1.AVPlayer,AVPlayerLayer和AVPlayerItem
AVPlayer是不可见组件,可以播放视听媒体,音频,视频都可以,即便不创建可见视图,它依然可以进行播放.
AVPlayerLayer即是让播放可见的组件,继承自CALayer
AVAsset是媒体资源的静态描述,AVPlayerItem则是媒体资源动态数据模型,例如seekToTime,currentTime等.
AVPlayerItem一个或多个媒体曲目组成,由AVPlayerItemTrack类建立模型,AVPlayerItemTrack用于表示某一种媒体流.
2.播放视频
//创建AVAsset
AVAsset *asset = [AVAsset assetWithURL:[[NSBundle mainBundle] URLForResource:@"测试录屏" withExtension:@"mov"]];
//创建AVPlayerItem
AVPlayerItem *item = [AVPlayerItem playerItemWithAsset:asset];
//创建AVPlayer
self.player = [AVPlayer playerWithPlayerItem:item];
//创建AVPlayerLayer
AVPlayerLayer *layer = [AVPlayerLayer playerLayerWithPlayer:self.player];
layer.bounds = self.view.bounds;
layer.position = CGPointMake(0, 0);
layer.anchorPoint = CGPointMake(0, 0);
[self.view.layer addSublayer:layer];
//监听AVPlayerItem的状态
[item addObserver:self forKeyPath:@"status" options:NSKeyValueObservingOptionNew context:nil];
//当状态是AVPlayerItemStatusReadyToPlay时,可以播放
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context{
if([keyPath isEqualToString:@"status"]){
AVPlayerItem *item = (AVPlayerItem *)object;
if(item.status == AVPlayerItemStatusReadyToPlay){
[self.player play];
}
}
}
自定义播放视图时,可以直接把播放View的layer变成AVPlayerLayer,方法是重写layerClass,uiview在初始化时,其默认的layer是CALayer,重写这个方法可以替换成CALayer的其他子类.
+ (Class)layerClass{
return [AVPlayerLayer class];
}
- (instancetype)initWithPlayer:(AVPlayer *)player{
if(self = [super initWithFrame:CGRectZero]){
self.backgroundColor = [UIColor blackColor];
self.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
//等同于[AVPlayerLayer playerLayerWithPlayer:];
[(AVPlayerLayer *)self.layer setPlayer:player];
}
return self;
}
3.CMTime处理时间
CMTime的结构为
typedef struct{
CMTimeValue value;
CMTimeScale timescale;
CMTimeFlags flags;
CMTimeEpoch epoch;
} CMTime;
其中最关键的是value和timescale,value是64位整数,timescale是32位整数,表示时间时,value是分子,timescale是分母,例如
CMTime half = CMTimeMake(1, 2); //0.5秒
CMTime fire = CMTimeMake(5, 1); //5秒
CMTime zero = kCMTimeZero; //0
AVFoundation提供了两种监听时间的API,一个是定时监听,一个是监听指定时间点
//定时0.5秒监听
[player addPeriodicTimeObserverForInterval:CMTimeMake(1, 2) queue:dispatch_get_main_queue() usingBlock:^(CMTime time) {
NSTimeInterval second = CMTimeGetSeconds(time);
}];
//指定几个时间点监听
[player addBoundaryTimeObserverForTimes:@[[NSValue valueWithCMTime:CMTimeMake(10, 1)],[NSValue valueWithCMTime:CMTimeMake(30, 1)]] queue:dispatch_get_main_queue() usingBlock:^{
//需求注意的是,这个方法不是遍历几个时间点,需要再计算确定一次当前走回调的是哪个时间点
}];
播放完成的通知,AVPlayerItemDidPlayToEndTimeNotification.
4.生成图片
AVAssetImageGenerator定义了两个方法,copyCGImageAtTime(获取指定时间的一张图片)和generateCGImagesAsynchronouslyForTimes(获取多个指定时间的一组图片)
//copyCGImageAtTime
NSTimeInterval timeSec = 10;
//获取视频图像实际开始时间 部分视频并非一开始就是有图像的 因此要获取视频的实际开始片段
AVAssetTrack *videoTrack = [asset tracksWithMediaType:AVMediaTypeVideo].firstObject;
NSArray<AVAssetTrackSegment *> *segs = videoTrack.segments;
CMTime currentStartTime = kCMTimeZero;
for (NSInteger i = 0; i < segs.count; i ++) {
if (!segs[i].isEmpty) {
currentStartTime = segs[i].timeMapping.target.start;
break;
}
}
CMTime coverAtTimeSec = CMTimeMakeWithSeconds(timeSec, asset.duration.timescale);
//如果想要获取的视频时间大于视频总时长 或者小于视频实际开始时间 则设置获取视频实际开始时间
if (CMTimeCompare(coverAtTimeSec, asset.duration) == 1 || CMTimeCompare(coverAtTimeSec, currentStartTime) == -1) {
coverAtTimeSec = currentStartTime;
}
AVAssetImageGenerator *assetGen = [AVAssetImageGenerator assetImageGeneratorWithAsset:asset];
assetGen.requestedTimeToleranceBefore = kCMTimeZero;
assetGen.requestedTimeToleranceAfter = kCMTimeZero;
assetGen.appliesPreferredTrackTransform = YES;
NSError *error = nil;
CGImageRef image = [assetGen copyCGImageAtTime:coverAtTimeSec actualTime:NULL error:&error];
if (!error) {
UIImage *videoImage = [UIImage imageWithCGImage:image];
CGImageRelease(image);
}
//generateCGImagesAsynchronouslyForTimes
NSMutableArray *times = @[].mutableCopy;
//一共生成20张
CMTimeValue unit = asset.duration.value/20;
CMTimeValue current = kCMTimeZero.value;
while(current <= asset.duration.value){
CMTime time = CMTimeMake(current, asset.duration.timescale);
[times addObject:[NSValue valueWithCMTime:time]];
current += unit;
}
[assetGen generateCGImagesAsynchronouslyForTimes:times completionHandler:^(CMTime requestedTime, CGImageRef _Nullable image, CMTime actualTime, AVAssetImageGeneratorResult result, NSError * _Nullable error) {
//requestedTime times中的某个时间点
//image 图片
//actualTime 实际生成图片的时间点
//result 结果
//error 错误信息
UIImage *img = [UIImage imageWithCGImage:image];
}];
