Indeo® Video Interactive
Video for Windows
Programming Interface Specification
Revision 1.6
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Copyright 1995, Intel Corporation. All Rights Reserved.
Video for Windows Programming Interface Specification
Codec Specific Messages
ICSendMessage
ICM_GETCODECSTATE
ICM_SETCODECSTATE
General Data Structures
Flags
Rectangle
Transparency Bitmask
Transparency Range
Decode Data Structures
R4_DEC_FRAME_DATA
R4_DEC_SEQ_DATA
Encode Data Structures
ENC_SEQ_DATA
Messages for the Decoder Using ICM_GETCODECSTATE
MT_DECODE_FRAME_DEFAULT
MT_DECODE_FRAME_VALUE
MT_DECODE_SEQ_DEFAULT
MT_DECODE_SEQ_VALUE
Messages for the Decoder Using ICM_SETCODECSTATE
MT_DECODE_FRAME_DEFAULT
MT_DECODE_FRAME_VALUE
MT_DECODE_SEQ_DEFAULT
MT_DECODE_SEQ_VALUE
Messages for the Encoder Using ICM_GETCODECSTATE
MT_ENCODE_SEQ_DEFAULT
MT_ENCODE_SEQ_VALUE
Messages for the Encoder Using ICM_SETCODECSTATE
MT_ENCODE_SEQ_DEFAULT
MT_ENCODE_SEQ_VALUE
Special Notes for 16-bit Applications
The Indeo video interactive codec will provide access to new features using codec-specific ICM_SETCODECSTATE and ICM_GETCODECSTATE messages. The following sections describe the new codec's SET and GET message interface.
The include file that contains this information is named "vfw_spec.h".
Indeo video interactive provides two new messages, ICM_GETCODECSTATE and ICM_SETCODECSTATE, for communicating with the Indeo video interactive codec. The function ICSendMessage() is used to send these messages. Note that these messages are specific to the Indeo video interactive codec; other codecs' responses to these messages are unpredictable.
LRESULT ICSendMessage(HIC hic, UINT wMsg, DWORD dw1, DWORD dw2)
This function sends a message to a codec.
Returns a message-specific result.
hic
Specifies the handle of the codec to receive the message. This should be the result of the ICM_OPEN message.
wMsg
Specifies the message to send. This should be set to either ICM_GETCODECSTATE or ICM_SETCODECSTATE.
dw1
Specifies additional message-specific information. This should be dwParam1 for ICM_GETCODECSTATE or ICM_SETCODECSTATE.
dw2
Specifies additional message-specific information. This should be dwParam2 for ICM_GETCODECSTATE or ICM_SETCODECSTATE.
This message is sent to a video compression driver to obtain driver state information. The definition of the ICM_GETCODECSTATE parameters are codec dependent. The following are the specifications used by the Indeo video interactive codec:
Returns ICERR_OK if successful. Otherwise, returns an error number. The following errors are defined:
ICERR_OK
No error.
ICERR_BADFORMAT
Either the parameter dwParam1 is NULL, the parameter dwParam2 is an incorrect size, or the type field has an unsupported value.
ICERR_UNSUPPORTED
Either the version or the four-cc are unsupported.
ICERR_BADSIZE
The size field is incorrect for the specified type.
ICERR_BADFLAGS
The flags field is invalid. The valid flag and at least one other flag must be set.
ICERR_INTERNAL
A codec error - this should not happen.
dwParam1
Specifies a pointer to a block of memory to be filled with the current state.
dwParam2
Should be set to the length of the block of memory passed in dwParam1.
The data structure used to represent state information is defined by the mtType field. Additional information regarding the effects of the mtType values is found below.
Use the ICSendMessage() function to send an ICM_GETCODECSTATE message.
This message is sent to a video compression driver to set driver state information. The definition of the ICM_SETCODECSTATE parameters are codec dependent. The following are the specifications used by the Indeo video interactive codec:
Returns ICERR_OK if successful. Otherwise, returns an error number. The following errors are defined:
ICERR_OK
No error.
