Using VoiceProcessingIO audio unit subtype instead of RemoteIO causes unwanted drop in output volume

Question

I am using RemoteIO in my voice chat application. To enable echo canceling, I changed "kAudioUnitSubType_RemoteIO" to "kAudioUnitSubType_VoiceProcessingIO" after setting "kAudioSessionCategory_PlayAndRecord" as the session type. Now echo canceling works but the output volume level has dropped significantly versus the previous RemoteIO output level. Does anyone know how to get the same output volume level when using VoiceProcessingIO as when using RemoteIO?

I would also be interested in knowing the underlying cause of this and any possible workarounds, since I've had this reported as an issue in my own projects. It doesn't seem like there is an intrinsic reason for VPIO to be quieter when just dropped into an otherwise-working RemoteIO unit with the same audio session settings, but that does seem to be the behavior. — Halle
I've had this problem as well. I've noticed that it was significantly more of a volume drop for iOS 6 and on as opposed to iOS 5. What iOS are you testing on? — nvrtd frst
I've also found that VPIO completely breaks on iOS 7 on iPhone models 5, 5s and I'm assuming 5c. — nvrtd frst

Chuck D Chuck D · Accepted Answer · 2014-10-30T16:50:30

I realize that this hasn't been answered in a long time, but I found that if you do the following between changing audio units:

AudioComponentInstanceDispose(_ioUnit);

[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryAmbient  error:&nsError];

[[AVAudioSession sharedInstance] setActive:NO error:&nsError];

Then it seems to not create such a huge loudness problem between each unit. At this point, just reinitialize your audio unit and set the session type to what you need.

Using VoiceProcessingIO audio unit subtype instead of RemoteIO causes unwanted drop in output volume

2 Answers