Change Buffer format of DJIVideoPreviewer

Question

Now I am creating app that uses video frame from the DJI aircraft and run it through tensorlite object detection model.

I managed to get my app to receive the frame from the aircraft.

However, frame type is VPFrameTypeYUV420Planer. I want to receive the frame of VPFrameTypeYUV420SemiPlanar. It's because I want to create kCVPixelFormatType_420YpCbCr8BiPlanarFullRange cvPixelBuffer from the frame.

I tried to change videopreviewr property as follows.

DJIVideoPreviewer.instance()?.frameOutputType = VPFrameTypeYUV420SemiPlaner

However, I got error.

I also tried to create kCVPixelFormatType_420YpCbCr8BiPlanarFullRange cvPixelBuffer from YUV420Planer frame. However, I don't know how to convert chromaR, chormaB to UV.

func createPixelBuffer(fromFrame frame: VideoFrameYUV) -> CVPixelBuffer? {
        var initialPixelBuffer: CVPixelBuffer?
        let _: CVReturn = CVPixelBufferCreate(kCFAllocatorDefault, Int(frame.width), Int(frame.height), kCVPixelFormatType_420YpCbCr8BiPlanarFullRange, nil, &initialPixelBuffer)

        guard let pixelBuffer = initialPixelBuffer,
            CVPixelBufferLockBaseAddress(pixelBuffer, []) == kCVReturnSuccess
            else {
                return nil
        }

        let yPlaneWidth = CVPixelBufferGetWidthOfPlane(pixelBuffer, 0)
        let yPlaneHeight = CVPixelBufferGetHeightOfPlane(pixelBuffer, 0)

        let uvPlaneWidth = CVPixelBufferGetWidthOfPlane(pixelBuffer, 1)
        let uvPlaneHeight = CVPixelBufferGetHeightOfPlane(pixelBuffer, 1)


        let yDestination = CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 0)
        memcpy(yDestination, frame.luma, yPlaneWidth * yPlaneHeight)

        let uvDestination = CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 1)

       // let chrB = frame.chromaB.pointee
//        let chrR = frame.chromaR.pointee
        // I don't know how to convert to uv Buffer.

        CVPixelBufferUnlockBaseAddress(pixelBuffer, [])

        return pixelBuffer

Is there good way to solve this problem?

score 0 · Answer 1 · edited Jun 05 '20 at 09:54

I think this will work:

func createPixelBuffer(fromFrame frame: VideoFrameYUV) -> CVPixelBuffer? {
        var initialPixelBuffer: CVPixelBuffer?
        let _: CVReturn = CVPixelBufferCreate(kCFAllocatorDefault, Int(frame.width), Int(frame.height), kCVPixelFormatType_420YpCbCr8Planar, nil, &initialPixelBuffer)

        guard let pixelBuffer = initialPixelBuffer
            , CVPixelBufferLockBaseAddress(pixelBuffer, []) == kCVReturnSuccess
            else {
                return nil
        }

        let yPlaneWidth = CVPixelBufferGetWidthOfPlane(pixelBuffer, 0)
        let yPlaneHeight = CVPixelBufferGetHeightOfPlane(pixelBuffer, 0)

        let uPlaneWidth = CVPixelBufferGetWidthOfPlane(pixelBuffer, 1)
        let uPlaneHeight = CVPixelBufferGetHeightOfPlane(pixelBuffer, 1)

        let vPlaneWidth = CVPixelBufferGetWidthOfPlane(pixelBuffer, 2)
        let vPlaneHeight = CVPixelBufferGetHeightOfPlane(pixelBuffer, 2)

        let yDestination = CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 0)
        memcpy(yDestination, frame.luma, yPlaneWidth * yPlaneHeight)

        let uDestination = CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 1)
        memcpy(uDestination, frame.chromaB, uPlaneWidth * uPlaneHeight)

        let vDestination = CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 2)
        memcpy(vDestination, frame.chromaR, vPlaneWidth * vPlaneHeight)

        CVPixelBufferUnlockBaseAddress(pixelBuffer, [])

        return pixelBuffer
    }

Change Buffer format of DJIVideoPreviewer

1 Answers1