ios - very strange behaviour for volume control

Question

My app performs recording and playing sound. Because of some recording algorithms, I used a library for recording. About playing, I use AVAudioPlayer to play file.

The problem is: It's seem the library has it's own volume control.

(1). Before the library is active (it's mean the library is inactive), I change the volume by iPhone's hard buttons (+ and -) to low volume

(2). Then, when the library is active, I change the volume to higher volume.

(3). Then, when the library is inactive again, the volume automatically changes back to low volume.

From now: If the library is active, the volume is as (2); if the library is inactive, the volume is as (3).

I read more about AVAudioSession and AudioToolbox but see any point about volume. Can you point me the mechanism here, so I can resolve my problem.

Sorry about the image, I just create a demo to show my problem, it's not my app UI, because of security.

Thank you all!

Answer 1

I found the problem.

These are volume for 2 different audio routes:

• one is speaker next to microphone, on bottom.

• one is receiver - the speaker for phone call, next to front camera, on top.

My app use speaker, but the library use the receiver.

Thanks for you time.