Is there any way to compress video quickly? - ios

Question

I am using AVAssetWriter for compressing video but it taking 20 to 25 seconds to compress a video of size 160 in 12 mb. i want fix bitrate of 1600 kbps and natural frame of video. Is there any way to compress quickly?
func compressFile(urlToCompress: URL, outputURL: URL, completion:#escaping (URL)->Void) {
//video file to make the asset
var audioFinished = false
var videoFinished = false
let asset = AVAsset(url: urlToCompress);
//create asset reader
do{
assetReader = try AVAssetReader(asset: asset)
} catch{
assetReader = nil
}
guard let reader = assetReader else{
fatalError("Could not initalize asset reader probably failed its try catch")
}
let videoTrack = asset.tracks(withMediaType: AVMediaType.video).first!
let audioTrack = asset.tracks(withMediaType: AVMediaType.audio).first!
let videoReaderSettings: [String:Any] = [(kCVPixelBufferPixelFormatTypeKey as String?)!:kCVPixelFormatType_32ARGB ]
// MARK: ADJUST BIT RATE OF VIDEO HERE
let videoSettings:[String:Any] = [
AVVideoCompressionPropertiesKey: [AVVideoAverageBitRateKey: self.bitrate] as Any,
AVVideoCodecKey: AVVideoCodecType.h264,
AVVideoHeightKey: videoTrack.naturalSize.height,//352,
AVVideoWidthKey: videoTrack.naturalSize.width //640//
]
let assetReaderVideoOutput = AVAssetReaderTrackOutput(track: videoTrack, outputSettings: videoReaderSettings)
let assetReaderAudioOutput = AVAssetReaderTrackOutput(track: audioTrack, outputSettings: nil)
if reader.canAdd(assetReaderVideoOutput){
reader.add(assetReaderVideoOutput)
}else{
fatalError("Couldn't add video output reader")
}
if reader.canAdd(assetReaderAudioOutput){
reader.add(assetReaderAudioOutput)
}else{
fatalError("Couldn't add audio output reader")
}
let audioInput = AVAssetWriterInput(mediaType: AVMediaType.audio, outputSettings: nil)
let videoInput = AVAssetWriterInput(mediaType: AVMediaType.video, outputSettings: videoSettings)
videoInput.transform = videoTrack.preferredTransform
//we need to add samples to the video input
let videoInputQueue = DispatchQueue(label: "videoQueue")
let audioInputQueue = DispatchQueue(label: "audioQueue")
do{
assetWriter = try AVAssetWriter(outputURL: outputURL, fileType: AVFileType.mov)
}catch{
assetWriter = nil
}
guard let writer = assetWriter else{
fatalError("assetWriter was nil")
}
writer.shouldOptimizeForNetworkUse = true
writer.add(videoInput)
writer.add(audioInput)
writer.startWriting()
reader.startReading()
writer.startSession(atSourceTime: CMTime.zero)
let closeWriter:()->Void = {
if (audioFinished && videoFinished){
self.assetWriter?.finishWriting(completionHandler: {
self.checkFileSize(sizeUrl: (self.assetWriter?.outputURL)!, message: "The file size of the compressed file is: ")
completion((self.assetWriter?.outputURL)!)
})
self.assetReader?.cancelReading()
}
}
audioInput.requestMediaDataWhenReady(on: audioInputQueue) {
while(audioInput.isReadyForMoreMediaData){
let sample = assetReaderAudioOutput.copyNextSampleBuffer()
if (sample != nil){
audioInput.append(sample!)
}else{
audioInput.markAsFinished()
DispatchQueue.main.async {
audioFinished = true
closeWriter()
}
break;
}
}
}
videoInput.requestMediaDataWhenReady(on: videoInputQueue) {
//request data here
while(videoInput.isReadyForMoreMediaData){
let sample = assetReaderVideoOutput.copyNextSampleBuffer()
if (sample != nil){
videoInput.append(sample!)
}else{
videoInput.markAsFinished()
DispatchQueue.main.async {
videoFinished = true
closeWriter()
}
break;
}
}
}
}
Edit:- Using above method it converts video on different bitrate not on defined bit rate why?
Any Direction will appreciate.
Thanks in advance

Answer 1

This is a non-trivial problem. There is no "simple" answer to how to encode faster. If you are unfamiliar with this, you are better off picking another codec bit-rates and codecs that encode faster. You have to assume the library is doing it's job. So, there a few things you can do:
Make the source file smaller -- or chunk it
Run it on a cloud service which has beefier hardware
You can choose another codec and a lower set of bit-rate + width and height. (https://developer.apple.com/documentation/avfoundation/avvideocodectype)
You can potentially spin up multiple threads and encode faster this way but I doubt it would gain you much