initializer

H264Coder.swift

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)
}