ios - 使用 AVMutableComposition iPhone

Question

我正在使用以下代码，按顺序流式传输两个视频。但模拟器中没有显示任何视频，完全是空白的。

另外我怎样才能找到这两个视频。例如，如果一个视频时长 2 分钟，第二个视频时长 3 分钟。现在我需要获取这些视频的总时间并进行搜索。当我将 slider 滑动到 4 分钟时，第二个视频应该从第 2 分钟开始播放。

可能吗？

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    NSURL *url1 = [NSURL URLWithString:@"http://www.tools4movies.com/dvd_catalyst_profile_samples/Harold%20Kumar%203%20Christmas%20bionic.mp4"];
    NSURL *url2 = [NSURL URLWithString:@"http://www.tools4movies.com/dvd_catalyst_profile_samples/Harold%20Kumar%203%20Christmas%20tablet.mp4"];

    NSDictionary *options = [NSDictionary dictionaryWithObject:[NSNumber numberWithBool:YES] forKey:AVURLAssetPreferPreciseDurationAndTimingKey];

    AVMutableComposition *composition = [[AVMutableComposition alloc] init];

    asset1 = [[AVURLAsset alloc] initWithURL:url1 options:options];
    AVURLAsset * asset2 = [[AVURLAsset alloc]initWithURL:url2 options:options];

    CMTime insertionPoint = kCMTimeZero;
    NSError * error = nil;
    composition = [AVMutableComposition composition];

    if (![composition insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset1.duration) 
                              ofAsset:asset1 
                               atTime:insertionPoint 
                                error:&error]) 
    {
        NSLog(@"error: %@",error);
    }

    insertionPoint = CMTimeAdd(insertionPoint, asset1.duration);

    if (![composition insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset2.duration) 
                              ofAsset:asset2 
                               atTime:insertionPoint 
                                error:&error]) 
    {
        NSLog(@"error: %@",error);
    }

    AVPlayerItem * item = [[AVPlayerItem alloc] initWithAsset:composition];
    player = [AVPlayer playerWithPlayerItem:item];
    AVPlayerLayer * layer = [AVPlayerLayer playerLayerWithPlayer:player];

    [layer setFrame:CGRectMake(0, 0, 320, 480)];
    [[[self view] layer] addSublayer:layer];
    [player play];   
}

谁能告诉我我的代码有什么错误吗？

Answer 1

模拟器无法显示视频。内置的 UIImagePickerController 和任何视频 Controller 都不起作用。它尚未实现，并且在 iOS 模拟器上大多显示为黑色或红色。您必须在 iOS 目标上进行调试。有时调试无法正常工作。使用 NSLog() 代替。这将始终有效(即，如果您使用“发布”代码在没有调试信息的情况下进行编译)

您可以使用播放器进行搜索:

如果 mp 是您的媒体播放器:

[mp pause];
CMTime position = mp.currentTime;

// maybe replace something
[mp replaceCurrentItemWithPlayerItem:[AVPlayerItem playerItemWithAsset:self.composition]];

[mp seekToTime:length];
[mp play];

总结:
编辑:使用组合和播放器项目
寻找:使用播放器

这是一个简短的正式示例，说明如何执行此操作(并且已经是线程安全的):

AVMutableComposition *_composition = [AVMutableComposition composition];

// iterate though all files
// And build mutable composition
for (int i = 0; i < filesCount; i++) {

    AVURLAsset* sourceAsset = nil;

    NSURL* movieURL = [NSURL fileURLWithPath:[paths objectAtIndex:i]];
    sourceAsset = [AVURLAsset URLAssetWithURL:movieURL options:nil];

    // calculate time
    CMTimeRange editRange = CMTimeRangeMake(CMTimeMake(0, 600), sourceAsset.duration);

    NSError *editError;
    BOOL result = [_composition insertTimeRange:editRange
                                        ofAsset:sourceAsset
                                        atTime:_composition.duration
                                        error:&editError];

    dispatch_sync(dispatch_get_main_queue(), ^{

        // maybe you need a progress bar
        self.loaderBar.progress = (float) i / filesCount;
        [self.loaderBar setNeedsDisplay];
     });

}

// make the composition threadsafe if you need it later
self.composition = [[_composition copy] autorelease];

// Player wants mainthread?    
dispatch_sync(dispatch_get_main_queue(), ^{

    mp = [AVPlayer playerWithPlayerItem:[[[AVPlayerItem alloc] initWithAsset:self.composition] autorelease]];

    self.observer = [mp addPeriodicTimeObserverForInterval:CMTimeMake(60, 600) queue:nil usingBlock:^(CMTime time){

        // this is our callback block to set the progressbar
        if (mp.status == AVPlayerStatusReadyToPlay) {

            float actualTime = time.value / time.timescale;

            // avoid division by zero
            if (time.value > 0.) {

                CMTime length = mp.currentItem.asset.duration;
                float lengthTime = length.value / length.timescale;

                if (lengthTime) {

                    self.progressBar.value = actualTime / lengthTime;
                } else {

                        self.progressBar.value = 0.0f;    
                }
            }];
        });

        // the last task must be on mainthread again
        dispatch_sync(dispatch_get_main_queue(), ^{

            // create our playerLayer
            self.playerLayer = [AVPlayerLayer playerLayerWithPlayer:mp];
            self.playerLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;  
            self.playerLayer.frame = [self view].layer.bounds;

            // insert into our view (make it visible)
            [[self view].layer insertSublayer:self.playerLayer atIndex:0];
        });

    // and now do the playback, maybe mp is global (self.mp)
    // this depends on your needs
    [mp play];
});

我希望这会有所帮助。