如何在播放m3u8视频流之前获取帧图像？iOS

Question

我有一个需求：在播放视频流（m3u8）之前获取帧图像，作为视频预览显示。我使用AVPlayerItemVideoOutput的copyPixelBufferForItemTime: itemTimeForDisplay:方法只能在播放视频流时获取到帧图像，你有其他方法吗？谢谢！

这是我的代码：

CMTime itemTime = self.playerItem.currentTime;
CVPixelBufferRef pixelBuffer = [_playerItemVideoOutput copyPixelBufferForItemTime:itemTime itemTimeForDisplay:nil];
CIImage *ciImage = [CIImage imageWithCVPixelBuffer:pixelBuffer];
CIContext *temporaryContext = [CIContext contextWithOptions:nil];
CGImageRef videoImage = [temporaryContext
                                 createCGImage:ciImage
                                 fromRect:CGRectMake(0, 0,
                                                     CVPixelBufferGetWidth(pixelBuffer),
                                                     CVPixelBufferGetHeight(pixelBuffer))];

UIImage *uiImage = [UIImage imageWithCGImage:videoImage];
CGImageRelease(videoImage);
NSLog(@"uiImage：%@", uiImage);

- Sanchain

Answer 1

编辑:
我已将此项目转换为Swift。这是新的存储库ACThumbnailGenerator-Swift。

使用方法:

var generator: ACThumbnailGenerator!

func captureSomeImage() {
    let streamUrl = URL(string: "https://p-events-delivery.akamaized.net/18oijbasfvuhbfsdvoijhbsdfvljkb6/m3u8/hls_vod_mvp.m3u8")!
    generator = ACThumbnailGenerator(streamUrl: streamUrl)
    generator.delegate = self
    generator.captureImage(at: 300)
}

func generator(_ generator: ACThumbnailGenerator, didCapture image: UIImage, at position: Double) {
    // Use `image`
}

原始答案：

正如您在问题中所述，AVPlayerItemVideoOutput是正确的方法，但是视频不需要播放，只需要“准备就绪”。

我创建了一个简单易用的实用程序，遵循这个原则从远程流中提取缩略图。 (https://github.com/acotilla91/ACThumbnailGenerator)

使用方法：

double bitRate = 1000000; // force video bit rate (can be use to cap video quality and improve performance). Pass 0 to use default bit rate.
self.thumbnailGenerator = [[ACThumbnailGenerator alloc] initWithPreferredBitRate:bitRate];

NSURL *videoURL = [NSURL URLWithString:@"http://qthttp.apple.com.edgesuite.net/1010qwoeiuryfg/sl.m3u8"];
int position = 10; // video position (in seconds) from where thumbnail should be extracted. Always pass 0 for live streams.

[self.thumbnailGenerator loadImageFrom:videoURL position:position withCompletionBlock:^(UIImage *image) {

    // use `image`            

}];

希望有所帮助。

- Alejandro Cotilla

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