ffmpeg Commands: Turn a 16:9 Video Into Vertical 9:16 Shorts

Short answer

Before you start

Use these commands only on footage you own or have the rights to use: your own podcast, webinar, coding tutorial, cooking show or stream. The examples assume a 16:9 file called input.mp4 (1920x1080) and write clip.mp4. If you have not yet decided which window to cut, read which part of a long video to clip first, or paste a transcript into the free clip moment finder (rule-based, runs in your browser) to get candidate windows.

We tested every command on a synthetic 20-second 1920x1080 file (a test pattern plus a sine tone) and checked each result with ffprobe. The version is listed in the Sources section. Different builds or very different inputs can behave differently, so run a short test clip first.

1. Cut a window by start and length

This cuts 10 seconds starting at the 5-second mark. For a long file, put the timestamp as HH:MM:SS, for example -ss 00:41:20.

ffmpeg -ss 5 -i input.mp4 -t 10 \
  -c:v libx264 -preset medium -crf 20 -pix_fmt yuv420p \
  -c:a aac -b:a 128k -movflags +faststart clip.mp4

• -ss 5 before -i: seek in the input to 5 seconds. The ffmpeg documentation says most formats cannot seek exactly, so ffmpeg seeks to the nearest point before it, and when transcoding it decodes and discards the extra segment (accurate seek is the default).
• -t 10: keep 10 seconds of output.
• The encoder flags are explained in step 6.

If you prefer an end time, put -to 15 after -i (as an output option) together with -ss 5 after -i. That form also worked in our test and produced a 10-second clip, but it decodes from the start of the file, so it is slower on long videos:

ffmpeg -i input.mp4 -ss 5 -to 15 \
  -c:v libx264 -preset medium -crf 20 -pix_fmt yuv420p \
  -c:a aac -b:a 128k -movflags +faststart clip.mp4

The output of this step is still 1920x1080. Steps 2-4 turn it vertical.

2. Centered 9:16 crop

The simplest reframe: keep a full-height vertical strip from the middle of the frame and scale it to 1080x1920.

ffmpeg -ss 5 -i input.mp4 -t 10 \
  -vf "crop=ih*9/16:ih:(iw-ih*9/16)/2:0,scale=1080:1920,setsar=1" \
  -c:v libx264 -preset medium -crf 20 -pix_fmt yuv420p \
  -c:a aac -b:a 128k -movflags +faststart clip.mp4

• crop=w:h:x:y: output width ih*9/16 (a 9:16 strip as tall as the source), full height ih, starting at x=(iw-w)/2 so it is centered. For a 1920x1080 source the strip is about 607 pixels wide.
• scale=1080:1920: enlarge the strip to the vertical canvas. A 607x1080 strip is enlarged by roughly 1.8x, so the result will look noticeably softer than the source.
• setsar=1: force square pixels so players do not stretch the picture.

To move the window left or right, replace the x expression with a fixed number of pixels, for example crop=ih*9/16:ih:300:0.

3. Blurred-background "fit" layout

If cropping would cut off something important (a slide, a screen recording, a wide shot), keep the whole 16:9 frame in the middle and fill the space above and below with a blurred, enlarged copy of the same video.

ffmpeg -ss 5 -i input.mp4 -t 10 \
  -filter_complex "[0:v]split=2[bg][fg];\
[bg]scale=1080:1920:force_original_aspect_ratio=increase,crop=1080:1920,boxblur=30:5[bgb];\
[fg]scale=1080:-2[fgs];\
[bgb][fgs]overlay=(W-w)/2:(H-h)/2,setsar=1[v]" \
  -map "[v]" -map 0:a \
  -c:v libx264 -preset medium -crf 20 -pix_fmt yuv420p \
  -c:a aac -b:a 128k -movflags +faststart clip.mp4

