How would I put together a video using the AVAssetWriter in swift? - macos

Question

I'm currently making a small app that timelapses the webcam on my mac, saves the captured frame to png, and I am looking into exporting the captured frames as a single video.
I use CGImage to handle the original images and have them set in an array but I'm unsure on there to go from there. I gather from my own research that I have to use AVAssetWriter and AVAssetWriterInput somehow.
I've had a look about on here, read the apple docs and searched google. But all the guides etc, are in obj-c rather than swift which is making it really difficult to understand (As I have no experience in Obj-C).
Any help would be very much appreciated.
Many Thanks,
Luke.

Answer 1

I solved the same problem in Swift. Starting from an array oh UIImage, try this (it's a little long :-) but works):
var choosenPhotos: [UIImage] = [] *** your array of UIImages ***
var outputSize = CGSizeMake(1280, 720)
func build(outputSize outputSize: CGSize) {
let fileManager = NSFileManager.defaultManager()
let urls = fileManager.URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
guard let documentDirectory: NSURL = urls.first else {
fatalError("documentDir Error")
}
let videoOutputURL = documentDirectory.URLByAppendingPathComponent("OutputVideo.mp4")
if NSFileManager.defaultManager().fileExistsAtPath(videoOutputURL.path!) {
do {
try NSFileManager.defaultManager().removeItemAtPath(videoOutputURL.path!)
} catch {
fatalError("Unable to delete file: \(error) : \(__FUNCTION__).")
}
}
guard let videoWriter = try? AVAssetWriter(URL: videoOutputURL, fileType: AVFileTypeMPEG4) else {
fatalError("AVAssetWriter error")
}
let outputSettings = [AVVideoCodecKey : AVVideoCodecH264, AVVideoWidthKey : NSNumber(float: Float(outputSize.width)), AVVideoHeightKey : NSNumber(float: Float(outputSize.height))]
guard videoWriter.canApplyOutputSettings(outputSettings, forMediaType: AVMediaTypeVideo) else {
fatalError("Negative : Can't apply the Output settings...")
}
let videoWriterInput = AVAssetWriterInput(mediaType: AVMediaTypeVideo, outputSettings: outputSettings)
let sourcePixelBufferAttributesDictionary = [kCVPixelBufferPixelFormatTypeKey as String : NSNumber(unsignedInt: kCVPixelFormatType_32ARGB), kCVPixelBufferWidthKey as String: NSNumber(float: Float(outputSize.width)), kCVPixelBufferHeightKey as String: NSNumber(float: Float(outputSize.height))]
let pixelBufferAdaptor = AVAssetWriterInputPixelBufferAdaptor(assetWriterInput: videoWriterInput, sourcePixelBufferAttributes: sourcePixelBufferAttributesDictionary)
