ICCOMPRESS

  • Article

The ICCOMPRESS structure contains compression parameters used with the ICM_COMPRESS message.

typedef struct { 
    DWORD              dwFlags; 
    LPBITMAPINFOHEADER lpbiOutput; 
    LPVOID             lpOutput; 
    LPBITMAPINFOHEADER lpbiInput; 
    LPVOID             lpInput; 
    LPDWORD            lpckid; 
    LPDWORD            lpdwFlags; 
    LONG               lFrameNum; 
    DWORD              dwFrameSize; 
    DWORD              dwQuality; 
    LPBITMAPINFOHEADER lpbiPrev; 
    LPVOID             lpPrev; 
} ICCOMPRESS;

Members

dwFlags

Flags used for compression. The following value is defined:

ICCOMPRESS_KEYFRAME

Input data should be treated as a key frame.

lpbiOutput

Pointer to a BITMAPINFOHEADER structure containing the output (compressed) format. The biSizeImage member must contain the size of the compressed data.

lpOutput

Pointer to the buffer where the driver should write the compressed data.

lpbiInput

Pointer to a BITMAPINFOHEADER structure containing the input (uncompressed) format.

lpInput

Pointer to the buffer containing input data.

lpckid

Address to contain the chunk identifier for data in the AVI file. If the value of this member is not NULL, the driver should specify a two-character code for the chunk identifier corresponding to the chunk identifier used in the AVI file.

lpdwFlags

Address to contain flags for the AVI index. If the returned frame is a key frame, the driver should set the AVIIF_KEYFRAME flag.

lFrameNum

Number of the frame to compress.

dwFrameSize

Desired maximum size, in bytes, for compressing this frame. The size value is used for compression methods that can make tradeoffs between compressed image size and image quality. Specify zero for this member to use the default setting.

dwQuality

Quality setting.

lpbiPrev

Pointer to a BITMAPINFOHEADER structure containing the format of the previous frame, which is typically the same as the input format.

lpPrev

Pointer to the buffer containing input data of the previous frame.

Remarks

Drivers that perform temporal compression use data from the previous frame (found in the lpbiPrev and lpPrev members) to prune redundant data from the current frame.

Requirements

**  Windows NT/2000/XP:** Included in Windows NT 3.1 and later.
**  Windows 95/98/Me:** Included in Windows 95 and later.
**  Header:** Declared in Vfw.h.

See Also

Video Compression Manager, Video Compression Structures, BITMAPINFOHEADER, ICM_COMPRESS