Swift AVFoundation Reading and Analyzing a file in real time - ios

Question

I am having trouble reading a file from the operating system using AVFoundation and performing rendering and analysis in real time.
I have a pipe line of code that I know runs in real time does analysis on a video file. This pipe line of code works in realtime via the camera session. However this is not the case when I read the file like so.Can anyone let me know where I might be going wrong ?
protocol VideoStreamTestBenchDelegate {
func frameBuffer(buffer:CMSampleBuffer)
}
class VideoStreamTestBench {
let asset:AVAsset
let assetReader:AVAssetReader
let playAtActualSpeed:Bool
let loop:Bool
var videoEncodingIsFinished = false
var previousFrameTime = kCMTimeZero
var previousActualFrameTime = CFAbsoluteTimeGetCurrent()
var numberOfFramesCaptured = 0
var totalFrameTimeDuringCapture:Double = 0.0
var delegate:VideoStreamTestBenchDelegate?
public convenience init(url:URL, playAtActualSpeed:Bool = false, loop:Bool = false) throws {
let inputOptions = [AVURLAssetPreferPreciseDurationAndTimingKey:NSNumber(value:true)]
let inputAsset = AVURLAsset(url:url, options:inputOptions)
try self.init(asset:inputAsset, playAtActualSpeed:playAtActualSpeed, loop:loop)
}
public init(asset:AVAsset, playAtActualSpeed:Bool = false, loop:Bool = false) throws {
self.asset = asset
self.playAtActualSpeed = playAtActualSpeed
self.loop = loop
assetReader = try AVAssetReader(asset:self.asset)
let outputSettings:[String:AnyObject] = [(kCVPixelBufferPixelFormatTypeKey as String):NSNumber(value:Int32(kCVPixelFormatType_32BGRA))]
let readerVideoTrackOutput = AVAssetReaderTrackOutput(track:self.asset.tracks(withMediaType: AVMediaTypeVideo)[0], outputSettings:outputSettings)
readerVideoTrackOutput.alwaysCopiesSampleData = false
assetReader.add(readerVideoTrackOutput)
// TODO: Audio here
}
public func start() {
asset.loadValuesAsynchronously(forKeys:["tracks"], completionHandler:{
DispatchQueue.global(priority:DispatchQueue.GlobalQueuePriority.default).async(execute: {
guard (self.asset.statusOfValue(forKey: "tracks", error:nil) == .loaded) else { return }
guard self.assetReader.startReading() else {
print("Couldn't start reading")
return
}
var readerVideoTrackOutput:AVAssetReaderOutput? = nil;
for output in self.assetReader.outputs {
if(output.mediaType == AVMediaTypeVideo) {
readerVideoTrackOutput = output;
}
}
while (self.assetReader.status == .reading) {
self.readNextVideoFrame(from:readerVideoTrackOutput!)
}
if (self.assetReader.status == .completed) {
self.assetReader.cancelReading()
if (self.loop) {
// TODO: Restart movie processing
} else {
self.endProcessing()
}
}
})
})
}
public func cancel() {
assetReader.cancelReading()
self.endProcessing()
}
func endProcessing() {
}
func readNextVideoFrame(from videoTrackOutput:AVAssetReaderOutput) {
if ((assetReader.status == .reading) && !videoEncodingIsFinished) {
if let sampleBuffer = videoTrackOutput.copyNextSampleBuffer() {
if (playAtActualSpeed) {
// Do this outside of the video processing queue to not slow that down while waiting
let currentSampleTime = CMSampleBufferGetOutputPresentationTimeStamp(sampleBuffer)
let differenceFromLastFrame = CMTimeSubtract(currentSampleTime, previousFrameTime)
let currentActualTime = CFAbsoluteTimeGetCurrent()
let frameTimeDifference = CMTimeGetSeconds(differenceFromLastFrame)
let actualTimeDifference = currentActualTime - previousActualFrameTime
if (frameTimeDifference > actualTimeDifference) {
usleep(UInt32(round(1000000.0 * (frameTimeDifference - actualTimeDifference))))
}
previousFrameTime = currentSampleTime
previousActualFrameTime = CFAbsoluteTimeGetCurrent()
}
DispatchQueue.global().sync {
self.delegate?.frameBuffer(buffer: sampleBuffer)
CMSampleBufferInvalidate(sampleBuffer)
}
} else {
if (!loop) {
videoEncodingIsFinished = true
if (videoEncodingIsFinished) {
self.endProcessing()
}
}
}
}
}
}
// This is the delegate
public func bufferReader(_ reader: BufferReader!, didGetNextVideoSample bufferRef: CMSampleBuffer!) {
// let posePoints:[Any] = self.visageBackend.posePoints(with: bufferRef)
// var regions:[Any]? = nil
//
// if (posePoints.count > 0) {
// regions = (self.luaBackend?.regions(forPosePoints: posePoints))!
// }
//
// // extract
// if(regions != nil) {
// let rois:[Any] = (self.luaBackend?.extractedRegionInfos(for: bufferRef, andRegions: regions))!
// print(rois)
// }
//
// self.dLibRenderEngine.render(with: bufferRef, andPoints: posePoints, andRegions: regions)
self.backgroundRenderQueue.async { [weak self] in
if self?.previewLayer?.isReadyForMoreMediaData == true {
self?.previewLayer?.enqueue(bufferRef!)
}
}
}