videoGetFieldMode(3mms) — Subroutines
Name
videoGetFieldMode --- Obtain the current video field mode value
Syntax
#include <mme/mme_api.h>
MMRESULT videoGetFieldMode(
HVIDEO hVideo,
DWORD ∗lpdwModeReturn);
Arguments
HVIDEO hVideo
Specifies a handle to a video device channel.
DWORD lpdwModeReturn
Specifies a pointer to return the field mode in. The memory must be allocated with the function mmeAllocMem. The return values will be one of the following if no error occurs:
VIDEO_MODE_FRAME
VIDEO_MODE_FRAME_EVEN_DOM
VIDEO_MODE_FRAME_ODD_DOM
VIDEO_MODE_FIELD_BOTH
VIDEO_MODE_FIELD_ODD_ONLY
VIDEO_MODE_FIELD_EVEN_ONLY
Description
The videoGetFieldMode function obtains the current video field mode value. The value returned is valid only as far as the configuration information of the device is valid. Before setting the standard or configuring the format, the field mode may be set to the default field mode. If not all standards and formats are supported for the default field mode, the field mode may change. Check the field mode after setting the standard and configuring the format to find out the final mode being used by the device.
Field Mode Dominance
The videoGetFieldMode function has been extended to include field mode dominance support. Capturing full-frame video requires combining two consecutive video fields in one frame. The first field in the pair is referred to as the dominant field. Source and destination video devices should agree on field dominance. If they do not, then reversed dominance, such as framing artifacts in full-frame mode, can occur. This can be seen by magnifying an area of motion in a captured frame to see temporal artifacts or jagged edges in the images.
The VIDEO_MODE_FRAME flag has been extended to indicate the default dominance of a hardware device. Two flags, VIDEO_MODE_FRAME_EVEN_DOM and VIDEO_MODE_FRAME_ODD_DOM, have been added to specify even and odd dominance, respectively. If the field mode is set to VIDEO_MODE_FRAME and a query of the field mode using the videoGetFieldMode function is made, the device will return the field mode dominance it is using (video capture only at this time).
Not all devices can be adjusted. Setting the field mode to VIDEO_MODE_FRAME_EVEN_DOM or VIDEO_MODE_FRAME_ODD_DOM may result in an error if that particular dominance is not currently supported. Use VIDEO_MODE_FRAME if the dominance is not important to an application. Be aware of this error if your application deinterlaces images on its own. Be careful about placing even and odd fields in the frames your application composes (video capture) or decomposes (video playback).
Extensions
None.
Return Values
Returns DV_ERR_OK if the function is successful; otherwise, it returns one of the following error codes:
DV_ERR_UNSUPPORTED@T{ The function is not supported for the device. T} DV_ERR_PARAM1@T{ The pointer to the mode is not valid. T} DV_ERR_INVALHANDLE@T{ The specified device handle is invalid. T}
Device-Specific Notes
The following notes regarding field mode dominance are specific to the Sound and Motion J300 and FullVideo Supreme option modules:
The Sound and Motion J300 option module does not permit adjustment of field dominance. It is always set to even.
The FullVideo Supreme JPEG option module and Revision B of the FullVideo Supreme (AV301) option module allow adjustment of video capture field dominance. By default, these option modules use odd dominance for video capture. Both boards use odd dominance for video playback, but the dominance cannot be adjusted.
The FullVideo Supreme option modules that support this can be determined by examining the part number on the module itself:
Revision A 54-23296-04.A01
Revision B 54-23296-04.B01