Appendix B: Parallax Video Variables B








Our Video Development Environment uses a number of video variables. This appendix describes the video variables and lists the valid values for each variable:

Note: These variables can be used with Parallax video development tools to configure X windows with one exception. The plx_hardware variable is used only once-- when an X window is initialized for I/O--to return the type of Parallax hardware in use and to set up defaults in the plx_* data structures.

The variables used in the plx_* data structures and defined in the XPlxExt.h include file are described in the following table.

Table 1: Parallax Video Variables
Variable Name Defines Valid Values
channel The Parallax video input or output channel to use for the signal carrier PLX_INPUT_0 (D for input, port#1) PLX_INPUT_1 (Input port #2 on XVideo-VIO/RGB/XTRA/XVC-700) PLX_IO_OFF (D for output, turn output off) PLX_OUTPUT_0 (Output port on XVideo-VIO/RGB/XTRA/XVC-700)
format The analog-to-digital signal conversion format to use when digitizing the signal PLX_COMP (D--composite) PLX_YC (SuperVHS) PLX_RGB (RGB Component) PLX_YUV (YUV Component)
nvselect The location of the non-volatile RAM which contains color values to be applied to an X window. USER_0 (user preferences stored in NVRAM location "0") USER_1 (user preferences stored in NVRAM location "1") FACTORY (D for new board; factory settings)
plx_hardware The hardware in use. PLX_VIDEO_24 (D--only available hardware type)
standard The broadcast standard that the analog signal conforms to. PLX_NTSC (D--US standard) PLX_PAL (European standard) PLX_SECAM (French standard, also used in Russia; unsupported)
unsigned b The height of the blanking interval. For NTSC: 21 lines/field For PAL: 26 lines/field
unsigned h The height of the viewable portion of the video signal. For NTSC: 525 pixels For PAL: 625 pixels
unsigned interlaced The interlace indicator. 0 (FALSE=noninterlaced) or 1 (TRUE=interlaced; D)
unsigned r The frame display rate. For NTSC: 60 Hz For PAL: 50 Hz
unsigned sync_ok The sync_ok indicator. 0 (FALSE=signal not in sync) or 1 (TRUE=signal in sync; D)
unsigned w The width of the video signal. For NTSC: 640 pixels For PAL: 768 pixels
NOTE: D indicates the value is the default for XVideo, PowerVideo, and MultiVideo.