Setting and Tracking the Frame Index

The frame index keeps track of the current frame in a movie. The Movie Player provides the following functions to query and change the frame index:

mmpGetCurFrame

Gets the number of the currently displayed frame.

mmpGoToFrame

Jumps to a given frame in a movie.

Getting the Current Frame

You can call mmpGetCurFrame at any time—even if you haven't called mmpStartAnimating. This function has the following syntax:

short mmpGetCurFrame(idMovie)

Pass the movie ID of the Movie Player instance in idMovie. Frame numbering in a movie starts at 1. The mmpGetCurFrame function returns zero if it fails.

Jumping to a Frame

Use mmpGoToFrame to jump to any frame in a movie file. You can do this before starting playback. This function has the following syntax:

BOOL mmpGoToFrame(idMovie, sFrame, wOptions)

Pass the movie ID of the Movie Player instance to idMovie.

The sFrame parameter, passed as a short integer, can contain any valid frame number in the movie. The function returns FALSE if you pass an invalid frame number. The following constants can be passed in sFrame:

You can pass the MMP_DRAW_FRAME flag to the wOptions parameter to jump to a specified movie frame and then display the image.

Frame-by-Frame Playback

Using the mmpGoToFrame and mmpGetCurFrame functions, you can play a movie one frame at a time. The following code fragment shows two cases of a message handler for a Movie Player application. This code sequence responds to user requests to step forward and backward frame-by-frame:

short nFrameNum;
    .
    .
    .
case IDM_STEPFORWARD:
    if((nFrameNum = mmpGetCurFrame(idMovie)) == MMP_FRAME_LAST)
    {
        MessageBox(hWnd, "Can't step beyond end.", szAppName, MB_OK);
        break;
    }

    if(! mmpGoToFrame(idMovie, ++nFrameNum, MMP_DRAW_FRAME))
        PrintError(idMovie, "Could not go to specified frame.");

    break;

case IDM_STEPBACKWARD:
    if((nFrameNum = mmpGetCurFrame(idMovie)) == MMP_FRAME_FIRST)
    {
        MessageBox(hWnd, "Can't step before beginning.",
                    szAppName, MB_OK);
        break;
    }

    if(! mmpGoToFrame(idMovie, --nFrameNum, MMP_DRAW_FRAME))
    {
        PrintError(idMovie, "Could not go to specified frame.");
        break;
    }
    break;