Generate .BIF media preview thumbnails (trick play)

bif_generator.sh

#!/bin/bash
#Generate .BIF media preview thumbnails
#REQUIRES: ffmpeg, mediainfo, and roku's biftool

if [ -z "$1" ]; then echo -e "\nGenerate .BIF media preview thumbnails\nFiles are stored in source folder\n\nUsage: ${0##*/} [video files/directories...] <Absolute or Relative paths. Recursive>\n";exit 1;fi

tmpdir="/tmp/bifgen"
[ -d "$tmpdir" ] && rm -f "$tmpdir"/* || mkdir -p "$tmpdir"

IFS=$'\n'
wd="$(pwd)"
cd /tmp/
new=0

#Store bif files in separate directory tree. The directory tree will match the folder structure of the input files, but with a different directory prefix
#e.g. /dir/vids/* => /bif/*
#disabled if null, .bif in source folder
indir=""
outdir=""

for z;do
  #Input parameter is a relative or absolute path
  [[ "$z" =~ ^/ ]] || z="$wd/$z"

  [ -e "$z" ] || continue
  [ -d "$z" ] && files=($(find "$z" -type f -regextype sed -regex ".*\.[mM][kKpP][vV4]"))
  [ -f "$z" ] && files=("$z")

  for i in "${files[@]}";do

    if [[ -n "$indir" && "$i" =~ ^"$indir" ]]; then
      outd=$(sed "s:^${indir}:${outdir}:" <<< ${i%/*})
      [ -d "$outd" ] || (mkdir -p "$outd" && echo -e "\e[35mMKDIR: $outd\e[39m")
      out="${outd}/${i##*/}.bif"
    else
      out="${i}.bif"
    fi
    #bif already exists, don't overwrite
    if [ -f "$out" ];then
      echo -e "\e[33mSKIP: $out\e[39m"
      continue
    fi

    duration=$(mediainfo --Inform="General;%Duration%" "$i")
    separation=10 #1-15min  1-90frames
    [ -n "$duration" ] && [ "$duration" -gt 900000 ] && separation=12 #15-70min  90-350frames (150frames/30min)
    [ -n "$duration" ] && [ "$duration" -gt 4200000 ] && separation=22 #70min-2hr  190-327frames
    [ -n "$duration" ] && [ "$duration" -gt 7200000 ] && separation=26 #2hr+  277frames+

    #Do not select frames at a fixed time interval, as the timecode will drift.
    #BIF does not contain timecodes, you have to calculate them by multiplying the framerate/separation by the frame number.
    #Selecting the first frame after the modulo of the separation time rolls over to zero, you ensure the frame number multiplication will line up with the timecode.

    ffmpeg -nostdin -i "$i" -vsync vfr -vf "select=gt(ld(1)\,st(1\,mod(t\,${separation})))+isnan(prev_selected_t),scale=240:160:force_original_aspect_ratio=decrease:flags=bicubic:sws_dither=none" -c:v mjpeg -qscale:v 4 -v 0 -y -f image2 "${tmpdir}/%08d.jpg"

    if [ $? -ne 0 ];then
      rm -f "${tmpdir}"/*
      continue
    fi

    #ffmpeg's image sequence output starts at number one. We must shift every image down one to start at zero in order to line up with the timecode
    j="${tmpdir}/00000000.jpg"
    for f in "$tmpdir"/*; do
      mv "$f" "$j"
      j="$f"
    done

    #Make sure biftool is in $PATH, or add absolute path to it
    biftool -t ${separation}000 "${tmpdir}"
    if [ -f "${tmpdir##*/}.bif" ]; then
      mv "${tmpdir##*/}.bif" "$out" && echo -e "\e[32m$out\e[39m" && chmod 664 "$out" || echo -e "\e[31mFAILED: $out\e[39m"
      ((new++))
    else
      echo -e "\e[31mFAILED: $i\e[39m"
    fi

    rm -f "${tmpdir}"/*
  done
done

rmdir "$tmpdir"
echo "new bif created: $new"