Name: Video Audio Merge API: Add or Replace Audio in Video
Brand: magicapi
SKU: api-magicapi-video-audio-merger-lucataco-video-audio-merge
Availability: InStock
Author: API Market

Shashank Agarwal

# 🎬 Video and Audio Merge API (lucataco Video Audio Merge)

## Overview
Video Audio Merge is a utility published by lucataco that combines a video file and an audio file.

Send a `video_file` and an `audio_file`. By default the new audio replaces the original sound (`replace_audio` true) and the output is as long as the video (`duration_mode` `video`). Set `replace_audio` to false to mix the new audio with the original, change `audio_volume` to make it quieter or louder, and choose the codecs and container of the output. Each request returns the URL of one merged video.

## Features
- **Replace or mix**: `replace_audio` true replaces the original audio; false mixes the two.
- **Length control**: `duration_mode` `video` (default) or `audio` decides which file sets the output length when they differ.
- **Volume**: `audio_volume` from 0 to 5 (1 is the original volume).
- **Codecs**: video `h264` (default), `h265`, `vp9` or `copy`; audio `aac` (default), `mp3` or `copy`.
- **Containers**: `mp4` (default), `mov`, `avi` or `mkv`.

## Use Cases
1. **Music for silent videos**: add a soundtrack to generated or screen-recorded clips.
2. **Voice-overs**: put a narration track on a product or tutorial video.
3. **Dubbing drafts**: swap the audio of a video for a translated track.
4. **Pipeline step**: join separately generated video and audio into one file.

## Visual Examples
### Example Input
Video: [Watch the input video](https://blog.api.market/wp-content/uploads/2026/10/video-audio-merge-input-2-api-market.mp4)

Audio: [Listen to the input audio](https://blog.api.market/wp-content/uploads/2026/10/video-audio-merge-input-api-market.mp3)

Settings: `duration_mode` `video`, `replace_audio` true, `audio_volume` 1, `video_codec` `h264`, `audio_codec` `aac`, `output_format` `mp4`.

### Example Output
[Watch the example output](https://blog.api.market/wp-content/uploads/2026/10/video-audio-merge-output-jw27s96z-api-market.mp4) (the input video with the input audio as its soundtrack)

## Input Parameters
| Field | Type | Required | Default | Allowed values | Description |
| --- | --- | --- | --- | --- | --- |
| `video_file` | string (URL) | No | none |  | Input video URL (MP4, MOV, AVI and similar) |
| `audio_file` | string (URL) | No | none |  | Input audio URL (MP3, WAV, AAC and similar) |
| `duration_mode` | string | No | `video` | `video`, `audio` | Which file sets the output length when the video and audio lengths differ |
| `replace_audio` | boolean | No | `true` |  | Replace the original audio completely (true) or mix with it (false) |
| `audio_volume` | number | No | `1` | 0 to 5 | Audio volume multiplier (1.0 is the original volume) |
| `output_format` | string | No | `mp4` | `mp4`, `mov`, `avi`, `mkv` | Output video format |
| `video_codec` | string | No | `h264` | `h264`, `h265`, `vp9`, `copy` | Video codec for the output |
| `audio_codec` | string | No | `aac` | `aac`, `mp3`, `copy` | Audio codec for the output |

## Pricing
- **Pay As You Go (PAYG) pricing**: you only pay for what you use.
- **Price**: $0.0027 per API unit.
- **1 API unit = 1 request with up to 24 seconds of processing.** A request that takes longer is billed one more unit for each started 24-second block of processing time.
- **Example cost**: the example request above took 1.95 seconds of processing, which is 1 started 24-second block, so it cost 1 unit = $0.0027.
- Longer files and re-encoding take longer than `copy`; one request covers up to 24 seconds of processing.
- **Failed or cancelled predictions are not billed.**
- **GET requests to check prediction status** are free and don't count toward API unit usage.
- **No monthly subscription fee.**

## API Documentation

### Base URL
All API requests go to: `https://prod.api.market/api/v1/magicapi/video-audio-merger-lucataco-video-audio-merge`

### Authentication
Send your api.market API key in the `x-api-market-key` header:
```
x-api-market-key: YOUR_API_MARKET_KEY
```

### Asynchronous Processing
**IMPORTANT**: This API is asynchronous. The flow is:
1. Send a POST request to `/predictions`. A successful request returns **201 Created** with a prediction `id` and a `status` of `starting` or `processing`.
2. Poll GET `/predictions/{id}` with that ID.
3. Keep polling while `status` is `starting` or `processing`.
4. Stop when `status` is `succeeded` (read `output`), `failed` or `canceled` (read `error`).

