react-native-vision-camera/ios/CameraView+RecordVideo.swift

//
//  CameraView+RecordVideo.swift
//  Cuvent
//
//  Created by Marc Rousavy on 16.12.20.
//  Copyright © 2020 mrousavy. All rights reserved.
//

import AVFoundation

private var hasLoggedFrameDropWarning = false

// MARK: - CameraView + AVCaptureVideoDataOutputSampleBufferDelegate, AVCaptureAudioDataOutputSampleBufferDelegate

extension CameraView: AVCaptureVideoDataOutputSampleBufferDelegate, AVCaptureAudioDataOutputSampleBufferDelegate {
  /**
   Starts a video + audio recording with a custom Asset Writer.
   */
  func startRecording(options: NSDictionary, callback jsCallbackFunc: @escaping RCTResponseSenderBlock) {
    cameraQueue.async {
      ReactLogger.log(level: .info, message: "Starting Video recording...")
      let callback = Callback(jsCallbackFunc)

      var fileType = AVFileType.mov
      if let fileTypeOption = options["fileType"] as? String {
        guard let parsed = try? AVFileType(withString: fileTypeOption) else {
          return callback.reject(error: .parameter(.invalid(unionName: "fileType", receivedValue: fileTypeOption)))
        }
        fileType = parsed
      }

      let errorPointer = ErrorPointer(nilLiteral: ())
      let fileExtension = fileType.descriptor ?? "mov"
      guard let tempFilePath = RCTTempFilePath(fileExtension, errorPointer) else {
        return callback.reject(error: .capture(.createTempFileError), cause: errorPointer?.pointee)
      }

      ReactLogger.log(level: .info, message: "File path: \(tempFilePath)")
      let tempURL = URL(string: "file://\(tempFilePath)")!

      if let flashMode = options["flash"] as? String {
        // use the torch as the video's flash
        self.setTorchMode(flashMode)
      }

      guard let videoOutput = self.videoOutput else {
        if self.video?.boolValue == true {
          return callback.reject(error: .session(.cameraNotReady))
        } else {
          return callback.reject(error: .capture(.videoNotEnabled))
        }
      }

      // TODO: The startRecording() func cannot be async because RN doesn't allow
      //       both a callback and a Promise in a single function. Wait for TurboModules?
      //       This means that any errors that occur in this function have to be delegated through
      //       the callback, but I'd prefer for them to throw for the original function instead.

      let enableAudio = self.audio?.boolValue == true

      let onFinish = { (status: AVAssetWriter.Status, error: Error?) -> Void in
        defer {
          self.recordingSession = nil
          if enableAudio {
            self.audioQueue.async {
              self.deactivateAudioSession()
            }
          }
        }
        ReactLogger.log(level: .info, message: "RecordingSession finished with status \(status.descriptor).")
        if let error = error as NSError? {
          let description = error.description
          return callback.reject(error: .capture(.unknown(message: "An unknown recording error occured! \(description)")), cause: error)
        } else {
          if status == .completed {
            return callback.resolve([
              "path": self.recordingSession!.url.absoluteString,
              "duration": self.recordingSession!.duration,
            ])
          } else {
            return callback.reject(error: .unknown(message: "AVAssetWriter completed with status: \(status.descriptor)"))
          }
        }
      }

      do {
        self.recordingSession = try RecordingSession(url: tempURL,
                                                     fileType: fileType,
                                                     completion: onFinish)
      } catch let error as NSError {
        return callback.reject(error: .capture(.createRecorderError(message: nil)), cause: error)
      }

      // Init Video
      guard let videoSettings = videoOutput.recommendedVideoSettingsForAssetWriter(writingTo: fileType),
            !videoSettings.isEmpty else {
        return callback.reject(error: .capture(.createRecorderError(message: "Failed to get video settings!")))
      }
      self.recordingSession!.initializeVideoWriter(withSettings: videoSettings,
                                                   isVideoMirrored: self.videoOutput!.isMirrored)

