Building CEF with Proprietary Codecs

Tracks issue #1223 — vendored CEF lacks H.264 / AAC support so Google Meet's dynamic (video) virtual backgrounds, embedded YouTube/Vimeo previews, and any HTML5 <video> source pulling H.264-in-MP4 fail with MEDIA_ERR_SRC_NOT_SUPPORTED: PipelineStatus::DEMUXER_ERROR_NO_SUPPORTED_STREAMS: FFmpegDemuxer: no supported streams. Empirical confirmation of the codec absence is in #1223 and in feedback_cef_runtime_gaps.md gap #3.

The Spotify CDN (cef-builds.spotifycdn.com) — which download-cef and all other public CEF wrappers default to — ships only open-source codecs. Every flavor (standard, minimal, client, tools, *_symbols) is built with proprietary_codecs = false. To get H.264 / AAC support into the embedded webview we have to compile CEF ourselves with Chrome-branded FFmpeg and host the resulting binary somewhere our build script can fetch it from.

This directory is the build infrastructure for that: scripts that drive the upstream automate-git.py toolchain, a local install helper that drops the result into CEF_PATH so cargo build picks it up, and the license posture / hosting documentation.

The actual built binary is NOT committed to this repo and never will be. It is multiple gigabytes and carries license obligations (see below). Hosting + distribution is a separate operational concern.

License posture (READ BEFORE BUILDING)

H.264 / AVC carries patent obligations under the MPEG-LA AVC Patent Portfolio License. Bundling an H.264 decoder into a redistributed application can require royalty payments depending on:

distribution model (free vs paid),
annual end-user count,
whether the decoder is hardware-accelerated by the OS (some royalty carve-outs apply for "system supplied" decoders),
jurisdiction.

Browsers like Firefox sidestep this by downloading Cisco's OpenH264 binary plugin at runtime — Cisco pays the royalties on their users' behalf. CEF does not currently ship that plugin path.

Before running this build, get sign-off from legal / business on:

Whether the AVC license fee is in budget for OpenHuman's distribution channels (desktop installer, GitHub releases, app stores).
Whether the AAC patent pool (separate licensor) is also in scope — AAC is bundled with H.264 in the same proprietary_codecs = true build flag, so you cannot have one without the other.
Whether HEVC / H.265 should also be enabled (separate flag, enable_hevc_parser_and_hw_decoder = true, which has its own MPEG-LA pool).

If the answer to (1) or (2) is no, stop here. The honest fallback is to surface "dynamic backgrounds not supported" in the Effects picker UI (see #1223 path D) rather than ship without a license.

Build inputs

Variable	Value (CEF 146 line)
Target CEF version	`146.0.9+g3ca6a87+chromium-146.0.7680.165` (matches `cef = "=146.4.1"` in `app/src-tauri/Cargo.toml`)
Chromium branch	`7680`
GN args added	`proprietary_codecs=true ffmpeg_branding="Chrome"`
Required GN args (already implied)	`is_official_build=true` (release builds only)
Optional HEVC extension	`enable_hevc_parser_and_hw_decoder=true` (separate license)
Build platforms	macOS arm64 + x86_64, Linux arm64 + x86_64, Windows x86_64
Disk required	~150 GB per platform (Chromium source + build cache)
Wall-clock	~2-4 hours per platform on M2/M3 Mac, longer on Linux/Windows
Output artifact	`cef_binary_<ver>_<platform>_minimal.tar.bz2`

The minimal flavor is what download-cef already targets (matches pub fn minimal() selection in download_cef::CefVersion). Skipping the standard flavor saves ~200 MB per artifact and the sample apps aren't shipped to users.

Build host requirements (per upstream CEF docs)

Per CEF Automated Build Setup:

macOS: Xcode + macOS SDK matching the target Chromium milestone.
Linux: Ubuntu 22.04 LTS recommended; needs clang, lld, libstdc++-12-dev, plus the chromium install-build-deps.sh package set.
Windows: Visual Studio 2022 with the C++ workload, Windows 11 SDK.

All platforms: Python 3, Git, depot_tools (the script will pull a fresh copy if --depot-tools-dir doesn't exist).

Quick start (single platform, local dev)

Prerequisites: the build-host requirements above, plus the legal sign-off documented in the license-posture section.

# 1. Run the build (2-4 hours on M2/M3 Mac).
#    Output lands at $CEF_BUILD_DIR/chromium/src/cef/binary_distrib/
./scripts/cef-with-codecs/build-cef-with-codecs.sh

# 2. Extract the resulting tarball to the cache that tauri-cef expects
#    so cargo build picks it up via the existing CEF_PATH wiring.
./scripts/cef-with-codecs/install-local.sh

# 3. Verify the codec gates inside dev:app:
pnpm dev:app
# In a second terminal once a webview is loaded:
node app/src-tauri/scripts/diagnose-cef-runtime.mjs probe   # path may vary
# Expect h264_baseline / h264_main / h264_high / aac_lc → true

If h264_baseline returns true after step 3, the codec build is correctly installed. Re-run #1053 Phase B smoke (Gmeet → Effects → pick a dynamic / video background) to confirm the original symptom is gone.

CI / shared distribution (out of scope for this PR)

The build script alone is enough for an individual developer to validate the fix end-to-end. To ship the binary to all developers + release builds without each machine needing a 4-hour compile:

Run the build on a powerful CI runner (GitHub Actions self-hosted, or a beefy on-prem box).
Upload the resulting cef_binary_*.tar.bz2 to a private CDN (s3://openhuman-cef-builds/<version>/<platform>/... or equivalent).
Set CEF_DOWNLOAD_URL in scripts/load-dotenv.sh (or as a per-developer env override) to point at that CDN.
The vendored download-cef crate will fetch from the new URL on first build, just like it currently does from Spotify CDN.

Tracking this hosting work as a follow-up issue once the legal sign-off comes back. The build script in this PR is the upstream half of that pipeline.

What this PR does not do

Does not compile any binary. The build is too long + too disk-heavy to run in CI on every PR. Maintainers run the script offline.
Does not host any binary. That belongs to the CDN follow-up above.
Does not flip any default in download-cef. Spotify CDN remains the default until the legal review + private CDN are in place.
Does not enable HEVC. That's a separate license pool; revisit if there's a concrete user-visible feature blocked on HEVC.
Does not change vendored tauri-cef. No submodule pin bump, no source-tree edits — the upstream crate already handles CEF_PATH / CEF_DOWNLOAD_URL overrides.

The only files this PR touches are this README, the two helper scripts, and the issue tracker (#1223 cross-link).

Issue #1223 — bug: dynamic Gmeet backgrounds fail on H.264 demux.
Issue #1053 — parent: Gmeet bg effects (this is the codec follow-up).
PR #1222 — surfaced + diagnosed the codec gap during gmeet routing- reliability work; harness scripts/diagnose-cef-runtime.mjs added there.
Memory feedback_cef_runtime_gaps.md — gap #3 reclassified, codec gap documented with full diagnostic procedure.

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