Working With Channel Devices(IM: QC)

Inside Macintosh: QuickTime Components /

Chapter 6 - Sequence Grabber Channel Components / Sequence Grabber Channel Components Reference

Working With Channel Devices
Sequence grabbers provide a number of functions that allow applications to determine the devices that can be, or the device that is, attached to a given sequence grabber channel. These devices, in turn, allow the channel component to control the digitizing equipment. For example, video channels use video digitizer components, and sound channels use sound input drivers. Applications can use these functions to present a list of available devices to the user, allowing the user to select a specific device for each channel. The sequence grabber passes these functions on to your channel component.
The sequence grabber may use the SGGetChannelDeviceList function to retrieve a list of devices that may be used by your channel.
The sequence grabber can use the SGSetChannelDevice function to assign a device to your channel.
The SGGetChannelDeviceList function uses a device list structure to pass information about one or more channel devices. The SGDeviceListRecord data type defines the format of the device list structure.
typedef struct SGDeviceListRecord {
   short          count;            /* count of devices */
   short          selectedIndex;    /* current device */
   long           reserved;         /* set to 0 */
   SGDeviceName   entry[1];         /* device names */
} SGDeviceListRecord, *SGDeviceListPtr, **SGDeviceList;
Field Description

count
Indicates the number of devices described by this structure. The value of this field corresponds to the number of entries in the device name array defined by the entry field.
selectedIndex

Identifies the currently active device. The value of this field corresponds to the appropriate entry in the device name array defined by the entry field. Note that this value is 0-relative; that is, the first entry has an index number of 0, the second's value is 1, and so on.
reserved
Reserved for Apple. Always set to 0.
entry
Contains an array of device name structures. Each structure corresponds to one valid device. The count field indicates the number of entries in this array. The SGDeviceName data type defines the format of a device name structure; this data type is discussed next.
Device list structures contain an array of device name structures. Each device name structure identifies a single device that may be used by the channel. The SGDeviceName data type defines the format of a device name structure.
typedef struct SGDeviceName {
   Str63       name;             /* device name */
   Handle      icon;             /* device icon */
   long        flags;            /* flags */
   long        refCon;           /* set to 0 */
   long        reserved;         /* set to 0 */
} SGDeviceName;
Field descriptions

name
Contains the name of the device. For video digitizer components, this field contains the component's name as specified in the component resource. For sound input drivers, this field contains the driver name.
icon
Contains a handle to the device's icon. Some devices may support an icon, which applications may choose to present to the user. If the device does not support an icon, or if the sequence grabber chooses not to retrieve this information (by setting the sgDeviceListWithIcons flag to 0 when it calls the SGGetChannelDeviceList function, which is described in the next section), set this field to nil.
flags
Reflects the current status of the device. The following flag is defined:
sgDeviceNameFlagDeviceUnavailable
When set to 1, this flag indicates that this device is not currently available.
refCon
Reserved for Apple. Always set to 0.
reserved
Reserved for Apple. Always set to 0.

Subtopics

SGGetChannelDeviceList

SGSetChannelDevice