# Live video input class.# Note that importing this module attempts to initialize video.# Check if video is available.# There are three reasons for failure here:# (1) this version of Python may not have the sv or imageop modules;# (2) this machine may not have a video board;# (3) initializing the video board may fail for another reason.# The global variable have_video is set to true iff we reall do have video.try:	import sv	import SV	import imageop	try:		v = sv.OpenVideo()		have_video = 1	except sv.error:		have_video = 0except ImportError:	have_video = 0# The live video input class.# Only instantiate this if have_video is true!class LiveVideoIn:	# Initialize an instance.  Arguments:	# vw, vh: size of the video window data to be captured.	# For some reason, vw MUST be a multiple of 4.	# Note that the data has to be cropped unless vw and vh are	# just right for the video board (vw:vh == 4:3 and vh even).	def __init__(self, pktmax, vw, vh, type):		if not have_video:			raise RuntimeError, 'no video available'		if vw % 4 != 0:			raise ValueError, 'vw must be a multiple of 4'		self.pktmax = pktmax		realvw = vh*SV.PAL_XMAX/SV.PAL_YMAX		if realvw < vw:			realvw = vw		self.realwidth, self.realheight = v.QuerySize(realvw, vh)		if not type in ('rgb8', 'grey', 'mono', 'grey2', 'grey4'):			raise 'Incorrent video data type', type		self.type = type		if type in ('grey', 'grey4', 'grey2', 'mono'):			v.SetParam([SV.COLOR, SV.MONO, SV.INPUT_BYPASS, 1])		else:			v.SetParam([SV.COLOR, SV.DEFAULT_COLOR, \				  SV.INPUT_BYPASS, 0])		# Initialize capture		(mode, self.realwidth, self.realheight, qsize, rate) = \			v.InitContinuousCapture(SV.RGB8_FRAMES, \				self.realwidth, self.realheight, 1, 2)		self.width = vw		self.height = vh		self.x0 = (self.realwidth-self.width)/2		self.x1 = self.x0 + self.width - 1		self.y0 = (self.realheight-self.height)/2		self.y1 = self.y0 + self.height - 1		# Compute # full lines per packet		self.lpp = pktmax / self.linewidth()		self.pktsize = self.lpp*self.linewidth()		self.data = None		self.dataoffset = 0		self.lpos = 0		self.justright = (self.realwidth == self.width and \			self.realheight == self.height)##		if not self.justright:##			print 'Want:', self.width, 'x', self.height,##			print '; grab:', self.realwidth, 'x', self.realheight	# Change the size of the video being displayed.	def resizevideo(self, vw, vh):		self.close()		self.__init__(self.pktmax, vw, vh, self.type)	# Remove an instance.	# This turns off continuous capture.	def close(self):		v.EndContinuousCapture()	# Get the length in bytes of a video line	def linewidth(self):		if self.type == 'mono':			return (self.width+7)/8		elif self.type == 'grey2':			return (self.width+3)/4		elif self.type == 'grey4':			return (self.width+1)/2		else:			return self.width	# Get the next video packet.	# This returns (lpos, data) where:	# - lpos is the line position	# - data is a piece of data	# The dimensions of data are:	# - pixel depth = 1 byte	# - scan line width = self.width (the vw argument to __init__())	# - number of scan lines = self.lpp (PKTMAX / vw)	def getnextpacket(self):		if not self.data or self.dataoffset >= len(self.data):			try:				cd, id = v.GetCaptureData()			except sv.error:				return None			data = cd.InterleaveFields(1)			cd.UnlockCaptureData()			if self.justright:				self.data = data			else:				self.data = imageop.crop(data, 1, \					  self.realwidth, \					  self.realheight, \					  self.x0, self.y0, \					  self.x1, self.y1)			self.lpos = 0			self.dataoffset = 0			if self.type == 'mono':				self.data = imageop.dither2mono(self.data, \					  self.width, self.height)			elif self.type == 'grey2':				self.data = imageop.dither2grey2(self.data, \					  self.width, self.height)			elif self.type == 'grey4':				self.data = imageop.grey2grey4(self.data, \					  self.width, self.height)		data = self.data[self.dataoffset:self.dataoffset+self.pktsize]		lpos = self.lpos		self.dataoffset = self.dataoffset + self.pktsize		self.lpos = self.lpos + self.lpp		return lpos, data