Chapter 3. Using VL Controls
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Chapter 3. Using VL Controls

VL controls enable you to:

This chapter explains

Device-independent controls are documented in /usr/include/dmedia/vl.h. Device-dependent controls for the Indigo2 Video board for Indigo2 IMPACT are documented in the header file /usr/include/media/vl_ev1.h).

Table 3-1 lists device-independent VL controls alphabetically, along with their values or ranges.

Table 3-1. Device-Independent VL Controls

Control

Purpose

Comments

VL_BLEND_A

Input source for foreground (channel A) image

VLNode type derived from vlGetNode(); must be one of the source nodes

VL_BLEND_B

Input source for background (channel B) image

VLNode type derived from vlGetNode(); must be one of the source nodes

VL_BLEND_A_ALPHA

Input source for foreground (channel A) alpha

 

VL_BLEND_B_ALPHA

Input source for background (channel B) alpha

 

VL_BLEND_A_FCN

Blend function that controls mixing of foreground (channel A) signals

VL_BLDFCN_ZERO
VL_BLDFCN_ONE
VL_BLDFCN_A_ALPHA:
foreground_alpha/255
VL_BLDFCN_MINUS_A_ALPHA:
1 - (foreground_alpha/255)

VL_BLEND_B_FCN

Blend function that controls mixing of background (channel B) signals

VL_BLDFCN_ZERO
VL_BLDFCN_ONE
VL_BLDFCN_B_ALPHA:
background_alpha/255
VL_BLDFCN_MINUS_B_ALPHA:
1 - (background_alpha/255)

VL_BLEND_A_NORMALIZE

 

1 = on; off is not supported

VL_BLEND_B_NORMALIZE

Follows Porter-Duff model (background [channel A]' pixels premultiplied by their corresponding alphas before blending); premultiplies foreground (channel B) by alpha

0 = off
1 = on

VL_BLEND_OUT_NORMALIZE

 

Not supported

VL_BRIGHTNESS

Brightness

 

VL_CAP_TYPE

Type of frame(s) or field(s) to capture; see “Interlacing” in Appendix A

 

VL_CONTRAST

 

 

VL_DEFAULT_SOURCE

Default source for the video path

 

VL_FORMAT

Video format

 

VL_FREEZE

Data transfer freeze; suspends transfer at the drain node, with no picture regeneration

0 = off
1 = on

VL_H_PHASE

Horizontal phase

 

VL_HUE

Hue; the control panel vcp calculates numerator and denominator

 

VL_MUXSWITCH

Switch between inputs on a single path, corresponding to the physical connector to the option

Y/C (RCA jacks)
set 0

Y/C (S-Video connector):
set 1

Composite input 1: set 3; input 2: set 4

VL_OFFSET

On VL_VIDEO nodes, the offset to the active region of the video; on all other nodes, the offset within the video

Because the default is 0,0, use negative values to get blanking data

 

VL_ORIGIN

Upper left corner of image in drain (usually a window); the offset within the node;

Coordinates; default is 0,0

VL_PACKING

Packing of video data at source or drain

 

VL_RATE

Transfer rate in fields or frames

 

VL_SIGNAL

 

N/A

VL_SIZE

On VL_VIDEO nodes, the size of the video; on all other nodes, the clipped size of the video

 

VL_SYNC

Sync mode

VL_SYNC_INTERNAL
VL_SYNC_GENLOCK
VL_SYNB_SLAVE

VL_SYNC_SOURCE

Sets sync source for analog breakout box

Composite 1: set 0
Composite 2: set 2

VL_TIMING

Video timing

 

VL_V_PHASE

Vertical phase

Integer

VL_WINDOW

Window ID for video in a window (screen node only)

Integer

VL_ZOOM

Zoom factor for video stream; fractions greater than 1 expand the picture, fractions less than one reduce the picture

4/1, 2/1, 1/1, 1/2, 1/3, 1/4, 1/5, 1/6, 1/7, 1/8


Note: For information on controls for keying, blending, or wipes, see Chapter 5, “Blending, Keying, and Transitions.”

For detailed information on using VL_CAP_TYPE, VL_FORMAT, VL_MUXSWITCH, VL_OFFSET, VL_PACKING, VL_RATE, VL_SIZE, VL_TIMING, and VL_ZOOM, see “Setting Parameters for Data Transfer to or From Memory” in Chapter 2.

VL Control Type and Values

The type of VL controls is:

typedef long VLControlType;

Common types used by the VL to express the values returned by the controls are:

typedef struct __vlControlInfo {
    char name[VL_NAME_SIZE]; /* name of control */
    VLControlType type;      /* e.g. WINDOW, HUE, BRIGHTNESS */
    VLControlClass ctlClass; /* SLIDER, DETENT, KNOB, BUTTON */
    VLControlGroup group;    /* BLEND, VISUAL QUALITY, SIGNAL, SYNC */
    VLNode node;             /* associated node */
    VLControlValueType valueType;       /* what kind of data do we have */
    int valueCount;             /* how many data items do we have */
    int numFractRanges;     /* number of ranges to describe control */
    VLFractionRange *ranges; /* range of values of control */

    int numItems;               /* number of enumerated items */
    VLControlItem *itemList;    /* the actual enumerations */
} VLControlInfo;

To store the value of different controls, libvl.a uses the struct:

typedef union {
    VLFraction  fractVal;
    VLBoolean   boolVal;
    int         intVal;
    VLXY        xyVal;
    char        stringVal[96];  /* beware of trailing NULLs! */
    float       matrixVal[3][3];        
    uint        pad[24];        /* reserved */
} VLControlValue;

typedef struct {
    int numControls;
    VLControlInfo *controls;
} VLControlList;

The control info structure is returned by a vlGetControlInfo() call, and it contains many of the items discussed above.