if videoWriter.canAddInput(videoWriterInput) {
videoWriter.addInput(videoWriterInput)
}
if videoWriter.startWriting() {
videoWriter.startSessionAtSourceTime(kCMTimeZero)
assert(pixelBufferAdaptor.pixelBufferPool != nil)
let media_queue = dispatch_queue_create("mediaInputQueue", nil)
videoWriterInput.requestMediaDataWhenReadyOnQueue(media_queue, usingBlock: { () -> Void in
let fps: Int32 = 1
let frameDuration = CMTimeMake(1, fps)
var frameCount: Int64 = 0
var appendSucceeded = true
while (!self.choosenPhotos.isEmpty) {
if (videoWriterInput.readyForMoreMediaData) {
let nextPhoto = self.choosenPhotos.removeAtIndex(0)
let lastFrameTime = CMTimeMake(frameCount, fps)
let presentationTime = frameCount == 0 ? lastFrameTime : CMTimeAdd(lastFrameTime, frameDuration)
var pixelBuffer: CVPixelBuffer? = nil
let status: CVReturn = CVPixelBufferPoolCreatePixelBuffer(kCFAllocatorDefault, pixelBufferAdaptor.pixelBufferPool!, &pixelBuffer)
if let pixelBuffer = pixelBuffer where status == 0 {
let managedPixelBuffer = pixelBuffer
CVPixelBufferLockBaseAddress(managedPixelBuffer, 0)
let data = CVPixelBufferGetBaseAddress(managedPixelBuffer)
let rgbColorSpace = CGColorSpaceCreateDeviceRGB()
let context = CGBitmapContextCreate(data, Int(self.outputSize.width), Int(self.outputSize.height), 8, CVPixelBufferGetBytesPerRow(managedPixelBuffer), rgbColorSpace, CGImageAlphaInfo.PremultipliedFirst.rawValue)
CGContextClearRect(context, CGRectMake(0, 0, CGFloat(self.outputSize.width), CGFloat(self.outputSize.height)))
let horizontalRatio = CGFloat(self.outputSize.width) / nextPhoto.size.width
let verticalRatio = CGFloat(self.outputSize.height) / nextPhoto.size.height
//aspectRatio = max(horizontalRatio, verticalRatio) // ScaleAspectFill
let aspectRatio = min(horizontalRatio, verticalRatio) // ScaleAspectFit
let newSize:CGSize = CGSizeMake(nextPhoto.size.width * aspectRatio, nextPhoto.size.height * aspectRatio)
let x = newSize.width < self.outputSize.width ? (self.outputSize.width - newSize.width) / 2 : 0
let y = newSize.height < self.outputSize.height ? (self.outputSize.height - newSize.height) / 2 : 0
CGContextDrawImage(context, CGRectMake(x, y, newSize.width, newSize.height), nextPhoto.CGImage)
CVPixelBufferUnlockBaseAddress(managedPixelBuffer, 0)
appendSucceeded = pixelBufferAdaptor.appendPixelBuffer(pixelBuffer, withPresentationTime: presentationTime)
} else {
print("Failed to allocate pixel buffer")
appendSucceeded = false
}
}
if !appendSucceeded {
break
}
frameCount++
}
videoWriterInput.markAsFinished()
videoWriter.finishWritingWithCompletionHandler { () -> Void in
print("FINISHED!!!!!")
}
})
}
}

