arkennemasis fal · Seedance 2.5 Image to Video · $0.22-1.16/s

Seedance is the video model the local community measures everything against and can't run. bytedance.json is unambiguous about the posture: the entire Seedream/Seedance line is API-only, and it's been that way through every version. So you either call it or you don't use it.

ArkFal_bytedance_seedance_2_5_image_to_video is the friendliest entry point to that line. One still frame, a prompt describing the motion, and you get up to 30 seconds of video with synchronized audio - sound effects, ambience, and lip-synced speech generated together, not bolted on. Pricing is per second: $0.22 at 480p, $0.47 at 720p, $1.16 at 1080p.

What you set

• image - required. The starting frame; JPEG, PNG or WebP, max 30MB. This is the whole reason to prefer image-to-video over text-to-video: the composition is already decided.
• prompt - the motion and action. Keep it about movement; the picture is already handled. It can be empty, but you'll get more with it than without.
• end_image - optional, and genuinely useful. Supply a last frame and the clip transitions from the start image to it. Two-frame control without the dedicated endpoint.
• resolution - 720p default, 480p for speed, 1080p for quality. This is the price dial, and it isn't linear: 1080p is two and a half times 720p.
• draft - off by default. Turn it on and the run becomes a 480p preview that overrides your resolution setting and returns a draft_id you can complete at 1080p within seven days. Cheapest sane way to find out whether a prompt works before committing $10.
• duration - auto, or 4–30 seconds. The model decides when left to auto.
• generate_audio - on by default and it costs nothing either way, so there's no reason to turn it off unless your NLE is fussy.
• bitrate_mode - standard or high; high asks for a larger, better encode. Doesn't change the price.
• codec - auto (default), H264 or H265.

Shared optional controls: max_cost_usd (default $20 - with a 30-second 1080p clip well above that, this node is exactly what the cap is for), reuse_identical_run (on; identical inputs come back from disk without a second charge), extra_json, max_concurrent.

Outputs: video, video_path, seed, draft_id (empty unless you drafted), info.

The money, plainly

At 720p the node is about $0.47 per second, so a 10-second clip is $4.70. That's the real price, not a markup by this pack - and the KB records the community's response to exactly this number when Seedance hit ComfyUI, which was mostly sticker shock plus the counter-argument that the cheap years were a subsidy. I'd only add: use the draft toggle. It's the difference between a two-dollar check and an eleven-dollar gamble.

Install

cd ComfyUI/custom_nodes
git clone https://github.com/Hishamahmer/comfyui-arkennemasis

Restart, or install through ComfyUI Manager by searching arkennemasis. Then your key goes in a .env in the folder holding run_nvidia_gpu.bat (or your ComfyUI folder):

FAL_KEY=your-key-from-fal.ai/dashboard/keys

No key input on the node - deliberate, so a key can't be saved into a shared workflow. Nothing to download; the weights are ByteDance's and they don't leave the API.

Where people get burned

Interfaces that don't ship as draft_id: if you turn draft on and then close the tab, the id is in this node's outputs and in output/fal/_requests.jsonl, and it's only good for seven days and only for the account that made it. Grab it while it's hot.

The rest is the usual API-node arithmetic. Your source image and prompt go to fal and on to ByteDance's model, with their filter in the loop - no local workaround, because there's nothing local to patch. The estimate reads your resolution and duration when both are set explicitly, and shows a rate when you leave things on auto. Files are saved to output/fal/bytedance_seedance-2.5_image-to-video/.