How to get the decoded data using rtsp and libs

[passionggg]

hi,every body
now i has set up a MFC project in VS2008 to use libvlc.lib, libvlccore.lib and the plugins. it used to read rtsp data in real time and display it in my window. the main code is as follows:
char path[100];
this->GetDlgItemText(IDC_EDIT1, path, 100); //path is "rtsp://192.168.1.1:6002/h264"
libvlc_exception_t ex;
libvlc_exception_init(&ex);
int vlc_argc = 0;
char *vlc_argv[100];
vlc_argv[vlc_argc++] = "--ignore-config";
libvlc_instance_t *p_instance = libvlc_new( vlc_argc, vlc_argv, &ex);
libvlc_media_t *p_media = libvlc_media_new( p_instance, path, &ex);
libvlc_media_player_t *p_media_player = libvlc_media_player_new_from_media( p_media, &ex);
libvlc_drawable_t hwnd = (libvlc_drawable_t) this->GetDlgItem(IDC_DISPLAY)->GetSafeHwnd();
libvlc_media_player_set_drawable(p_media_player, hwnd, &ex);
libvlc_media_player_play(p_media_player, &ex);
But i want to do some changes about the video before displaying it. So what did i do to get the each decoded frame data?

[passionggg]

if anyone knows how to get each frame rtsp stream data, please help me. very appreciated!!!
In the logger, I can see how the program run.
(1)first open the path from rtsp;
(2)then use LIVE555 to read rtsp stream;
(3)then search decoder and get avdecoder(ffmpeg) to decode the video data;
(4)last display it.
I just want to get the decoded data after step 3.
is there a callback function to do this?
Thanks all in advance.