updated H264Coder

H264Coder.swift

import AVFoundation
import VideoToolbox

class H264Coder {

    var session: VTCompressionSession?
    var onFrame: ((CMSampleBuffer) -> Void)?

    let outputCallback: VTCompressionOutputCallback = { refcon, sourceFrameRefCon, status, infoFlags, sampleBuffer in
        guard let refcon = refcon,
              status == noErr,
              let sampleBuffer = sampleBuffer else {
            print("H264Coder outputCallback sampleBuffer NIUL or status: \(status)")
            return
        }

        let encoder: H264Coder = Unmanaged<H264Coder>.fromOpaque(refcon).takeUnretainedValue()
        encoder.didEncodeFrame(frame: sampleBuffer)
    }

    init(width: Int32, height: Int32) {
        let status = VTCompressionSessionCreate(allocator: kCFAllocatorDefault, width: width, height: height, codecType: kCMVideoCodecType_H264, encoderSpecification: nil, imageBufferAttributes: nil, compressedDataAllocator: nil, outputCallback: outputCallback, refcon: Unmanaged.passUnretained(self).toOpaque(), compressionSessionOut: &session)

        guard let session = session else { return }
        VTSessionSetProperty(session, key: kVTCompressionPropertyKey_RealTime, value: kCFBooleanTrue)
        VTSessionSetProperty(session, key: kVTCompressionPropertyKey_AllowFrameReordering, value: kCFBooleanFalse)
        VTSessionSetProperty(session, key: kVTCompressionPropertyKey_MaxKeyFrameInterval, value: NSNumber(1))
        VTSessionSetProperty(session, key: kVTCompressionPropertyKey_ProfileLevel, value: kVTProfileLevel_H264_Main_AutoLevel)
        VTSessionSetProperty(session, key: kVTCompressionPropertyKey_ExpectedFrameRate, value: NSNumber(30))

        VTCompressionSessionPrepareToEncodeFrames(session)

        print("H264Coder init \(status == noErr) \(status)")
    }

    func encode(_ sampleBuffer: CMSampleBuffer) {
        guard let compressionSession = session,
              let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else { return }
        let timestamp = CMSampleBufferGetPresentationTimeStamp(sampleBuffer)
        let _ = VTCompressionSessionEncodeFrame(compressionSession, imageBuffer: imageBuffer, presentationTimeStamp: timestamp, duration: .invalid, frameProperties: nil, sourceFrameRefcon: nil, infoFlagsOut: nil)
    }

    func didEncodeFrame(frame: CMSampleBuffer) {
        print ("Received encoded frame in delegate...")
        onFrame?(frame)
    }

}