AAC with no global headers is currently not supported
I assume you're the same poster as at ffmpeg-user who posted this.

.aac stores a raw bitstream and the demuxer has no facility to extract the stream parameters as extradata. So, you can try streaming like this,

./ffmpeg -re -i ~/Downloads/test_audio.aac -acodec copy -vn -rtpflags latm -f rtsp rtsp://shafi:shafi at 192.168.1.135:1935/live/myStream