User Profile

So I've been trying for weeks now to implement a compression mechanism into my app project that compresses MV-HEVC video files in-app without stripping videos of their 3D properties, but every single implementation I have tried has either stripped the encoded MV-HEVC video file of its 3D properties (making the video monoscopic), or has crashed with a fatal error. I've read the Reading multiview 3D video files and Converting side-by-side 3D video to multiview HEVC documentation files, but was unable to myself come out with anything useful. My question therefore is: How do you go about compressing/encoding an MV-HEVC video file in-app whilst preserving the stereoscopic/3D properties of that MV-HEVC video file? Below is the best implementation I was able to come up with (which simply compresses uploaded MV-HEVC videos with an arbitrary bit rate). With this implementation (my compressVideo function), the MV-HEVC files that go through it are compressed fine, but the final result is the loss of that MV-HEVC video file's stereoscopic/3D properties. If anyone could point me in the right direction with anything it would be greatly, greatly appreciated. My current implementation (that strips MV-HEVC videos of their stereoscopic/3D properties): static func compressVideo(sourceUrl: URL, bitrate: Int, completion: @escaping (Result<URL, Error>) -> Void) { let asset = AVAsset(url: sourceUrl) asset.loadTracks(withMediaType: .video) { videoTracks, videoError in guard let videoTrack = videoTracks?.first, videoError == nil else { completion(.failure(videoError ?? NSError(domain: "VideoUploader", code: -1, userInfo: [NSLocalizedDescriptionKey: "Failed to load video track"]))) return } asset.loadTracks(withMediaType: .audio) { audioTracks, audioError in guard let audioTrack = audioTracks?.first, audioError == nil else { completion(.failure(audioError ?? NSError(domain: "VideoUploader", code: -2, userInfo: [NSLocalizedDescriptionKey: "Failed to load audio track"]))) return } let outputUrl = sourceUrl.deletingLastPathComponent().appendingPathComponent(UUID().uuidString).appendingPathExtension("mov") guard let assetReader = try? AVAssetReader(asset: asset), let assetWriter = try? AVAssetWriter(outputURL: outputUrl, fileType: .mov) else { completion(.failure(NSError(domain: "VideoUploader", code: -3, userInfo: [NSLocalizedDescriptionKey: "AssetReader/Writer initialization failed"]))) return } let videoReaderSettings: [String: Any] = [kCVPixelBufferPixelFormatTypeKey as String: kCVPixelFormatType_32ARGB] let videoSettings: [String: Any] = [ AVVideoCompressionPropertiesKey: [AVVideoAverageBitRateKey: bitrate], AVVideoCodecKey: AVVideoCodecType.hevc, AVVideoHeightKey: videoTrack.naturalSize.height, AVVideoWidthKey: videoTrack.naturalSize.width ] let assetReaderVideoOutput = AVAssetReaderTrackOutput(track: videoTrack, outputSettings: videoReaderSettings) let assetReaderAudioOutput = AVAssetReaderTrackOutput(track: audioTrack, outputSettings: nil) if assetReader.canAdd(assetReaderVideoOutput) { assetReader.add(assetReaderVideoOutput) } else { completion(.failure(NSError(domain: "VideoUploader", code: -4, userInfo: [NSLocalizedDescriptionKey: "Couldn't add video output reader"]))) return } if assetReader.canAdd(assetReaderAudioOutput) { assetReader.add(assetReaderAudioOutput) } else { completion(.failure(NSError(domain: "VideoUploader", code: -5, userInfo: [NSLocalizedDescriptionKey: "Couldn't add audio output reader"]))) return } let audioInput = AVAssetWriterInput(mediaType: .audio, outputSettings: nil) let videoInput = AVAssetWriterInput(mediaType: .video, outputSettings: videoSettings) videoInput.transform = videoTrack.preferredTransform assetWriter.shouldOptimizeForNetworkUse = true assetWriter.add(videoInput) assetWriter.add(audioInput) assetReader.startReading() assetWriter.startWriting() assetWriter.startSession(atSourceTime: CMTime.zero) let videoInputQueue = DispatchQueue(label: "videoQueue") let audioInputQueue = DispatchQueue(label: "audioQueue") videoInput.requestMediaDataWhenReady(on: videoInputQueue) { while videoInput.isReadyForMoreMediaData { if let sample = assetReaderVideoOutput.copyNextSampleBuffer() { videoInput.append(sample) } else { videoInput.markAsFinished() if assetReader.status == .completed { assetWriter.finishWriting { completion(.success(outputUrl)) } } break } } } audioInput.requestMediaDataWhenReady(on: audioInputQueue) { while audioInput.isReadyForMoreMediaData { if let sample = assetReaderAudioOutput.copyNextSampleBuffer() { audioInput.append(sample) } else { audioInput.markAsFinished() break } } } } } }