obs-studio/plugins/mac-virtualcam/src/dal-plugin/CMSampleBufferUtils.mm

//
//  CMSampleBufferUtils.m
//  dal-plugin
//
//  Created by John Boiles  on 5/8/20.
//

#import "CMSampleBufferUtils.h"

CMSampleTimingInfo CMSampleTimingInfoForTimestamp(uint64_t timestampNanos,
						  uint32_t fpsNumerator,
						  uint32_t fpsDenominator)
{
	// The timing here is quite important. For frames to be delivered correctly and successfully be recorded by apps
	// like QuickTime Player, we need to be accurate in both our timestamps _and_ have a sensible scale. Using large
	// timestamps and scales like mach_absolute_time() and NSEC_PER_SEC will work for display, but will error out
	// when trying to record.
	//
	// 600 is a common default in Apple's docs https://developer.apple.com/documentation/avfoundation/avmutablemovie/1390622-timescale
	CMTimeScale scale = 600;
	CMSampleTimingInfo timing;
	timing.duration =
		CMTimeMake(fpsDenominator * scale, fpsNumerator * scale);
	timing.presentationTimeStamp = CMTimeMake(
		(timestampNanos / (double)NSEC_PER_SEC) * scale, scale);
	timing.decodeTimeStamp = kCMTimeInvalid;
	return timing;
}