Audio play from my phone to PC over BT only works for 1 sec

My android system is Lollipop, and my computer is Windows 7 64bit.

I setup the BT connection and want to play musics on my phone using my PC's speaker over BT. However, I can only hear the music playing for less than 1 sec. I can still use my PC to control the music play on my phone, but I just cannot hear the music. Not from my PC, nor my phone.