视音频播放

视音频播放可以说是视频开发中比较简单的了，只要创建几个对象，监听一些属性值即可完成一个视音频播放器。

我们需要了解下面几个类:

• AVPlayer
• AVPlayerLayer
• AVPlayerItem

AVPlayer是播放器对象，用来控制视音频的播放和暂停，还可以用来跳转进度；
AVPlayerLayers用于展示视频，AVPlayer需要在AVPlayerLayer上才能展示；
AVPlayerItem是资源管理器，用于加载资源；

播放器的创建

- (void)initializedPlayerWith:(NSURL *)url {
    AVPlayerItem *playerItem = [AVPlayerItem playerItemWithURL:url];    //资源管理器
    
    if (_player.currentItem != nil) {
        [self removeObserverFromPlayerItem:_player.currentItem];    //移除之前的监听
        [_player replaceCurrentItemWithPlayerItem:playerItem];  //切换资源
        [self pause];
    }else {
        _player = [AVPlayer playerWithPlayerItem:playerItem];
    }
    
    [_playerLayer removeFromSuperlayer];
    _playerLayer = nil;
    
    if (_containerView != nil) {
        _playerLayer = [AVPlayerLayer playerLayerWithPlayer:_player];
        _playerLayer.videoGravity = _videoGravity;    //视频填充模式
        _playerLayer.frame = _containerView.bounds;
        [_containerView.layer addSublayer:_playerLayer];
    }
    
    //监听播放器
    [self addObserverFromPlayerItem:playerItem];
    [self addProgressNotification];
    [self addPlayerFinishNotification];
}

当AVPlayerLayer父视图的frame发生了变化，记得及时修改AVPlayerLayer的frame
其他的代码很简单，关于监听的函数下面会讲

缓冲、播放、暂停和跳转进度

缓冲
在播放器创建之后，会自动进行缓冲

//缓存
- (void)buffer {
    if (_playerLayer == nil && self.fileUrl) {
        [self initializedPlayerWith:self.fileUrl];
    }
}

播放

- (void)play {
    [self buffer];
    if (_player && _player.rate == 0) {
        [_player play];
    }
}

暂停

- (void)pause {
    if (_player && _player.rate != 0) {
        [_player pause];
    }
}

跳转进度
这里value取值范围是0-1，
说明一点，被注释掉的跳转函数seekToTime只能跳转大于1秒的进度，要实现精确跳转，使用后面那个

- (void)jumpProgressWith:(CGFloat)value {
    if (_playerLayer == nil) return;
    CMTime time = CMTimeMakeWithSeconds(value * CMTimeGetSeconds(_player.currentItem.duration), _player.currentItem.currentTime.timescale);
    [self jumpProgressWithTime:time];
}

- (void)jumpProgressWithTime:(CMTime)time {
    if (_playerLayer == nil) return;
//    [_player seekToTime:time];    //该方法无法进行精确的跳转，只能跳转大于1秒后的进度
    [self.player seekToTime:time toleranceBefore:kCMTimeZero toleranceAfter:kCMTimeZero];   //这样才可以进行1秒内的精确跳转
}

视频填充模式

• AVLayerVideoGravityResizeAspect 默认，按视频比例显示，直到宽或高占满，未达到的地方显示父视图
• AVLayerVideoGravityResizeAspectFill 按原比例显示视频，直到两边屏幕占满，但视频部分内容可能无法显示
• AVLayerVideoGravityResize 按父视图尺寸显示，可能与原视频比例不同

AVPlayerLayer.videoGravity

播放器状态监听

在创建播放器对象后，通过监听资源管理器AVPlayerItem的属性，可以得知视音频的总长度和缓冲进度

//开始监听
- (void)addObserverFromPlayerItem:(AVPlayerItem *)playerItem {
    [playerItem addObserver:self forKeyPath:@"status" options:NSKeyValueObservingOptionNew context:nil];    //开始或暂停
    [playerItem addObserver:self forKeyPath:@"loadedTimeRanges" options:NSKeyValueObservingOptionNew context:nil];  //缓存进度
}

//监听回调
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
    AVPlayerItem *playerItem = object;
    if ([keyPath isEqualToString:@"status"]) {
        AVPlayerStatus status = [[change valueForKey:@"new"] integerValue];
        if (status ==AVPlayerStatusReadyToPlay) {
            CGFloat totalTime = CMTimeGetSeconds(playerItem.duration);
            NSLog(@"正在播放，视频总长度为 %.2f",totalTime);
        }
    }else if ([keyPath isEqualToString:@"loadedTimeRanges"]) {
        NSArray *array = playerItem.loadedTimeRanges;
        //本次缓冲时间范围
        CMTimeRange timeRange = [array.firstObject CMTimeRangeValue];
        CGFloat startSecond = CMTimeGetSeconds(timeRange.start);
        CGFloat durationSecond = CMTimeGetSeconds(timeRange.duration);
        CGFloat totalTime = CMTimeGetSeconds(playerItem.duration);
        //缓冲总长度
        NSTimeInterval totalBuffer = startSecond + durationSecond;
        CGFloat bufferProgress = totalBuffer / totalTime;
        if (_bufferBlock) {
            _bufferBlock(bufferProgress);
        }
    }
}

//别忘了移除监听
- (void)removeObserverFromPlayerItem:(AVPlayerItem *)playerItem {
    [playerItem removeObserver:self forKeyPath:@"status"];
    [playerItem removeObserver:self forKeyPath:@"loadedTimeRanges"];
}

播放进度

//监听播放进度
- (void)addProgressNotification {
    AVPlayerItem *playerItem = _player.currentItem;
    if (playerItem == nil) return;
    
    id playProgressObserver; //播放进度监听对象
    
    //先移除上一个视频的监听
    if (playProgressObserver) {
        [_player removeTimeObserver:playProgressObserver];
    }
    
    //每秒监听一次播放进度
    __weak typeof(self) weekSelf = self;
    /*
     CMTimeMake(value,timeScale):
     value表示第几帧，timeScale表示帧率，即每秒多少帧
     CMTimeMake(1,10):第一帧，帧率为每秒10帧，转换为时间公式:value/timeScale,即1/10=0.1,表示在视频的0.1秒时刻
     CMTimeMakeWithSeconds的第一个参数可以使float，其他都一样,不过因为这个比较好用，所以我一般用这个
     */
    playProgressObserver = [_player addPeriodicTimeObserverForInterval:CMTimeMake(playerProgressTime, playerProgressTime) queue:dispatch_get_main_queue() usingBlock:^(CMTime time) {
        CGFloat currentTime = CMTimeGetSeconds(time);
        CGFloat totalTime = CMTimeGetSeconds(playerItem.duration);
        
        if (currentTime) {
            CGFloat playProgress = currentTime / totalTime;
            if (weekSelf.progressBlock) {
                weekSelf.progressBlock(playProgress,currentTime,totalTime);
            }
        }
    }];
}

关于CMTime的使用建议先去百度了解一下，对视频开发的理解会很有好处

播放完成回调

- (void)addPlayerFinishNotification {
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(playFinishNotification) name:AVPlayerItemDidPlayToEndTimeNotification object:_player.currentItem];
}

现在我们完成了视音频的播放，使用本地/网络资源去试试吧。

GitHub链接