#!/bin/bash

file=$(basename "$1")

ffprobe -loglevel quiet -show_frames "$1" | while read line
do
  [[ "$line" = "media_type=video" ]] && videoframe=1
  [[ "$line" = "key_frame=1" ]] && [[ $videoframe ]] && keyframe=1
  [[ "$line" == "[/FRAME]" ]] && unset videoframe && unset keyframe
  if [[ "$line" = pkt_dts_time=* && $videoframe && $keyframe ]]
  then
    IFS="= " read key time <<< $line
    if [[ $(echo "$time<$2"| bc) == 1 ]]
    then
      prevtime=$time
    else
      s=$(echo "$prevtime-0.05" | bc)
      diff=$(echo "$2-$s" | bc)
      t=$(echo "$diff+$3" | bc)
      ffmpeg -i "$1" -ss $s -t $t -acodec copy -vcodec copy -sn "$file-$s.mp4"
      exit
    fi
  fi
done