VLControlInfo.number is the number of the VLControlInfo.node that the info pertains to. There may be several controls of the same type on a particular node, but usually there is just one.

VLControlInfo.numFractRanges is the number of fraction ranges for a particular control. The names correspond 1-to-1 with the rangeNames, up to the number of range names, numRangeNames. That is, there may be fewer names than ranges, but never more.

VL Control Fraction Ranges

The VL uses fraction ranges to represent the values possible for a control. A VLFractionRange generated by the VL is guaranteed never to generate a fraction with a zero denominator, or a fractional numerator or denominator.

For a VLProgressionType of VL_LINEAR, numerator.increment and denominator.increment are guaranteed to be greater than zero, and the limit is always guaranteed to be {numerator,denominator}.base, plus some integral multiple of {numerator,denominator}.increment.

The type definition for fraction types in the header file is: 

typedef struct {
    VLRange numerator;
    VLRange denominator;
} VLFractionRange;

VL Control Classes

The VL defines control classes for user-interface developers. The classes are hints only; they are the VL developer's idea of how the control is commonly represented in the real world.

#define VL_CLASS_NO_UI            0
#define VL_CLASS_SLIDER           1
#define VL_CLASS_KNOB             2
#define VL_CLASS_BUTTON           3
#define VL_CLASS_TOGGLE           4
#define VL_CLASS_DETENT_KNOB      5
#define VL_CLASS_LIST             6

In the list above, VL_CLASS_NO_UI is often used for controls that have no user-interface metaphor and are not displayed in the video control panel or saved in the defaults file.

The VL controls can be read-only, write-only, or both. The VL includes these macros:

#define VL_CLASS_RDONLY         0x8000  /* control is read-only */
#define VL_CLASS_WRONLY         0x4000  /* control is write-only */
#define VL_CLASS_NO_DEFAULT     0x2000  /* don't save in default files */

#define VL_IS_CTL_RDONLY(x)     ((x)->ctlClass & VL_CLASS_RDONLY)
#define VL_IS_CTL_WRONLY(x)     ((x)->ctlClass & VL_CLASS_WRONLY)
#define VL_IS_CTL_RW(x)         (!(VL_IS_CTL_RDONLY(x) && VL_IS_CTL_WRONLY(x)))

to test these conditions:

#define VL_CLASS_MASK        0xfff

typedef unsigned long VLControlClass; /* from list above */

VL Control Groupings

Like control class, control grouping is an aid for the user-interface developer. The groupings are the VL developer's idea of how the controls would be grouped in the real world. These groupings are implemented in the video control panel vcp.

The type definition for groupings is: 

typedef char NameString[80];
#define VL_CTL_GROUP_PATH     9    /* Path Controls */

The maximum length of a control or range name is VL_NAME_SIZE.

Table 3-2 summarizes the VL control groupings.

Table 3-2. VL Control Groupings

Grouping

Includes controls for...

VL_CTL_GROUP_BLENDING

Blending; for example, VL_BLEND_B

VL_CTL_GROUP_VISUALQUALITY

Visual quality of sources or drains; for example, VL_H_PHASE or VL_V_PHASE

VL_CTL_GROUP_SIGNAL

Signal of sources or drains; for example, VL_MUXSWITCH or VL_HUE

VL_CTL_GROUP_CODING

Encoding or decoding sources or drains; for example, VL_TIMING or VL_FORMAT

VL_CTL_GROUP_SYNC

Synchronizing video sources or drains; for example, VL_SYNC

VL_CTL_GROUP_ORIENTATION

Orientation or placement of video signals; for example, VL_ORIGIN

VL_CTL_GROUP_SIZING

Setting the size of the video signal; for example, VL_SIZE

VL_CTL_GROUP_RATES

Setting the rate of the video signal; for example, VL_RATE

VL_CTL_GROUP_WS

Specifying the windowing system of the workstation; for example, VL_WINDOW

VL_CTL_GROUP_PATH

Specifying the data path through the system; these controls, often marked with the VL_CLASS_NO_UI, are often internal to the VL, with no direct access for the user

VL_CTL_GROUP_SIGNAL_ALL

Specifying properties of all signals

VL_CTL_GROUP_SIGNAL_COMPOSITE

Specifying properties of composite signals

VL_CTL_GROUP_SIGNAL_CLUT_COMPOSITE

Specifying properties of composite color lookup table (CLUT) controls

VL_CTL_GROUP_KEYING

Specifying properties of chroma or luma keying controls, such as VL_KEYER_FG_OPACITY

VL_CTL_GROUP_PRO

Specifying values not commonly found on the front panel of a real-world video device; for example, a wipe control

VL_CTL_GROUP_MASK

Masking optional bits to extract only the control group


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Chapter 2. Creating Video Programs With the Video Library  Chapter 4. VL Event Handling