Preview the first frame before an avatar render: Sume vs credits

If you want to approve how an avatar scene looks before paying for the whole video, Sume has a separate preview stage: POST /v1/avatar-video-previews creates first-frame stills only, and you call generate-video on the one you like. The Synthesia and HeyGen pricing pages I read describe credit allowances, not a preview-first workflow, so I make no claim about whether either offers one.

This matters most for ads, where a wrong product placement or composition costs a full render to find out.

How the Sume preview works

A preview takes the same body as an avatar video: a script or video_inputs, not both, plus optional product_image, scene, quality, aspect_ratio, title and captions. The default quality is plus. The response gives job URLs and an avatar_video_preview_id, and the resource later holds preview_image_url and one scene_previews entry per input scene.

You can regenerate the stills, then call generate-video. Caption intent can be stored at create time; Sume never burns captions into preview stills and applies them only when the final video generates.

• Multi-scene plans get one still per scene.
• Poll the job like any other generation, or use a webhook.
• Prefer resource_status and job_status over the legacy status field.

Where this saves money

The preview exists so you do not pay for a failed composition. Compare that with a credit pool: when a clip is wrong on a plan, you spend credits to find out, and you can run out before month end. On a balance, the same mistake is a charge you can see in the usage ledger.

The catch is that a preview is its own job. Use it when the first frame is where the risk is, such as a product shot or a scene with a specific background. For a plain talking head on a studio backdrop, skip it and render directly.

Verdict

Plan-based tools are simpler to budget if you always generate several variations a month. A preview stage is better when each video is a separate decision. If you already have a plan with credits in hand, keep using it for that; if you submit avatar jobs from code, add the preview call to your pipeline.

If you want a rule of thumb, preview when the scene is new and skip it when it is a repeat. A first run of a product ad with a specific setting deserves a preview, and so does any multi-scene plan where each scene has a different backdrop. A weekly update with the same avatar, scene and framing does not need one. Keep the preview id with the project so you can tell later which still was approved.