FFmpeg API

Typical run

4 to 46 s

for the recipes on this page

Price

$0.01

per compute minute

Inputs

500 MB each

1,000 MB per job

Example#

Turn a landscape video into a 1080x1920 vertical one, with a blurred copy filling the space above and below. Point in.mp4 at a public link to your video or an upload.

curl -sS "https://api.reelsdk.com/v1/ffmpeg" \
  -H "Authorization: Bearer $REELSDK_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "inputs": {
      "in.mp4": "https://example.com/landscape.mp4"
    },
    "args": [
      "-i", "in.mp4", "-filter_complex",
      "[0:v]scale=1080:1920:force_original_aspect_ratio=increase,crop=1080:1920,boxblur=24:2[bg];[0:v]scale=1080:-2[fg];[bg][fg]overlay=(W-w)/2:(H-h)/2",
      "-c:a", "copy", "vertical.mp4"
    ]
  }'

Parameters#

Send a JSON body with args. Fields we don't recognize are ignored.

How a job runs#

• We download every file in inputs into an empty job directory, under the name you gave it.
• We run ffmpeg 8.1 in that directory with your args, straight from the array, with no shell in between. Existing files are overwritten unless you pass -n.
• When ffmpeg exits with code 0, every file in outputs must exist and not be empty. Each one comes back as a URL under job.outputs, keyed by its file name.

Inputs can be up to 500 MB each and 1,000 MB together, and a job may write up to 8 GB while it runs. The outputs you get back can add up to 2 GB, and the whole job has 10 minutes.

Sandbox rules#

The job directory is all ffmpeg can see. We check your arguments before the job starts, and a blocked option returns 400 naming the argument, such as args[3]: the movie filter is not supported, add the file as another -i instead.

• No URLs or protocols like http:, tcp:, concat: or pipe: in inputs, outputs or file options. List remote files in inputs instead.
• No absolute paths, ~ or ... The one exception is fontfile= and fontsdir= pointing into /usr/share/fonts/reelapi/.
• No movie or amovie filters. Add the file as another -i.
• No -f tee, -pattern_type glob or -safe 0. Use a %d image sequence, and list concat files by name.
• No -filter_script, -filter_complex_script, -pre preset files, hardware devices, or protocol and format whitelists.
• -progress pipe:1 and pipe:2 are allowed.

Fonts#

drawtext, subtitles and ass can use the fonts we bundle in /usr/share/fonts/reelapi/, the same ones the captions use. Point fontfile= at a file, or fontsdir= at the folder and pick a font by name.

Recipes#

Each of these ran on the live API. Swap in your own URLs and send the body to POST /v1/ffmpeg.

{
  "inputs": {
    "in.mp4": "https://example.com/clip.mp4"
  },
  "args": [
    "-ss", "5", "-i", "in.mp4", "-frames:v", "1", "-q:v", "2",
    "poster.jpg"
  ]
}

{
  "inputs": {
    "in.mp4": "https://example.com/clip.mp4"
  },
  "args": [
    "-t", "4", "-i", "in.mp4", "-vf",
    "fps=12,scale=480:-1:flags=lanczos,split[a][b];[a]palettegen[p];[b][p]paletteuse",
    "-loop", "0", "preview.gif"
  ]
}

{
  "inputs": {
    "in.mp4": "https://example.com/clip.mp4"
  },
  "args": ["-i", "in.mp4", "-vn", "-c:a", "libmp3lame", "-q:a", "2", "audio.mp3"]
}

{
  "inputs": {
    "in.mp4": "https://example.com/clip.mp4",
    "subs.srt": "https://example.com/subs.srt"
  },
  "args": [
    "-i", "in.mp4", "-vf",
    "subtitles=subs.srt:fontsdir=/usr/share/fonts/reelapi:force_style='FontName=Poppins Black,FontSize=16'",
    "-c:a", "copy", "subtitled.mp4"
  ]
}

{
  "inputs": {
    "in.mp4": "https://example.com/clip.mp4"
  },
  "args": [
    "-i", "in.mp4", "-vf",
    "drawtext=fontfile=/usr/share/fonts/reelapi/Anton-Regular.ttf:text='Day 1':fontsize=120:fontcolor=white:borderw=6:bordercolor=black:x=(w-text_w)/2:y=h*0.1",
    "-c:a", "copy", "titled.mp4"
  ]
}

{
  "inputs": {
    "a.mp4": "https://example.com/a.mp4",
    "b.mp4": "https://example.com/b.mp4"
  },
  "args": [
    "-i", "a.mp4", "-i", "b.mp4", "-filter_complex",
    "[0:v][0:a][1:v][1:a]concat=n=2:v=1:a=1[v][a]", "-map", "[v]",
    "-map", "[a]", "joined.mp4"
  ]
}

{
  "inputs": {
    "in.mp4": "https://example.com/clip.mp4"
  },
  "args": "ffmpeg -i in.mp4 -vf \"scale=640:-2\" -an small.mp4"
}

Response#

outputs is keyed by the file names you asked for, so read job.outputs["vertical.mp4"]. usage.output_seconds adds up the length of every audio and video output, and images count as 0. duration_s is the length of the first one.

{
  "job": {
    "id": "job_tc4682j24vighvp5f5op",
    "op": "ffmpeg",
    "status": "succeeded",
    "stage": null,
    "created_at": "2026-10-26T01:21:16.435Z",
    "finished_at": "2026-10-26T01:21:39.971Z",
    "outputs": {
      "vertical.mp4": "https://api.reelsdk.com/f/out/job_tc4682j24vighvp5f5op/vertical.mp4"
    },
    "result": null,
    "duration_s": 30,
    "error": null,
    "usage": {
      "output_seconds": 30,
      "audio_seconds": 0,
      "tts_characters": 0,
      "images": 0
    },
    "poll_url": "https://api.reelsdk.com/v1/jobs/job_tc4682j24vighvp5f5op"
  }
}

Errors#

When ffmpeg fails, the job fails with 422 and the message is the last useful line ffmpeg printed. The body carries the job next to the error.

{
  "error": {
    "code": "FFMPEG_FAILED",
    "message": "Error opening output files: Filter not found"
  },
  "job": {
    "id": "job_o1d0oim2n3bxs867jivv",
    "op": "ffmpeg",
    "status": "failed",
    "stage": null,
    "created_at": "2026-10-26T02:12:35.197Z",
    "finished_at": "2026-10-26T02:12:38.421Z",
    "outputs": {},
    "result": null,
    "duration_s": null,
    "error": {
      "code": "FFMPEG_FAILED",
      "message": "Error opening output files: Filter not found"
    },
    "usage": {
      "output_seconds": 0,
      "audio_seconds": 0,
      "tts_characters": 0,
      "images": 0
    },
    "poll_url": "https://api.reelsdk.com/v1/jobs/job_o1d0oim2n3bxs867jivv"
  }
}

Last updated 26 October 2026