Introductory video documentation

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+	CMIF video tools
+
+This document gives a quick introduction to some of the tools useful
+for recording, editing and playing back video data in CMIF video
+format. All the tools mentioned currently live in /ufs/guido/bin/sgi.
+A description of the CMIF video file format can be found in
+/ufs/jack/cmif-film.ms. 
+
+	Recording video
+
+There are two tools to record video, Vrec and and Vrecb. Vrec does
+continuous capture, but can capture at most 15 frames per second.
+Vrecb uses burst capture, enabling it to capture all frames. It
+captures to main memory, however, so it cannot handle long video
+fragments. The following options are common to both programs:
+
+ -r rate	Capture one out of 'rate' frames. Default (and
+		minimum) is 1 for Vrecb, 2 for Vrec. There are some
+		caveats for recording PAL, see below.
+ -w width	Set initial window width (and height, implicitly).
+ -g bits	Create greyscale film in stead of 8-bit dithered color
+		film. Allowable values for 'bits' are 2, 4 or 8.
+ -m		Create monochrome dithered film. These look horrible.
+ -M threshold	Create monochrome thresholded film with specified
+		threshold (in range 0..255).
+ -G		Create 2-bit dithered greyscale film.
+ -f		Capture fields in stead of frames. The film is created
+		in such a way that the picture will be suitably
+		enlarged on playback, so aspect ratio, etc. are
+		maintained.
+ -d		Drop fields if they would cause data from two video
+		fields to be combined. See the section on PAL for more
+		details. 
+
+Options for Vrec:
+ -a		Record audio as well. You will have to twiddle audio
+		and video later if you want lipsync playback.
+ -q queuesize	Set size of the video board circular buffer. A little
+		experimentation with this may lead to more video being
+		captured, but not always.
+ -r rate	Set video rate. A rate of 2 tries to capture every
+		second frame, etc.
+ -P frames	Preallocate diskspace for 'frames' images. This may
+		enable you to capture more frames.
+
+Options for Vrecb:
+ -n number	Capture 'number' frames. Default is 60 (2 seconds).
+
+Both programs accept a filename to store the video on (default
+film.video) and Vrec also accepts an audio file name (default
+film.aiff). When you want to record you press the left mouse button.
+Vrec stops recording when you release the mouse button and Vrecb stops
+after the predetermined number of frames have been recorded. During
+recording the picture may look funny, but do not let this worry you,
+the film will be ok.
+
+After recording and saving, Vrec will print the deltas of the field
+numbers recorded. A list of '4 4 4 4'... means that all possible
+frames (one out of two) have been recorded. Vrecb will tell you how
+many duplicate fields have been skipped. See below on PAL useage
+again.
+
+	PAL caveats
+
+The IndigoVideo board converts the incoming video signal to the 60Hz
+(59.something, actually) display rate. All further operations,
+including capture, are done with respect to display rate. This is
+especially bothersome in the case of PAL video, since it means one out
+of 5 frames will be duplicated. Together with the fact that, in
+continuous capture, you can only capture every second frame this leads
+to strange and wondrous effects. The frame numbers returned by the
+video board (and displayed by Vrec) are display frame numbers, and so
+bear only a very complicated (and probably non-deterministic) relation
+to PAL frame numbers. For recording simple videos this is probably no
+problem. You can use Vrec and try using -d to see which gives the best
+result. On the other hand, if you need every frame and no duplicates
+either you have to use Vrecb and supply the -d and -f option. This
+will give you exactly the fields as they appeared on the PAL tape.
+
+	Video playback
+
+The easiest way to play back a video is to use Vplay. Calling it with
+an argument of -? will make it list all its options. A few options may
+need a bit of explanation:
+ -M magnify	Magnify the images by the given factor. This still
+		takes any magnification specified in the film (if it
+		is a field film, for instance) in account.
+ -w width and
+ -h height	Normally the window will be the correct size for the
+		film. You can set height and width, though, if you
+		want the window to be bigger. This is especially
+		useful if you want to record the film back to
+		videotape, since you can playback in a window that is
+		bigger than PAL size with a black background and you
+		will have no distracting window-manager thingies on
+		your videotape.
+
+	Video Editing
+
+Vedit is a (very simple) video editor that allows you to select images
+from the input movie and copy them to an output movie. Both input and
+output films have a modest buffer that you can move around in.
+
+Vaddcache takes a movie and adds a frame location cache to it. This
+will make some other programs run faster.
+
+rgb2video converts a set of SGI .rgb files to a movie.
+
+There are a few programs that can do image format conversion on movies
+(i.e. convert an 8-bit dithered RGB movie to a greyscale movie), but
+nothing very complete yet. Look at Vcopy.py for more information.