ICERR_BADFORMAT
Either the parameter dwParam1 is NULL, the parameter dwParam2 is non-zero, or the type field has an unsupported value.
ICERR_UNSUPPORTED
Either the version or the four-cc are unsupported.
ICERR_BADSIZE
The size field is incorrect for the specified type.
ICERR_BADFLAGS
The flags field is invalid. The valid flag and at least one other flag must be set.
ICERR_BADPARAM
One of the fields has a value that is out of range. The flags field will be set to indicate which field.
ICERR_INTERNAL
A codec error - this should not happen.
dwParam1
Specifies a pointer to a block of memory containing state information.
dwParam2
Should be set to the length of the block of memory passed in dwParam1.
The data structure used to represent state information is defined by the mtType field. Additional information regarding the effects of the mtType values is found below.
Use the ICSendMessage() function to send an ICM_GETCODECSTATE message.
The following general data structures are used by the Indeo video interactive codec when processing the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages.
A flag is either true (non-zero) or false (zero).
typedef DWORD R4_FLAG;
A pointer to a flag is used by the codec to write status information at a later time.
typedef R4_FLAG FAR * PTR_R4_FLAG;
The following structure is used to describe a rectangle.
typedef struct R4_RECT, FAR * PTR_R4_RECT;
dwX
Specifies the 'X' value of the top left corner.
dwY
Specifies the 'Y' value of the top left corner.
dwWidth
Specifies the width of the rectangle.
dwHeight
Specifies the height of the rectangle.
A transparency bitmask contains one bit for each pixel in the source image. If a bit is zero the data is transparent. The first bit in each byte is identified by the mask 0x80. The last bit in each byte is identified by the mask 0x01. To allow faster access each row must begin on a DWORD boundary and the total number of bytes must be rounded-up to a multiple of four.
typedef BYTE FAR * PTR_R4_BITMASK;
A transparency range is specified using minimum and maximum values for R, G, and B. Any pixel with values within this range (inclusive) is considered transparent.
typedef struct R4_RANGE, FAR * PTR_R4_RANGE;
Note: The reserved field should be set to zero.
Some parameters can be changed prior to either an ICM_DECOMPRESS or ICM_DECOMPRESSEX message. These are found in the R4_DEC_FRAME_DATA structure. Use ICM_SETCODECSTATE to change these values. Use ICM_GETCODECSTATE to obtain these values.
Other parameters can only be changed prior to either an ICM_DECOMPRESS_BEGIN or an ICM_DECOMPRESSEX_BEGIN message. These are found in the R4_DEC_SEQ_DATA structure. Use ICM_SETCODECSTATE to change these values. Use ICM_GETCODECSTATE to obtain these values.
The "DECFRAME" flags are used to identify the fields that are active. The "VALID" flag must be set to indicate that the flags variable has valid data.
#define DECFRAME_TIME_LIMIT (1UL<<0)
#define DECFRAME_DECODE_RECT (1UL<<1)
#define DECFRAME_VIEW_RECT (1UL<<2)
#define DECFRAME_BOUNDING_RECT (1UL<<3)
#define DECFRAME_TRANS_BITMASK (1UL<<4)
#define DECFRAME_BRIGHTNESS (1UL<<5)
#define DECFRAME_SATURATION (1UL<<6)
#define DECFRAME_CONTRAST (1UL<<7)
#define DECFRAME_VALID (1UL<<31)
typedef struct R4_DEC_FRAME_DATA, FAR * PTR_R4_DEC_FRAME_DATA;
The R4_DEC_FRAME_DATA structure contains the parameters that can be changed on a frame by frame basis. Any changes affect decoding of the next frame.
dwSize
Should be set to the size of an R4_DEC_FRAME_DATA structure.
dwFourCC
Should be set to the codec four-cc.
dwVersion
Should be set to the interface version as specified in the "vfw_spec.h" include file.
