Getting audio route gives empty string - iphone

Question

I'm currently working with a piece of code to detect whether a user has plugged in/unplugged headphones with their iPhone. The method I'm using to detect it is shown below.
void audioRouteChangeListenerCallback (void *inUserData, AudioSessionPropertyID inPropertyID,UInt32 inPropertyValueSize, const void *inPropertyValue){
if (inPropertyID != kAudioSessionProperty_AudioRouteChange) return;
CFStringRef route; UInt32 routeSize = sizeof(CFStringRef);
AudioSessionGetProperty(kAudioSessionProperty_AudioRoute,&routeSize, &route);
NSString *oldroute = (NSString*)route;
NSLog(#"Audio Route changed to: %#",oldroute);
}
My issue occurs when I go to unplug the headphones. Plugging them in works as I expect, with the Log file showing "Audio Route changed to: Headphones", however, when I unplug I get an empty string for oldroute. I was hoping that this value would be "Speaker" as it says in the Apple documents. Has anyone seen this before? Am I doing something wrong in getting the string oldroute? Thanks

Answer 1

I still have not found a good answer for the exact issue that I have posted as the question. Here is a workaround that may work for some people with a similar problem. This solution gives you the route that was active before the change. Ex. if you unplug your headphones you will get a string that is "Headphones" or if you put in your headphones you'll get a string that is "Speaker".
void audioRouteChangeListenerCallback (void *inUserData, AudioSessionPropertyID inPropertyID,UInt32 inPropertyValueSize, const void *inPropertyValue){
if (inPropertyID != kAudioSessionProperty_AudioRouteChange) return;
CFDictionaryRef routeChangeDictionary = (CFDictionaryRef)inPropertyValue;
CFStringRef oroute;
oroute = (CFStringRef)CFDictionaryGetValue(routeChangeDictionary, CFSTR(kAudioSession_AudioRouteChangeKey_OldRoute));
NSString *oldroute = (NSString*)oroute;
}
Hope this helps.
Edit: I'm going to accept my answer until a better one comes along

Answer 2

I currently use the following:
void _propertyListener( void * inClientData,
AudioSessionPropertyID inID,
UInt32 inDataSize,
const void * inData) {
if (inID != kAudioSessionProperty_AudioRouteChange) {
return;
}
dispatch_async(dispatch_get_main_queue(), ^{
[[NSNotificationCenter defaultCenter] postNotificationName:kAudioRouteChanged object:nil];
});
}
- (void) _audioRouteChanged:(NSNotification*)notification
{
NSLog(#"audioRouteChanged");
UInt32 routeSize = sizeof (CFStringRef);
CFStringRef route;
OSStatus error = AudioSessionGetProperty (kAudioSessionProperty_AudioRoute, &routeSize, &route);
/* Known values of route:
* "Headset"
* "Headphone"
* "Speaker"
* "SpeakerAndMicrophone"
* "HeadphonesAndMicrophone"
* "HeadsetInOut"
* "ReceiverAndMicrophone"
* "Lineout"
*/
if (!error && (route != NULL)) {
NSString* routeStr = (__bridge NSString*)route;
NSRange headphoneRange = [routeStr rangeOfString : #"Head"];
[self.cardSwipeDelegate headphoneListener:(headphoneRange.location != NSNotFound)];
if (headphoneRange.location != NSNotFound) {
[self startSession];
} else {
[self stopSession];
}
}
}
And where ever you do your initialization add the notification:
NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];
[nc addObserver:self selector:#selector(_audioRouteChanged:) name:kAudioRouteChanged object:nil];