count_frames.sh

#!/usr/bin/env bash

if [ $#  -ne 1 ] ; then
    echo "Usage: $0 DIRECTORY"
fi

cd "$1" &&
    find . -type f -name '*.avi' -print0 |
        while IFS= read -r -d $'\0' file; do
            printf "%s\t" "$file"
            ffmpeg -i "$file" -map 0:v:0 -c copy -f null -y /dev/null </dev/null 2>&1 | grep -Eo 'frame= *[0-9]+ *' | grep -Eo '[0-9]+' | tail -1
        done