Merge Audio + Video API — Combine Video and Audio into MP4

Merge a video URL with an audio URL into a single MP4. Replace original audio or mix new audio on top of existing. 1 credit per merge.

New: Merge audio and video files into a single MP4 with a single API call. Video stream is copied without re-encoding when possible — fast and cheap.

Pricing

Operation	Credits	Price (Pro Yearly)	Price (Pro Monthly)
Merge (any mode)	1	$0.006	$0.012

Credits are deducted upfront. Refunded automatically if the merge fails.

Endpoint

POST https://vicsee.com/api/v1/tools/merge-audio-video

See Authentication for API key setup.

Parameters

Parameter	Type	Required	Description
video_url	string	Yes	Source video URL (MP4, MOV, WebM)
audio_url	string	Yes	Audio track URL (MP3, WAV, AAC, OGG, M4A)
mode	string	No	`"replace"` (default) = discard original audio. `"mix"` = overlay new audio on existing.
volume	number	No	Volume of new audio (0.0-1.0). Default: 1.0 for replace, 0.5 for mix.

Modes

Replace (default): Discards the video's original audio and uses the new audio track. Use this when merging AI-generated video (no audio) with separately generated TTS or sound effects.

Mix: Overlays the new audio on top of the video's existing audio. Use this when adding background music or sound effects to a video that already has dialogue. If the source video has no audio stream, falls back to replace mode automatically.

Example Request

curl -X POST https://vicsee.com/api/v1/tools/merge-audio-video \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "video_url": "https://example.com/video.mp4",
    "audio_url": "https://example.com/audio.mp3",
    "mode": "replace"
  }'

Response

{
  "success": true,
  "data": {
    "id": "task_abc123",
    "model": "merge-audio-video",
    "status": "completed",
    "output": {
      "url": "https://assets.vicsee.com/vicsee/dew/2026-02-28-xyz/merge.mp4",
      "duration": 5.2
    },
    "creditsUsed": 1,
    "creditsRemaining": 499,
    "createdAt": "2026-02-28T12:00:00.000Z"
  }
}

The response returns immediately with the merged video URL — no polling needed. The duration field contains the output video duration in seconds.

Mix Mode Example

Overlay background music at 30% volume on a video with existing dialogue:

curl -X POST https://vicsee.com/api/v1/tools/merge-audio-video \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "video_url": "https://example.com/interview.mp4",
    "audio_url": "https://example.com/background-music.mp3",
    "mode": "mix",
    "volume": 0.3
  }'

Limits

Constraint	Value
Supported video formats	MP4, MOV, WebM
Supported audio formats	MP3, WAV, AAC, OGG, M4A
Audio longer than video	Truncated at video end
Video longer than audio	Continues with silence

Errors

Code	HTTP	Description
`MISSING_VIDEO_URL`	400	`video_url` not provided
`MISSING_AUDIO_URL`	400	`audio_url` not provided
`INVALID_MODE`	400	Mode not `"replace"` or `"mix"`
`INVALID_VOLUME`	400	Volume not between 0.0 and 1.0
`INSUFFICIENT_CREDITS`	402	Not enough credits
`MERGE_FAILED`	500	FFmpeg merge failed

ElevenLabs Audio — Generate TTS and sound effects to merge with video
Tasks API — Check task history
Credits API — Check your credit balance

Merge Audio + Video

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