Inside Macintosh: QuickTime Components

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Selecting an Input Source

This section discusses the video digitizer component functions that allow applications to select an input video source.

Some of these functions provide information about the available video inputs. Applications can use the VDGetNumberOfInputs function to determine the number of video inputs supported by the digitizer component. The VDGetInputFormat function allows applications to find out the video format (composite, s-video, or component) employed by a specified input.

You can use the VDSetInput function in your application to specify the input to be used by the digitizer component. The VDGetInput function returns the currently selected input.

The VDSetInputStandard function allows you to specify the video signaling standard to be used by the video digitizer component.

VDGetNumberOfInputs

The VDGetNumberOfInputs function returns the number of input video sources that a video digitizer component supports.

All video digitizer components must support this function.

pascal VideoDigitizerError VDGetNumberOfInputs
                                          (VideoDigitizerComponent ci,
                                          short *inputs);
ci
Specifies the video digitizer component for the request. Applications obtain this reference from the Component Manager's OpenComponent function.
inputs
Contains a pointer to an integer that is to receive the number of input video sources supported by the specified component. Video digitizer components number video sources sequentially, starting at 0. So, if a digitizer component supports two inputs, this function sets the field referred to by the inputs parameter to 1.

RESULT CODE

noErr

0

No error

VDSetInput

The VDSetInput function allows applications to select the input video source for a video digitizer component.

All video digitizer components must support this function.

pascal VideoDigitizerError VDSetInput (VideoDigitizerComponent ci,
                                          short input);
ci
Specifies the video digitizer component for the request. Applications obtain this reference from the Component Manager's OpenComponent function.
input
Specifies the input video source for this request. Video digitizer components number video sources sequentially, starting at 0. So, to request the first video source, an application sets this parameter to 0.

RESULT CODES

noErr

0

No error

qtParamErr

-2202

Invalid parameter value

SEE ALSO

Applications can get the number of video sources supported by a video digitizer component by calling the VDGetNumberOfInputs function (described in the previous section). Applications can get more information about a video source by calling the VDGetInputFormat function (described on VDGetInputFormat ).

VDGetInput

The VDGetInput function returns data that identifies the currently active input video source.

All video digitizer components must support this function.

pascal VideoDigitizerError VDGetInput (VideoDigitizerComponent ci,
                                          short *input);
ci
Specifies the video digitizer component for the request. Applications obtain this reference from the Component Manager's OpenComponent function.
input
Contains a pointer to a short integer that is to receive the identifier for the currently active input video source. Video digitizer components number video sources sequentially, starting at 0. So, if the first source is active, this function sets the field referred to by the input parameter to 0.

RESULT CODES

noErr

0

No error

qtParamErr

-2202

Invalid parameter value

VDGetInputFormat

The VDGetInputFormat function allows applications to determine the format of the video signal provided by a specified video input source.

pascal VideoDigitizerError VDGetInputFormat
                                         (VideoDigitizerComponent ci,
                                          short input, short *format);
ci
Specifies the video digitizer component for the request. Applications obtain this reference from the Component Manager's OpenComponent function.
input
Specifies the input video source for this request. Video digitizer components number video sources sequentially, starting at 0. So, to request information about the first video source, an application sets this parameter to 0. Applications can get the number of video sources supported by a video digitizer component by calling the VDGetNumberOfInputs function, discussed on VDGetNumberOfInputs .
format
Contains a pointer to a short integer that is to receive the specification of the video format of the specified input source. This function updates the field referred to by the format parameter. Valid values are
compositeIn
The input video signal is in composite format
sVideoIn
The input video signal is in s-video format
rgbComponentIn
The input video signal is in RGB component format

DESCRIPTION

Video digitizer components support three video formats: composite video, s-video, and component video (RGB signal).

All video digitizer components must support this function.

RESULT CODES

noErr

0

No error

qtParamErr

-2202

Invalid parameter value

VDSetInputStandard

The VDSetInputStandard function allows applications to specify the input signaling standard to digitize. Video digitizer components support three input signaling standards: NTSC, PAL, and SECAM.

pascal VideoDigitizerError VDSetInputStandard
                                          (VideoDigitizerComponent ci,
                                          short inputStandard);
ci
Specifies the video digitizer component for the request. Applications obtain this reference from the Component Manager's OpenComponent function.
inputStandard
A short integer that specifies the signaling standard used in the source video signal. Valid values are
ntscIn
Input video signal to digitize is in NTSC format
palIn
Input video signal to digitize is in PAL format
secamIn
Input video signal to digitize is in SECAM format

DESCRIPTION

Applications can use the VDGetDigitizerInfo function (described on VDGetDigitizerInfo ) to determine the capabilities of a specified video digitizer component. Applications can use the VDGetCurrentFlags function (described on VDGetCurrentFlags ) to determine the current input state of a digitizer component.

All video digitizer components must support this function.

SPECIAL CONSIDERATIONS

Your digitizer component should ensure that spatial characteristics that were set for one standard are not interpreted within another standard.

RESULT CODES

noErr

0

No error

qtParamErr

-2202

Invalid parameter value

© 1997 Apple Computer, Inc.

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