ffmpeg-progress.sh

#!/bin/bash
#updated ffmpeg progress indicator
#by Rupert Plumridge
#for updates visit www.prupert.co.uk
#Creative Commons Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales Licence
# Based on the ffmpegprogress bar from: http://handybashscripts.blogspot.com/2011/01/ffmpeg-with-progress-bar-re-work.html
# which was based on my initital progress script - circle of life and all that ;)
# version 2.0
# 07.04.2011
# now uses apparently better progress detection, based on duration of overall video and progress along the conversion
####################################################################################
# USAGE #
# 1) Run the script with the name of the file to be converted after the name of the script (e.g. ./ffmpeg-progress.sh "My Awesome Video.mpg)
###################################################################################
# Please adjust the following variables as needed. 
# It is recommended you at least adjust the first variable, the name of the script
SCRIPT=ffmpeg-progress.sh
LOG=$HOME/ffmpegprog.log

display () # Calculate/collect progress 
{
START=$(date +%s); FR_CNT=0; ETA=0; ELAPSED=0
while [ -e /proc/$PID ]; do                         # Is FFmpeg running?
    sleep 2
    VSTATS=$(awk '{gsub(/frame=/, "")}/./{line=$1-1} END{print line}' \
    /tmp/vstats)                                  # Parse vstats file.
    if [ $VSTATS -gt $FR_CNT ]; then                # Parsed sane or no?
        FR_CNT=$VSTATS
        PERCENTAGE=$(( 100 * FR_CNT / TOT_FR ))     # Progbar calc.
        ELAPSED=$(( $(date +%s) - START )); echo $ELAPSED > /tmp/elapsed.value
        ETA=$(date -d @$(awk 'BEGIN{print int(('$ELAPSED' / '$FR_CNT') *\
        ('$TOT_FR' - '$FR_CNT'))}') -u +%H:%M:%S)   # ETA calc.
    fi
    echo -ne "\rFrame:$FR_CNT of $TOT_FR Time:$(date -d @$ELAPSED -u +%H:%M:%S) ETA:$ETA Percent:$PERCENTAGE"                # Text for stats output.

done
}

trap "killall ffmpeg $SCRIPT; rm -f "$RM/vstats*"; exit" \
INT TERM EXIT                                       # Kill & clean if stopped.

# Get duration and PAL/NTSC fps then calculate total frames.
    FPS=$(ffprobe "$1" 2>&1 | sed -n "s/.*, \(.*\) tbr.*/\1/p")
    DUR=$(ffprobe "$1" 2>&1 | sed -n "s/.* Duration: \([^,]*\), .*/\1/p")
    HRS=$(echo $DUR | cut -d":" -f1)
    MIN=$(echo $DUR | cut -d":" -f2)
    SEC=$(echo $DUR | cut -d":" -f3)
    TOT_FR=$(echo "($HRS*3600+$MIN*60+$SEC)*$FPS" | bc | cut -d"." -f1)
    if [ ! "$TOT_FR" -gt "0" ]; then echo error; exit; fi

    # Re-code with it.

	nice -n 15 ffmpeg -deinterlace -vstats_file /tmp/vstats -y -i "$1" -vcodec libx264 -level 41 -vpre main -vpre medium -crf 24 -threads 0 -sn -acodec libfaac -ab 128k -ac 2 -ar 48000 -vsync 1 -async 1000 -map 0.0:0.0 -map 0.1:0.1 "$1".mkv 2>/dev/null &                       # CHANGE THIS FOR YOUR FFMPEG COMMAND.
        PID=$! && 
	echo "ffmpeg PID = $PID"
	echo "Length: $DUR - Frames: $TOT_FR  "
	display                               # Show progress.
        rm -f "$RM"/vstats*                             # Clean up tmp files.

    # Statistics for logfile entry.
    ((BATCH+=$(cat /tmp/elapsed.value)))                # Batch time totaling.
    ELAPSED=$(cat /tmp/elapsed.value)                   # Per file time.
    echo "\nDuration: $DUR - Total frames: $TOT_FR" >> $LOG
    AV_RATE=$(( TOT_FR / ELAPSED ))
    echo -e "Re-coding time taken: $(date -d @$ELAPSED -u +%H:%M:%S)"\
    "at an average rate of $AV_RATE""fps.\n" >> $LOG

exit

you might be able to remove few sed/cut commands by getting raw values from ffprobe.
for example:

#outputs the bitrate (in "bit" which is 1000 now not 1024 on newer FFMPEGs)
ffprobe -v "error" -hide_banner -i "input_video.mp4" -select_streams "v:0" -show_entries "stream=bit_rate" -print_format "default=noprint_wrappers=1:nokey=1"
#you can divide it with 1024 or 1000 (depending if you want to work with MB or MiB...)

this will give you duration of an audio file (for example)

ffprobe -i "input.mp3" -v "error" -select_streams "a:0" -show_entries "stream=duration" -print_format "default=noprint_wrappers=1:nokey=1"
#will output float numbers such as 607.503673 which can be used as a value for ffmpeg concat-lists (for example)

#add -sexagesimal to get readable duration.
ffprobe -i "input.mp3" -v "error" -select_streams "a:0" -show_entries "stream=duration" -print_format "default=noprint_wrappers=1:nokey=1" -sexagesimal
#will output 0:10:07.503673

you can run ffprobe -i "input.mp3" you can figure out the all the values you can fetch from the output (such as stream=duration).

_{from: https://trac.ffmpeg.org/wiki/FFprobeTips and http://icompile.eladkarako.com/?s=ffmpeg}