使用 AVPlayer 和 AVPlayerViewController，但音频和视频不存在

Question

我的代码如下所示：

_player = [AVPlayer playerWithURL:destination];
_playerVC = [AVPlayerViewController new];
_playerVC.player = _player;
dispatch_async(dispatch_get_main_queue(), ^{
    [self presentViewController:_playerVC animated:YES completion:^{
        [_player play];
    }];
});

_player 代表 AVPlayer，_playerVC 代表 AVPlayerViewController。我对这些对象有很强的全局引用。

使用终端，我播放了位于目的地的文件（打开 -a quicktime\ player destinationURLAbsoluteString），并看到文件在播放后已正确加载。

这是一个 m4v 文件。我播放了一个 m4a 文件，它正确地给了我音频。我还将目的地的 url 替换为一些远程 url，并且适用于视频。这让我相信它与我的视频有关。奇怪的是，我的 AVPlayerViewController 确实显示所有正常控件的黑屏，甚至显示视频为 2 分 23 秒。手动打开视频文件，我看到也是2分23秒。

我可以通过拖动指示视频位置的白点正确地向前浏览视频，但我什么也没听到，除了黑屏和控件我什么也看不到。

TL;DR

NSLog(@"目的地：%@",destination); 打印：file:///Users/MyLogin/Library/Developer/CoreSimulator/Devices/694F4C94-F785-4931-A312-4C3E7DE8673A/data/Containers/Data/Application/76C923BE-5B25-41F7-9145-63414657FDF6/Documents/mzvf_59140025198 .640x352.h264lc.D2.p.m4v

总而言之，看起来我正在正确检索视频，但由于某种原因，我的播放器控制器完全变黑并且没有音频。非常感谢任何帮助。

源代码：

.m 文件：

#import "ViewController.h"
#import "View2ViewController.h"

#import <AVKit/AVKit.h>
#import <AVFoundation/AVFoundation.h>



@interface ViewController ()
@property NSDictionary *requestedSong;
@property (strong) AVPlayer *player;  //Declare Globally
@property (strong) AVPlayerViewController *playerVC;
@end

@implementation ViewController

- (void)viewDidLoad {
    
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor yellowColor];

    UIButton *button = [[UIButton alloc]initWithFrame:CGRectMake(0, 0, 200, 50)];
    button.center = self.view.center;
    button.backgroundColor = [UIColor blueColor];
    [button setTitle:@"Query Songs" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonClicked) forControlEvents:UIControlEventTouchDown];
    [self.view addSubview:button];
    
    UIButton *button2 = [[UIButton alloc]initWithFrame:CGRectMake(0, 0, 200, 50)];
    button2.center = CGPointMake(button.center.x, button.center.y + 200);
    button2.backgroundColor = [UIColor blueColor];
    [button2 setTitle:@"Listen to the first song" forState:UIControlStateNormal];
    [button2 addTarget:self action:@selector(button2Clicked) forControlEvents:UIControlEventTouchDown];
    [self.view addSubview:button2];

}
-(void)button2Clicked{
    NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[[NSOperationQueue alloc]init]];
    NSURL *url = [NSURL URLWithString:[_requestedSong objectForKey:@"previewUrl"]];
    NSMutableURLRequest *req = [[NSMutableURLRequest alloc]initWithURL:url];
    NSURLSessionDownloadTask *task = [session downloadTaskWithRequest:req];
    [task resume];
}

-(void)buttonClicked{
    
    NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[[NSOperationQueue alloc]init]];
    NSURL *url = [NSURL URLWithString:@"https://itunes.apple.com/search?media=movie&entity=movie&term=Mad"];
    NSMutableURLRequest *req = [[NSMutableURLRequest alloc]initWithURL:url];
    NSURLSessionDataTask *task = [session dataTaskWithRequest:req];
    [task resume];
}

-(NSURL*)localFilePathForURL:(NSURL *) previewUrl{
    //get the directory to use
    NSString *documentsPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, true) objectAtIndex:0];
    //create the full path
    NSString *fullPath = [documentsPath stringByAppendingPathComponent:previewUrl.lastPathComponent];
    //append the filename and append to document path url
    return [NSURL fileURLWithPath:fullPath];
}

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
didFinishDownloadingToURL:(NSURL *)location{
    NSURL* originalURL = downloadTask.originalRequest.URL;
    NSURL *destination = [self localFilePathForURL:originalURL];
    NSLog(@"Destination: %@",destination);
    NSFileManager *defaultFileManager = [NSFileManager defaultManager];
    if([defaultFileManager fileExistsAtPath:destination.absoluteString]){
        [defaultFileManager removeItemAtURL:destination error:nil];
    }
    
    NSError *error;

    @try {
        [defaultFileManager copyItemAtURL:location toURL:destination error:&error];
    } @catch (NSException *exception) {
        NSLog(@"copy caught with exception: %@",exception);
        return;
    }

    
    dispatch_async(dispatch_get_main_queue(), ^{
        _player = [AVPlayer playerWithURL:destination];
        _playerVC = [AVPlayerViewController new];
        _playerVC.player = _player;
        [self presentViewController:_playerVC animated:YES completion:^{
            [_player play];
        }];
        
    });
   
    
    
    NSLog(@"Hello");
}

- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask
    didReceiveData:(NSData *)data{
    NSError *error2;
    NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:data options:1 error:&error2];
    _requestedSong = [[dict valueForKey:@"results"] objectAtIndex:0];
    NSLog(@"Searched: %@",[_requestedSong objectForKey:@"trackName"]);
}

- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response
 completionHandler:(void (^)(NSURLSessionResponseDisposition disposition))completionHandler {
    completionHandler(NSURLSessionResponseAllow);
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

.h 文件：

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController <NSURLSessionDataDelegate, NSURLSessionDownloadDelegate>


@end

更新：

在使用 mad max 的实际 URL 端点而不是下载视频时，它还会显示一个空白视频。这一定意味着视频的格式或它与 AVPlayer 的交互方式有些奇怪。

Answer 1

您应该为 AVPlayer 状态设置观察者，以便仅在准备好播放时调用播放。 怎么做 - 在这里查看答案：AVPlayer And Local Files

Answer 2

检查以下内容

if ((_playerVC.player.rate != 0) && (_playerVC.player.error == nil)) {
    // player is playing
} else {
   // Something wrong
}

您还可以观察播放器的速率属性。更多信息here