mtType
Should be set to either MT_DECODE_FRAME_DEFAULT or MT_DECODE_FRAME_VALUE. This field identifies the ICM_GETCODECSTATE or ICM_SETCODECSTATE operation type. Additional information on this field is found in the sections "Messages for the Decoder using ICM_GETCODECSTATE" and "Messages for the Decoder using ICM_SETCODECSTATE".
oeEnvironment
Should be set to OE_16 for 16-bit applications or OE_32 for 32-bit applications.
dwFlags
Should be set to indicate which variables are in use. There is a flag corresponding to each variable (or set of variables) in the structure. See the "DECFRAME_*" definitions.
dwTimeLimit
Should be set to the maximum number of milliseconds for the codec's decode and color conversion process. This is only used if playback salability is on. If this field has a value of zero, the number of milliseconds is estimated based on the frame rate. This field is only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the DECFRAME_TIME_LIMIT flag is true.
rDecodeRect
Specifies the decode rectangle (or local decode rectangle). Legal values for the 'X' value range from zero to the image width minus one. Legal values for the 'Y' value range from zero to the image height minus one. The decode rectangle may not extend outside the image. The decode rectangle may only be changed immediately before key frames. The decode rectangle defaults to the entire frame if all four fields are zero. The decode rectangle specifies the portion of the rectangle that should be decoded. This field is only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the DECFRAME_DECODE_RECT flag is true.
rViewRect
Specifies the view rectangle (or clipping rectangle). The view rectangle may not extend beyond the current decode rectangle. The view rectangle defaults to the decode rectangle if all four fields are zero. This field is only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the DECFRAME_VIEW_RECT flag is true.
prBoundingRect
Specifies a pointer to a bounding rectangle. The bounding rectangle outlines the pixels written to when transparency is on. A bounding rectangle with all fields set to zero indicates that no pixels were written. The codec will write to this rectangle after decoding a frame if both the decoder selectively wrote non-transparent pixels and this pointer is not NULL. The bounding rectangle information is relative to the source image. This field is only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the DECFRAME_BOUNDING_RECT flag is true.
pbmTransparencyBitmask
Specifies a pointer to a transparency bitmask. The codec will write to this buffer after decoding a frame if both the decoder selectively wrote non-transparent pixels and this pointer is not NULL. The transparency bitmask is relative to the source image. However, the data outside the view rectangle is undefined. This field is only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the DECFRAME_TRANS_BITMASK flag is true.
pfUpdatedTransparencyBitmask
Specifies a pointer to a flag variable. After decoding each frame the codec will test this variable. If it is not NULL, the codec will set this flag to indicate if it has written transparency bitmask using the pbmTransparencyBitmask pointer. This field is only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the DECFRAME_TRANS_BITMASK flag is true.
lBrightness
Should be set to the brightness value. Legal value range from -255 to 255. The value of zero represents the default brightness level. Negative values have less brightness. Positive values have more brightness. This field is only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the DECFRAME_BRIGHTNESS flag is true.
lSaturation
Should be set to the saturation value. Legal value range from -255 to 255. The value of zero represents the default saturation level. Negative values have less saturation. Positive values have more saturation. This field is only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the DECFRAME_SATURATION flag is true.
lContrast
Should be set to the contrast value. Legal value range from -255 to 255. The value of zero represents the default contrast level. Negative values have less contrast. Positive values have more contrast. This field is only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the DECFRAME_CONTRAST flag is true.
Notes:
The view rectangle, rViewRect, may not extend beyond the current decode rectangle. This test will not be done until the next ICM_DECOMPRESS or ICM_DECOMPRESSEX call. If the rectangle extends beyond the decode rectangle ICERR_BADPARAM will be returned from the decompress call; the frame will not be decoded.
The decode rectangle, rDecodeRect, may only change before key frames. This test will not be done until the next ICM_DECOMPRESS or ICM_DECOMPRESSEX call. If the decode rectangle changes on a frame other than a key frame ICERR_BADPARAM will be returned from the decompress call; the frame will not be decoded.
