MFX_PICSTRUCT_FIELD_TFF breaks my encoder

Hi,

I'm trying to initialise my encoder for field/interlace encoding. The only parameter I change is PicStruct from MFX_PICSTRUCT_PROGRESSIVE to MFX_PICSTRUCT_FIELD_TFF, however doing that results in mfxENC->Query returning MFX_WRN_INCOMPATIBLE_VIDEO_PARAM. But setting the PicStruct to progressive works just fine.

What apart from setting PicStruct to MFX_PICSTRUCT_FIELD_TFF do I need to configure for QSV to accept my settings?

Is there a simpler way of setting the parameters, or any helper methods that I can use?..

See my code below and thanks for helping.

/Anders

 // Initialize encoder parameters
    mfxVideoParam mfxEncParams;
    memset(&mfxEncParams, 0, sizeof (mfxEncParams));
    if (encParamFieldCount == 1) {
        mfxEncParams.mfx.FrameInfo.PicStruct = MFX_PICSTRUCT_PROGRESSIVE;
    } else if (encParamFieldCount == 2) {
        mfxEncParams.mfx.FrameInfo.PicStruct = MFX_PICSTRUCT_FIELD_TFF;
    } else {
        std::cout << "Failed init.. Encoding field structure unknown."<< std::endl;
        return;
    }
    mfxU16 adjustedVideoWidth = MSDK_ALIGN16(videoWidth);
    mfxU16 adjustedVideoHeight = (MFX_PICSTRUCT_PROGRESSIVE == mfxEncParams.mfx.FrameInfo.PicStruct) ? MSDK_ALIGN16(videoHeight) : MSDK_ALIGN32(videoHeight);
    mfxEncParams.mfx.FrameInfo.Width = adjustedVideoWidth;
    mfxEncParams.mfx.FrameInfo.Height = adjustedVideoHeight;
    mfxEncParams.mfx.CodecId = MFX_CODEC_AVC;
    mfxEncParams.mfx.CodecProfile = MFX_PROFILE_AVC_HIGH;
    mfxEncParams.mfx.CodecLevel = MFX_LEVEL_AVC_42;
    mfxEncParams.mfx.GopPicSize = videoFPS;
    mfxEncParams.mfx.GopRefDist = 1; //I and P frames only
    mfxEncParams.mfx.TargetUsage = MFX_TARGETUSAGE_BEST_SPEED; //TODO test quality and see if speed is at all changed
    mfxEncParams.mfx.TargetKbps = 4000;
    mfxEncParams.mfx.RateControlMethod = MFX_RATECONTROL_CBR;
    mfxEncParams.mfx.FrameInfo.FrameRateExtN = videoFPS;
    mfxEncParams.mfx.FrameInfo.FrameRateExtD = 1;
    mfxEncParams.mfx.FrameInfo.FourCC = MFX_FOURCC_NV12;
    mfxEncParams.mfx.FrameInfo.ChromaFormat = MFX_CHROMAFORMAT_YUV420;
    mfxEncParams.mfx.FrameInfo.CropX = 0;
    mfxEncParams.mfx.FrameInfo.CropY = 0;
    mfxEncParams.mfx.FrameInfo.CropW = videoWidth;
    mfxEncParams.mfx.FrameInfo.CropH = videoHeight;
    mfxEncParams.mfx.FrameInfo.BitDepthLuma = 8;
    mfxEncParams.mfx.FrameInfo.BitDepthChroma = 8;
    mfxEncParams.mfx.FrameInfo.Shift = 0;
    
    mfxEncParams.IOPattern = MFX_IOPATTERN_IN_SYSTEM_MEMORY;
    mfxEncParams.AsyncDepth = 1;

    mfxExtCodingOption extendedCodingOptions;
    memset(&extendedCodingOptions, 0, sizeof (extendedCodingOptions));
    extendedCodingOptions.Header.BufferId = MFX_EXTBUFF_CODING_OPTION;
    extendedCodingOptions.Header.BufferSz = sizeof (extendedCodingOptions);
    extendedCodingOptions.MaxDecFrameBuffering = 1;
    mfxExtBuffer * extendedBuffers[1];
    extendedBuffers[0] = (mfxExtBuffer*) & extendedCodingOptions;
    mfxEncParams.ExtParam = extendedBuffers;
    mfxEncParams.NumExtParam = 1;

    // Create Media SDK encoder
    // MFXVideoENCODE* mfxENC = new MFXVideoENCODE(mfxSES);

    mfxENC = std::shared_ptr<MFXVideoENCODE>(new MFXVideoENCODE(mfxSES));
    if (mfxENC == nullptr) {
        std::cout << "Creating a MFXVideoENCODE returned nullptr."<< std::endl;
        return;
    }
    std::cout << "QSV Video encoder created."<< std::endl;

    //Probe to see if the encoder parameters are valid
    sts = mfxENC->Query(&mfxEncParams, &mfxEncParams);
    if (sts != MFX_ERR_NONE) {
        std::cout << __LINE__ << ": QSV Got error "<< sts << std::endl;
        return;
    }
    std::cout << "QSV Video encoder accepted encoding parameters."<< std::endl;