* <<HAL.0020>> ffmpeg/avconv, GIF
Some gyrations for scaling, dithering to GIF...

Crop, scale, error-diffusion dither from the source video directly to 
a GIF: 
$ avconv -i video.file -vf "crop=width:height:left:top, 
scale=width:height:sws_dither=ed" output.gif

Additional filters can be chained inside the -vf argument string; 
separate them with a comma; ex.:

-vf "crop=100:200:300:400, scale=50:-1:sws_dither=ed, 
curves=strong_contrast"

To get better colors, crop and scale the source video to another 
high-color video format first:
$ avconv -i video.file -vf "crop=width:height:left:top, 
scale=width:height" video2.m4v

Then, get a palette from the video and save it to a PNG file:
$ avconv -i video2.file -vf palettegen palette.png

And convert the second video to a GIF using the palette from the PNG:
$ avconv -i video2.file -i palette.png -filter_complex paletteuse 
video3.gif

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