The decode rectangle must contain the view rectangle. Although view rectangles may change on every frame decode rectangles may only change on key frames. For that reason the decode rectangle must cover the area used by all the view rectangles until the next key frame.
The transparency information returned via the bounding rectangle and transparency bitmask describes the pixels in terms of the original image dimensions and not the view rectangle.
The "DECSEQ" flags are used to identify the sequence data fields that are active. The "VALID" flag must be set to indicate that the flags variable has valid data.
#define DECSEQ_KEY (1UL<<0)
#define DECSEQ_SCALABILITY (1UL<<1)
#define DECSEQ_FILL_TRANSPARENT (1UL<<2)
#define DECSEQ_ALT_LINE (1UL<<3)
#define DECSEQ_VALID (1UL<<31)
typedef struct R4_DEC_SEQ_DATA, FAR * PTR_R4_DEC_SEQ_DATA;
dwSize
Should be set to the size of an R4_DEC_SEQ_DATA structure.
dwFourCC
Should be set to the codec four-cc.
dwVersion
Should be set to the interface version as specified in the "vfw_spec.h" include file.
mtType
Should be set to either MT_DECODE_SEQ_DEFAULT or MT_DECODE_SEQ_VALUE. This field identifies the ICM_GETCODECSTATE or ICM_SETCODECSTATE operation type. Additional information on this field is found in the sections "Messages for the Decoder using ICM_GETCODECSTATE" and "Messages for the Decoder using ICM_SETCODECSTATE".
oeEnvironment
Should be set to OE_16 for 16-bit applications or OE_32 for 32-bit applications.
dwFlags
Should be set to indicate which variables are in use. There is a flag corresponding to each variable in the structure. See the "DECSEQ_*" definitions. The DECSEQ_ALT_LINE flag requests an alternate line display. In the zoom by 2 mode with this flag set to 0, every line is duplicated and written to the screen on every frame. With the DECSEQ_ALT_LINE flag set to 1, that duplicate information is replaced with black and written only once a sequence. This flag is a request only. Not all color depths or formats will support this feature.
dwKey
Specifies a four-byte access key. This field is only valid if fEnabledKey is true. If the value does not match the value specified at encode time the codec will not decode the frames. It will instead return an ICERR_ERROR value from the ICM_DECOMPRESS and ICM_DECOMPRESSEX messages. This field is only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the DECSEQ_KEY flag is true.
fEnabledKey
Specifies whether the dwKey field should be used.
fScalability
Specifies if decode scalability is on. Should be set to 1 to turn scalability on. Should be set to zero to turn scalability off. This field is only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the DECSEQ_SCALABILITY flag is true.
fFillTransparentPixels
Specifies if transparent pixels should be displayed using a default color. The default color used is one of the transparency colors unless the sequence was created using TM_BITMASK transparency. In that case the default color is black. This field should be set to one to indicate that the transparent pixels be output in the default color. This field should be set to zero to indicate that the transparent pixels not be output (they will not be written). This field is only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the DECSEQ_FILL_TRANSPARENT flag is true.
Encode parameters can only be changed prior to an ICM_COMPRESS_BEGIN message. These are found in the R4_ENC_SEQ_DATA structure (these include the items that can be set in the advanced compression parameters dialog box). Use ICM_SETCODECSTATE to change these values. Use ICM_GETCODECSTATE to obtain these values.
The "ENCSEQ" flags are used to identify the sequence data fields that are active. The "VALID" flag must be set to indicate that the flags variable has valid data.
#define ENCSEQ_KEY (1UL<<0)
#define ENCSEQ_MINIMUM_VIEWPORT (1UL<<1)
#define ENCSEQ_TRANSPARENCY (1UL<<2)
#define ENCSEQ_SCALABILITY (1UL<<3)
#define ENCSEQ_BI_DIR_PREDICTION (1UL<<4)
#define ENCSEQ_PLAYBACK_PLATFORM (1UL<<5)
#define ENCSEQ_RANDOM_KEY_AND_BIDIR (1UL<<6)
#define ENCSEQ_FRAME_INFO (1UL<<7)
#define ENCSEQ_VALID (1UL<<31)
typedef struct R4_ENC_SEQ_DATA, FAR * PTR_R4_ENC_SEQ_DATA;
dwSize
Should be set to the size of an R4_ENC_SEQ_DATA structure.
