# Build a Before/After Frame Strip From a Short Video With FFmpeg

Short transformation clips are hard to show in places that only take images: a blog post, a README, a newsletter, an Open Graph card. A frame strip solves it: three or four frames side by side, taken at chosen timestamps, so a reader sees the change without pressing play.

This tutorial builds one with FFmpeg only. It works for any short clip; the examples use a 15-second vertical video.

## 1. Inspect the clip first

You need the duration, frame rate and size before you choose timestamps.

~~~bash
ffprobe -v error \
  -show_entries stream=width,height,r_frame_rate \
  -show_entries format=duration \
  -of compact input.mp4
~~~

Typical output for a phone-style clip:

~~~text
stream|width=720|height=1280|r_frame_rate=24/1
format|duration=15.070000
~~~

At 24 fps, any timestamp you pick lands within about 42 ms of a real frame, which is precise enough for a strip.

## 2. Grab single frames with fast, accurate seeking

Putting `-ss` before `-i` seeks on the input. Modern FFmpeg decodes from the previous keyframe up to your timestamp, so the result is both fast and frame-accurate.

~~~bash
for t in 10.75 11.75 14.5; do
  ffmpeg -v error -y -ss "$t" -i input.mp4 \
    -frames:v 1 -q:v 2 "frame_$t.jpg"
done
~~~

`-q:v 2` keeps JPEG quality high. Use `.png` if you will edit the frames further.

## 3. Stack them in one command

You can skip the temporary files. Open the same input three times, each with its own seek, and stack the first frame of each:

~~~bash
ffmpeg -v error -y \
  -ss 10.75 -i input.mp4 \
  -ss 11.75 -i input.mp4 \
  -ss 14.5  -i input.mp4 \
  -filter_complex "
    [0:v]trim=end_frame=1,scale=-2:900[a];
    [1:v]trim=end_frame=1,scale=-2:900[b];
    [2:v]trim=end_frame=1,scale=-2:900[c];
    [a][b][c]hstack=inputs=3[s]" \
  -map "[s]" -frames:v 1 strip.jpg
~~~

`trim=end_frame=1` keeps one frame per input. `scale=-2:900` sets a shared height and keeps the width even, which `hstack` and most encoders want. Three 9:16 frames at 900 px tall give a strip about 1518 px wide.

## 4. Fit it to a fixed canvas

Blogs and social cards prefer fixed sizes such as 1600x900. Pad instead of stretching:

~~~bash
ffmpeg -v error -y -i strip.jpg -vf "
  scale=1600:900:force_original_aspect_ratio=decrease,
  pad=1600:900:(ow-iw)/2:(oh-ih)/2:color=0x111111" \
  strip_1600x900.jpg
~~~

## 5. Add labels

`drawtext` needs a font file on most systems. Label each panel before stacking so the text stays aligned:

~~~bash
FONT=/System/Library/Fonts/Supplemental/Arial Bold.ttf
ffmpeg -v error -y -ss 10.75 -i input.mp4 -frames:v 1 -vf "
  scale=-2:900,
  drawtext=fontfile='$FONT':text='10.75 s':
  x=24:y=h-th-24:fontsize=40:fontcolor=white:
  box=1:boxcolor=black@0.55:boxborderw=12" \
  label_a.png
~~~

On Linux, point `FONT` at a file from `fc-list`, for example a Noto Sans path.

## 6. Keep sensitive frames out of thumbnails

Transformation clips often change tone halfway: a horror effect adds blood makeup, an action template shows a prop weapon. Platforms treat the thumbnail more strictly than the video, so choose frames on purpose:

- Use the **first frame** when the change happens later, for example 0.2 s, before anything starts.
- Use the **resolution** frame for story clips, such as the final hug after a twist.
- Write the chosen timestamps down next to the asset so the next export uses the same frames.

The image below is a strip built with the commands above, from the last five seconds of a 15-second story clip (10.75 s, 11.75 s, 14.5 s).

![Three frames from the end of a short story clip, joined with FFmpeg hstack](https://cdn.hashnode.com/uploads/covers/6ac7155f8cadc38d9e483af7/84eacf9b-363d-4e0d-a4f5-4f8596c08201.jpg)

## 7. Check the result

~~~bash
ffprobe -v error -show_entries stream=width,height \
  -of csv=p=0 strip_1600x900.jpg
# 1600,900
~~~

Open it at 100 % once. JPEG artefacts around text are the most common problem; raise quality with `-q:v 1` or export PNG.

## Wrap-up

The full recipe is: probe, pick timestamps, stack with `trim` and `hstack`, pad to a fixed canvas, label, and check. Everything runs in a shell script, so a whole folder of clips can get strips in one pass.

The example clip is an AI-generated preview from the [Zombie Love Story effect on MixVio](https://mixvio.ai/ai-effects/zombie-love-story?utm_source=hashnode&utm_medium=blog&utm_campaign=halloween-zombie&utm_content=ffmpeg-frame-strip#effect-workspace), which we build.