#!/bin/bash
#
# A script to correct the resolution of an AVI file and
# make a DVD without any stretching or squashing
#
if [ "$1" == help ]
then
  echo "When encoding to a 16:9
  Aspect MPEG (*see note below*)
  Source Aspect   NTSC/PAL CVD    NTSC/PAL SVCD   NTSC/PAL DVD
  1.33    1.33 Not Applicable: See above table for 1.33 resolutions

  1.78    *352x480 / *352x576     *480x480 / *480x576     352x480 / 352x576 704x480 / 704x576 720x480 / 720x576

  1.85    *352x460 / *352x552     *480x460 / *480x552     352x460 / 352x552 704x460 / 704x552 720x460 / 720x552

  2.20    *352x388 / *352x432     *480x388 / *480x464     352x388 / 352x464 704x388 / 704x464 720x388 / 720x464

  2.35    *352x360 / *352x432     *480x360 / *480x432     352x360 / 352x432 704x360 / 704x432 720x360 / 720x432
  See http://www.transcoding.org/cgi-bin/transcode?Calculating_Frame_Size_And_Aspect_Ratio"
    exit
    fi


    # dw = dvd_width see above table for allowed widths I use 720x576
    # dh = dvd_height see table above for allowed heights
    dw=720
    dh=576

    if [ ! -n "$1" ]
    then
      echo "Usage: `basename $0` <avi_width> <avi_height>"
        exit
	fi

	if [ ! -n "$2" ]
	then
	  echo "Usage: `basename $0` <avi_width> <avi_height>"
	    exit
	    fi

	    # aw = avi_width; ah = avi_height, dar is the aspecraation of avi
	    aw=$1
	    ah=$2
	    dar_avi=`echo "scale=5; $aw/$ah" | bc`

	    #dvd_dar this is either 16:9 or 4:3 the Display Aspect Ratio

	    dvd_dar=1.77778
	    par=`echo "scale=5; ($dh*$dvd_dar)/$dw" | bc`

	    # when width of DVD is going to be 720
	    # And working out height is even if not +1 to make even

	    h=`echo "scale=0; $par*$dw/$dar_avi" | bc`
	    h22=`echo "scale=0; ($h/2)*2" | bc`

	    if [ $h != $h22 ]
	    then
	      h=`expr $h + 1`
	      fi

	      #Padding needed
	      #And test if even pixels

	      p=`echo "scale=0; ($dh-$h)/2" | bc`
	      p22=`echo "scale=0; ($p/2)*2" | bc`

	      if [ $p != $p22 ]
	      then
	        p_top=`expr $p - 1`
		  p_bottom=`expr $p + 1`
		  else
		    p_bottom=$p
		      p_top=$p
		      fi

		      # if [ $p == $p22 ]
		      # then
		      #   p_top=`echo "scale=0; ($dh-$h)/2" | bc`
		      #   p_bottom=`echo "scale=0; ($dh-$h)/2" | bc`
		      # fi

		      echo "#put the folowing into ffmpeg options assuming its a PAL dvd you want:"
		      echo "    -target pal-dvd -s "$dw"x"$h" -padtop "$p_top" -padbottom "$p_bottom

		      exit