Generate multiple thumbnails from a video - Rendi - FFmpeg API

Extract multiple frames from a video in a single call, each at its own timestamp. Cheaper than N separate calls since the input is decoded once.

Code

Node.js
Python
cURL

const API_KEY = process.env.RENDI_API_KEY;

const submit = await fetch("https://api.rendi.dev/v1/run-ffmpeg-command", {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    "X-API-KEY": API_KEY,
  },
  body: JSON.stringify({
    input_files: {
      in_1: "https://storage.rendi.dev/sample/sample.avi",
    },
    output_files: {
      out_1: "thumbnail1.jpg",
      out_2: "thumbnail2.jpg",
    },
    ffmpeg_command:
      "-i {{in_1}} -filter_complex \"[0:v]split=2[first][second];[first]select='gte(t,10)'[thumb1];[second]select='gte(t,20)'[thumb2]\" -map [thumb1] -frames:v 1 {{out_1}} -map [thumb2] -frames:v 1 {{out_2}}",
  }),
});
const { command_id } = await submit.json();

while (true) {
  const res = await fetch(`https://api.rendi.dev/v1/commands/${command_id}`, {
    headers: { "X-API-KEY": API_KEY },
  });
  const data = await res.json();
  if (data.status === "SUCCESS") {
    console.log("Thumb 1:", data.output_files.out_1.storage_url);
    console.log("Thumb 2:", data.output_files.out_2.storage_url);
    break;
  }
  if (data.status === "FAILED") throw new Error("Command failed");
  await new Promise((r) => setTimeout(r, 2000));
}

import os
import time
import requests

API_KEY = os.environ["RENDI_API_KEY"]
BASE = "https://api.rendi.dev/v1"
headers = {"X-API-KEY": API_KEY}

submit = requests.post(
    f"{BASE}/run-ffmpeg-command",
    headers=headers,
    json={
        "input_files": {"in_1": "https://storage.rendi.dev/sample/sample.avi"},
        "output_files": {"out_1": "thumbnail1.jpg", "out_2": "thumbnail2.jpg"},
        "ffmpeg_command": "-i {{in_1}} -filter_complex \"[0:v]split=2[first][second];[first]select='gte(t,10)'[thumb1];[second]select='gte(t,20)'[thumb2]\" -map [thumb1] -frames:v 1 {{out_1}} -map [thumb2] -frames:v 1 {{out_2}}",
    },
)
command_id = submit.json()["command_id"]

while True:
    res = requests.get(f"{BASE}/commands/{command_id}", headers=headers).json()
    if res["status"] == "SUCCESS":
        print("Thumb 1:", res["output_files"]["out_1"]["storage_url"])
        print("Thumb 2:", res["output_files"]["out_2"]["storage_url"])
        break
    if res["status"] == "FAILED":
        raise RuntimeError("Command failed")
    time.sleep(2)

curl --request POST \
  --url https://api.rendi.dev/v1/run-ffmpeg-command \
  --header 'Content-Type: application/json' \
  --header 'X-API-KEY: <api-key>' \
  --data '{
    "input_files": {"in_1": "https://storage.rendi.dev/sample/sample.avi"},
    "output_files": {"out_1": "thumbnail1.jpg", "out_2": "thumbnail2.jpg"},
    "ffmpeg_command": "-i {{in_1}} -filter_complex \"[0:v]split=2[first][second];[first]select='\''gte(t,10)'\''[thumb1];[second]select='\''gte(t,20)'\''[thumb2]\" -map [thumb1] -frames:v 1 {{out_1}} -map [thumb2] -frames:v 1 {{out_2}}"
  }'

curl --request GET \
  --url https://api.rendi.dev/v1/commands/<command_id> \
  --header 'X-API-KEY: <api-key>'

How the FFmpeg command works

split=2[first][second] — duplicate the video stream so we can select frames at two different times
select='gte(t,10)'[thumb1] — pick the first frame at or after 10 s
select='gte(t,20)'[thumb2] — pick the first frame at or after 20 s
-map [thumb1] -frames:v 1 {{out_1}} — write one frame to thumbnail1.jpg
-map [thumb2] -frames:v 1 {{out_2}} — write one frame to thumbnail2.jpg

For N thumbnails, extend the split count and add another select + -map pair per output.

Response

{
  "output_files": {
    "out_1": {
      "file_id": "eba1a713-...",
      "size_mbytes": 0.085,
      "file_type": "image",
      "file_format": "jpg",
      "storage_url": "https://storage.rendi.dev/temp_files/.../thumbnail1.jpg",
      "width": 1280,
      "height": 720
    },
    "out_2": {
      "file_id": "d8278ca9-...",
      "size_mbytes": 0.039,
      "file_type": "image",
      "file_format": "jpg",
      "storage_url": "https://storage.rendi.dev/temp_files/.../thumbnail2.jpg",
      "width": 1280,
      "height": 720
    }
  },
  "status": "SUCCESS",
  "command_type": "FFMPEG_COMMAND"
}