Recording video with AVAssetWriter

ViewController.swift

import UIKit

import AVFoundation

class ViewController: UIViewController {
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)

        switch AVCaptureDevice.authorizationStatus(for: .video) {
        case .notDetermined:
            AVCaptureDevice.requestAccess(for: .video) { granted in
                if granted {
                    self._setupCaptureSession()
                }
            }
        case .restricted:
            break
        case .denied:
            break
        case .authorized:
            _setupCaptureSession()
        }
    }

    private var _captureSession: AVCaptureSession?
    private var _videoOutput: AVCaptureVideoDataOutput?
    private var _assetWriter: AVAssetWriter?
    private var _assetWriterInput: AVAssetWriterInput?
    private var _adpater: AVAssetWriterInputPixelBufferAdaptor?
    private var _filename = ""
    private var _time: Double = 0
    private func _setupCaptureSession() {
        let session = AVCaptureSession()
        session.sessionPreset = .hd1920x1080

        guard
            let device = AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: .unspecified),
            let input = try? AVCaptureDeviceInput(device: device),
            session.canAddInput(input) else { return }

        session.beginConfiguration()
        session.addInput(input)
        session.commitConfiguration()

        let output = AVCaptureVideoDataOutput()
        guard session.canAddOutput(output) else { return }
        output.setSampleBufferDelegate(self, queue: DispatchQueue(label: "com.yusuke024.video"))
        session.beginConfiguration()
        session.addOutput(output)
        session.commitConfiguration()

        DispatchQueue.main.async {
            let previewView = _PreviewView()
            previewView.videoPreviewLayer.session = session
            previewView.frame = self.view.bounds
            previewView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
            self.view.insertSubview(previewView, at: 0)
        }

        session.startRunning()
        _videoOutput = output
        _captureSession = session
    }

    private enum _CaptureState {
        case idle, start, capturing, end
    }
    private var _captureState = _CaptureState.idle
    @IBAction func capture(_ sender: Any) {
        switch _captureState {
        case .idle:
            _captureState = .start
        case .capturing:
            _captureState = .end
        default:
            break
        }
    }
}

extension ViewController: AVCaptureVideoDataOutputSampleBufferDelegate {
    func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
        let timestamp = CMSampleBufferGetPresentationTimeStamp(sampleBuffer).seconds
        switch _captureState {
        case .start:
            // Set up recorder
            _filename = UUID().uuidString
            let videoPath = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!.appendingPathComponent("\(_filename).mov")
            let writer = try! AVAssetWriter(outputURL: videoPath, fileType: .mov)
            let settings = _videoOutput!.recommendedVideoSettingsForAssetWriter(writingTo: .mov)
            let input = AVAssetWriterInput(mediaType: .video, outputSettings: settings) // [AVVideoCodecKey: AVVideoCodecType.h264, AVVideoWidthKey: 1920, AVVideoHeightKey: 1080])
            input.mediaTimeScale = CMTimeScale(bitPattern: 600)
            input.expectsMediaDataInRealTime = true
            input.transform = CGAffineTransform(rotationAngle: .pi/2)
            let adapter = AVAssetWriterInputPixelBufferAdaptor(assetWriterInput: input, sourcePixelBufferAttributes: nil)
            if writer.canAdd(input) {
                writer.add(input)
            }
            writer.startWriting()
            writer.startSession(atSourceTime: .zero)
            _assetWriter = writer
            _assetWriterInput = input
            _adpater = adapter
            _captureState = .capturing
            _time = timestamp
        case .capturing:
            if _assetWriterInput?.isReadyForMoreMediaData == true {
                let time = CMTime(seconds: timestamp - _time, preferredTimescale: CMTimeScale(600))
                _adpater?.append(CMSampleBufferGetImageBuffer(sampleBuffer)!, withPresentationTime: time)
            }
            break
        case .end:
            guard _assetWriterInput?.isReadyForMoreMediaData == true, _assetWriter!.status != .failed else { break }
            let url = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!.appendingPathComponent("\(_filename).mov")
            _assetWriterInput?.markAsFinished()
            _assetWriter?.finishWriting { [weak self] in
                self?._captureState = .idle
                self?._assetWriter = nil
                self?._assetWriterInput = nil
                DispatchQueue.main.async {
                    let activity = UIActivityViewController(activityItems: [url], applicationActivities: nil)
                    self?.present(activity, animated: true, completion: nil)
                }
            }
        default:
            break
        }
    }
}

private class _PreviewView: UIView {
    override class var layerClass: AnyClass {
        return AVCaptureVideoPreviewLayer.self
    }

    var videoPreviewLayer: AVCaptureVideoPreviewLayer {
        return layer as! AVCaptureVideoPreviewLayer
    }
}

Thank you for the speedy reply!!! It turns out it was just an issue with the video settings. Thanks again!

For reference

https://developer.apple.com/library/archive/samplecode/RosyWriter/Introduction/Intro.html#//apple_ref/doc/uid/DTS40011110

I already got the solution. I added two CASampleBuffer using YUVLib. And created a single PixcelBuffer and created the Video.

…

On Sat, Apr 9, 2022 at 4:15 PM kalpesh jethva ***@***.***> wrote: ***@***.**** commented on this gist. ------------------------------ *For reference* https://developer.apple.com/library/archive/samplecode/RosyWriter/Introduction/Intro.html#//apple_ref/doc/uid/DTS40011110 — Reply to this email directly, view it on GitHub <https://gist.github.com/b5cd3909d9d7f9e919291491f6b381f0#gistcomment-4126877>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEVLCZIG6JTYDFHXGRETFY3VEFNTZANCNFSM42YFFLSQ> . You are receiving this because you commented.Message ID: ***@***.***>

this code is getting 6 to 7 frames per second I want 30 fps i.e captureOutput(_:didOutput:from:) should get called 30 times in second is there any way

i guess the device has issues with frame rate or you might have configured some preset which is too heavy to process many frames at once. The delegate is called directly from AVCameraSession.

Hey - thanks for sharing that code.
The initialization of this takes ages for me, it introduces up to 5 seconds of delay on an iPhone 11 Pro (in debug mode). In release it's a bit faster, but still far from what the default Movie output can achieve.
Any tips?