參考
1.iOS通過AVPlayer打造自己的視頻播放器
2.基于 AVPlayer 自定義播放器
3.AVPlayer的基本使用

        if (_player) {
            return;
        }
        _playerItem = [AVPlayerItem playerItemWithURL:[NSURL URLWithString:imageModel.videoPath]];
        _player = [AVPlayer playerWithPlayerItem:_playerItem];
        _playerLayer = [AVPlayerLayer playerLayerWithPlayer:_player];
        _playerLayer.frame = gesture.view.bounds;
        [gesture.view.layer addSublayer:_playerLayer];
        [_player play];
        
        //監聽當視頻播放結束時
        [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(playbackFinished:) name:AVPlayerItemDidPlayToEndTimeNotification object:[self.player currentItem]];
        //    //監聽播放失敗時
            [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(playbackFailed:) name:AVPlayerItemFailedToPlayToEndTimeNotification object:[self.player currentItem]];

- (void)playbackFinished:(NSNotification *)notification {
    AVPlayerItem *item = [notification object];
    [item seekToTime:kCMTimeZero]; // item 跳轉到初始
    if (item == _playerItem) {
        [self resetPlayer];
    }
}
- (void)resetPlayer {
    if (_playerLayer) {
        [_player pause];
        [_playerLayer removeFromSuperlayer];
        [_player replaceCurrentItemWithPlayerItem:nil];
        [[NSNotificationCenter defaultCenter] removeObserver:self];
        _playerLayer = nil;
        _playerItem = nil;
        _player = nil;
    }
}
- (void)playbackFailed:(NSNotification *)notification {
    AVPlayerItem *item = [notification object];
    [item seekToTime:kCMTimeZero]; // item 跳轉到初始
    if (item == _playerItem) {
        [self resetPlayer];
    }
}

KVO 獲取視頻信息， 觀察緩沖進度

觀察 AVPlayerItem 的 status 屬性，當狀態變為 AVPlayerStatusReadyToPlay 時才可以使用。
也可以觀察 loadedTimeRanges 獲取緩沖進度

注冊觀察者
[_playerItem addObserver:self forKeyPath:@"status" options:(NSKeyValueObservingOptionNew) context:nil]; // 觀察status屬性
監聽觀察者

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSString *,id> *)change context:(void *)context {
    AVPlayerItem *item = (AVPlayerItem *)object;
    if ([keyPath isEqualToString:@"status"]) {
            AVPlayerStatus status = [[change objectForKey:@"new"] intValue]; // 獲取更改后的狀態
            if (status == AVPlayerStatusReadyToPlay) {
                CMTime duration = item.duration; // 獲取視頻長度
                // 設置視頻時間
                [self setMaxDuration:CMTimeGetSeconds(duration)];
                // 播放
                [self play];
            } else if (status == AVPlayerStatusFailed) {
                NSLog(@"AVPlayerStatusFailed");
            } else {
                NSLog(@"AVPlayerStatusUnknown");
            }

    } else if ([keyPath isEqualToString:@"loadedTimeRanges"]) {
        NSTimeInterval timeInterval = [self availableDurationRanges]; // 緩沖時間
        CGFloat totalDuration = CMTimeGetSeconds(_playerItem.duration); // 總時間
        [self.loadedProgress setProgress:timeInterval / totalDuration animated:YES]; // 更新緩沖條
    }
}