# Replace Background

Try out this capability in Bria's sandbox


Description

an asynchronous job that detects the video background and composites a user-provided image or video asset behind the subject. Size and duration mismatches between the input video and the background asset are handled automatically.



behavior:

- Returns HTTP 202 with request_id and status_url

- Check job status by polling status_url or by calling the Status Service with the request_id until a terminal status is returned



foreground input containers:

- .mp4, .mov, .webm, .avi, .gif



foreground input codecs:*

- H.264, H.265 (HEVC), VP9, AV1, PhotoJPEG



background input formats:

- Image: .jpg, .png, .webp, .gif

- Video: .mp4, .mov, .webm, .avi



attributes preserved in output:

- Aspect Ratio and resolution (matches foreground video)

- Frame Rate (matches foreground video)

- Foreground audio if present and preserve_audio is true. Background audio is always discarded.


Limitations:

- Max foreground duration: 60 seconds

- Max background video duration: 60 seconds

- Resolutions: Input resolution up to 16000x16000 (16K) for both foreground and background. Inputs larger than this return 413 Payload Too Large. Output resolution matches the foreground input resolution.

- Video Background spect ratio: provided background video must be of same aspect ratio as the foeground video.

mismatch handling (image bakground):

- Background is scaled to cover the full frame, then center-cropped to exactly match the foreground resolution. Some background edges may be clipped.


mismatch handling (video backgrounds only):

- Background video shorter than foreground: loop from 0s until foreground ends.

- Background video longer than foreground: play from 0s, trim at foreground end.


Output transparency:

- Output is fully opaque (composited).

Endpoint: POST /replace_background

## Header parameters:

  - `api_token` (string, required)

## Request fields (application/json):

  - `video` (string, required)
    Publicly accessible URL of the input (foreground) video. Input resolution supported up to 16000x16000 (16K).

  - `background_url` (string, required)
    Publicly accessible URL of the background asset. Accepts images (.jpg, .png, .webp, .gif). Max resolution 16000x16000.

  - `background_type` (string)
    the background input type
    Enum: "image", "video"

  - `output_container_and_codec` (string)
    Output container and codec preset. Alpha is not needed for replace-background output.
    Enum: "mp4_h264", "mp4_h265", "webm_vp9", "mov_h265", "mov_proresks", "mkv_h264", "mkv_h265", "mkv_vp9", "gif"

  - `preserve_audio` (boolean)
    Preserve foreground audio if present.

## Response 202 fields (application/json):

  - `request_id` (string, required)

  - `status_url` (string, required)

## Response 400 fields (application/json):

  - `error` (object, required)

  - `error.code` (integer, required)
    Example: 123

  - `error.message` (string, required)

  - `error.details` (string, required)

  - `request_id` (string, required)