Script to generate thumbnails of a video and combine into one tile image. Uses FFmpeg and ImageMagick.

thumbnails.sh

#!/bin/zsh
# Script to generate thumbnails of a video and combine into one tile image.
#
# CAUTION:
# FFprobe might fail to extract duration info from a MKV container. Use
#     ffmpeg -i video.mkv -c:v copy -c:a copy video.mp4
# to swap to an MP4 container.
#
# Dependencies:
# 1. ffmpeg
# 2. ImageMagick
#
# Usage:
# ./thumbnails.sh NFRAMES TILE SIZE INPUT OUTPUT
#
# NFRAMES is the number of frames (thumbnails) to generate, e.g., 16;
# TILE is in the form "MxN" (where M * N should match NFRAMES), e.g., 4x4;
# SIZE is the length of the longer side of the output, e.g., 1920 if you want
# to get an 1920*1080 output image;
# INPUT is the path to the input file;
# OUTPUT is the path to the output file (make sure intermediate directories
# exist).
#
# Example:
# ./thumbnail.sh 16 4x4 1920 video.mp4 thumbnails.png
#
# Credit:
# http://goo.gl/vzXW1b (FFmpeg wiki: generate thumbnails)
# http://stackoverflow.com/q/7395343 (extract video length)
# http://apple.stackexchange.com/q/52879 (combine images)

if [[ $# != 5 ]]; then
    echo "wrong number of arguments

Usage:
./thumbnails.sh NFRAMES TILE SIZE INPUT OUTPUT

NFRAMES is the number of frames (thumbnails) to generate, e.g., 16;
TILE is in the form 'MxN' (where M * N should match NFRAMES), e.g., 4x4;
SIZE is the length of the longer side of the output, e.g., 1920 if you want
to get an 1920*1080 output image;
INPUT is the path to the input file;
OUTPUT is the path to the output file (make sure intermediate directories
exist).

Example:
./thumbnail.sh 16 4x4 1920 video.mp4 thumbnails.png
"
    return 1
fi

NFRAMES=$1
TILE=$2
SIZE=$3
INPUT=$4
OUTPUT=$5

DURATION=$(ffprobe -loglevel error -show_streams $INPUT | grep duration= | cut -f2 -d= | head -1)
FPS=$(echo "$NFRAMES / $DURATION" | bc -l)
OFFSET=$(echo "$DURATION / $NFRAMES / 2" | bc -l)

# generate thumbnails in the /tmp folder
TMPDIR=/tmp/thumbnails-${RANDOM}/
mkdir $TMPDIR
ffmpeg -ss $OFFSET -i $INPUT -f image2 -vf fps=fps=$FPS ${TMPDIR}thumb%04d.jpg
montage ${TMPDIR}thumb*.jpg -background white -geometry +5+5 -tile $TILE ${TMPDIR}output.jpg
convert ${TMPDIR}output.jpg -resize ${SIZE}x${SIZE} $OUTPUT

Hi, i've downloaded this and am very interested in using it, but I have no idea how to. I tried moving a video file into the same folder as thumbnails.sh and double clicking the .sh but nothing happens. i've tried opening git bash into the folder and using ur example: ./thumbnail.sh 16 4x4 1920 video.mp4 thumbnails.png with the right info filled in, but also nothing happens. even tried using it in the cmd, but I didn't get anywhere. Obviously I don't know what i'm doing here, lol.

Is it possible to help a beginner out? Or at least point me in the right direction. Thank you.

@Syl0pt
Your command is correct. Make sure you have ffmpeg and imagemagick installed (listed as "Dependencies" above).
Ubuntu: sudo apt-get install ffmpeg imagemagick
macOS: install Homebrew, then run brew install ffmpeg imagemagick

then the gist should work as described. (tested on mac)

this is the best script to generate thumbnail collages from video files. thanks!

Swapped:
DURATION=$(ffprobe -loglevel error -show_streams $INPUT | grep duration= | cut -f2 -d= | head -1)

For:
DURATION=$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 $INPUT)

First of all great job.
Script works for mkv, by calculating duration in seconds with ffmpeg -i (one long line):
DURATION=$(ffmpeg -i "$4" 2>&1 | grep "Duration"| cut -d ' ' -f 4 | sed s/,// | sed 's@\..*@@g' | awk '{ split($1, A, ":"); split(A[3], B, "."); print 3600*A[1] + 60*A[2] + B[1] }')

I chose another approach in script, by making snapshots ffmpeg ... -vframes 1 ... ...
This way is really faster for small amount of thumbnails.
I debugged approach to using the script parameters, in the origianl script, space in filename is a problem: see how use "$4" in DURATION=....
I changed usage to . th.sh COLUMNS ROWS SIZE "INPUT", thus NFRAMES=$(echo "scale=0;$1*$2" | bc) and TILE=$(echo "$1x$2")
I also added more stuff from imagemagick to put info about video (name, resolution, size, duration), though I had to edit /etc/ImageMagick-6/policy.xml by commenting all the policy to produce thumbnails

I'm having day off so I've removed all dependencies from ImageMagick: combining images, making white backgroud and adding text using only ffmpeg: https://github.com/romanwarlock/thumbnails/blob/master/thumbgen.sh

It turned out existing bc dependency NFRAMES=$(echo "scale=0;$X*$Y" | bc) which I removed by using awk: NFRAMES=echo | awk '{print (X*Y)}' X="$X" Y="$Y}}"``. Github doesn't show all the symbols correctly.