最近工作需要用到媒体播放器，所以开始在看这方面的资料。
先是做了一个使用 AVPlayer 播放网络视频的 Demo, 由于需要使用 rtsp 协议连接设备来进行视频实时播放，AVFoundation 并不对此进行支持。
不过既然做了，就还是做一下笔记吧。
如果需要简单的播放 http 协议的网络视频，可以直接套用。

1. 基本步骤

1.1 自定义播放视图

该视图就是播放器的载体。
主要是要重设该视图的 Layer，让他成为 AVPlayerLayer，才能用来播放视频。

NJPreviewPlayerView.h

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

@interface NJPreviewPlayerView : UIView

- (void)setPlayer:(AVPlayer *)player;

@end

NJPreviewPlayerView.m

#import "NJPreviewPlayerView.h"
#import "FFMpegPlayer.h"

@interface NJPreviewPlayerView()

@property (nonatomic) AVPlayer *player;

@end

@implementation NJPreviewPlayerView

+ (Class)layerClass {
    return [AVPlayerLayer class];
}

- (AVPlayer*)player {
    return [(AVPlayerLayer *)[self layer] player];
}

- (void)setPlayer:(AVPlayer *)player {
    [(AVPlayerLayer *)[self layer] setVideoGravity:AVLayerVideoGravityResize];
    [(AVPlayerLayer *)[self layer] setPlayer:player];
}

@end

1.2 配置与控制播放器

设置属性 AVPlayer，AVPlayerItem。如果是本地视频还有一个 AVAssets。
基本流程：配置 AVPlayerItem，配置 AVPlayer，监听 AVPlayerItem 状态，然后进行播放。
主要代码在 configurationPlayer 以及 observeValueForKeyPath 中。

NJPreviewPlayerView.h

#import <UIKit/UIKit.h>
#import "NJPreviewPlayerView.h"

@interface NJPreviewViewController : UIViewController

@end

NJPreviewPlayerView.m

#import "NJPreviewViewController.h"

@interface NJPreviewViewController ()

@property (weak, nonatomic) IBOutlet NJPreviewPlayerView *preview;

@property (nonatomic) AVPlayer * player;
@property (nonatomic) AVPlayerItem * playerItem;

@end

@implementation NJPreviewViewController

#pragma mark - Lift cycle

- (void)viewDidLoad {
    [super viewDidLoad];
}

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    [self configurationPlayer];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    [self removeObservers];
}

#pragma mark - Preview

- (void)configurationPlayer {
    NSURL * url = [NSURL URLWithString:@"http://devimages.apple.com/iphone/samples/bipbop/bipbopall.m3u8"];
    
    self.playerItem = [AVPlayerItem playerItemWithURL:url];
    self.player = [AVPlayer playerWithPlayerItem:self.playerItem];
    
    [self setObservers];
    
    [self.preview setPlayer:self.player];
}

#pragma mark - KVO

- (void)setObservers {
    [self.playerItem addObserver:self forKeyPath:@"status" options:0 context:nil];
}

- (void)removeObservers {
    [self.playerItem removeObserver:self forKeyPath:@"status"];
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSString *,id> *)change context:(void *)context {
    if ([keyPath isEqualToString:@"status"]) {
        NSLog(@"%@", self.playerItem.error);
        
        switch (self.playerItem.status) {
            case AVPlayerItemStatusReadyToPlay:
                NSLog(@"AVPlayerItemStatusReadyToPlay");
                [self.player play];
                break;
            case AVPlayerItemStatusUnknown:
                NSLog(@"AVPlayerItemStatusUnknown");
                break;
            case AVPlayerItemStatusFailed:
                NSLog(@"AVPlayerItemStatusFailed");
                break;
        }
    }
}

@end

2. 参考资料

我用到的就是这么简单的，所以没有写复杂，但是其实 AVFoundation 家族非常强大，录音，录像也可以用它来做。
具体参考官方文档，讲得非常详细。

Apple: AVFoundation Programming Guide