Audio output device setting issues

[Mr Chen]

Hello, I encountered another trouble. When linphone ends the call, it will change the audio output device from Speaker to Receiver. If I use the speaker to play a long audio before the incoming call, linphone hangs up after the incoming call. I found that the audio originally played will change from Speaker to Receiver. How can I modify the program to use Speaker? (Because I tried to change the output device, but it was invalid) Or is there any way to directly set my output device to always be the speaker?