A polling interval of 1 second and an overall timeout of 600 seconds (10 minutes) work well.

### Endpoints

#### Create a Prediction
```bash
curl -X POST "https://prod.api.market/api/v1/magicapi/video-audio-merger-lucataco-video-audio-merge/predictions" \
  -H "Content-Type: application/json" \
  -H "x-api-market-key: YOUR_API_MARKET_KEY" \
  -d '{
    "version": "8c3d57c9c9a1aaa05feabafbcd2dff9f68a5cb394e54ec020c1c2dcc42bde109",
    "input": {
      "audio_file": "https://blog.api.market/wp-content/uploads/2026/10/video-audio-merge-input-api-market.mp3",
      "video_file": "https://blog.api.market/wp-content/uploads/2026/10/video-audio-merge-input-2-api-market.mp4",
      "audio_codec": "aac",
      "video_codec": "h264",
      "audio_volume": 1,
      "duration_mode": "video",
      "output_format": "mp4",
      "replace_audio": true
    }
  }'
```

Response (201 Created):
```json
{
  "id": "jw27s96zcsrmr0d1d138q8ez88",
  "version": "8c3d57c9c9a1aaa05feabafbcd2dff9f68a5cb394e54ec020c1c2dcc42bde109",
  "status": "starting",
  "created_at": "2026-10-23T10:20:37.767Z"
}
```

#### Check Prediction Status
```bash
curl -X GET "https://prod.api.market/api/v1/magicapi/video-audio-merger-lucataco-video-audio-merge/predictions/{id}" \
  -H "x-api-market-key: YOUR_API_MARKET_KEY"
```

Response when the prediction has finished (200 OK):
```json
{
  "id": "jw27s96zcsrmr0d1d138q8ez88",
  "status": "succeeded",
  "output": "https://blog.api.market/wp-content/uploads/2026/10/video-audio-merge-output-jw27s96z-api-market.mp4",
  "error": null,
  "created_at": "2026-10-23T10:20:37.767Z",
  "started_at": "2026-10-23T10:20:55.798Z",
  "completed_at": "2026-10-23T10:20:57.744Z"
}
```

`output` is a single URL string pointing to the merged video in the chosen `output_format`.

### Status Codes
- **201 Created**: prediction created (POST `/predictions`). This is the normal success response.
- **200 OK**: prediction details returned (GET `/predictions/{id}`).
- **400 Bad Request**: invalid input, for example an `audio_volume` above 5 or a `video_codec` that is not in the list.
- **401 Unauthorized**: missing or invalid API key.
- **404 Not Found**: no prediction with that ID.
- **429 Too Many Requests**: rate limit exceeded.
- **500 Internal Server Error** or **503 Service Unavailable**: temporary server problem; retry later.

## Rate Limits
All plans allow 10 requests per second. Requests above that return `429 Too Many Requests`; back off before retrying and honour any `Retry-After` header. Polling a prediction with GET is free but still counts toward the per-second limit, so poll every 1 to 5 seconds rather than in a tight loop.

## Error Handling
- Check the HTTP status code of every request and read the response body for the error message.
- A prediction can also end with `status` set to `failed`; the `error` field then explains why. Failed predictions are not billed.
- Retry 429, 500 and 503 responses with exponential backoff. Fix the input before retrying a 400.