dwFourCC
Should be set to the codec four-cc.
dwVersion
Should be set to the interface version as specified in the "vfw_spec.h" include file.
mtType
Should be set to either MT_ENCODE_SEQ_DEFAULT or MT_ENCODE_SEQ_VALUE. This field identifies the ICM_GETCODECSTATE or ICM_SETCODECSTATE operation type. Additional information on this field is found in the sections "Messages for the Encoder using ICM_GETCODECSTATE" and "Messages for the Encoder using ICM_SETCODECSTATE".
oeEnvironment
Should be set to OE_16 for 16-bit applications or OE_32 for 32-bit applications.
dwFlags
Should be set to indicate which variables are in use. There is a flag corresponding to each variable in the structure. See the "ENCSEQ_*" definitions.
dwKey
Specifies a four-byte key. This field is only valid if fEnabledKey is true. If the same key value is not also sent to the decoder at decode time, the codec will not decode the frames. This field is only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the ENCSEQ_KEY flag is true.
dwMinViewportWidth
Specifies the minimum viewport width. Legal values range from 0 to the image width. This field is only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the ENCSEQ_MINIMUM_VIEWPORT flag is true. The width may only be zero if the height is zero. The special zero,zero value is used to turn off the viewport.
dwMinViewportHeight
Specifies the minimum viewport height. Legal values range from 0 to the image height. This field is only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the ENCSEQ_MINIMUM_VIEWPORT flag is true. The height may only be zero if the width is zero. The special zero,zero value is used to turn off the viewport.
rngTransparencyRange
Specifies the transparency range if the tmTransparencyMethod field has a value of TM_RANGE. The transparency fields are only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the ENCSEQ_TRANSPARENCY flag is true.
pbmTransparencyBitmask
Specifies a pointer to a transparency bitmask buffer if the tmTransparencyMethod field has a value of TM_BITMASK. The transparency fields are only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the ENCSEQ_TRANSPARENCY flag is true.
tmTransparencyMethod
Specifies the transparency method. If the transparency method is TM_NONE the encoder will encode without transparency. If the transparency method is TM_RANGE the encoder will use the rngTransparencyRange field to create the transparency bitmask. If the transparency method is TM_BITMASK the encoder will read the transparency data from the bitmask buffer pointed to by the pbmTransparencyBitmask field. It is the application's responsibility to update the buffer before calling to compress the next frame. If the transparency method is TM_FRAME the encoder will use the first frame in the sequence to create the transparency range. It will use that range to create the transparency bitmask when encoding later frames in the sequence. If the transparency method is TM_ALPHA_CHANNEL, the encoder will extract the transparency bitmask from the alpha channel. This method only has meaning on the XRGB32 color depth. On all other color depths, this method generates no transparency. This field is only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the ENCSEQ_TRANSPARENCY flag is true.
fEnabledKey
Specifies whether a key has been specified.
fScalability
Specifies whether to enable scalability. This feature is disabled if the flag is false (Zero). It is enabled if the flag is true (non-zero). This field is only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the ENCSEQ_SCALABILITY flag is true.
fBiDirPrediction
Specifies whether to enable bi-directional prediction. This feature is disabled if the flag is false (Zero). It is enabled if the flag is true (non-zero). This field is only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if the ENCSEQ_BI_DIR_PREDICTION flag is true.
fRandomKeyAndBiDir
Specifies that the application understands the two frame latency associated with bi-directional prediction. Some applications assert key frames to implement the key frame interval but do not understand that the requested key frame is returned two frames later. To work-around the problems that result the Indeo video interactive codec ignores the random key frame flag if bi-directional prediction is on. The application can override this behavior by setting this flag to true.
