Phonon Video Player : Can not play videos with a size of more than 1 GB

I am trying to play rawvideo(not compressed) in HD 1920×1080 with Phonon VideoPlayer. It works if the videos size are small (1Go) but if not the player crash. I check the buffering process and only around 2Mega of datas are send to the buffer. With my videos size, I need to send more datas in the buffer(buffer size 8 Go). The problem is that I don’t know how control the process. Do you think it can be link with the backend I use? I install DirectX and Directshow but I can’t configue it. Do you know if it’s possible? I don’t even knows what’s the backend I use in phonon. Where can I find the information? Tanks in avance