• split=2[bg][fg]: duplicate the video into a background copy and a foreground copy.
• scale=1080:1920:force_original_aspect_ratio=increase,crop=1080:1920: enlarge the background until it covers the whole 1080x1920 canvas, then trim the overflow.
• boxblur=30:5: blur the background. The first number is the box radius in pixels and the second is how many times the blur is applied; raise the radius for a softer background.
• scale=1080:-2: fit the foreground to 1080 pixels wide, with the height calculated to keep the aspect ratio (and kept even, which H.264 with yuv420p needs).
• overlay=(W-w)/2:(H-h)/2: place the foreground in the center of the background.
• -map "[v]" -map 0:a: use the filtered video and the original audio. When you use -filter_complex you must pick the streams yourself.

4. Stacked layout for two speakers (optional)

For a side-by-side interview, you can crop the left and right halves of the frame and stack them: speaker A on top, speaker B below. This assumes each person sits inside their half of the frame, which you must check yourself.

ffmpeg -ss 5 -i input.mp4 -t 10 \
  -filter_complex "[0:v]split=2[a][b];\
[a]crop=960:854:0:113,scale=1080:960[top];\
[b]crop=960:854:960:113,scale=1080:960[bot];\
[top][bot]vstack=inputs=2,setsar=1[v]" \
  -map "[v]" -map 0:a \
  -c:v libx264 -preset medium -crf 20 -pix_fmt yuv420p \
  -c:a aac -b:a 128k -movflags +faststart clip.mp4

• crop=960:854:0:113 and crop=960:854:960:113: take the left and right 960-pixel halves of a 1920x1080 frame, 854 pixels tall, starting 113 pixels down so the crop is vertically centered. Adjust the y value (113) to move the window up or down.
• scale=1080:960: each half becomes 1080x960, so the two halves together are exactly 1080x1920.
• vstack=inputs=2: stack the two inputs vertically. The ffmpeg documentation says all inputs must share the same pixel format and width, which the scale step guarantees.

The numbers above are for a 1920x1080 source. For other sizes, recompute the crop dimensions so each tile has a 9:8 shape (half of a 9:16 canvas).

5. Burn in an SRT or ASS file

"Burned in" means the captions become part of the picture, so they show on any platform. Save your captions as captions.srt. Make sure the timestamps are relative to the start of the clip (step 1 resets the timeline to 0):

1
00:00:01,000 --> 00:00:04,000
First caption line

2
00:00:05,000 --> 00:00:08,000
Second caption line

Cut, center-crop and caption in one pass:

ffmpeg -ss 5 -i input.mp4 -t 10 \
  -vf "crop=ih*9/16:ih:(iw-ih*9/16)/2:0,scale=1080:1920,setsar=1,subtitles=captions.srt:force_style='FontName=Arial,FontSize=14,Alignment=2,MarginV=120,Outline=2'" \
  -c:v libx264 -preset medium -crf 20 -pix_fmt yuv420p \
  -c:a aac -b:a 128k -movflags +faststart clip.mp4

The same subtitles=... filter can be appended to the end of the blurred-background filtergraph (put it right after setsar=1 inside the final chain, before [v]); we tested that as well.

• subtitles=captions.srt: the filter draws subtitles on the video using the libass library. ffmpeg converts the SRT to ASS internally. Your ffmpeg build must include libass (--enable-libass).
• force_style: overrides style parameters with ASS style KEY=VALUE pairs separated by commas. Alignment=2 is bottom-center, MarginV=120 lifts the text off the bottom edge, Outline=2 adds a border. Tune FontSize by eye on a test frame.
• Already have an ASS file? Use ass=captions.ass instead of subtitles=.... We converted our SRT with ffmpeg -i captions.srt captions.ass and burned it with ass=captions.ass without errors.

Captions are only as good as the transcript you feed in. Check names, numbers and line breaks before you render, because a typo is baked into every frame.

