capture Mic + stereoMix together using directshow in windows

ffmpeg.exe -rtbufsize 200k -framerate 30 -f dshow -i video=MYVIDEODEVICE -f dshow -i audio=MYMICROPHONEDEVICE -f dshow -i audio=STEREOMIXDEVICE -threads 0 -filter:v "crop=1280:720:0:0" -c:v h264 -qp 0 -preset ultrafast -b:v 500k -c:a aac -b:a 128k -strict -2 out.mp4