Here is the submux-dvd latest interface spec (see the .sub for example too).
bitmap_filename hh:mm:ss:dd hh:mm:ss:dd xsize ysize xpos ypos
extra values1: set colors and contrast in this bitmap
 background_contrast pattern_contrast outline1_contrast outline2_contrast 
 background_color pattern_color emphasis1_color emphasis2_color

  extra values 2: select special submux command handling (optional1 MUST then be present)
  submux_command_nr

   extra values3:  if submux_command & 4, the COL_CON is executed, bitmap data is ignored,
              this allows to select a vertical area, with up to 16
              horizontal start points in that area, each with its own color.
              It seems the not selected parts are then set to the default as in the
              original bitmap

    vertical_area_start vertical_area_end
    maximal 16 groups of:
     horizontal_area_start 
     background_contrast pattern_contrast emphasis1_contrast emphasis2_contrast
     background_color pattern_color emphasis1_color emphasis2_color 
NOTE: the last 2 lines are reversed since -0.4 test release!
      so it is more consistent: contrast values always first, the color values.  


The submux-commands:
USE BITMAP DATA   1
USE STOP  2
USE COL_CON       4
USE FORCED START  8
USE START         16


So:
To display a bitmap that stays on the screen until the next bitmap shown         1 + 8 = 9
frame0500.bmp 00:00:10:00 00:05:30:00 656 480 38 83 0 15 15 0   0 13 2 3  9

To only change the colors and contrast in a bit bitmap on the screen                     4
frame1000.bmp 00:00:20:00 00:00:21:00 296 36 218 125 0 15 15 0  0 5 2 3   4  10 400    30  0 15 15 0  0 1 2 3   200  0 15 15 0  0 5 2 3   400  0 15 15 0  0 9 2 3  

To display a normal bitmap. leave out submux command (default will be used) 1 + 2 + 8 = 11
frame4000.bmp 00:02:08:00 00:02:57:00 296 36 218 425 0 15 15 0  0 1 2 3 11


