#!/bin/bash
#
# A script to correct the resolution of an AVI file and
# make a DVD without any stretching or squashing
#

# NTSC values
dvd_width=720
dvd_height=480

# Precision of computations
BC_SCALE=10

print_usage()
{
    echo "Usage: ${PROG_NAME} [OPTION]...  WIDTHxHEIGHT"
    echo
    echo "Outputs ffmpeg options to correctly convert an AVI file,"
    echo "of width WIDTH and height HEIGHT, for creating a"
    echo "video DVD."
    echo
    echo "Options:"
    echo "  -h     display this help and exit"
    echo "  -w     output in widescreen format (preferred)"
    echo "  -v     verbose output"
    echo
    echo "When encoding to a 16:9 aspect MPEG (*see note below*)"
    echo "
Source   NTSC/PAL               NTSC/PAL               NTSC/PAL
Aspect   CVD                    SVCD                   DVD
 4:3     Not Applicable: See above table for 1.33 resolutions

16:9     *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"
}

#dvd_dar this is either 16:9 or 4:3 the Display Aspect Ratio
dvd_dar=`echo "scale=${BC_SCALE}; 4/3" | bc`
DISPLAY_DAR="4:3"

while getopts "hwv" flag ;do
    case ${flag} in
	h)
	    print_usage
            exit 0
	    ;;
	w)
            # Widescreen, 16:9
            dvd_dar=`echo "scale=${BC_SCALE}; 16/9" | bc`
            DISPLAY_DAR="16:9"
            widescreen=yes
	    ;;
	v)
	    VERBOSE=yes
	    ;;
	?)
	    echo "${PROG_NAME}: Invalid option: ${OPTARG}."
	    echo "Try \`${PROG_NAME} --help' for more information."
	    exit 1
	    ;;
    esac
done
shift `expr "${OPTIND}" - 1`

# `$#' now represents the number of arguments after the options.
# `$1' is the first argument, etc.
if [ $# -ne 1 ]; then
    print_usage
    exit 1
fi


calc_par()
{
    width=$1
    height=$2
    dar=$3

    echo "scale=${BC_SCALE}; ($height*$dar)/$width" | bc
}

src_width=$(echo $1 | sed "s!\([0-9]*\)x[0-9]*!\1!")
src_height=$(echo $1 | sed "s![0-9]*x\([0-9]*\)!\1!")

src_dar=`echo "scale=${BC_SCALE}; $src_width/$src_height" | bc`
src_par=$(calc_par $src_width $src_height $src_dar)

dvd_par=$(calc_par $dvd_width $dvd_height $dvd_dar)

# when width of DVD is going to be 720, height will be:
out_height=`echo "scale=0; ($dvd_par*$dvd_width)/$src_dar" | bc`

# Temporaire:
if [ ${out_height} -gt 480 -a ${out_height} -lt 485 ]; then
    out_height=${dvd_height}
fi

h22=`echo "scale=0; ($out_height/2)*2" | bc`

# ...and working out height is even, if not add 1 to make it even
if [ $out_height != $h22 ]; then
    out_height=`expr $out_height + 1`
fi

#Padding needed
#And test if even pixels

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

# Padding values must be even.
if [ $p != $p22 ]; then
    p_top=`expr $p - 1`
    p_bot=`expr $p + 1`
else
    p_bot=$p
    p_top=$p
fi

if [ "x${VERBOSE}" = "xyes" ]; then
    out_par=$(calc_par $dvd_width $out_height $dvd_dar)
    echo "Source:"
    echo "  Size................: ${src_width}x${src_height}"
    echo "  Display Aspect Ratio: ${src_dar}"
    echo "  Pixel Aspect Ratio..: ${src_par}"
    echo
    echo "DVD:"
    echo "  Size................: ${dvd_width}x${dvd_height}"
    echo "  Display Aspect Ratio: ${dvd_dar}"
    echo "  Pixel Aspect Ratio..: ${dvd_par}"
    echo
    echo "Output:"
    echo "  Size................: ${dvd_width}x${out_height}"
    echo "  Display Aspect Ratio: ${dvd_dar}"
    echo "  Pixel Aspect Ratio..: ${out_par}"
    echo "  Padding Top.........: ${p_top}"
    echo "  Padding Bottom......: ${p_bot}"
    echo
    echo "ffmpeg options:"
fi

echo " -s ${dvd_width}x${out_height} -padtop ${p_top} -padbottom ${p_bot} -aspect ${DISPLAY_DAR}"

exit $?