我有一个应用程序,它使用 MPAudioPlayerController 访问 iPod 音乐库,以及一个 AVAudioPlayer 将音频覆盖在音乐之上。我已将此文档用作指南。具体来说:
最后,您可以增强类别以在播放音频时自动降低其他音频的音量。例如,这可以在锻炼应用程序中使用。假设当您的应用程序想要覆盖口头消息时,用户正在使用他们的 iPod 进行锻炼——例如,“您已经划船 10 分钟”。为确保来自应用程序的消息可理解,请将 kAudioSessionProperty_OtherMixableAudioShouldDuck 属性应用于音频会话。发生闪避时,设备上的所有其他音频(除了电话音频)的音量都会降低。
但我没有看到这种行为。事实上,我看到(或听到)是,如果我设置 AudioSession 并将 kAudioSessionProperty_OtherMixableAudioShouldDuck 设置为 true,MPAudioPlayerController 初始音量会降低,如果我随后在 MPAudioPlayerController 上调用暂停(然后再次播放)音量级别提高到“正常”水平。播放 AVAudioPlayer 对音频电平没有任何影响...
所以我设置了一个简单的测试用例来重现这个。
在 ViewController 标头中:
#import <UIKit/UIKit.h>
#import <MediaPlayer/MediaPlayer.h>
#import <AudioToolbox/AudioToolbox.h>
#import <AVFoundation/AVFoundation.h>
@interface MusicPlayerVolumeTestViewController : UIViewController <AVAudioPlayerDelegate>
{
UIButton *musicButton;
UIButton *soundButton;
AVAudioPlayer *audioPlayer;
MPMusicPlayerController *musicPlayerController;
}
@property (nonatomic, retain) IBOutlet UIButton *musicButton;
@property (nonatomic, retain) IBOutlet UIButton *soundButton;
@property (nonatomic, retain) MPMusicPlayerController *musicPlayerController;
- (IBAction)musicAction;
- (IBAction)soundAction;
@end
并在实施中:
- (void)viewDidLoad
{
[super viewDidLoad];
//Setup our Audio Session
OSStatus status = AudioSessionInitialize(NULL, NULL, NULL, NULL);
//We want our audio to play if the screen is locked or the mute switch is on
UInt32 sessionCategory = kAudioSessionCategory_MediaPlayback;
status = AudioSessionSetProperty (kAudioSessionProperty_AudioCategory, sizeof (sessionCategory), &sessionCategory);
//We want our audio to mix with other app's audio
UInt32 shouldMix = true;
status = AudioSessionSetProperty (kAudioSessionProperty_OverrideCategoryMixWithOthers, sizeof (shouldMix), &shouldMix);
//Enable "ducking" of the iPod volume level while our sounds are playing
UInt32 shouldDuck = true;
AudioSessionSetProperty(kAudioSessionProperty_OtherMixableAudioShouldDuck, sizeof(shouldDuck), &shouldDuck);
//Activate our audio session
AudioSessionSetActive(YES);
//Setup the Music Player to access the iPod music library
self.musicPlayerController = [MPMusicPlayerController applicationMusicPlayer];
[self.musicPlayerController setShuffleMode: MPMusicShuffleModeSongs];
[self.musicPlayerController setRepeatMode: MPMusicRepeatModeNone];
[self.musicPlayerController setQueueWithQuery:[MPMediaQuery songsQuery]];
//Setup a AVAudioPlayer sound to overlay against the Music Player audio
NSURL *soundURL = [NSURL URLWithString:[[NSBundle mainBundle] pathForResource:@"overlay" ofType:@"mp3"]];
NSError *error = nil;
audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:soundURL error: &error];
if (!audioPlayer)
{
NSLog(@"Could not create audio effect player: %@", [error localizedDescription]);
}
[audioPlayer prepareToPlay];
}
- (IBAction)musicAction
{
if (self.musicPlayerController.playbackState == MPMusicPlaybackStatePlaying)
{
[self.musicPlayerController pause];
}
else if (self.musicPlayerController.playbackState == MPMusicPlaybackStateStopped
|| self.musicPlayerController.playbackState == MPMusicPlaybackStatePaused)
{
[self.musicPlayerController play];
}
}
- (IBAction)soundAction
{
if (audioPlayer.playing)
{
[audioPlayer pause];
}
else
{
[audioPlayer play];
}
}
我已经连接了几个 UIButtons。一个用于musicAction(用于播放/暂停MPMusicPlayerController),一个用于soundAction(用于播放/暂停AVAudioPlayer)。
如前所述,如果我点击 musicAction 按钮,音乐会播放,但音量会降低,如果我点击 soundAction 按钮,则覆盖播放,但不会影响 MPMusicPlayerController 的音量。而且,更类似于错误的是,当我暂停然后播放 MPMusicPlayerController 时,音乐的音量会增加到我没有设置 AudioSession 时的水平。
我很想知道是否有其他人有过这种经历,如果有的话,如果你找到了解决方法(或者可以告诉我我做错了什么)。否则,我想我要去雷达了。
非常感谢,
列维