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
- Apple HEVC with Alpha: WWDC 2019 Session 506 (Retrieved: August 19, 2026)
- Apple HEVC Interoperability Profile: PDF documentation (Retrieved: August 19, 2026)
- kCMVideoCodecType_HEVCWithAlpha: Apple CoreMedia documentation (Retrieved: August 19, 2026)
- Apple ProRes support and alpha channels: Official support page (Retrieved: August 19, 2026)
- WebM Project: webmproject.org (Retrieved: August 19, 2026)
- WebM VP9 encoding documentation: WebM Project Docs (Retrieved: August 19, 2026)
- MDN Video Codecs Guide: MDN Web Docs (Retrieved: August 19, 2026)
- MDN Video Concepts: MDN Web Docs (Retrieved: August 19, 2026)
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 to explain temporal consistency in video matting. It is not a description of ExportAlpha's processing stack.
OBS Studio
- OBS Media Sources: Official Knowledge Base (Retrieved: August 19, 2026)
- OBS Browser Source: Official Knowledge Base (Retrieved: August 19, 2026)
- OBS Track Matte Stinger Transitions: Official Knowledge Base (Retrieved: September 8, 2026)
Background Removal and Editing Tools
- Unscreen shutdown: Canva help: Unscreen Officially Closed (Retrieved: September 8, 2026). Canva states Unscreen.com has closed as of June 29, 2026, and is focusing on Canva's Video Background Remover.
- After Effects output modules (RGB+Alpha writes an alpha channel): Adobe help: Basics of rendering and exporting (Retrieved: September 8, 2026)
- After Effects footage interpretation (alpha can be set per item): Adobe help: Interpreting footage items (Retrieved: September 18, 2026)
Method and Processing
Public product facts we can state:
- Authentication: Google sign-in
- Payments: Stripe Checkout, Billing, and Customer Portal
Default export: VP9 WebM with yuva420p pixel format, background_color set to Transparent
Optional export: ProRes 4444 MOV
Service limits (v1): Maximum 60 seconds, 1080p, ~200MB per file, 1 concurrent job
Retention: Results and uploads from finished jobs are deleted automatically 7 days after processing finishes. Uploads that never finish processing (failed or abandoned) are deleted automatically 7 days after upload.
Known Gaps (缺口)
The following are documented as unknown or untested as of August 19, 2026:
- HEVC-with-alpha in Safari: We have not verified Safari transparency with our own HEVC exports. Treat that path as experimental.
- Duration and resolution: We enforce 60 seconds and 1080p on upload.
- 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: September 24, 2026