iphone开发之多媒体播放参考源码

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OS sdk中提供了很多方便的方法来播放多媒体。本文将利用这些SDK做一个demo，来讲述一下如何使用它们来播放音频文件。

AudioToolbox framework

使用AudioToolbox framework。这个框架可以将比较短的声音注册到 system sound服务上。被注册到system sound服务上的声音称之为 system sounds。它必须满足下面几个条件。

1、播放的时间不能超过30秒

2、数据必须是 PCM或者IMA4流格式

3、必须被打包成下面三个格式之一：Core Audio Format (.caf), Waveform audio (.wav), 或者 Audio Interchange File (.aiff)

声音文件必须放到设备的本地文件夹下面。通过AudioServicesCreateSystemSoundID方法注册这个声音文件，AudioServicesCreateSystemSoundID需要声音文件的url的CFURLRef对象。看下面注册代码：

#import <AudioToolbox/AudioToolbox.h>
@interface MediaPlayerViewController : UIViewController
{
IBOutlet UIButton *audioButton;
SystemSoundID shortSound;
}

- (id)init
{
    self = [super initWithNibName:@"MediaPlayerViewController" bundle:nil];
    if (self) {
        // Get the full path of Sound12.aif
        NSString *soundPath = [[NSBundle mainBundle] pathForResource:@"Sound12"
                                                              ofType:@"aif"];
        // If this file is actually in the bundle...
        if (soundPath) {
            // Create a file URL with this path
            NSURL *soundURL = [NSURL fileURLWithPath:soundPath];

            // Register sound file located at that URL as a system sound
            OSStatus err = AudioServicesCreateSystemSoundID((CFURLRef)soundURL,
                                                            &shortSound);
            if (err != kAudioServicesNoError)
                NSLog(@"Could not load %@, error code: %d", soundURL, err);
        }
    }
    return self;
}

这样就可以使用下面代码播放声音了：

- (IBAction)playShortSound:(id)sender
{
AudioServicesPlaySystemSound(shortSound);
}

使用下面代码，还加一个震动的效果：

- (IBAction)playShortSound:(id)sender
{
AudioServicesPlaySystemSound(shortSound);
AudioServicesPlaySystemSound(kSystemSoundID_Vibrate);
}

AVFoundation framework

对于压缩过Audio文件，或者超过30秒的音频文件，可以使用AVAudioPlayer类。这个类定义在AVFoundation framework中。

下面我们使用这个类播放一个mp3的音频文件。首先要引入AVFoundation framework，然后MediaPlayerViewController.h中添加下面代码：

#import <AVFoundation/AVFoundation.h>
@interface MediaPlayerViewController : UIViewController <AVAudioPlayerDelegate>
{
    IBOutlet UIButton *audioButton;
    SystemSoundID shortSound;
    AVAudioPlayer *audioPlayer;

AVAudioPlayer类也是需要知道音频文件的路径，使用下面代码创建一个AVAudioPlayer实例：

- (id)init
{
    self = [super initWithNibName:@"MediaPlayerViewController" bundle:nil];

    if (self) {

        NSString *musicPath = [[NSBundle mainBundle] pathForResource:@"Music"
                                                              ofType:@"mp3"];
        if (musicPath) {
            NSURL *musicURL = [NSURL fileURLWithPath:musicPath];
            audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:musicURL
                                                                 error:nil];
            [audioPlayer setDelegate:self];
        }
        NSString *soundPath = [[NSBundle mainBundle] pathForResource:@"Sound12"
                                                              ofType:@"aif"];

我们可以在一个button的点击事件中开始播放这个mp3文件，如：

- (IBAction)playAudioFile:(id)sender
{
    if ([audioPlayer isPlaying]) {
        // Stop playing audio and change text of button
        [audioPlayer stop];
        [sender setTitle:@"Play Audio File"
                forState:UIControlStateNormal];
    }
    else {
        // Start playing audio and change text of button so
        // user can tap to stop playback
        [audioPlayer play];
        [sender setTitle:@"Stop Audio File"
                forState:UIControlStateNormal];
    }
}

这样运行我们的程序，就可以播放音乐了。

这个类对应的AVAudioPlayerDelegate有两个委托方法。一个是 audioPlayerDidFinishPlaying:successfully:当音频播放完成之后触发。当播放完成之后，可以将播放按钮的文本重新回设置成：Play Audio File

