#!/bin/bash

# ipodconv script
# Copyright (C) 2007 Greg Methvin (greg@methvin.net)

# This program is free software. You may distribute it under the terms of
# the GNU General Public License as published by the Free Software
# Foundation, version 2.
# 
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
# Public License for more details.
# 
# This script converts video files to the iPod video's mp4 format. It
# attempts to maintain the aspect ratio of the video while fitting the
# size of the iPod's display.

IFS=

# use these arguments to ffmpeg for all converted videos
BASE_ARGS="-f mp4 -vcodec xvid -maxrate 1000 -qmin 3 -qmax 5 -bufsize 4096 -g 300 -acodec aac"

# define dimensions of screen
WIDTH=320
HEIGHT=240

# default bitrate values
AUDIO_BITRATE=128
VIDEO_BITRATE=400

function usage {
echo "Usage: `basename $0` [-a <audio_bitrate>] [-b <video_bitrate>] <file> [<file2>...]"
echo "options:"
echo " -a <audio_bitrate> Set bitrate in kbps of output audio (default: $AUDIO_BITRATE)"
echo " -b <video_bitrate> Set bitrate in kbps of output video (default: $VIDEO_BITRATE)"
exit 1
}

abr=$AUDIO_BITRATE
vbr=$VIDEO_BITRATE

while getopts ":a:b:" options; do
    case $options in
        a) abr=`echo "$OPTARG" | grep "^[0-9]\+k\?$"`
        if [ -z "$abr" ]; then usage; fi;;
        b) vbr=`echo "$OPTARG" | grep "^[0-9]\+k\?$"`
        if [ -z "$vbr" ]; then usage; fi;;
        *) usage;;
    esac
done

shift $(($OPTIND - 1))

if [ -z "$*" ]; then
    usage
fi

for infile in $*; do
    if [ ! -f "$infile" ]; then
        echo "$inf: No such file">&2
    fi

    # adjust height to aspect ratio; make sure it's a multiple of 2
    re="^.*Video:.\+[^0-9]\([0-9]\+\)x\([0-9]\+\)[^0-9].*$"
    let "pad = ($HEIGHT - ($WIDTH * `ffmpeg -i \"$infile\" 2>&1 | grep $re | sed \"s/$re/\2\/\1/\"`)) / 4 * 2"
    let "height = $HEIGHT - 2 * $pad"

    # replace certain file extensions with .mp4; just add .mp4 to the end if it doesn't match those extensions
    outfile=`echo "$infile.mp4" | sed "s/\.\(avi\|mpg\|mpeg\|asf\).mp4$/.mp4/i"`

    # run ffmpeg to transcode
    bash -c "ffmpeg $BASE_ARGS -i \"$infile\" -s ${WIDTH}x${height} -padtop $pad -padbottom $pad -ab $abr -b $vbr \"$outfile\""
done

exit 0