IAMExtDevice::GetCapability method (strmif.h)
[The feature associated with this page, DirectShow, is a legacy feature. It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation. Those features have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer, IMFMediaEngine and Audio/Video Capture in Media Foundation instead of DirectShow, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]
The GetCapability method retrieves the capabilities of the external device.
Syntax
HRESULT GetCapability(
[in] long Capability,
[out] long *pValue,
[out] double *pdblValue
);
Parameters
[in] Capability
Specifies the capability to check. See Remarks for more information.
[out] pValue
Pointer to a variable that receives a long integer. See Remarks for more information.
[out] pdblValue
Pointer to a variable that receives a double. See Remarks for more information.
Return value
When this method succeeds, it returns S_OK. Otherwise it returns an HRESULT error code.
Remarks
The Capability parameter is a flag that specifies which capability to check. The method returns the result either in the pValue parameter or in the pdblValue parameter, depending on the capability flag.
For the following flags, the method returns the value OATRUE or OAFALSE in the pValue parameter. The value OATRUE indicates that the capability is present, while the value OAFALSE indicates it is absent.
| Capability flag | Description |
|---|---|
| ED_DEVCAP_AUDIO_INPUTS | Device accepts audio input. |
| ED_DEVCAP_CAN_MONITOR_SOURCES | Device can send any input to the monitored output, regardless of the input that is currently selected. |
| ED_DEVCAP_CAN_PREVIEW | Device can preview. |
| ED_DEVCAP_CAN_RECORD | Device can record. |
| ED_DEVCAP_CAN_RECORD_STROBE | Device can strobe record. This capability applies to multitrack devices that can record to selected tracks. |
| ED_DEVCAP_CAN_SAVE | Device can save data. |
| ED_DEVCAP_CTLTRK_READ | Device can read control tracks. |
| ED_DEVCAP_HAS_AUDIO | Device has audio. |
| ED_DEVCAP_HAS_VIDEO | Device has video. |
| ED_DEVCAP_INDEX_READ | Device can read index marks. |
| ED_DEVCAP_NEEDS_CALIBRATING | Device needs calibrating. See IAMExtDevice::Calibrate. |
| ED_DEVCAP_TIMECODE_READ | Device can read SMPTE time code. |
| ED_DEVCAP_TIMECODE_WRITE | Device can set SMPTE time code. |
| ED_DEVCAP_USES_FILES | Device has a built-in file system. |
| ED_DEVCAP_VIDEO_INPUTS | Device accepts video input. |
For the following flags, the method returns a defined constant in the pValue parameter.
ED_DEVCAP_DEVICE_TYPE: Returns the device type.
| Returned Constant | Description |
|---|---|
| ED_DEVTYPE_ATR | Audio tape recorder |
| ED_DEVTYPE_CG | Character generator |
| ED_DEVTYPE_DDR | Digital disk recorder |
| ED_DEVTYPE_DVE | Digital video effects unit |
| ED_DEVTYPE_GPI | General purpose interface trigger |
| ED_DEVTYPE_KEYER | Video keyer |
| ED_DEVTYPE_LASERDISK | Laserdisc |
| ED_DEVTYPE_MIXER_AUDIO | Audio mixer |
| ED_DEVTYPE_MIXER_VIDEO | Video mixer |
| ED_DEVTYPE_ROUTER | Video router |
| ED_DEVTYPE_TBC | Timebase corrector |
| ED_DEVTYPE_TCG | Timecode generator/reader |
| ED_DEVTYPE_VCR | VCR, or camcorder with full VCR capabilities |
| ED_DEVTYPE_WIPEGEN | Video wipe generator |
| ED_DEVTYPE_JOYSTICK | Joystick |
| ED_DEVTYPE_KEYBOARD | Keyboard |
ED_DEVCAP_SYNC_ACCURACY: Returns an indication of the device's synchronization accuracy.
| Returned Constant | Description |
|---|---|
| ED_SYNCACC_PRECISE | Device has precise accuracy. |
| ED_SYNCACC_FRAME | Device is frame accurate. |
| ED_SYNCACC_ROUGH | Device is less than frame accurate. |
ED_DEVCAP_NORMAL_RATE: Returns the device's normal frame rate.
| Returned Constant | Description |
|---|---|
| ED_RATE_24 | 24 frames per second (fps) |
| ED_RATE_25 | 25 fps |
| ED_RATE_2997 | 29.97 fps |
| ED_RATE_30 | 30 fps |
ED_DEVCAP_SEEK_TYPE: Returns an indication of the device's seeking accuracy.
| Returned Constant | Description |
|---|---|
| ED_SEEK_PERFECT | Device can seek within one video frame without a signal break. |
| ED_SEEK_FAST | Device can seek quickly, with a short break in the signal. |
| ED_SEEK_SLOW | Device seeks slowly; such as tape transport. |
For the following flags, the method returns a numeric value in the pValue parameter.
| Capability Flag | Returned Value |
| ED_DEVCAP_EXTERNAL_DEVICE_ID | Manufacturer-specific identifier. |
| ED_DEVCAP_PREROLL | Device preroll time. |
| ED_DEVCAP_POSTROLL | Device postroll time. |
In Windows XP Service Pack 2 and later, the following additional flags are supported for ED_DEVCAP_DEVICE_TYPE.
| Returned Constant | Description |
|---|---|
| ED_DEVTYPE_CAMERA_STORAGE | Storage for still images or short video files. |
| ED_DEVTYPE_DTV | Digital television with serial bus interface. |
| ED_DEVTYPE_PC_VIRTUAL | Virtual or emulated device on a computer. |
To use these constants, include the header file Xprtdefs.h.
DV Implementation
The MSDV and UVC drivers support the following behaviors.The ED_DEVCAP_NORMAL_RATE flag returns the frame rate.
| Returned Constant | Description |
|---|---|
| ED_RATE_25 | 25 fps (default PAL frame rate) |
| ED_RATE_2997 | 29.997 fps (default NTSC frame rate) |
For MSDV only, the ED_DEVCAP_DEVICE_TYPE flag returns the device type. Possible values are shown in the following table. For UVC devices, use the IKsTopologyInfo interface instead.
| Returned Constant | Description |
|---|---|
| ED_DEVTYPE_CAMERA | Simple camera that can record or pause-record, but lacks full VCR capabilities. |
| ED_DEVTYPE_DVHS | Device supports D-VHS format. |
| ED_DEVTYPE_UNKNOWN | Unknown device type. |
| ED_DEVTYPE_VCR | Device has full VCR capabilities. |
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows 2000 Professional [desktop apps only] |
| Minimum supported server | Windows 2000 Server [desktop apps only] |
| Target Platform | Windows |
| Header | strmif.h (include Dshow.h) |
| Library | Strmiids.lib |