Thumbnails generator

[theprojectsomething]

Just an FYI I've created a preview thumbnails generator specifically for use with Cloudflare Stream. We use this process fairly extensively, embedded into the admin side of our site - I thought it might be useful to others as a standalone utility.

https://www.npmjs.com/package/plyr-stream-thumbs

[campiotto]

Could you give an example of how to use this from the command line?

I have a 30 minute video file, I can generate a mosaic of the frames, but this vtt file can't.

Do you think your program can do this from the command line to be run by a shell?

[theprojectsomething]

Hi @campiotto this tool is intended specifically for generating thumbs for videos hosted on Cloudflare Stream. Take a look at the VTT portion of the code .. You could easily repurpose/reinvent it to work with ffmpeg or similar, but you'd need to wrap it appropriately for cli use.

[salivity]

i did an online tool to create thumbnails for videos, here https://davidclews.com/article/54.html

[klemens]

I wrote a small, configurable bash script that uses ffmpeg and montage from ImageMagick to create thumbnail sprites for plyr:

#!/usr/bin/bash

FRAME_WIDTH=178
FRAME_HEIGHT=100
MAX_COLUMNS=8
MAX_ROWS=6
SECONDS_BETWEEN_FRAMES=5
SPRITE_JPEG_QUALITY=80

if [[ $# -lt 2 ]]; then
    echo "Usage: $0 my_video.mp4 my_video_thumbs"
    exit 1
fi

video_file=$1
output_prefix=$2

sprite_file_prefix=${output_prefix}_
vtt_file=${output_prefix}.vtt

tmpdir=$(mktemp --tmpdir --directory video-thumbnails.XXX)
trap 'rm -rf -- "$tmpdir"' EXIT

# Extract frames from video file with ffmpeg

ffmpeg -v quiet -stats -i "$video_file" \
    -vf "fps=1/${SECONDS_BETWEEN_FRAMES},scale=${FRAME_WIDTH}:${FRAME_HEIGHT}" \
    "$tmpdir/frame_%08d.png"

num_images=$(ls -1 "$tmpdir" | wc -l)

# Combine frames into one or more sprites

montage "$tmpdir"/frame_*.png -tile "${MAX_COLUMNS}x${MAX_ROWS}" -geometry "+0+0" \
    -background black -quality "$SPRITE_JPEG_QUALITY" "${sprite_file_prefix}%d.jpg"

# Generate index file in WEBVTT format

printf "WEBVTT\n" > "$vtt_file"

let column=0 row=0 file=0
for (( image=1; image<=$num_images; ++image )); do
    start_time=$(date "+%T.000" -d "2020-01-01T00:00:00 $(( (image - 1) * SECONDS_BETWEEN_FRAMES )) seconds")
    end_time=$(date "+%T.000" -d "2020-01-01T00:00:00 $(( image * SECONDS_BETWEEN_FRAMES )) seconds")
    printf "\n%d\n%s --> %s\n%s#xywh=%d,%d,%d,%d\n" \
        "$image" "$start_time" "$end_time" "$(basename "$sprite_file_prefix")$file.jpg" \
        "$(( column * FRAME_WIDTH ))" "$(( row * FRAME_HEIGHT ))" \
        "$FRAME_WIDTH" "$FRAME_HEIGHT" >> "$vtt_file"

    let ++column
    if (( column >= MAX_COLUMNS )); then let column=0 ++row; fi
    if (( row >= MAX_ROWS )); then let row=0 ++file; fi
done