在Mac OS X 10.7中播放視頻

Question

在Mac OS X 10.7（Lion）中使用Objective-C以編程方式播放視頻的最簡單方法是什么？ 如果我也想支持OS X 10.6（Snow Leopard）呢？

我注意到iOS AV Foundation已經引入了OS X 10.7。 不幸的是，文檔似乎是為iOS編寫的，我發現它令人困惑。

Answer 1

這是一個NSView子類，使用AV Foundation（僅限Mac OS X 10.7）播放給定URL的視頻。 基於AVSimplePlayer示例代碼。

標題：

@interface RMVideoView : NSView

@property (nonatomic, readonly, strong) AVPlayer* player;
@property (nonatomic, readonly, strong) AVPlayerLayer* playerLayer;
@property (nonatomic, retain) NSURL* videoURL;

- (void) play;

@end

執行：

static void *RMVideoViewPlayerLayerReadyForDisplay = &RMVideoViewPlayerLayerReadyForDisplay;
static void *RMVideoViewPlayerItemStatusContext = &RMVideoViewPlayerItemStatusContext;

@interface RMVideoView()

- (void)onError:(NSError*)error;
- (void)onReadyToPlay;
- (void)setUpPlaybackOfAsset:(AVAsset *)asset withKeys:(NSArray *)keys;

@end

@implementation RMVideoView

@synthesize player = _player;
@synthesize playerLayer = _playerLayer;
@synthesize videoURL = _videoURL;

- (id)initWithFrame:(NSRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        self.wantsLayer = YES;
        _player = [[AVPlayer alloc] init];
        [self addObserver:self forKeyPath:@"player.currentItem.status" options:NSKeyValueObservingOptionNew context:RMVideoViewPlayerItemStatusContext];
    }

    return self;
}

- (void) dealloc {
    [self.player pause];
    [self removeObserver:self forKeyPath:@"player.currentItem.status"];
    [self removeObserver:self forKeyPath:@"playerLayer.readyForDisplay"];
    [_player release];
    [_playerLayer release];
    [_videoURL release];
    [super dealloc];
}

- (void) setVideoURL:(NSURL *)videoURL {
    _videoURL = videoURL;

    [self.player pause];
    [self.playerLayer removeFromSuperlayer];

    AVURLAsset *asset = [AVAsset assetWithURL:self.videoURL];
    NSArray *assetKeysToLoadAndTest = [NSArray arrayWithObjects:@"playable", @"hasProtectedContent", @"tracks", @"duration", nil];
    [asset loadValuesAsynchronouslyForKeys:assetKeysToLoadAndTest completionHandler:^(void) {
        dispatch_async(dispatch_get_main_queue(), ^(void) {
            [self setUpPlaybackOfAsset:asset withKeys:assetKeysToLoadAndTest];
        });
    }];
}

#pragma mark - KVO

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
    if (context == RMVideoViewPlayerItemStatusContext) {
        AVPlayerStatus status = [[change objectForKey:NSKeyValueChangeNewKey] integerValue];
        switch (status) {
            case AVPlayerItemStatusUnknown:
                break;
            case AVPlayerItemStatusReadyToPlay:
                [self onReadyToPlay];
                break;
            case AVPlayerItemStatusFailed:
                [self onError:nil];
                break;
        }
    } else if (context == RMVideoViewPlayerLayerReadyForDisplay) {
        if ([[change objectForKey:NSKeyValueChangeNewKey] boolValue]) {
            self.playerLayer.hidden = NO;
        }
    } else {
        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
    }
}


#pragma mark - Private

- (void)onError:(NSError*)error {
    // Notify delegate 
}

- (void)onReadyToPlay {
    // Notify delegate
}

- (void)setUpPlaybackOfAsset:(AVAsset *)asset withKeys:(NSArray *)keys {
    for (NSString *key in keys) {
        NSError *error = nil;
        if ([asset statusOfValueForKey:key error:&error] == AVKeyValueStatusFailed) {
            [self onError:error];
            return;
        }
    }

    if (!asset.isPlayable || asset.hasProtectedContent) {
        [self onError:nil];
        return;
    }

    if ([[asset tracksWithMediaType:AVMediaTypeVideo] count] != 0) { // Asset has video tracks
        _playerLayer = [AVPlayerLayer playerLayerWithPlayer:self.player];
        self.playerLayer.frame = self.layer.bounds;
        self.playerLayer.autoresizingMask = kCALayerWidthSizable | kCALayerHeightSizable;
        self.playerLayer.hidden = YES;
        [self.layer addSublayer:self.playerLayer];
        [self addObserver:self forKeyPath:@"playerLayer.readyForDisplay" options:NSKeyValueObservingOptionInitial | NSKeyValueObservingOptionNew context:RMVideoViewPlayerLayerReadyForDisplay];
    }

    // Create a new AVPlayerItem and make it our player's current item.
    AVPlayerItem *playerItem = [AVPlayerItem playerItemWithAsset:asset];
    [self.player replaceCurrentItemWithPlayerItem:playerItem];  
}

#pragma mark - Public

- (void) play {
    [self.player play];
}

@end

Answer 2

“最簡單”取決於您正在嘗試做什么。 如果您想要更多控制（例如，將電影渲染為OpenGL紋理）或更少（例如，您可以彈出並忽略的完全獨立的窗口），可能會有不同的答案。

但對於大多數用例，如果你想要10.6+支持，最簡單的電影放映方式是QTKit。 請參閱Xcode文檔中的文章“使用QTKit進行媒體播放”，以獲得良好的起點。