I am currently working on a macOS app which will be creating very large video files with up to an hour of content. However, generating the images and adding them to AVAssetWriter leads to VTDecoderXPCService using 16+ GB of memory and the kernel-task using 40+ GB (the max I saw was 105GB).
It seems like the generated video is not streamed onto the disk but rather written to memory for it to be written to disk all at once. How can I force it to stream the data to disk while the encoding is happening?
Btw. my app itself consistently needs around 300MB of memory, so I don't think I have a memory leak here.
Here is the relevant code:
func analyse()
{
				self.videoWritter = try! AVAssetWriter(outputURL: outputVideo, fileType: AVFileType.mp4)
				let writeSettings: [String: Any] = [
						AVVideoCodecKey: AVVideoCodecType.h264,
						AVVideoWidthKey: videoSize.width,
						AVVideoHeightKey: videoSize.height,
						AVVideoCompressionPropertiesKey: [
								AVVideoAverageBitRateKey: 10_000_000,
						]
				]
				self.videoWritter!.movieFragmentInterval = CMTimeMake(value: 60, timescale: 1)
				self.frameInput = AVAssetWriterInput(mediaType: AVMediaType.video, outputSettings: writeSettings)
				self.frameInput?.expectsMediaDataInRealTime = true
				self.videoWritter!.add(self.frameInput!)
				if self.videoWritter!.startWriting() == false {
						print("Could not write file: \(self.videoWritter!.error!)")
						return
				}
}
func writeFrame(frame: Frame)
{
				/* some more code to determine the correct frame presentation time stamp */
				let newSampleBuffer = self.setTimeStamp(frame.sampleBuffer, newTime: self.nextFrameStartTime!)
				self.frameInput!.append(newSampleBuffer)
				/* some more code */
}
func setTimeStamp(_ sample: CMSampleBuffer, newTime: CMTime) -> CMSampleBuffer {
				var timing: CMSampleTimingInfo = CMSampleTimingInfo(
						duration: CMTime.zero,
						presentationTimeStamp: newTime,
						decodeTimeStamp: CMTime.zero
				)
				var newSampleBuffer: CMSampleBuffer?
				CMSampleBufferCreateCopyWithNewTiming(
						allocator: kCFAllocatorDefault,
					 sampleBuffer: sample,
					 sampleTimingEntryCount: 1,
					 sampleTimingArray: &timing,
					 sampleBufferOut: &newSampleBuffer
			 )
				return	newSampleBuffer!
		}
My specs:
MacBook Pro 2018
32GB Memory
macOS Big Sur 11.1
