This is the base class of a set of classes dedicated to interact with sequence grabbber channel components also known simply as channel components. These components are used by higher–level sequence grabber components, and act to isolate the sequence grabber from the details of working with actual data types. Channel components may, in turn, depend on the services of still lower–level components, such as components. It defines properties and methods common to any channel object created during a grab session performed by instances of the class. Characteristics specific to a type of channel can be accessed by using the appropriate QTPlgChannel’s derived class.
→ →
The QTPlgChannel class constructors are called when you create a new instance of the class, while the ˜QTPlgChannel class destructor, is called automatically when the class is no more in use. Also, you can invoke the class destructor by setting the instance of the class to nil. Once a new class instance is returned, it is good practice to check the class property to be sure that the new object can be used. You will obtain valid instances of this class and its derived classes only from the list of the class.
The class provides you with the following initializer methods:
(other as QTPlgChannel)
This is the copy constructor. The properties of the object to be copied will be used to initialize the
new class instance properties
a reference to the identifier of the connection to the channel component (aka component instance). useful for toolbox programmers
(use with care: you could invalidate the reference causing unpredictable results
(probably an application crash))
if this property is set to true, the channel has a visual representation
if this property is set to true, the channel has an audio representation
if this property is set to true, the grabber component may limit the number of frames processed
in a record operation or the rate at which those frames are processed.
If the channel’s data is not organized into frames, this property is set to false
specifies if the channel is being used for previewing
specifies if the channel is being used for recording
specifies if you want the channel to play its captured data during a record operation
specifies if you want the channel to return the freshest frame possible during videoconferencing,
live broadcast, and live image processing
specifies if you want the channel to tell VDIGs to always use timebase time instead of creating uniform frame durations.
This produces more accurate live sync with audio
specifies if the channel component uses its default playback methodology. This property along with
and
class properties are mutually exclusive
specifies if the channel sacrifices playback quality to achieve the specified playback rate. This property along with
and
class properties are mutually exclusive
specifies if the channel plays the channel’s data at the highest possible quality.
This option sacrifices playback rate for the sake of image quality. It may reduce the amount of processor time available
to other programs in the computer. This option does not affect the quality of the recorded data,
however. This property along with
and
class properties are mutually exclusive
specifies if the channel tries to play all of the data it captures, even the data that is stored in offscreen buffers.
This option is useful when you want to be sure that the user sees as much of the captured data as possible.
This property can be combined with all of the play... class properties seen above
specifies the channel’s time scale.
This value typically corresponds to the time scale of the media that has been created by the channel
specifies the device assigned to a channel; this property supersedes the class
method listed below
this property lets you access to the list of the
that are valid for the channel. This list will include the list of inputs as well as the list of devices. If the channel is an instance of the
class, then, the list will be populated with instances of the
class
this property allows you wether to retrieve informations about the channel configuration or modify it programmatically.
The type of
class instance used depends on the
type of channel. For example, a object will use
instances of the class. If the channel
has not a particular data descriptor associated to it, this property will return objects of type
. You can use the
isA RealBasic operator to find about the data descriptor’s type.
if the channel provides support for this, this property specifies the digitizer associated to it, otherwise
is set to nil.This allows you to interact with low–level channel digitizer components.
See the QTPlgChannel derived classes for details
determines the size of the source video boundary rectangle. For video channel components that work
with video digitizer components, the source video boundary rectangle corresponds to the video digitizer’s
active source rectangle
(device as
)
use this function if you want to change the device assigned to a channel. You specify the device by using the
device parameter that must be a valid
class instance.
You can obtain informations about the device currently in use, by inspecting the
class property
([onlyForPreview as boolean=
false])
as boolean
causes the channel to display its settings dialog box to the user. If the user confirms the changes done to the
channel configuration parameters, the channel configuration will be automatically update as appropriate.
By using the optional parameter onlyForPreview , you can indicate that the dialog box provided by this function
will be used to configure the sequence grabber for previewing only, not for recording. If you set this parameter to
true, this function automatically excludes any panels that aren't necessary for preview configuring,
such as video or audio compression settings. If you omit this parameter, the function will assign it the default value of
false