我能在iphone12上得到PHAsset / AVAsset是hdr视频/杜比视觉吗？

Question

我想添加HDR图标以指示某些资产是HDR，但如果这是来自iphone12的HDR视频记录，我无法获得任何信息来检查视频

Answer 1

+ (BOOL)isHDRVideo:(AVAsset *)avasset {
    if (!avasset) {
        return NO;
    }
    __block BOOL isHDRVideo = NO;
    [avasset.tracks enumerateObjectsUsingBlock:^(AVAssetTrack * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stopTracks) {
        [obj.formatDescriptions enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stopFormatDescriptions) {
            CMFormatDescriptionRef desc = (__bridge  CMVideoFormatDescriptionRef)obj;
            NSDictionary *dic = (__bridge NSDictionary *)CMFormatDescriptionGetExtensions(desc);
            NSString *imageBufferColorPrimaries = dic[(__bridge  id)kCVImageBufferColorPrimariesKey];
            if ([imageBufferColorPrimaries isEqualToString:(__bridge  id)kCVImageBufferColorPrimaries_ITU_R_2020]) {
                *stopFormatDescriptions = YES;
                *stopTracks = YES;
                isHDRVideo = YES;
            }
        }];
    }];
    
    return isHDRVideo;
}

Answer 2

更好的方法是使用simpleVideo.tracks.forEach{$0.hasMediaCharacteristic(.containsHDRVideo)}或avasset.tracks(withMediaCharacteristic：.containsHDRVideo)

Answer 3

这篇文章真的对我很有帮助，所以我觉得我必须分享我的发现，为未来的读者提供一种快速的方法。

可以扩展AVAssetTrack以移动定义CMFormatDescription的所有逻辑：

public extension AVAssetTrack {
  var isHDRVideo: Bool {
    guard
      self.mediaType == .video, // If is not a video track is not HDR
      let cmFormatDescription = self.formatDescriptions.map { $0 as!  CMFormatDescription }.first, // Safely get the description
      let transferFunction = CMFormatDescriptionGetExtension(
        cmFormatDescription,
        extensionKey: kCVImageBufferTransferFunctionKey), // It can be nil, which will make the as! CFString fail
    else { return false }

    return [
      kCVImageBufferTransferFunction_ITU_R_2020,
      kCVImageBufferTransferFunction_ITU_R_2100_HLG,
      kCVImageBufferTransferFunction_SMPTE_ST_2084_PQ
    ].contains(transferFunction as! CFString)
  }
}

然后假设你有一个名为asset的AVAsset，你可以这样做：

asset.tracks(withMediaType: .video).map { $0.isHDRVideo }

并在此基础上建立你的逻辑。