webrtc native ios usb headphones

Question

We're trying to use a usb headset (speaker + microphone) on ios using native webrtc library (from cocoapods)

The following code activate the usb microphone:

- (void)handleRouteChange:(NSNotification *) notification
{
    NSLog(@"Route change");
    NSError *error;
    AVAudioSession* session = [AVAudioSession sharedInstance];
    [session setCategory:AVAudioSessionCategoryMultiRoute error:&error];
    for (AVAudioSessionPortDescription *destPort in session.availableInputs){
        NSLog(@"PORT DESC %@", destPort.portName);
        if ([destPort.portType isEqualToString:AVAudioSessionPortUSBAudio]) {
            NSLog(@"USB");
            [session setPreferredInput:destPort error:&error];
            [session setOutputDataSource:destPort.selectedDataSource error:&error];
            if (error!=nil){
                NSLog(@"Error %@", error);
            }
        }
    }
}

But we don't have any output in the usb speakers

Any tip?