6. Encode settings for upload

These are the encoder flags used in every command above:

-c:v libx264 -preset medium -crf 20 -pix_fmt yuv420p -c:a aac -b:a 128k -movflags +faststart

• -c:v libx264: H.264 video encoded with x264. Requires an ffmpeg build with libx264.
• -preset medium: the default speed-versus-compression trade-off. Slower presets give smaller files at the same quality.
• -crf 20: constant-quality mode. The H.264 guide describes a 0-51 scale with 23 as the default, a sane range of 17-28, and lower numbers meaning higher quality and bigger files.
• -pix_fmt yuv420p: 8-bit 4:2:0 pixels. The H.264 guide notes that yuv420p or similar means 8-bit output, the common case; setting it explicitly avoids ending up with a different pixel format from an unusual source.
• -c:a aac -b:a 128k: AAC audio at 128 kbit/s.
• -movflags +faststart: moves the MP4 index (the moov atom) to the start of the file so playback can begin before the whole file has downloaded. We confirmed the moov atom sits before the media data in our output.

To confirm what you produced, run:

ffprobe -v error -show_entries stream=codec_name,width,height,pix_fmt -show_entries format=duration -of csv=p=0 clip.mp4

For the commands above the result was h264,1080,1920,yuv420p, aac, and a duration of 10 seconds. (The first-pass cut in step 1 reports 1920,1080 because it is not yet reframed.) Check the current upload requirements of each platform yourself before you publish; this post does not list them.

What ffmpeg will not do for you

• It does not find the moment. You pick every start and length by hand, so you have to watch or read the video first.
• The center crop cuts off anything off-center. There is no face tracking or speaker detection in these commands. A speaker who sits to one side needs a manual x offset, the blurred-background layout, or the stacked layout.
• No transcript. The subtitles filter only draws a caption file you provide; it does not transcribe speech.
• Upscaling softens the picture. A 1080p source cropped to a vertical strip is enlarged by roughly 1.8x to reach 1080x1920.
• Every clip is a separate command. Ten clips means ten commands (or a script of your own).

Doing this in RemixViral

RemixViral does the cut, the vertical reframe and the burned-in captions for you, then shows a review step before export. You upload a long video you own (MP4, MOV, MKV or WebM, up to 120 minutes; there is no link import), it proposes the moments worth posting, and you check each clip before you export it. It does not translate or dub.

Pricing: there is no free plan. Every monthly plan starts with a paid trial. $5 to start: 100 credits for 3 days, enough for two source videos of about 10 minutes. Then the plan price (from $19/month) unless you cancel. Cancel anytime in Billing. Trial credits expire after 3 days. The trial covers up to 20 minutes of source video in total during the trial. Card required. Starter is $19 a month with 1,200 credits. A clip project costs 50 credits per source video up to 60 minutes, plus 1 credit per extra minute. See pricing for the current terms, and RemixViral vs OpusClip for a comparison with prices read from the other tool's own page. If you only need a handful of clips, the commands above are enough.

Sources

Tested with ffmpeg 8.0.1 (ffmpeg version 8.0.1 Copyright (c) 2000-2025 the FFmpeg developers) on 30 October 2026, on macOS arm64, using a synthetic 20-second 1920x1080 test source and a two-line SRT. Every published command exited with code 0, and ffprobe reported h264, 1080x1920, yuv420p, aac and a 10-second duration for the vertical outputs.

• FFmpeg Filters Documentation (crop, scale, boxblur, split, overlay, vstack, subtitles, ass): https://ffmpeg.org/ffmpeg-filters.html (read 30 October 2026)
• ffmpeg Documentation (-ss, -t, -to, -accurate_seek, -map): https://ffmpeg.org/ffmpeg.html (read 30 October 2026)
• FFmpeg Formats Documentation (MOV/MP4 muxer, faststart): https://ffmpeg.org/ffmpeg-formats.html (read 30 October 2026)
• FFmpeg H.264 Video Encoding Guide (CRF, presets, faststart): https://trac.ffmpeg.org/wiki/Encode/H.264 (read 30 October 2026)

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