Essential snippet for compressing original CMSampleBufferRef into H.264 sample

FXDsampleBufferCompression.m

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
	CMFormatDescriptionRef formatDescription = CMSampleBufferGetFormatDescription(sampleBuffer);
	CMVideoDimensions videoDimensions = CMVideoFormatDescriptionGetDimensions(formatDescription);


	static VTCompressionSessionRef compressionSession;

	if (compressionSession == NULL) {
		VTCompressionSessionCreate
		(NULL,
		 videoDimensions.width,
		 videoDimensions.height,
		 kCMVideoCodecType_H264,
		 NULL,
		 NULL,
		 NULL,
		 NULL,
		 NULL,
		 &compressionSession);
	}


	CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);

	CMTime presentationTimestamp = CMSampleBufferGetPresentationTimeStamp(sampleBuffer);
	CMTime duration = CMSampleBufferGetDuration(sampleBuffer);

	VTCompressionSessionEncodeFrameWithOutputHandler
	(compressionSession,
	 pixelBuffer,
	 presentationTimestamp,
	 duration,
	 NULL,
	 NULL,
	 ^(OSStatus status,
	   VTEncodeInfoFlags infoFlags,
	   CMSampleBufferRef  _Nullable compressedSample) {

		 //MARK: The compressedSample can also be used for display
	 });
}