generate_video_between_frames
Generate the transition between TWO given frames: the video starts at the first image and ends at the second one, Flow invents everything in between.
This is Flow's "Кадры" with both slots filled — a different mechanism from
generate_video_from_image, which only pins the FIRST frame and lets the ending drift.
Use this when the ending matters: a logo that must resolve exactly, a character that
must land in a specific pose, two stills from a storyboard that need connecting.
Both images are raw base64 bytes, no data: URI prefix. The default model
(veo_3_1_interpolation_lite, 10 credits, 8 seconds) is the cheap one — transitions
are something you retry a few times, and defaulting to the 100-credit key would make
every experiment expensive.
beats: how many DISTINCT action phases the prompt describes — "ears flick back",
"tail lashes", "strikes the ball", "ball flies off" are four. Give it and the server
picks the clip length for you (about two phases per second) and says in the reply what
it picked and why. Measured 31.08.2026: the model STRETCHES whatever you describe over
whatever length you ask for, so one phase in four seconds comes out as slow motion, and
the same text at six seconds instead of four loses 15% of its movement. Adjectives are
not phases: "springy cartoon motion" adds nothing. Leave beats out and the length you
passed is used unchanged.
project_id: put the clip into a project made with create_project instead of the
account's default one.
beats: how many DISTINCT action phases the prompt describes. The server then picks
the clip length itself (about two phases per second) and says so in the reply. For a
first+last-frame transition keep it low: the two frames already fix the endpoints, and
asking for more seconds than the action needs only stretches it — measured 31.08.2026,
the same text at six seconds instead of four lost 15% of its movement.
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| beats | No | ||
| aspect | No | VIDEO_ASPECT_RATIO_LANDSCAPE | |
| prompt | Yes | ||
| project_id | No | ||
| include_preview | No | ||
| video_model_key | No | veo_3_1_interpolation_lite | |
| end_image_base64 | Yes | ||
| start_image_base64 | Yes |