int w, h;
format Overlay format (see below)
w, h Width and height of overlay
planes Number of planes in the overlay. Usually either 1 or 3
pitches An array of pitches, one for each plane. Pitch is the length of a row in bytes.
pixels An array of pointers to teh data of each plane. The overlay should be locked before these pointers are used.
hw_overlay This will be set to 1 if the overlay is hardware accelerated.
A SDL_Overlay is similar to a SDL_Surface except it stores a YUV overlay. All the fields are read only, except for pixels which should be
locked before use. The format field stores the format of the overlay which is one of the following:
#define SDL_YV12_OVERLAY 0x32315659 /* Planar mode: Y + V + U */
#define SDL_IYUV_OVERLAY 0x56555949 /* Planar mode: Y + U + V */
#define SDL_YUY2_OVERLAY 0x32595559 /* Packed mode: Y0+U0+Y1+V0 */
#define SDL_UYVY_OVERLAY 0x59565955 /* Packed mode: U0+Y0+V0+Y1 */
#define SDL_YVYU_OVERLAY 0x55595659 /* Packed mode: Y0+V0+Y1+U0 */
More information on YUV formats can be found at http://www.webartz.com/fourcc/indexyuv.htm (link to URL