不少遊戲可以讓玩家一邊玩遊戲, 一邊聽著自己音樂, 怎麼做呢? 主要是要在起動sound engine 前, 設定一個 kAudioSessionCategory_AmbientSound 的 AudioSession, 詳情看下面的代碼:

        OSStatus result = AudioSessionInitialize(NULL, NULL, NULL, self);
        if (result) printf("Error initializing audio session! %d\n", result);
        else {
            UInt32 category = kAudioSessionCategory_AmbientSound;
            result = AudioSessionSetProperty(kAudioSessionProperty_AudioCategory, sizeof(category), &category);
            if (result) printf("Error setting audio session category! %d\n", result);
            else {
                result = AudioSessionSetActive(true);
                if (result) printf("Error setting audio session active! %d\n", result);
            }
        }

By Dr. Watson, http://www.cocoachina.com/bbs/read.php?tid=2774