How do I draw text in CIImage?

How to draw CIImage

(or maybe in CVPixelBuffer

, but it seems to me that adding text in CIImage

) is easier)? not UIImage

I am recording video (.mp4 file) using AVAssetWriter

and CMSampleBuffer

(from video, audio inputs). While recording, I want to add text to video frames, I am already converting CMSampleBuffer

to CIImage

, now I need to somehow add text to CIImage

and convert back to CVPixelBuffer

. I haven't really found any simple examples in Swift of adding (drawing) text to CIImage

or adding anything else (like lines, rectangles, not just text).

/// encode video buffer
func appendVideoSampleBuffer(_ sampleBuffer: CMSampleBuffer) {

    // before encoding video frames into a file I would like process it
    // 1. convert CMSampleBuffer to ciImage

    let cvPixelBuffer: CVPixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)!
    let ciimage : CIImage = CIImage(cvPixelBuffer: cvPixelBuffer)

    // 2. do something with CIImage


    // 3. convert CIImage back to CMSampleBuffer

    let sampleBufferWithText == ...


    appendSampleBuffer(sampleBufferWithText, ofMediaType: AVMediaType.video.rawValue)
}

/// encode audio buffer
func appendAudioSampleBuffer(_ sampleBuffer: CMSampleBuffer) {
    appendSampleBuffer(sampleBuffer, ofMediaType: AVMediaType.audio.rawValue)
}