獲取視頻元數據，如何檢測視頻是從前置還是后置攝像頭拍攝的

Question

我想知道視頻是從前置還是后置攝像頭拍攝的。 作為info返回零。

let asset: PHAsset! 
 let manager = PHImageManager.default()
    if asset.mediaType == .video {
      let options: PHVideoRequestOptions = PHVideoRequestOptions()
      options.version = .original
      options.isNetworkAccessAllowed = true
      manager.requestAVAsset(forVideo: asset, options: options) { (asset, audiomix, info) in
}

Answer 1

令人驚訝的是，您可以將PHImageManager.requestImageDataAndOrientation用於視頻資產。

Xcode 12.5
iPhone SE 2020 (iOS 14.6)

觀察

let imageManager = PHImageManager.default()
imageManager.requestImageDataAndOrientation(for: videoPHAsset, options: nil) { (data, string, orientation, info) in
    if let data = data, let ciImage = CIImage(data: data) {
        print(ciImage.properties)
    }
}

將ciImage.properties序列化為 JSON 后，我得到以下結果。

1. 視頻（后置攝像頭）

{"ColorModel":"RGB","PixelHeight":1920,"{Exif}":{"ColorSpace":1,"PixelXDimension":1080,"ExifVersion":[2,2,1],"FlashPixVersion":[1,0],"PixelYDimension":1920,"SceneCaptureType":0,"ComponentsConfiguration":[1,2,3,0]},"ProfileName":"HDTV","DPIHeight":72,"PixelWidth":1080,"{TIFF}":{"YResolution":72,"ResolutionUnit":2,"XResolution":72},"{JFIF}":{"DensityUnit":0,"YDensity":72,"JFIFVersion":[1,0,1],"XDensity":72},"Depth":8,"DPIWidth":72}

2.視頻（前置攝像頭）

{"Depth":8,"{TIFF}":{"YResolution":72,"ResolutionUnit":2,"XResolution":72},"PixelHeight":1334,"{JFIF}":{"DensityUnit":0,"YDensity":72,"JFIFVersion":[1,0,1],"XDensity":72},"ProfileName":"sRGB IEC61966-2.1","PixelWidth":750,"ColorModel":"RGB","DPIHeight":72,"DPIWidth":72,"{Exif}":{"ColorSpace":1,"PixelXDimension":750,"ExifVersion":[2,2,1],"FlashPixVersion":[1,0],"PixelYDimension":1334,"SceneCaptureType":0,"ComponentsConfiguration":[1,2,3,0]}}

3. 截圖

{"ColorModel":"RGB","{Exif}":{"PixelXDimension":750,"PixelYDimension":1334,"DateTimeOriginal":"2021:01:21 14:25:56","UserComment":"Screenshot"},"{PNG}":{"InterlaceType":0},"HasAlpha":true,"Depth":16,"{TIFF}":{"Orientation":1},"PixelHeight":1334,"ProfileName":"Display P3","PixelWidth":750,"Orientation":1}

4. 照片（有大量信息和 JSON 序列化崩潰，所以我只提取了“{Exif}”部分）

{"ExifVersion":[2,3,1],"Flash":24,"LensModel":"iPhone SE (2nd generation) back camera 3.99mm f\\/1.8","OffsetTimeDigitized":"+05:30","SubsecTimeOriginal":"630","LensSpecification":[3.990000009536743,3.990000009536743,1.7999999523162842,1.7999999523162842],"ExposureMode":0,"CompositeImage":2,"LensMake":"Apple","FNumber":1.8,"OffsetTimeOriginal":"+05:30","PixelYDimension":3024,"ApertureValue":1.6959938128383605,"ExposureBiasValue":0,"MeteringMode":5,"ISOSpeedRatings":[400],"ShutterSpeedValue":4.6443251405083465,"SceneCaptureType":0,"FocalLength":3.99,"DateTimeOriginal":"2021:01:21 20:47:05","SceneType":1,"FlashPixVersion":[1,0],"ColorSpace":65535,"SubjectArea":[2013,1511,2217,1330],"PixelXDimension":4032,"FocalLenIn35mmFilm":28,"SubsecTimeDigitized":"630","OffsetTime":"+05:30","SensingMethod":2,"BrightnessValue":0.06030004492448258,"DateTimeDigitized":"2021:01:21 20:47:05","ComponentsConfiguration":[1,2,3,0],"WhiteBalance":0,"ExposureTime":0.04,"ExposureProgram":2}

視頻有"ExifVersion":[2,2,1]而照片有"ExifVersion":[2,3,1] 。 視頻的 exif 根本不提供有關相機的任何有用信息 - 而照片的 exif 提供。 所有的視頻和照片都是在同一部手機上拍攝的。

在這一點上，如果這些信息甚至被編碼到視頻幀中，仍然毫無頭緒。

Answer 2

這可能對你有幫助。 如果您通過 PHAssetCollectionSubtype.smartAlbumSelfPortraits 過濾獲得 PHAssets，這些資產似乎是用前置攝像頭拍攝的視頻。

 let collection = PHAssetCollection.fetchAssetCollections(with: PHAssetCollectionType.smartAlbum,
                                                        subtype: PHAssetCollectionSubtype.smartAlbumSelfPortraits,
                                                        options: nil)

盡管該視頻沒有人臉，但它目前在 iOS 上被歸類為自拍。 我用 iPhone 12 mini/ iOS15 測試過。

蘋果也這樣說：

一個智能相冊，將使用設備的前置攝像頭拍攝的所有照片和視頻分組。

塊引用

https://developer.apple.com/documentation/photokit/phassetcollectionsubtype/smartalbumselfportraits

所以也許你可以預取自拍相冊資產，然后檢查相冊中是否包含資產以檢測它是由前置攝像頭拍攝的。