Preparing videos for blog posts

Here's a short cheat sheet of how to get videos ready for blog posts. We convert them to the widely supported webm (mp4 will for example not work on Fedora out of the box), and create short and smaller video thumbnails. These thumbnails will be embedded into the blog post directly as little animated pictures, just like gifs, but much more size efficient.

Convert to webm

$ ffmpeg -i video.mp4 video.webm

Shorten

Start at 10 seconds and cut after the next 5 seconds:

$ ffmpeg -ss 00:10:00 -i video.webm -c copy -t 00:00:05 video-short.webm

Scale down

Resize to 300x533 px:

$ ffmpeg -y -i video-short.webm -vf scale=300:533 video-thumb.webm

Add bottom text

#!/bin/sh -e

if [ "$#" -ne 3 ]; then
        echo "usage: $(basename $0) input output text"
        exit 1
fi

set -x
font="/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf"
ffmpeg -i "$1" -vf drawtext="fontfile=$font: \
        text=\'$3\': fontcolor=white: fontsize=24: box=1: boxcolor=black@0.5: \
        boxborderw=5: x=(w-text_w)/2: y=h-text_h-15" -codec:a copy "$2"

Merge multiple videos

#!/bin/sh -e

if [ "$#" -lt 1 ]; then
        echo "usage: $(basename $0) video1 video2 video3 ..."
        exit 1
fi

set -x
{
        for i in $@; do
                echo "file $i"
        done
} > inputlist

ffmpeg -f concat -i inputlist -c copy merged.webm

Embed into a post

<video controls width="300" height="533" class="border" autoplay="autoplay" loop mute>
<source src="/static/video/2019-00/video-thumb.webm" />
<a href="/static/video/2019-00/video.webm">Description of the video here</a>
</video>

Make sure to embed the link to the full video somewhere in the text related to the video:

Some text talking about the video ([video](/static/video/2019-00/video.webm)).