
On I have streaming software.
it's ok withe stereo caspar channel but not working with an 8ch channel.
I'am working with casparCG 2.1
Any idea ?