      // Init Audio (optional, async)
      if enableAudio {
        self.audioQueue.async {
          // Activate Audio Session (blocking)
          self.activateAudioSession()

          guard let recordingSession = self.recordingSession else {
            // recording has already been cancelled
            return
          }
          if let audioOutput = self.audioOutput,
             let audioSettings = audioOutput.recommendedAudioSettingsForAssetWriter(writingTo: fileType) as? [String: Any] {
            recordingSession.initializeAudioWriter(withSettings: audioSettings)
          }

          // Finally start recording, with or without audio.
          recordingSession.start()
          self.isRecording = true
        }
      } else {
        // start recording session without audio.
        self.recordingSession!.start()
        self.isRecording = true
      }
    }
  }

  func stopRecording(promise: Promise) {
    cameraQueue.async {
      self.isRecording = false

      withPromise(promise) {
        guard let recordingSession = self.recordingSession else {
          throw CameraError.capture(.noRecordingInProgress)
        }
        recordingSession.finish()
        return nil
      }
    }
  }

  // TODO: Implement for JS
  func pauseRecording(promise: Promise) {
    cameraQueue.async {
      withPromise(promise) {
        if self.isRecording {
          self.isRecording = false
          return nil
        } else {
          throw CameraError.capture(.noRecordingInProgress)
        }
      }
    }
  }

  // TODO: Implement for JS
  func resumeRecording(promise: Promise) {
    cameraQueue.async {
      withPromise(promise) {
        if !self.isRecording {
          self.isRecording = true
          return nil
        } else {
          throw CameraError.capture(.noRecordingInProgress)
        }
      }
    }
  }

  public final func captureOutput(_ captureOutput: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from _: AVCaptureConnection) {
    if isRecording {
      guard let recordingSession = recordingSession else {
        return invokeOnError(.capture(.unknown(message: "isRecording was true but the RecordingSession was null!")))
      }
      switch captureOutput {
      case is AVCaptureVideoDataOutput:
        recordingSession.appendBuffer(sampleBuffer, type: .video, timestamp: CMSampleBufferGetPresentationTimeStamp(sampleBuffer))
      case is AVCaptureAudioDataOutput:
        let timestamp = CMSyncConvertTime(CMSampleBufferGetPresentationTimeStamp(sampleBuffer),
                                          from: audioCaptureSession.masterClock!,
                                          to: captureSession.masterClock!)
        recordingSession.appendBuffer(sampleBuffer, type: .audio, timestamp: timestamp)
      default:
        break
      }
    }

    if let frameProcessor = frameProcessorCallback, captureOutput is AVCaptureVideoDataOutput {
      // check if last frame was x nanoseconds ago, effectively throttling FPS
      let diff = DispatchTime.now().uptimeNanoseconds - lastFrameProcessorCall.uptimeNanoseconds
      let secondsPerFrame = 1.0 / frameProcessorFps.doubleValue
      let nanosecondsPerFrame = secondsPerFrame * 1_000_000_000.0
      if diff > UInt64(nanosecondsPerFrame) {
        frameProcessor(sampleBuffer)
        lastFrameProcessorCall = DispatchTime.now()
      }
    }
  }

  #if DEBUG
    public final func captureOutput(_ captureOutput: AVCaptureOutput, didDrop buffer: CMSampleBuffer, from _: AVCaptureConnection) {
      if frameProcessorCallback != nil && !hasLoggedFrameDropWarning && captureOutput is AVCaptureVideoDataOutput {
        let reason = findFrameDropReason(inBuffer: buffer)
        ReactLogger.log(level: .warning,
                        message: "Dropped a Frame. This might indicate that your Frame Processor is doing too much work. " +
                          "Either throttle the frame processor's frame rate, or optimize your frame processor's execution speed. Frame drop reason: \(reason)",
                        alsoLogToJS: true)
        hasLoggedFrameDropWarning = true
      }
    }

    private final func findFrameDropReason(inBuffer buffer: CMSampleBuffer) -> String {
      var mode: CMAttachmentMode = 0
      guard let reason = CMGetAttachment(buffer,
                                         key: kCMSampleBufferAttachmentKey_DroppedFrameReason,
                                         attachmentModeOut: &mode) else {
        return "unknown"
      }
      return String(describing: reason)
    }
  #endif
}