システムの音量とは異なる音量でiPodの音楽ライブラリ（ユーザー定義のプレイリストなど）の音楽を再生するにはどうすればよいですか？
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2
これは、システムの音量とは異なる音量でiPodミュージックライブラリの音楽/プレイリストを再生しようとしている人を対象としています。これができるという投稿がいくつかありますが[MPMusicPlayerController applicationMusicPlayer]、applicationMusicPlayerの音量を変更すると、システムの音量も変更されることがわかりました。
AVAudioPlayerクラスを使用して音楽を再生するより複雑な方法がありますが、iPodライブラリからアプリケーションバンドルに音楽ファイルをコピーする必要があり、ユーザー生成プレイリストなどの動的なものを再生する場合は注意が必要です。ただし、この手法を使用するとバイトにアクセスでき、データを処理する場合（DJアプリなど）に使用できます。ここにそのソリューションへのリンク。
私が行った解決策はAVPlayerクラスを使用しており、その方法についていくつかの良い投稿があります。この投稿は基本的に、Stackoverflowや他の場所で見つけたいくつかの異なるソリューションを組み合わせたものです。
次のフレームワークがリンクされています。
AVFoundation
MediaPlayer
AudioToolbox
CoreAudio
CoreMedia
（これらすべてが重要かどうかはわかりませんが、それが私が持っているものです。次のコードには表示されていないOpenALのものもいくつか実装しています）
// Presumably in your SoundManage.m file (or whatever you call it) ...
#import <CoreAudio/CoreAudioTypes.h>
#import <AudioToolbox/AudioToolbox.h>
@interface SoundManager()
@property (retain, nonatomic) AVPlayer* audioPlayer;
@property (retain, nonatomic) AVPlayerItem* currentItem;
@property (retain, nonatomic) MPMediaItemCollection* currentPlaylist;
@property (retain, nonatomic) MPMediaItem* currentTrack;
@property (assign, nonatomic) MPMusicPlaybackState currentPlaybackState;
@end
@implementation SoundManager
@synthesize audioPlayer;
@synthesize currentItem = m_currentItem;
@synthesize currentPlaylist;
@synthesize currentTrack;
@synthesize currentPlaybackState;
- (id) init
{
...
//Define an AVPlayer instance
AVPlayer* tempPlayer = [[AVPlayer alloc] init];
self.audioPlayer = tempPlayer;
[tempPlayer release];
...
//load the playlist you want to play
MPMediaItemCollection* playlist = [self getPlaylistWithName: @"emo-pop-unicorn-blood-rage-mix-to-the-max"];
if(playlist)
[self loadPlaylist: playlist];
...
//initialize the playback state
self.currentPlaybackState = MPMusicPlaybackStateStopped;
//start the music playing
[self playMusic];
...
}
//Have a way to get a playlist reference (as an MPMediaItemCollection in this case)
- (MPMediaItemCollection*) getPlaylistWithName:(NSString *)playlistName
{
MPMediaQuery* query = [[MPMediaQuery alloc] init];
MPMediaPropertyPredicate* mediaTypePredicate = [MPMediaPropertyPredicate predicateWithValue: [NSNumber numberWithInteger: MPMediaTypeMusic] forProperty:MPMediaItemPropertyMediaType];
[query addFilterPredicate: mediaTypePredicate];
[query setGroupingType: MPMediaGroupingPlaylist];
NSArray* playlists = [query collections];
[query release];
for(MPMediaItemCollection* testPlaylist in playlists)
{
NSString* testPlaylistName = [testPlaylist valueForProperty: MPMediaPlaylistPropertyName];
if([testPlaylistName isEqualToString: playlistName])
return testPlaylist;
}
return nil;
}
//Override the setter on currentItem so that you can add/remove
//the notification listener that will tell you when the song has completed
- (void) setCurrentItem:(AVPlayerItem *)currentItem
{
if(m_currentItem)
{
[[NSNotificationCenter defaultCenter] removeObserver:self name:AVPlayerItemDidPlayToEndTimeNotification object:m_currentItem];
[m_currentItem release];
}
if(currentItem)
m_currentItem = [currentItem retain];
else
m_currentItem = nil;
if(m_currentItem)
{
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleMusicTrackFinished) name:AVPlayerItemDidPlayToEndTimeNotification object:m_currentItem];
}
}
//handler that gets called when the name:AVPlayerItemDidPlayToEndTimeNotification notification fires
- (void) handleMusicTrackFinished
{
[self skipSongForward]; //or something similar
}
//Have a way to load a playlist
- (void) loadPlaylist:(MPMediaItemCollection *)playlist
{
self.currentPlaylist = playlist;
self.currentTrack = [playlist.items objectAtIndex: 0];
}
//Play the beats, yo
- (void) playMusic
{
//check the current playback state and exit early if we're already playing something
if(self.currentPlaybackState == MPMusicPlaybackStatePlaying)
return;
if(self.currentPlaybackState == MPMusicPlaybackStatePaused)
{
[self.audioPlayer play];
}
else if(self.currentTrack)
{
