Sources & Method

All factual claims in our guides are backed by official documentation, technical specifications, or research papers. This page lists every source referenced across the site, with retrieval dates.

Video Formats and Codecs

Browser Support and Compatibility

  • Safari WebM alpha limitation (WebKit bug #275908): WebKit Bugzilla (Retrieved: August 19, 2026)
  • Jake Archibald: Video with transparency (2024): Article (Retrieved: August 19, 2026)
  • CSS-Tricks: Overlaying Video with Transparency: Article (Retrieved: August 19, 2026)

Encoding Tools and FFmpeg

  • FFmpeg VP9 encoding guide: FFmpeg Wiki (Retrieved: August 19, 2026)
  • Shotcut forum on MP4 alpha limitations: Forum discussion (Retrieved: August 19, 2026)

AI Video Matting Research

  • Robust Video Matting (RVM): Project page (Retrieved: August 19, 2026)
  • RVM paper: arXiv 2108.11515 (Retrieved: August 19, 2026)
  • Note: RVM is cited as a principle explanation of temporal consistency in video matting. ExportAlpha uses Bria VRMBG 3.0, not RVM.

OBS Studio

Background Removal Services and Models

  • Bria video background removal API: Official documentation (Retrieved: August 19, 2026)
  • fal.ai Bria model (v3): Model page (Retrieved: August 19, 2026)
  • Pricing: $0.0042 per second as of August 19, 2026 (subject to change)
  • Unscreen shutdown: Canva announcement (Retrieved: August 19, 2026). Service closed December 1, 2025, 09:00 CET.

Method and Processing

ExportAlpha uses the following stack:

  • Infrastructure: Cloudflare Workers, D1, R2, Queues
  • Framework: Next.js with OpenNext Cloudflare adapter
  • Authentication: Google OAuth
  • Payments: Stripe Checkout, Billing, and Customer Portal
  • Video inference: fal.ai API calling Bria VRMBG 3.0

Default export: VP9 WebM with yuva420p pixel format, background_color set to Transparent

Optional export: ProRes 4444 MOV (mov_proresks preset)

Service limits (v1): Maximum 60 seconds, 1080p, ~200MB per file, 1 concurrent job

Retention: Uploaded videos and processed results are deleted after 7 days

Known Gaps (缺口)

The following are documented as unknown or untested as of August 19, 2026:

  • HEVC-with-alpha in Safari: Bria documentation lists mov_h265 as "HEVC with Alpha," but we have not verified Safari transparency with our own exports. Feature marked as experimental.
  • fal.ai v3 limits: Older Bria endpoint documented 30-second and 4000px limits. v3 llms.txt does not list these. We enforce 60 seconds (Bria REST stated limit) and 1080p conservatively.
  • CapCut, iMovie, DaVinci Resolve WebM alpha import: Public documentation is contradictory. Users should test with their specific software version.
  • HEVC support in OBS on Windows/Linux: May depend on system codecs. VP9 WebM is the recommended cross-platform format.

Updates and Corrections

This page is updated when:

  • New guides are added
  • Referenced specifications or documentation change
  • Pricing or service limits are adjusted
  • Gaps are resolved through testing

Last updated: August 19, 2026

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