iOS:AVPlayer - 获取视频当前帧的快照

Question

我花了一整天时间,经历了很多SO答案,Apple参考文献,文档等,但都没有成功.

我想要一个简单的事情:我正在使用AVPlayer播放视频,我想暂停它并获取当前帧UIImage.而已.

我的视频是一个位于互联网上的m3u8文件,它在AVPlayerLayer没有任何问题的情况下正常播放.

我试过了什么:

1. AVAssetImageGenerator.它不起作用,该方法copyCGImageAtTime:actualTime: error:返回null image ref.根据答案,此处 AVAssetImageGenerator不适用于流媒体视频.
2. 拍摄玩家视图的快照.我第一次尝试renderInContext:的AVPlayerLayer,但后来我意识到,这不是渲染这种"特殊"层.然后我发现了iOS 7中引入的一种新方法 - drawViewHierarchyInRect:afterScreenUpdates:它应该能够渲染特殊的图层,但没有运气,仍然可以获得带有空白黑色区域的UI快照,其中显示视频.
3. AVPlayerItemVideoOutput.我为我添加了一个视频输出AVPlayerItem,但每当我调用hasNewPixelBufferForItemTime:它时返回NO.我想问题是再次流式传输视频,我并不孤单.
4. AVAssetReader.我正在考虑尝试,但决定在这里找到相关问题后不要浪费时间.

所以,有没有办法得到我现在在屏幕上看到的东西的快照？我简直不敢相信.

Answer 1

AVPlayerItemVideoOutput从m3u8对我来说效果很好。也许是因为我不咨询hasNewPixelBufferForItemTime而只是打电话copyPixelBufferForItemTime吗？这段代码产生了a CVPixelBuffer而不是a UIImage，但是有描述如何做到的答案。

这个答案大多来自这里

#import "ViewController.h"
#import <AVFoundation/AVFoundation.h>

@interface ViewController ()

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

@end

@implementation ViewController
- (void)setupPlayerWithLoadedAsset:(AVAsset *)asset {
    NSDictionary* settings = @{ (id)kCVPixelBufferPixelFormatTypeKey : @(kCVPixelFormatType_32BGRA) };
    self.playerOutput = [[AVPlayerItemVideoOutput alloc] initWithPixelBufferAttributes:settings];
    self.playerItem = [AVPlayerItem playerItemWithAsset:asset];
    [self.playerItem addOutput:self.playerOutput];
    self.player = [AVPlayer playerWithPlayerItem:self.playerItem];

    AVPlayerLayer *playerLayer = [AVPlayerLayer playerLayerWithPlayer:self.player];
    playerLayer.frame = self.view.frame;
    [self.view.layer addSublayer:playerLayer];

    [self.player play];
}

- (IBAction)grabFrame {
    CVPixelBufferRef buffer = [self.playerOutput copyPixelBufferForItemTime:[self.playerItem currentTime] itemTimeForDisplay:nil];
    NSLog(@"The image: %@", buffer);
}

- (void)viewDidLoad {
    [super viewDidLoad];


    NSURL *someUrl = [NSURL URLWithString:@"http://qthttp.apple.com.edgesuite.net/1010qwoeiuryfg/sl.m3u8"];
    AVURLAsset *asset = [AVURLAsset URLAssetWithURL:someUrl options:nil];

    [asset loadValuesAsynchronouslyForKeys:[NSArray arrayWithObject:@"tracks"] completionHandler:^{

        NSError* error = nil;
        AVKeyValueStatus status = [asset statusOfValueForKey:@"tracks" error:&error];
        if (status == AVKeyValueStatusLoaded)
        {
            dispatch_async(dispatch_get_main_queue(), ^{
                [self setupPlayerWithLoadedAsset:asset];
            });
        }
        else
        {
            NSLog(@"%@ Failed to load the tracks.", self);
        }
    }];
}

@end

Answer 2

AVAssetImageGenerator是拍摄视频快照的最佳方式,此方法异步返回UIImage:

import AVFoundation

// ...

var player:AVPlayer? = // ...

func screenshot(handler:@escaping ((UIImage)->Void)) {
    guard let player = player ,
        let asset = player.currentItem?.asset else {
            return
    }

    let imageGenerator = AVAssetImageGenerator(asset: asset)
    imageGenerator.appliesPreferredTrackTransform = true
    let times = [NSValue(time:player.currentTime())]

    imageGenerator.generateCGImagesAsynchronously(forTimes: times) { _, image, _, _, _ in
        if image != nil {
            handler(UIImage(cgImage: image!))
        }
    }
}

(这是Swift 4.2)