After 10+ hours of study, I got the answer - for those who wants to use this decent module to hold your video (for me, FLV) and make thumbnail, first thing, put the FFMPEG path to ImageMagick field, (so I am telling myAlbum-p to use the path of ImageMagick but actually it is looking to run my FFMPEG, change to your own path!!)

then go to functions.php, mod the followings:

STEP #1

UNDER:
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function myalbum_create_thumb( $src_path , $node , $ext )
{
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FIND:

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return myalbum_copy_thumb_from_icons( $src_path , $node , $ext ) ;
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CHANGE TO:
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return myalbum_create_thumb_by_imagick( $src_path , $node , $ext ) ;
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STEP #2

UNDER:
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function myalbum_create_thumb_by_imagick( $src_path , $node , $ext )

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find:

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if( $width <= $new_w && $height <= $new_h ) {
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then use the followings to do the job:
(you have to change the path accordingly)
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exec( "{$myalbum_imagickpath}ffmpeg -i $src_path -vcodec png -vframes 1 -an -f rawvideo -ss 00:00:03 -y -s 200x150 $thumbs_dir/$node.png" ) ;

exec( "/usr/bin/mogrify -format gif $thumbs_dir/$node.png");
@unlink( "$thumbs_dir/$node.png" ) ;
exec( "rm -i $thumbs_dir/$node.png");


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It works perfect to me, and even works for rebuilding the thumbnails under admin.

Thanks to GI Joe for this wonderful module and now it 100% server my needs!!!!