录音过程有时候需要判断用户当前是插入耳机，具体判断如下:
- (BOOL)isHeadSetPlugging {
AVAudioSessionRouteDescription* route = [[AVAudioSession sharedInstance] currentRoute];
for (AVAudioSessionPortDescription* desc in [route outputs]) {
if ([[desc portType] isEqualToString:AVAudioSessionPortHeadphones])
return YES;
}
return NO;
}
