Weird noise going in reverse

Hi everyone. I have this weird sounding noise from what looks to be rear and was wondering if any of you have experienced or have some knowledge what might be the cause. Its not a grinding noise. It also makes it going forward but not as intense. Originally I thought some electronic noise but now thinking mechanical since going forward coincide with tire spin (increase as you increase speed) Again forward not near as intense as in reverse. I like to post a video but can't seem to know how. Can someone show me how? I added it to technical video but mot sure if its the right place. Any help on this troubleshoot would be much appreciated.
thanks

 

Actually I just did, I had assumed electronic noise from the start, since you hear those typical noise when parked sometimes. Something doesn't look right at both rear rotors, especially driver side. I don't see the typical shine where pads hits. As if the rotor hasn't spun in a while. I replaced brakes on there maybe a year and half ago. I reengaged and released parking brakes and didn't help. Weird only rear rotors. I'm gonna pull the tire and look closely.
thanks.

 

Update: It was rear brakes after all. Just did a complete rotor and pads on front and rear. If someone reading this without starting a new thread how important are the rear V clips. It seems the rear pads I got didn't have holes for them.