COMPVARS structure (vfw.h)

The COMPVARS structure describes compressor settings for functions such as ICCompressorChoose, ICSeqCompressFrame, and ICCompressorFree.

Syntax

typedef struct {
  LONG         cbSize;
  DWORD        dwFlags;
  HIC          hic;
  DWORD        fccType;
  DWORD        fccHandler;
  LPBITMAPINFO lpbiIn;
  LPBITMAPINFO lpbiOut;
  LPVOID       lpBitsOut;
  LPVOID       lpBitsPrev;
  LONG         lFrame;
  LONG         lKey;
  LONG         lDataRate;
  LONG         lQ;
  LONG         lKeyCount;
  LPVOID       lpState;
  LONG         cbState;
} COMPVARS, *PCOMPVARS;

Members

cbSize

Size, in bytes, of this structure. This member must be set to validate the structure before calling any function using this structure.

dwFlags

Applicable flags. The following value is defined:

hic

Handle to the compressor to use. You can open a compressor and obtain a handle of it by using the ICOpen function. You can also choose a compressor by using ICCompressorChoose. ICCompressorChoose opens the chosen compressor and returns the handle of the compressor in this member. You can close the compressor by using ICCompressorFree.

fccType

Type of compressor used. Currently only ICTYPE_VIDEO (VIDC) is supported. This member can be set to zero.

fccHandler

Four-character code of the compressor. Specify NULL to indicate the data is not to be recompressed. Specify "DIB" to indicate the data is an uncompressed, full frame. You can use this member to specify which compressor is selected by default when the dialog box is displayed.

lpbiIn

Reserved; do not use.

lpbiOut

Pointer to a BITMAPINFO structure containing the image output format. You can specify a specific format to use or you can specify NULL to use the default compressor associated with the input format. You can also set the image output format by using ICCompressorChoose.

lpBitsOut

Reserved; do not use.

lpBitsPrev

Reserved; do not use.

lFrame

Reserved; do not use.

lKey

Key-frame rate. Specify an integer to indicate the frequency that key frames are to occur in the compressed sequence or zero to not use key frames. You can also let ICCompressorChoose set the key-frame rate selected in the dialog box. The ICSeqCompressFrameStart function uses the value of this member for making key frames.

lDataRate

Data rate, in kilobytes per second. ICCompressorChoose copies the selected data rate from the dialog box to this member.

lQ

Quality setting. Specify a quality setting of 1 to 10,000 or specify ICQUALITY_DEFAULT to use the default quality setting. You can also let ICCompressorChoose set the quality value selected in the dialog box. ICSeqCompressFrameStart uses the value of this member as its quality setting.

lKeyCount

Reserved; do not use.

lpState

Reserved; do not use.

cbState

Reserved; do not use.

Remarks

You can let ICCompressorChoose fill the contents of this structure or you can do it manually. If you manually fill the structure, you must provide information for the following members: cbSize, hic, lpbiOut, lKey, and lQ. Also, you must set the ICMF_COMPVARS_VALID flag in the dwFlags member.

Requirements

See also

ICCompressorChoose

ICCompressorFree

ICSeqCompressFrame

ICSeqCompressFrameStart

Video Compression Manager

Video Compression Structures