iPhone audio playback: force through internal speaker?

Question

Does anyone know if it is possible to implement playback of an audio file through the internal speaker even if the headphones are plugged in?

Answer 1

I'm not sure how you are doing your audio playback, but try having a look at the "Redirecting Output Audio" section of the Audio Session Programming Guide

It looks something like this:

UInt32 audioRouteOverride = kAudioSessionOverrideAudioRoute_Speaker;  // 1 
AudioSessionSetProperty ( 
    kAudioSessionProperty_OverrideAudioRoute,                         // 2 
    sizeof (audioRouteOverride),                                      // 3 
    &audioRouteOverride                                               // 4 
); 

Answer 2

Actually i think this is not possible, as there seems to be some kind of mechanical switch, which indicates a plugged in headset thus preventing speaker output when this is the case. (read here)

Some other hints can be found in the description of kAudioSessionProperty_OverrideCategoryDefaultToSpeaker: "Specifies whether or not to route audio to the speaker (instead of to the receiver) when no other audio route, such as a headset, is connected."