预加载视频即可播放 [英] Preloading video to play without delay

问题描述

有很多关于视频预加载的主题，但对我来说仍然不是很清楚。

目标：

1. 从网络加载视频，提供URL


2. 等待完全加载视频


3. 立即播放视频（因为我说它已经100％缓存）

理想情况下，计算下载速度，预测fe当缓冲60％的视频时，我们开始播放，40％将在没有延迟的情况下进行缓冲。

我尝试的内容：

  NSURL * url = [NSURL URLWithString：@video url address here]; 
 AVURLAsset * avasset = [[AVURLAsset alloc] initWithURL：url options：nil]; 
 
 AVPlayerItem * item = [[AVPlayerItem alloc] initWithAsset：avasset]; 
 self.player = [[AVPlayer alloc] initWithPlayerItem：item]; 
 
 self.playerLayer = [AVPlayerLayer playerLayerWithPlayer：self.player]; 
 CGSize size = self.view.bounds.size; 
 float x = size.width / 2.0-202.0; 
 float y = size.height / 2.0  -  100; 
 
 self.playerLayer.frame = CGRectMake（x，y，404,200）; 
 self.playerLayer.backgroundColor = [UIColor blackColor] .CGColor; 
 
 [self.view.layer addSublayer：self.playerLayer]; 
 NSString * tracksKey = @tracks; 
 
 [avasset loadValuesAsynchronouslyForKeys：[NSArray arrayWithObject：tracksKey] completionHandler：
 ^ {
 dispatch_async（dispatch_get_main_queue（），
 ^ {
 NSError * error = nil; 
 AVKeyValueStatus status = [avasset statusOfValueForKey：tracksKey error：& error]; 
 NSLog（@Status％d，status）; 
 if（status == AVKeyValueStatusLoaded）{
 [self.player play]; 
} 
 else {
 NSLog（@未加载资产的曲目：\ n％@，[error localizedDescription]）; 
} 
}）; 
}]; 
} 
  

视频开始播放和慢速连接挂起，但如果我们开始播放，让我们说1分钟之后，它会很好地发挥。

主要问题 - 是否能够在没有延迟的情况下开始播放直到结束时获得通知？

注意：不管它是 AVFoundation还是MPMovieController

<并不重要p>我假设只能通过单独下载视频，在本地存储然后播放来完成。负面因素 - 我们无法在下载整个文件之前开始播放。

解决方案

你可以在AVPlayerItem上进行键值观察playbackLikelyToKeepUp，playbackBufferEmpty和playbackBufferFull属性可以了解玩家的状态。在 docs <中查看有关这些值何时为真的详细信息/ A>。值得注意的是：

当属性playbackBufferFull指示YES时，playbackLikelyToKeepUp可以指示NO。在这种情况下，回放缓冲区已达到容量，但没有统计数据支持预测回放可能在将来保持。您可以决定是否继续播放媒体。

there are tons of topics on SO about video preloading but still isn't crystal clear for me.

Objectives:

1. Load video from the network, URL is given
2. Wait for video loaded completely
3. Play video without delay (as I said it's already buffered 100%)

Ideally, calculate download speed, predict f.e when buffered 60% of video, we start playing and 40% will be buffered while playing without delay.

what I tried:

 NSURL *url = [NSURL URLWithString:@"video url address here"];
 AVURLAsset *avasset = [[AVURLAsset alloc] initWithURL:url options:nil];

 AVPlayerItem *item = [[AVPlayerItem alloc] initWithAsset:avasset];
 self.player = [[AVPlayer alloc] initWithPlayerItem:item];

 self.playerLayer = [AVPlayerLayer playerLayerWithPlayer:self.player];
 CGSize size = self.view.bounds.size;
 float x = size.width/2.0-202.0;
 float y = size.height/2.0 - 100;

 self.playerLayer.frame = CGRectMake(x, y, 404, 200);
 self.playerLayer.backgroundColor = [UIColor blackColor].CGColor;

 [self.view.layer addSublayer:self.playerLayer];
 NSString *tracksKey = @"tracks";

 [avasset loadValuesAsynchronouslyForKeys:[NSArray arrayWithObject:tracksKey] completionHandler:
     ^{
         dispatch_async(dispatch_get_main_queue(),
                        ^{
                            NSError *error = nil;
                            AVKeyValueStatus status = [avasset statusOfValueForKey:tracksKey error:&error];
                                NSLog(@"Status %d", status);
                            if (status == AVKeyValueStatusLoaded) {
                                [self.player play];
                            }
                            else {
                                NSLog(@"The asset's tracks were not loaded:\n%@", [error localizedDescription]);
                            }
                        });
     }];
}

Video starts playing and on slow connection hangs out, but if we start playing, let's say after 1 minute, it plays nicely.

The main question - is there ability to get notified when it can be start and play till the end without delaying?

Note: not really important whether it's a AVFoundation or MPMovieController

My assuming that it only can be done by downloading video separately, storing it locally and then playing. Negative aspect there - we can't start playing until whole file is downloaded.

解决方案

You could key-value observe on the AVPlayerItem's playbackLikelyToKeepUp, playbackBufferEmpty, and playbackBufferFull properties to get a sense of your player's status. See finer details about when these values are true in the docs. Notably:

It is possible for playbackLikelyToKeepUp to indicate NO while the property playbackBufferFull indicates YES. In this event the playback buffer has reached capacity but there isn't the statistical data to support a prediction that playback is likely to keep up in the future. It is up to you to decide whether to continue media playback.

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