ios - 预加载视频以立即播放

Question

SO 上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，给定URL
2. 等待视频完全加载
3. 立即播放视频(正如我所说，它已经缓冲了 100%)

理想情况下，计算下载速度，预测 f.e 当缓冲 60% 的视频时，我们开始播放，40% 将在播放时缓冲而不会延迟。

我的尝试:

 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]);
                            }
                        });
     }];
}

视频开始播放，连接速度慢时挂断，但如果我们开始播放，比方说 1 分钟后，播放效果很好。

主要问题 - 是否有能力在可以开始并播放到结束时得到通知而不会延迟？

注意:它是 AVFoundation 还是 MPMovieController 并不重要

我假设只能通过单独下载视频，将其存储在本地然后播放来完成。消极方面 - 在下载整个文件之前我们无法开始播放。

Answer 1

您可以对 AVPlayerItem 的 playbackLikelyToKeepUp、playbackBufferEmpty 和 playbackBufferFull 属性进行键值观察，以了解播放器的状态。在 docs 中查看有关这些值何时为真的更详细信息.特别是:

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.