select a screen section ffmpeg c++ on macos

Question

I am trying to record the screen on macos, with ffmpeg. I would like to be able to select a section of the screen instead of the whole desktop. I tried to set several options such as vf, with values like "crop=150:150:0:0", or video_size with value "150x150". The result was that the output video had the correct dimensions (150x150) but whole screen has been recorded instead of the specified section. Does anybody know another way to do that?

int ScreenRecorder::openVideoDevice() {
    value = 0;
    videoOptions = nullptr;
    pAVFormatContext = nullptr;

    pAVFormatContext = avformat_alloc_context();


    string dimension = to_string(width) + "x" + to_string(height);
    av_dict_set(&videoOptions, "video_size", dimension.c_str(), 0);   //option to set the dimension of the screen section to record
    value = av_dict_set(&videoOptions, "framerate", "25", 0);
    if (value < 0) {
        cerr << "Error in setting dictionary value (setting framerate)" << endl;
        exit(-1);
    }

    value = av_dict_set(&videoOptions, "preset", "ultrafast", 0);
    if (value < 0) {
        cerr << "Error in setting dictionary value (setting preset value)" << endl;
        exit(-1);
    }

    //The distance from the left edge of the screen or desktop
    value = av_dict_set(&videoOptions, "vf", ("crop=" + to_string(width) + ":" + to_string(height) + ":" + to_string(x_offset) + ":" +
        to_string(y_offset)).c_str(), 0);

    if (value < 0) {
        cerr << "Error in setting crop" << endl;
        exit(-1);
    }

    value = av_dict_set(&videoOptions, "pixel_format", "yuv420p", 0);
    if (value < 0) {
        cerr << "Error in setting pixel format" << endl;
        exit(-1);
    }
    
    pAVInputFormat = av_find_input_format("avfoundation");

    if (avformat_open_input(&pAVFormatContext, "1:none", pAVInputFormat, &videoOptions) != 0) {
        cerr << "Error in opening input device" << endl;
        exit(-1);
    }
    //get video stream infos from context
    value = avformat_find_stream_info(pAVFormatContext, nullptr);
    if (value < 0) {
        cerr << "Error in retrieving the stream info" << endl;
        exit(-1);
    }

    VideoStreamIndx = -1;
    for (int i = 0; i < pAVFormatContext->nb_streams; i++) {
        if (pAVFormatContext->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
            VideoStreamIndx = i;
            break;
        }
    }
    if (VideoStreamIndx == -1) {
        cerr << "Error: unable to find video stream index" << endl;
        exit(-2);
    }

    pAVCodecContext = pAVFormatContext->streams[VideoStreamIndx]->codec;
    pAVCodec = avcodec_find_decoder(pAVCodecContext->codec_id/*params->codec_id*/);
    if (pAVCodec == nullptr) {
        cerr << "Error: unable to find decoder video" << endl;
        exit(-1);
    }

    return 0;
}