- (void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player
                       successfully:(BOOL)flag
{
    [audioButton setTitle:@"Play Audio File"
                 forState:UIControlStateNormal];
}

另一个是audioPlayerEndInterruption:，当程序被应用外部打断之后，重新回到应用程序的时候触发。在这里当回到此应用程序的时候，继续播放音乐。

- (void)audioPlayerEndInterruption:(AVAudioPlayer *)player
{
[audioPlayer play];
}

MediaPlayer framework

播放电影文件：

iOS sdk中可以使用MPMoviePlayerController来播放电影文件。但是在iOS设备上播放电影文件有严格的格式要求，只能播放下面两个格式的电影文件。

• H.264 (Baseline Profile Level 3.0)
• MPEG-4 Part 2 video (Simple Profile)

幸运的是你可以先使用iTunes将文件转换成上面两个格式。
MPMoviePlayerController还可以播放互联网上的视频文件。但是建议你先将视频文件下载到本地，然后播放。如果你不这样做，iOS可能会拒绝播放很大的视频文件。

这个类定义在MediaPlayer framework中。在你的应用程序中，先添加这个引用，然后修改MediaPlayerViewController.h文件。

#import <MediaPlayer/MediaPlayer.h>
@interface MediaPlayerViewController : UIViewController <AVAudioPlayerDelegate>
{
MPMoviePlayerController *moviePlayer;

下面我们使用这个类来播放一个.m4v格式的视频文件。与前面的类似，需要一个url路径。

- (id)init
{
    self = [super initWithNibName:@"MediaPlayerViewController" bundle:nil];
    if (self) {

        NSString *moviePath = [[NSBundle mainBundle] pathForResource:@"Layers"
                                                              ofType:@"m4v"];
        if (moviePath) {
            NSURL *movieURL = [NSURL fileURLWithPath:moviePath];
            moviePlayer = [[MPMoviePlayerController alloc]
                                    initWithContentURL:movieURL];
        }

MPMoviePlayerController有一个视图来展示播放器控件，我们在viewDidLoad方法中，将这个播放器展示出来。

- (void)viewDidLoad
{
    [[self view] addSubview:[moviePlayer view]];
    float halfHeight = [[self view] bounds].size.height /2.0;
    float width = [[self view] bounds].size.width;
    [[moviePlayer view] setFrame:CGRectMake(0, halfHeight, width, halfHeight)];
}

还有一个MPMoviePlayerViewController类，用于全屏播放视频文件，用法和MPMoviePlayerController一样。

MPMoviePlayerViewController *playerViewController =
[[MPMoviePlayerViewController alloc] initWithContentURL:movieURL];
[viewController presentMoviePlayerViewControllerAnimated:playerViewController];

我们在听音乐的时候，可以用iphone做其他的事情，这个时候需要播放器在后台也能运行，我们只需要在应用程序中做个简单的设置就行了。

1、在Info property list中加一个 Required background modes节点，它是一个数组，将第一项设置成设置App plays audio。

2、在播放mp3的代码中加入下面代码：

   if (musicPath) {
        NSURL *musicURL = [NSURL fileURLWithPath:musicPath];
        [[AVAudioSession sharedInstance]
                    setCategory:AVAudioSessionCategoryPlayback error:nil];
        audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:musicURL
                                                             error:nil];
        [audioPlayer setDelegate:self];
    }

在后台运行的播放音乐的功能在模拟器中看不出来，只有在真机上看效果。

总结：本文通过例子详细讲解了iOS sdk中用于播放音频文件的类，文章后面有本文的代码提供下载。

代码：http://files.cnblogs.com/zhuqil/MediaPlayer.zip

1. - (void) applicationDidFinishLaunching:(UIApplication*)application

2. {

3. // Init the window

4. window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

5.

6. // Try to use CADisplayLink director

7. // if it fails (SDK < 3.1) use the default director

8. if( ! [CCDirector setDirectorType:kCCDirectorTypeDisplayLink] )

9. [CCDirector setDirectorType:kCCDirectorTypeDefault];

10.

11. CCDirector *director = [CCDirector sharedDirector];

12.

