Exchange char buffer between Qt c++ and QML

Hello, I am quite new to QML and face a problem when trying to draw a chart from a char buffer. I use QML as GUI frontend and connect the backend application written in Qt C++ via signals and slots to the UI. This works fine for primitive types. There i use a signal in my app like newDataAvailable(QVariant data), connect it to a function in my main.qml which then forwards the data by emitting signals that are fetched by the respective components. But i don’t know how to exchange more involved types. I have a buffer of audio data which needs to be displayed from time to time in the UI. Therefore i made a Chart Component with the respective drawing logic using canvas. But how can i forward the data from the application to the UI, such that it is available for drawing? This question is quite vague, but I hope you get my problem. Thank you for your help! Kind regards