HowTo: Generate d.tube Video Sprites
What are sprites?
Sprites are small preview pictures which pop-up whenever you're hovering with your mouse above the player's time-line / seek-line.
If you upload your videos manually via IPFS you'll have to generate those sprites by yourself.
You'll have to install on your computer:
I've created a shell script for that task. I've linked that at the bottom of this post. The script is Linux-only. If you need a Windows version please let me know in the comments.
A d.tube video may have up to 100 sprites. Each sprite has a size of 210 x 118 pixel. The sprites are stored in a large JPEG image file, attached vertically to each other. Example.
When a video is shorter than 100 seconds, each second of the video is a separate sprite. A 40 second long video only has 40 sprite images.
First you'll have to calculate your jumps in the video. For a video longer than 99 seconds you'll need 100 frames from the video distributed evenly.
I'm using FFmpeg to extract a specific frame and store that frame as a bitmap image file.
ffmpeg -accurate_seek -ss 150 -i myvideo.mp4 -s 210x118 -frames:v 1 sprite_second150.bmp
FFmpeg accepts on parameters:
- ss: the timestamp of a specific frame in seconds or in the format of HH:MM:SS
- i: path to source video file
- output path
You'll have to loop that command multiple times to get the desired number of sprite-fragments.
Then I'm using ImageMagick's "montage" tool to combine the fragments into one file.
montage sprite_*.bmp -mode Concatenate -tile 1x100 myvideo-sprite.jpg
Montage's parameters explained:
- input file(s): with an asterisk to catch all sprite-fragments
- mode Concatenate: just put the images next to each other leaving no space bewteen
- tile: how to order the fragments on a grid. d.tube wants ab straight vertical line so 1x[number of fragments] would do the trick
- output path: where to store the sprite-image. Don't forget the .jpg file extension.
The script requires an index on the video's container (which is the case on most video files with MPEG 4 containers with H.264 content) and an aspect ratio of 16:9. Other aspect ratios may lead to a unproportional sprite-image.
I've made a shell script for calculating the sprite image for a specific video.
./dtube-sprite.sh /path/to/myvideo.mp4 myvideo-sprite.jpg
The script is licensed under CC0 / public domain.