Generate a short looping transparent video (HEVC `hvc1` with alpha) from a single still image. Pipeline: SeedDance 2 image-to-video with optional end-frame anchoring for a seamless loop → ffmpeg split → BiRefNet v2 Matting per frame in parallel → ffmpeg encode HEVC with alpha. Output is a small (~1-2 MB) `.mov` that plays natively in iOS `AVPlayer`, web video tags, and any HEVC-alpha-capable runtime. Use when the user wants to animate a static character/hero image into an empty-state loop, ambi…
Generate a short looping transparent video (HEVC `hvc1` with alpha) from a single still image.
Pipeline: SeedDance 2 image-to-video with optional end-frame anchoring for a seamless loop → ffmpeg split → BiRefNet v2 Matting per frame in parallel → ffmpeg encode HEVC with alpha.
Output is a small (~1-2 MB) `.mov` that plays natively in iOS `AVPlayer`, web video tags, and any HEVC-alpha-capable runtime.
Use when the user wants to animate a static character/hero image into an empty-state loop, ambient onboarding hero, badge animation, or any short transparent video.
Don't use for chroma-key/green-screen footage (BiRefNet is ML segmentation, not color-keying), long videos (cost scales linearly with frame count), or audio.
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Package contents
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skill mdSKILL.md4,069 B
docsSUMMARY.md757 B
History
First seen on skills.sh
First recorded snapshot · 6 installs
SKILL.md
Transparent Video Loop
Workflow
Confirm prerequisites. The user needs genmedia (fal.ai CLI, configured with API key), ffmpeg (Homebrew ffmpeg with hevc_videotoolbox — bundled on macOS), and a still image they want to animate. Check with genmedia setup --status and which ffmpeg.
Pick the inputs. Ask the user (or infer from context) for:
- still image — local path or URL. Subject on transparent or solid background, ideally already isolated. If it's a complex scene with subject + environment, the loop will animate the whole frame. - motion prompt — what subtle ambient motion to apply. Keep it small: "characters breathe gently, hand waves slowly, leaves rustle." Big camera motion or scene changes break the closed-loop seam. - closed loop or open? — recommend closed for ambient UI loops; open is fine if the clip plays once or you don't mind a tiny seam. - output path — where to save the final .mov.
Run the orchestrator.scripts/transparent-loop.sh handles the full pipeline. Recommended invocation for a closed UI loop:
``bash scripts/transparent-loop.sh \ --image ./hero.png \ --prompt "Subtle ambient idle motion that returns to the starting pose. Static camera." \ --output ./hero_loop.mov \ --duration 5 \ --closed-loop ``
The script uploads the still to fal if it's a local path, runs SeedDance 2 fast image-to-video with endimageurl = image_url (closed-loop mode), splits frames with ffmpeg, processes each frame through BiRefNet v2 Matting in parallel (10 workers by default), then encodes HEVC alpha at 720×720 24fps.
Inspect the output before shipping. Open the .mov in QuickTime to verify: the loop is seamless, the alpha is clean (no halo, no missing characters), the file size is reasonable (1-3 MB for a 5s 720² clip). If a character disappeared, see the BiRefNet failure mode in references/troubleshooting.md — usually means the still had thin/translucent details the matting model can't recover.
Wire into the target app. iOS uses AVPlayer directly; the .mov plays with alpha out of the box if playerLayer.pixelBufferAttributes is set to kCVPixelFormatType_32BGRA. Web uses <video> with the same .mov. See references/playback.md for the per-platform integration snippet.
Reference
Read these in order when implementing or debugging:
references/pipeline.md — every command, every flag, what each step does, cost breakdown.
references/troubleshooting.md — failure modes I hit and how to recognize them (hypervideo chroma-key trap, ProRes oversize trap, seam without endimageurl, halo without refine_foreground).
references/playback.md — minimal iOS / web / Android playback integration with alpha preserved.
Scope
This skill is for short transparent animation loops, typically 3–10 seconds. For longer videos, the per-frame BiRefNet cost scales linearly (~$0.005/frame, ~$0.60 for a 2-min clip at 24fps) and the resulting .mov grows quickly. For real-time effects, transparent live video, or scenes with complex semi-transparency (glass, smoke, hair on cluttered backgrounds), a dedicated VFX matting tool is better than this open-source pipeline.