13. // Init the View Controller

14. viewController = [[RootViewController alloc] initWithNibName:nil bundle:nil];

15. viewController.wantsFullScreenLayout = YES;

16.

17. //

18. // Create the EAGLView manually

19. // 1. Create a RGB565 format. Alternative: RGBA8

20. // 2. depth format of 0 bit. Use 16 or 24 bit for 3d effects, like CCPageTurnTransition

21. //

22. //

23. EAGLView *glView = [EAGLView viewWithFrame:[window bounds]

24. pixelFormat:kEAGLColorFormatRGBA8

25. depthFormat:0 // GL_DEPTH_COMPONENT16_OES

26. preserveBackbuffer:NO];

27.

28. // attach the openglView to the director

29. [director setOpenGLView:glView];

30.

31. // To enable Hi-Red mode (iPhone4)

32. // [director setContentScaleFactor:2];

33.

34. //

35. // VERY IMPORTANT:

36. // If the rotation is going to be controlled by a UIViewController

37. // then the device orientation should be "Portrait".

38. //

39. #if GAME_AUTOROTATION == kGameAutorotationUIViewController

40. [director setDeviceOrientation:kCCDeviceOrientationPortrait];

41. #else

42. [director setDeviceOrientation:kCCDeviceOrientationLandscapeLeft];

43. #endif

44.

45. [director setAnimationInterval:1.0/60];

46. [director setDisplayFPS:NO];

47.

48. // make the OpenGLView a child of the view controller

49. //[viewController setView:glView];

50.

51. [viewController.view addSubview:glView];

52.

53. // make the View Controller a child of the main window

54. [window addSubview: viewController.view];

55.

56. [window makeKeyAndVisible];

57.

58. NSURL *url = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"Schwarzweisskratzer" ofType:@"mov"]];

59. MPMoviePlayerController *moviePlayer = [[MPMoviePlayerController alloc] initWithContentURL:url];

60.

61. // Register to receive a notification when the movie has finished playing.

62. [[NSNotificationCenter defaultCenter] addObserver:self

63. selector:@selector(moviePlayBackDidFinish:)

64. name:MPMoviePlayerPlaybackDidFinishNotification

65. object:moviePlayer];

66.

67. if ([moviePlayer respondsToSelector:@selector(setFullscreen:animated:)]) {

68. // Use the new 3.2 style API

69. moviePlayer.controlStyle = MPMovieControlStyleNone;

70. moviePlayer.shouldAutoplay = YES;

71. moviePlayer.repeatMode = MPMovieRepeatModeOne;

72. //[moviePlayer setFullscreen:YES animated:YES];

73. CGRect win = [[UIScreen mainScreen] bounds];

74. //[moviePlayer.view setTransform:CGAffineTransformMakeRotation((float)M_PI_2)];

75.

76. moviePlayer.view.frame = CGRectMake(0, 0, win.size.height, win.size.width);

77. [viewController.view addSubview:moviePlayer.view];

78. [viewController.view sendSubviewToBack:moviePlayer.view];

79. printf("\n\nsoso\n");

80. } else {

81. // Use the old 2.0 style API

82. moviePlayer.movieControlMode = MPMovieControlModeHidden;

83. [moviePlayer play];

84. }

85.

86. // Default texture format for PNG/BMP/TIFF/JPEG/GIF images

87. // It can be RGBA8888, RGBA4444, RGB5_A1, RGB565

88. // You can change anytime.

89. [CCTexture2D setDefaultAlphaPixelFormat:kCCTexture2DPixelFormat_RGBA8888];

90.

91. // Run the intro Scene

92. [[CCDirector sharedDirector] runWithScene: [overlay scene]];

}

NSBundle *appBundle = [NSBundle mainBundle];

NSString *contentURLString = [mainBundle pathForResource:@"Movie" ofType:@"mov"];

if (contentURLString == nil) {

// Do whatever you do if the file can't be found

}

NSURL *contentURL = [NSURL urlWithString:contentURLString];

mMoviePlayer = [[MPMoviePlayerController alloc] initWithContentURL:contentURL];

http://www.techotopia.com/index.php/Video_Playback_from_within_an_iOS_4_iPhone_Application

http://www.iphonedevsdk.com/forum/iphone-sdk-development/18833-need-some-help-using-mpmovieplayer-play-video-file-app.html

http://www.vellios.com/downloads/