Answer 2

Following is code to generate video from images working in Xcode 11.3.1 and Swift 5.1. This code is generated from the answer of #aleciufs Sep 25 '15 answer. The following function assumes the images are loaded and available var images array [UIImage]
func build(outputSize: CGSize) {
let fileManager = FileManager.default
let urls = fileManager.urls(for: .cachesDirectory, in: .userDomainMask)
guard let documentDirectory = urls.first else {
fatalError("documentDir Error")
}
let videoOutputURL = documentDirectory.appendingPathComponent("OutputVideo.mp4")
if FileManager.default.fileExists(atPath: videoOutputURL.path) {
do {
try FileManager.default.removeItem(atPath: videoOutputURL.path)
} catch {
fatalError("Unable to delete file: \(error) : \(#function).")
}
}
guard let videoWriter = try? AVAssetWriter(outputURL: videoOutputURL, fileType: AVFileType.mp4) else {
fatalError("AVAssetWriter error")
}
let outputSettings = [AVVideoCodecKey : AVVideoCodecType.h264, AVVideoWidthKey : NSNumber(value: Float(outputSize.width)), AVVideoHeightKey : NSNumber(value: Float(outputSize.height))] as [String : Any]
guard videoWriter.canApply(outputSettings: outputSettings, forMediaType: AVMediaType.video) else {
fatalError("Negative : Can't apply the Output settings...")
}
let videoWriterInput = AVAssetWriterInput(mediaType: AVMediaType.video, outputSettings: outputSettings)
let sourcePixelBufferAttributesDictionary = [
kCVPixelBufferPixelFormatTypeKey as String : NSNumber(value: kCVPixelFormatType_32ARGB),
kCVPixelBufferWidthKey as String: NSNumber(value: Float(outputSize.width)),
kCVPixelBufferHeightKey as String: NSNumber(value: Float(outputSize.height))
]
let pixelBufferAdaptor = AVAssetWriterInputPixelBufferAdaptor(assetWriterInput: videoWriterInput, sourcePixelBufferAttributes: sourcePixelBufferAttributesDictionary)
if videoWriter.canAdd(videoWriterInput) {
videoWriter.add(videoWriterInput)
}
if videoWriter.startWriting() {
videoWriter.startSession(atSourceTime: CMTime.zero)
assert(pixelBufferAdaptor.pixelBufferPool != nil)
let media_queue = DispatchQueue(__label: "mediaInputQueue", attr: nil)
videoWriterInput.requestMediaDataWhenReady(on: media_queue, using: { () -> Void in
let fps: Int32 = 2
let frameDuration = CMTimeMake(value: 1, timescale: fps)
var frameCount: Int64 = 0
var appendSucceeded = true
while (!self.images.isEmpty) {
if (videoWriterInput.isReadyForMoreMediaData) {
let nextPhoto = self.images.remove(at: 0)
let lastFrameTime = CMTimeMake(value: frameCount, timescale: fps)
let presentationTime = frameCount == 0 ? lastFrameTime : CMTimeAdd(lastFrameTime, frameDuration)
var pixelBuffer: CVPixelBuffer? = nil
let status: CVReturn = CVPixelBufferPoolCreatePixelBuffer(kCFAllocatorDefault, pixelBufferAdaptor.pixelBufferPool!, &pixelBuffer)
if let pixelBuffer = pixelBuffer, status == 0 {
let managedPixelBuffer = pixelBuffer
CVPixelBufferLockBaseAddress(managedPixelBuffer, [])
let data = CVPixelBufferGetBaseAddress(managedPixelBuffer)
let rgbColorSpace = CGColorSpaceCreateDeviceRGB()
let context = CGContext(data: data, width: Int(outputSize.width), height: Int(outputSize.height), bitsPerComponent: 8, bytesPerRow: CVPixelBufferGetBytesPerRow(managedPixelBuffer), space: rgbColorSpace, bitmapInfo: CGImageAlphaInfo.premultipliedFirst.rawValue)
context?.clear(CGRect(x: 0, y: 0, width: outputSize.width, height: outputSize.height))
let horizontalRatio = CGFloat(outputSize.width) / nextPhoto.size.width
let verticalRatio = CGFloat(outputSize.height) / nextPhoto.size.height
let aspectRatio = min(horizontalRatio, verticalRatio) // ScaleAspectFit
let newSize = CGSize(width: nextPhoto.size.width * aspectRatio, height: nextPhoto.size.height * aspectRatio)
let x = newSize.width < outputSize.width ? (outputSize.width - newSize.width) / 2 : 0
let y = newSize.height < outputSize.height ? (outputSize.height - newSize.height) / 2 : 0
context?.draw(nextPhoto.cgImage!, in: CGRect(x: x, y: y, width: newSize.width, height: newSize.height))
CVPixelBufferUnlockBaseAddress(managedPixelBuffer, [])
appendSucceeded = pixelBufferAdaptor.append(pixelBuffer, withPresentationTime: presentationTime)
} else {
print("Failed to allocate pixel buffer")
appendSucceeded = false
}
}
if !appendSucceeded {
break
}
frameCount += 1
}
videoWriterInput.markAsFinished()
videoWriter.finishWriting { () -> Void in
print("FINISHED!!!!!")
saveVideoToLibrary(videoURL: videoOutputURL)
}
})
}
}
The extra function I provide is:
func saveVideoToLibrary(videoURL: URL) {
PHPhotoLibrary.shared().performChanges({
PHAssetChangeRequest.creationRequestForAssetFromVideo(atFileURL: videoURL)
}) { saved, error in
if let error = error {
print("Error saving video to librayr: \(error.localizedDescription)")
}
if saved {
print("Video save to library")
}
}
}