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diff --git a/Demo/sgi/video/video.doc b/Demo/sgi/video/video.doc new file mode 100755 index 0000000..c380a10 --- /dev/null +++ b/Demo/sgi/video/video.doc @@ -0,0 +1,111 @@ + 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. |