//Get the system url of the current track, and use that to make an AVAsset object
NSURL* url = [self.currentTrack valueForProperty:MPMediaItemPropertyAssetURL];
AVAsset* asset = [AVURLAsset URLAssetWithURL:url options:nil];
//Get the track object from the asset object - we'll need to trackID to tell the
//AVPlayer that it needs to modify the volume of this track
AVAssetTrack* track = [[asset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
//Build the AVPlayerItem - this is where you modify the volume, etc. Not the AVPlayer itself
AVPlayerItem* playerItem = [[AVPlayerItem alloc] initWithAsset: asset]; //initWithURL:url];
self.currentItem = playerItem;
//Set up some audio mix parameters to tell the AVPlayer what to do with this AVPlayerItem
AVMutableAudioMixInputParameters* audioParams = [AVMutableAudioMixInputParameters audioMixInputParameters];
[audioParams setVolume: 0.5 atTime:kCMTimeZero]; //replace 0.5 with your volume
[audioParams setTrackID: track.trackID]; //here's the track id
//Set up the actual AVAudioMix object, which aggregates effects
AVMutableAudioMix* audioMix = [AVMutableAudioMix audioMix];
[audioMix setInputParameters: [NSArray arrayWithObject: audioParams]];
//apply your AVAudioMix object to the AVPlayerItem
[playerItem setAudioMix:audioMix];
//refresh the AVPlayer object, and play the track
[self.audioPlayer replaceCurrentItemWithPlayerItem: playerItem];
[self.audioPlayer play];
}
self.currentPlaybackState = MPMusicPlaybackStatePlaying;
}
- (void) pauseMusic
{
if(self.currentPlaybackState == MPMusicPlaybackStatePaused)
return;
[self.audioPlayer pause];
self.currentPlaybackState = MPMusicPlaybackStatePaused;
}
- (void) skipSongForward
{
//adjust self.currentTrack to be the next object in self.currentPlaylist
//start the new track in a manner similar to that used in -playMusic
}
- (void) skipSongBackward
{
float currentTime = self.audioPlayer.currentItem.currentTime.value / self.audioPlayer.currentItem.currentTime.timescale;
//if we're more than a second into the song, just skip back to the beginning of the current track
if(currentTime > 1.0)
{
[self.audioPlayer seekToTime: CMTimeMake(0, 1)];
}
else
{
//otherwise, adjust self.currentTrack to be the previous object in self.currentPlaylist
//start the new track in a manner similar to that used in -playMusic
}
}
//Set volume mid-song - more or less the same process we used in -playMusic
- (void) setMusicVolume:(float)vol
{
AVPlayerItem* item = self.audioPlayer.currentItem;
AVAssetTrack* track = [[item.asset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
AVMutableAudioMixInputParameters* audioParams = [AVMutableAudioMixInputParameters audioMixInputParameters];
[audioParams setVolume: vol atTime:kCMTimeZero];
[audioParams setTrackID: track.trackID];
AVMutableAudioMix* audioMix = [AVMutableAudioMix audioMix];
[audioMix setInputParameters: [NSArray arrayWithObject: audioParams]];
[item setAudioMix:audioMix];
}
@end
表示されたエラーはご容赦ください。コメントでお知らせください。修正します。そうでなければ、誰かが私がしたのと同じ挑戦に遭遇した場合、これが役立つことを願っています！
于 2013-02-14T18:19:57.623 に答える
2
実際、MPMusicPlayer から iPod の URL を読み込んでから、AVAudioPlayerを介して再生するという、非常に簡単な方法を見つけました。
// Get-da iTunes player thing
MPMusicPlayerController* iTunes = [MPMusicPlayerController iPodMusicPlayer];
// whazzong
MPMediaItem *currentSong = [iTunes nowPlayingItem];
// whazzurl
NSURL *currentSongURL = [currentSong valueForProperty:MPMediaItemPropertyAssetURL];
info( "AVAudioPlayer playing %s", [currentSongURL.absoluteString UTF8String] ) ;
// mamme AVAudioPlayer
NSError *err;
avAudioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:currentSongURL error:&err] ;
if( err!=nil )
{
error( "AVAudioPlayer couldn't load %s", [currentSongURL.absoluteString UTF8String] ) ;
}
avAudioPlayer.numberOfLoops = -1; //infinite
// Play that t
[avAudioPlayer prepareToPlay] ;
[avAudioPlayer play];
[avAudioPlayer setVolume:0.5]; // set the AVAUDIO PLAYER's volume to only 50%. This
// does NOT affect system volume. You can adjust this music volume anywhere else too.
于 2013-05-20T17:54:51.003 に答える