Default [Q] BT handsfree - missing sound in movies recorded???

I am riding bike a lot and using BT hands free, so far so good But yestarday i got beutiful jurney and took some pictures and shoot a movie or too (aist's on lamp posts ), but for my surprice all movies taken during BT connected are without any sound. Obviousley phone expects audio from BT but when there's no active call BT do not suply such
Please help me how to solve this problem, as to disconect BT befor shooting is Inpractical riding a bike