dwPlaybackPlatform
Specifies the playback platform. Legal values are zero ("Low-End"), one ("Medium"), and two ("High End"). This field is only used by the ICM_GETCODECSTATE and ICM_SETCODECSTATE messages if ENCSEQ_PLAYBACK_PLATFORM is true.
wFrameLatency
Specifies the number of frames to pad at the end of a sequence. With Indeo video interactive this value will be 2 when bi-directional prediction is enabled and 0 otherwise. This read-only field is only used by the ICM_GETCODECSTATE message if ENCSEQ_FRAME_INFO is true.
wDeadFrames
Specifies the number of frames to discard at the beginning of the sequence in order to re-synchronize the audio to the video. This read-only field is only used by the ICM_GETCODECSTATE message if ENCSEQ_FRAME_INFO is true.
Notes:
If bi-directional prediction is enabled the encoder will repeat the first frame as the output of the first three encode requests and will never return the last two frames. Thus, the application must provide two dummy frames at the end of the sequence, remove the repeated frames from the beginning of the sequence, and re-synchronize the audio and video. See wFrameLatency and wDeadFrames.
The ICM_GETCODECSTATE message is used to get either default or current values. The mtType field is used to specify both the operation type and structure type.
When ICM_GETCODECSTATE is used with mtType set to MT_DECODE_FRAME_DEFAULT the codec assigns the default frame values to the structure members without changing its current values. The ICM_GETCODECSTATE parameter dwParam1 should point to an R4_DEC_FRAME_DATA structure, and dwParam2 should be the size of R4_DEC_FRAME_DATA in bytes.
When ICM_GETCODECSTATE is used with mtType set to MT_DECODE_FRAME_VALUE the codec assigns the current frame values to the structure members. The ICM_GETCODECSTATE parameter dwParam1 should point to an R4_DEC_FRAME_DATA structure, and dwParam2 should be the size of R4_DEC_FRAME_DATA in bytes.
When ICM_GETCODECSTATE is used with mtType set to MT_DECODE_SEQ_DEFAULT the codec assigns the default sequence values to the structure members without changing its current values. The ICM_GETCODECSTATE parameter dwParam1 should point to an R4_DEC_SEQ_DATA structure, and dwParam2 should be the size of R4_DEC_SEQ_DATA in bytes.
When ICM_GETCODECSTATE is used with mtType set to MT_DECODE_SEQ_VALUE the codec assigns the current sequence values to the structure members. The ICM_GETCODECSTATE parameter dwParam1 should point to an R4_DEC_SEQ_DATA structure, and dwParam2 should be the size of R4_DEC_SEQ_DATA in bytes.
The ICM_SETCODECSTATE message is used to set either default or current values. The mtType field is used to specify both the operation type and structure type.
When ICM_SETCODECSTATE is used with mtType set to MT_DECODE_FRAME_DEFAULT the codec assigns the default frame values to the structure members and changes its current values to these defaults. These changes do not take affect until the next ICM_DECOMPRESS or ICM_DECOMPRESSEX. The ICM_GETCODECSTATE parameter dwParam1 should point to an R4_DEC_FRAME_DATA structure, and dwParam2 should be the size of R4_DEC_FRAME_DATA in bytes.
When ICM_SETCODECSTATE is used with mtType set to MT_DECODE_FRAME_VALUE the codec changes its current frame values to the values specified in the structure. These changes do not take affect until the next ICM_DECOMPRESS or ICM_DECOMPRESSEX. The ICM_GETCODECSTATE parameter dwParam1 should point to an R4_DEC_FRAME_DATA structure, and dwParam2 should be the size of R4_DEC_FRAME_DATA in bytes.
When ICM_SETCODECSTATE is used with mtType set to MT_DECODE_SEQ_DEFAULT the codec assigns the default sequence values to the structure members and changes its current values to these defaults. These changes do not take affect until the next ICM_DECOMPRESS_BEGIN or ICM_DECOMPRESSEX_BEGIN. The ICM_GETCODECSTATE parameter dwParam1 should point to an R4_DEC_SEQ_DATA structure, and dwParam2 should be the size of R4_DEC_SEQ_DATA in bytes.
