How can I get stream using SDK?

Question

I want to create a mosaic for cameras on the TV, but my DVR is old and doesn't have RTSP support.

I figured out that I can use the SDK from Dahua. I followed this question to help me with the login process.

It worked, and now I really want to get the buffer and try to stream using WebRTC. Here is my code:

const ffi = require('ffi-napi');
const ref = require('ref-napi');

const libm = ffi.Library('./dhnetsdk', {
    CLIENT_Init: [ref.types.bool, []],
    CLIENT_LoginEx2: [ref.types.int64, [
        'string', // pchDVRIP
        ref.types.ushort, // wDVRPort
        'string', // pchUserName
        'string', // pchPassword
        ref.types.int, // emSpecCap
        'pointer', // pCapParam
        'pointer', // lpDeviceInfo
        'int*', // error
    ]],
    CLIENT_Cleanup: [ref.types.void, []],
    CLIENT_GetLastError: [ref.types.long, []],
    CLIENT_SetNetworkParam: [ref.types.void, [
        ref.types.Object
    ]],
    CLIENT_GetSDKVersion: [ref.types.long, []],
    CLIENT_RealPlay: [ref.types.int64, [
        ref.types.int64, // lLoginID
        ref.types.int, // nChannelID
    ]],
    CLIENT_SetRealDataCallBackEx2: [ref.types.bool, [
        ref.types.int64, // lRealHandle
        'pointer', // fRealDataCallBackEx
        ref.types.uchar, // dwUser
        ref.types.uchar, // dwFlag
    ]],
    CLIENT_Logout: [ref.types.bool, [
        ref.types.int64
    ]]
});

const sleep = (ms) => new Promise(resolve => setTimeout(resolve, ms));

(async () => {
    if (libm.CLIENT_Init()) {
        try {
            const pchDVRIP = 'myDVRIP';
            const wDVRPort = 37777;
            const pchUserName = 'user';
            const pchPassword = '******';

            const emSpecCap = 0;
            const pCapParam = null;
            const lpDeviceInfo = null;
            const error = ref.alloc('int');

            const loginID = libm.CLIENT_LoginEx2(pchDVRIP, wDVRPort, pchUserName, pchPassword, emSpecCap, pCapParam, lpDeviceInfo, error);

            if (loginID == 0) {
                throw new Error('Failed login: ' + error.deref().toString());
            }

            await sleep(1000);

            const realID = libm.CLIENT_RealPlay(loginID, 0);

            if (0 == realID) {
                throw new Error("CLIENT_RealPlayEx: failed! Error code: " + libm.CLIENT_GetLastError().toString());
            }


            const fRealDataCallBackEx = ffi.Callback('void', ['int64', 'uchar', 'pointer', 'uchar', 'int64', 'uchar'],
                function (lRealHandle, dwDataType, pBuffer, dwBufSize, param, dwUser) {
                    console.log('onca');
                    console.log({
                        lRealHandle, dwDataType, pBuffer, dwBufSize, param, dwUser
                    });
                });

            await sleep(1000);
            const result = libm.CLIENT_SetRealDataCallBackEx2(realID, fRealDataCallBackEx, null, 2);

            console.log(result);

            libm.CLIENT_Logout(loginID);
        } catch (error) {
            console.log(error);
        }

        libm.CLIENT_Cleanup();
    } else {
        console.log('Init failed');
    }
})();

The result of libm.CLIENT_SetRealDataCallBackEx2 is true, indicating that it worked. However, the callback function is not being called.

I attempted to create the callback as per the documentation, but I didn't receive the buffer information in the callback function. It seems like the callback function is being ignored.