Documentation Index
Fetch the complete documentation index at: https://rendi.dev/docs/llms.txt
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Concatenate two or more video clips into a single output. The concat filter re-encodes on the fly so it works even when the clips have different codecs, resolutions, or frame rates.
Code
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",
in_2: "https://storage.rendi.dev/sample/sample.avi",
},
output_files: {
out_1: "merged.mp4",
},
ffmpeg_command:
'-i {{in_1}} -i {{in_2}} -filter_complex "[0:v][0:a][1:v][1:a]concat=n=2:v=1:a=1[v][a]" -map "[v]" -map "[a]" -c:v libx264 -c:a aac {{out_1}}',
}),
});
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("Merged URL:", data.output_files.out_1.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",
"in_2": "https://storage.rendi.dev/sample/sample.avi",
},
"output_files": {"out_1": "merged.mp4"},
"ffmpeg_command": '-i {{in_1}} -i {{in_2}} -filter_complex "[0:v][0:a][1:v][1:a]concat=n=2:v=1:a=1[v][a]" -map "[v]" -map "[a]" -c:v libx264 -c:a aac {{out_1}}',
},
)
command_id = submit.json()["command_id"]
while True:
res = requests.get(f"{BASE}/commands/{command_id}", headers=headers).json()
if res["status"] == "SUCCESS":
print("Merged URL:", res["output_files"]["out_1"]["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",
"in_2": "https://storage.rendi.dev/sample/sample.avi"
},
"output_files": {"out_1": "merged.mp4"},
"ffmpeg_command": "-i {{in_1}} -i {{in_2}} -filter_complex \"[0:v][0:a][1:v][1:a]concat=n=2:v=1:a=1[v][a]\" -map \"[v]\" -map \"[a]\" -c:v libx264 -c:a aac {{out_1}}"
}'
curl --request GET \
--url https://api.rendi.dev/v1/commands/<command_id> \
--header 'X-API-KEY: <api-key>'
How the FFmpeg command works
-i {{in_1}} -i {{in_2}} — two input videos (add more with in_3, in_4, etc.)concat=n=2:v=1:a=1 — concatenate 2 inputs, each contributing 1 video stream + 1 audio stream[v][a] — named outputs for the concatenated streams-map "[v]" -map "[a]" — route concatenated streams to the output-c:v libx264 -c:a aac — re-encode (required by the concat filter){{out_1}} — output file
For N videos, add -i {{in_N}} per input, update n=N, and extend the stream-selection list: [0:v][0:a][1:v][1:a]...[N-1:v][N-1:a].
If all clips share the same codec/resolution/framerate, the demuxer approach (concat as a protocol, no re-encode) is faster — but requires a concat list file.
Response
{
"output_files": {
"out_1": {
"file_id": "d4c5b6a7-...",
"size_mbytes": 58.3,
"duration": 1192.918,
"file_type": "video",
"file_format": "mp4",
"storage_url": "https://storage.rendi.dev/temp_files/.../merged.mp4",
"width": 854,
"height": 480,
"codec": "h264"
}
},
"status": "SUCCESS",
"command_type": "FFMPEG_COMMAND"
}