## Implementation Guide
### Example Code

#### JavaScript
```javascript
const apiKey = "YOUR_API_MARKET_KEY";
const baseUrl = "https://prod.api.market/api/v1/magicapi/video-audio-merger-lucataco-video-audio-merge";

async function createAndWaitForPrediction(input) {
  const response = await fetch(`${baseUrl}/predictions`, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "x-api-market-key": apiKey
    },
    body: JSON.stringify({ version: "8c3d57c9c9a1aaa05feabafbcd2dff9f68a5cb394e54ec020c1c2dcc42bde109", input })
  });

  if (response.status !== 201) {
    throw new Error(`API error: ${response.status} ${await response.text()}`);
  }

  const prediction = await response.json();
  return pollForResults(prediction.id);
}

const delay = (ms) => new Promise((resolve) => setTimeout(resolve, ms));

async function pollForResults(predictionId) {
  const maxTimeout = 600000;
  const pollInterval = 1000;
  const startTime = Date.now();

  while (Date.now() - startTime < maxTimeout) {
    const response = await fetch(`${baseUrl}/predictions/${predictionId}`, {
      headers: { "x-api-market-key": apiKey }
    });

    if (!response.ok) {
      throw new Error(`API error: ${response.status} ${await response.text()}`);
    }

    const prediction = await response.json();

    if (prediction.status === "succeeded") {
      return prediction.output;
    }

    if (prediction.status === "failed" || prediction.status === "canceled") {
      throw new Error(`Prediction ${prediction.status}: ${prediction.error || "Unknown error"}`);
    }

    await delay(pollInterval);
  }

  throw new Error("Prediction timed out after 10 minutes");
}

createAndWaitForPrediction({
    "audio_file": "https://blog.api.market/wp-content/uploads/2026/10/video-audio-merge-input-api-market.mp3",
    "video_file": "https://blog.api.market/wp-content/uploads/2026/10/video-audio-merge-input-2-api-market.mp4",
    "audio_codec": "aac",
    "video_codec": "h264",
    "audio_volume": 1,
    "duration_mode": "video",
    "output_format": "mp4",
    "replace_audio": true
  }).then((output) => console.log(output));
```

#### Python
```python
import time
import requests

API_KEY = "YOUR_API_MARKET_KEY"
BASE_URL = "https://prod.api.market/api/v1/magicapi/video-audio-merger-lucataco-video-audio-merge"


def create_and_wait_for_prediction(input_data):
    headers = {"Content-Type": "application/json", "x-api-market-key": API_KEY}
    response = requests.post(
        f"{BASE_URL}/predictions",
        headers=headers,
        json={"version": "8c3d57c9c9a1aaa05feabafbcd2dff9f68a5cb394e54ec020c1c2dcc42bde109", "input": input_data},
    )

    if response.status_code != 201:
        raise Exception(f"API error: {response.status_code} {response.text}")

    return poll_for_results(response.json()["id"])


def poll_for_results(prediction_id):
    max_timeout = 600
    poll_interval = 1
    headers = {"x-api-market-key": API_KEY}
    start_time = time.time()

    while time.time() - start_time < max_timeout:
        response = requests.get(f"{BASE_URL}/predictions/{prediction_id}", headers=headers)

        if response.status_code != 200:
            raise Exception(f"API error: {response.status_code} {response.text}")

        prediction = response.json()

        if prediction["status"] == "succeeded":
            return prediction["output"]

        if prediction["status"] in ("failed", "canceled"):
            raise Exception(f"Prediction {prediction['status']}: {prediction.get('error') or 'Unknown error'}")

        time.sleep(poll_interval)

    raise Exception("Prediction timed out after 10 minutes")


print(create_and_wait_for_prediction({
    "audio_file": "https://blog.api.market/wp-content/uploads/2026/10/video-audio-merge-input-api-market.mp3",
    "video_file": "https://blog.api.market/wp-content/uploads/2026/10/video-audio-merge-input-2-api-market.mp4",
    "audio_codec": "aac",
    "video_codec": "h264",
    "audio_volume": 1,
    "duration_mode": "video",
    "output_format": "mp4",
    "replace_audio": True
}))
```

## FAQ
- **What if the audio is longer than the video?**
  - With `duration_mode` `video` (default) the output is as long as the video. Set it to `audio` to make the audio decide the length.
- **Can I keep the original sound?**
  - Yes. Set `replace_audio` to false to mix the new audio with the original track.
- **What does `copy` mean for the codecs?**
  - The stream is copied without re-encoding, which is usually faster. Use it when the source codec already suits the output container.
- **Are both files required?**
  - Send both `video_file` and `audio_file`; the merge needs one of each.
- **What if my prediction fails?**
  - Failed predictions are not billed. Read the `error` field, adjust the input and try again.

## Contact Us
If you have any questions, reach out to us through the chat on the bottom right of the page. You can also email our support team at hello@magicapi.com.


Merge a video file and an audio file into one video: replace or mix the sound, set the volume, choose which file sets the length, and pick codecs and container.