When ICM_SETCODECSTATE is used with mtType set to MT_DECODE_SEQ_VALUE the codec changes its current sequence values to the values specified in the structure. These changes do not take affect until the next ICM_DECOMPRESS_BEGIN or ICM_DECOMPRESSEX_BEGIN. The ICM_GETCODECSTATE parameter dwParam1 should point to an R4_DEC_SEQ_DATA structure, and dwParam2 should be the size of R4_DEC_SEQ_DATA in bytes.
When ICM_GETCODECSTATE is used with mtType set to MT_ENCODE_SEQ_DEFAULT the codec assigns the default sequence values to the structure members without changing its current values. The ICM_GETCODECSTATE parameter dwParam1 should point to an R4_ENC_SEQ_DATA structure, and dwParam2 should be the size of R4_ENC_SEQ_DATA in bytes.
When ICM_GETCODECSTATE is used with mtType set to MT_ENCODE_SEQ_VALUE the codec assigns the current sequence values to the structure members. The ICM_GETCODECSTATE parameter dwParam1 should point to an R4_ENC_SEQ_DATA structure, and dwParam2 should be the size of R4_ENC_SEQ_DATA in bytes.
When ICM_SETCODECSTATE is used with mtType set to MT_ENCODE_SEQ_DEFAULT the codec assigns the default sequence values to the structure members and changes its current values to these defaults. These changes do not take affect until the next ICM_COMPRESS_BEGIN. The ICM_GETCODECSTATE parameter dwParam1 should point to an R4_ENC_SEQ_DATA structure, and dwParam2 should be the size of R4_ENC_SEQ_DATA in bytes.
When ICM_SETCODECSTATE is used with mtType set to MT_ENCODE_SEQ_VALUE the codec changes its current sequence values to the values specified in the structure. These changes do not take affect until the next ICM_COMPRESS_BEGIN. The ICM_SETCODECSTATE parameter dwParam1 should point to an R4_ENC_SEQ_DATA structure, and dwParam2 should be the size of R4_ENC_SEQ_DATA in bytes.
There are special concerns for 16-bit applications that must use the extended features on a 32-bit operating system like Window 95. Due to the thunking implementation of Video for Windows it is necessary to set up an ICM_GETCODECSTATE message before performing it. The following code illustrates the method to use.
R4_ENC_SEQ_DATA FAR* pState;
pState->dwSize = sizeof(R4_ENC_SEQ_DATA);
pState->dwFourCC = mmioFOURCC('I', 'V', '4', '1');
pState->dwVersion = SPECIFIC_INTERFACE_VERSION;
pState->dwFlags = ENCSEQ_VALID | ENCSEQ_TRANSPARENCY;
// 16-bit operation requires that the request be
// setup. OR the MT_* code with MT_QUEUE.
pState->mtType = MT_ENCODE_SEQ_VALUE | MT_QUEUE;
pState->oeEnvironment = OE_16;
// Setup the desired structure with an ICM_SETCODECSTATE
ICSendMessage(hCodec, ICM_SETCODECSTATE, (DWORD) pState,
(DWORD)sizeof(R4_ENC_SEQ_DATA));
// Clear the FourCC for the queued 'get' operation
pState->dwFourCC = 0;
// Note that any non-negative return value is acceptable for 16-bit
// operation. For 32-bit operation, the return value must be 0.
iResult = ICSendMessage(hCodec, ICM_GETCODECSTATE,
(DWORD) pState, (DWORD) sizeof(R4_ENC_SEQ_DATA)));
It is a three step process. Setup the structure as usual. Issue an ICM_SETCODECSTATE message with its mtType field ORed with MT_QUEUE. Then send an ICM_GETCODECSTATE message with its dwFourCC member set to zero.
This method is necessary for all three data structures.
If there is an error in the structure of either an ICM_GETCODECSTATE or ICM_SETCODECSTATE message, an error code will be returned, but the dwFlags field will not indicate which structure member caused the error.
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