Subtitle Fps Convert API

POST https://api.findutils.com/api/tools/subtitle-fps-convert/execute

Rescale every cue in a SubRip (.srt) or WebVTT (.vtt) caption file from one frame rate to another, so a track that slowly drifts out of sync after a frame-rate conversion lines up again. Each timestamp is multiplied by source_fps divided by target_fps: going from 23.976 to 25 makes the file play about 4 percent shorter, and the mismatch that was a second at the ten-minute mark becomes several seconds by the end. This is the drift a fixed offset cannot fix, because the error grows with time rather than staying constant. The output keeps the input format, cue text, order and WebVTT cue settings. Use subtitle_shift instead when the whole track is early or late by a constant amount.

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Request body

application/json

input

string required

Caption file contents, either SubRip or WebVTT.
source_fps

number required

The frame rate the caption timings were written for, e.g. 23.976. Between 1 and 1000.
target_fps

number required

The frame rate of the video the captions must match, e.g. 25. Between 1 and 1000, and different from source_fps.

Example arguments

Verified

{
  "input": "1\n00:00:10,000 --> 00:00:12,000\nTen seconds in.\n\n2\n01:00:00,000 --> 01:00:02,000\nAn hour in, where the drift shows.\n",
  "source_fps": 23.976,
  "target_fps": 25
}

curl -X POST https://api.findutils.com/api/tools/subtitle-fps-convert/execute \
  -H "Content-Type: application/json" \
  -d '{
    "input": "1\n00:00:10,000 --> 00:00:12,000\nTen seconds in.\n\n2\n01:00:00,000 --> 01:00:02,000\nAn hour in, where the drift shows.\n",
    "source_fps": 23.976,
    "target_fps": 25
  }'

const response = await fetch('https://api.findutils.com/api/tools/subtitle-fps-convert/execute', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({"input":"1\n00:00:10,000 --> 00:00:12,000\nTen seconds in.\n\n2\n01:00:00,000 --> 01:00:02,000\nAn hour in, where the drift shows.\n","source_fps":23.976,"target_fps":25}),
});
const data = await response.json();

import requests

response = requests.post(
    "https://api.findutils.com/api/tools/subtitle-fps-convert/execute",
    json={"input":"1\n00:00:10,000 --> 00:00:12,000\nTen seconds in.\n\n2\n01:00:00,000 --> 01:00:02,000\nAn hour in, where the drift shows.\n","source_fps":23.976,"target_fps":25},
)
data = response.json()

$ch = curl_init('https://api.findutils.com/api/tools/subtitle-fps-convert/execute');
curl_setopt_array($ch, [
    CURLOPT_POST => true,
    CURLOPT_HTTPHEADER => ['Content-Type: application/json'],
    CURLOPT_POSTFIELDS => '{"input":"1\n00:00:10,000 --> 00:00:12,000\nTen seconds in.\n\n2\n01:00:00,000 --> 01:00:02,000\nAn hour in, where the drift shows.\n","source_fps":23.976,"target_fps":25}',
    CURLOPT_RETURNTRANSFER => true,
]);
$data = json_decode(curl_exec($ch), true);

Also an MCP tool

Call subtitle_fps_convert from Claude, Cursor or any MCP client. Same arguments, same output.

https://mcp.findutils.com

MCP reference

Rate limit: 60 a minute, per IP
Auth: None
REST id: subtitle-fps-convert
MCP name: subtitle_fps_convert
Category: Media
Machine-readable: openapi.json · markdown.md

Request body

Example arguments

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