Hi all you eager MPEG Encoders,

Here is a short  guide to using the DOS port of PVRG MPEG, these guide lines
should apply to other platforms as well.

I will concentrate my explanation on making XING compatible files as this 
would appear to be the most popular player on DOS platforms. These files only 
include I frames but are viewable by all the players I have used.

The tools required to make the sample movie on a DOS platform are as follows:

	1)      The DOS port of PVRG MPEG CODEC called pvrgmpeg.exe
	2)      The DOS port of PPM2CYUV called ppm2cyuv.exe
	3)      Image Alchemy from a number of ftp sites.
			eg /mirrors4/garbo.uwasa.fi/graphics/alch16.zip
				at wuarchive.wustl.edu
 

Image Alchemy may be replaced with giftoppm.exe from the pbmplus set of
graphics tools.


The description is centred around creating a movie called short which consists
of 10 frames. In the zip file of the binaries of the DOS port you find 6 GIF
files, these are reduced to 160*120 from the movie supplied with the PVRG
source code.
	short0.gif.........short5.gif

Step 1
	Create the 160 by 120 PPM files
		alchemy -k -X160 -Y120 short*.gif

	Note Image Alchemy use the extension PNM.
	
Step 2
	Split the images into Y, U and V files.

	ppm2cyuv short0.ppm short -CCIR601
	
	Repeat for each frame.

Step 3
	Create a copy of the middle frames to form a ping-pong effect.(See
	note later on)

	copy short4.? short6.?
	copy short3.? short7.?
	copy short2.? short8.?
	copy short1.? short9.?
Step 3
	Create the movie.

	pvrgmpeg -XING -a 0 -b 9 short -s short.mpg


Step 4 
	Play the movie.


The PVRG MPEG CODEC (pvrgmpeg.exe) has many command line settings, you will
really need to read the full documentation supplied by PVRG to see what they 
all do.


Directing Your Movies:

Hint 1

Select your video clip carefully. It is best if the sequence is suited to a
ping-pong approach, this simply means that you grab say 5 frames of motion and
make a movie which consists of the following frame order.

	1,2,3,4,5,4,3,2
The XING player loops the movie and this frame order means there is continous
movement, this is not such a problem for longer movies but for short 5-10
second clips it is important.

Hint 2

The XING player files must be 160*120 and this is not give a very clear picture
for objetcs/people that are in the distance of the shot. Stick to sequences
where the object fills the screen rather than lots of still background.

Hint 3

If the object/person is entering the shot try to get it such that they are
approaching the camera so that they gradually fill the shot.

Hint 4

Remember the images stored are compressed and some image quality is lost. Start
with a good quality video source.


Enjoy the Movies and don't each too much PopCorn.

Graham Logan
June 15th 1993
mitgml@dct.ac.uk

"You can't fool me there ain't no Sanity Clause", Chico Marx