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

I ended up using your algorithm for ffmkv: https://github.com/Fmstrat/ffmkv which is a bash wrapper for FFMPEG with an Inquirer menu interface and progress monitoring. During that I did a rewrite after noticing a few division by 0 issues and some inefficiencies with things like the repeated parsing of ffmpeg1.log and calculating variables. Much of this may just be because it's now 2019 and this code is 10 years old. If you'd like to pull code from there, feel free!

This is my personal use Here.

Pretty much same algo as yours, i just did a few optimizations.