update-media-lib

name	update-media-lib
description	Update vendored Firefox media libraries. Use for libvpx, dav1d, aom, opus, cubeb, Rust media crates, cherry-picking upstream media fixes, and running mach vendor workflows.
metadata	{"short-description":"Update media libraries"}

Update Media Libraries

Overview

This skill helps update vendored third-party media libraries in Firefox. Each library has its own update process documented in its README and moz.yaml files.

Supported Libraries

Fully Automated (mach vendor)

Library	Path	Source Location	Update Method
libvpx	media/libvpx	media/libvpx/libvpx/	Two-step with patches
libaom	media/libaom	third_party/aom/	Two-step with patches
libsoundtouch	media/libsoundtouch	media/libsoundtouch/	Two-step with patches
libspeex_resampler	media/libspeex_resampler	media/libspeex_resampler/	Two-step with patches
highway	media/highway	third_party/highway/	Two-step with patches
libcubeb	media/libcubeb	media/libcubeb/	Two-step with patches
libpng	media/libpng	media/libpng/	Two-step with patches
libogg	media/libogg	media/libogg/	Two-step with patches
libyuv	media/libyuv	media/libyuv/libyuv/	Two-step with patches
libdav1d	media/libdav1d	third_party/dav1d/	Simple vendor
libvorbis	media/libvorbis	media/libvorbis/	Simple vendor (file renames)
libwebp	media/libwebp	media/libwebp/	Simple vendor
libjxl	media/libjxl	third_party/jpeg-xl/	Simple vendor
libnestegg	media/libnestegg	media/libnestegg/	Simple vendor
libopus	media/libopus	media/libopus/	Script-based (update.sh)
Rust crates (git)	(Cargo.toml)	third_party/rust/*	Git crate (update rev + cargo update + mach vendor rust)
Rust crates (crates.io)	(Cargo.toml)	third_party/rust/*	Crates.io (update version + cargo update + mach vendor rust)
libjpeg	media/libjpeg	media/libjpeg/	Script-based (update-libjpeg.sh)

Manual Update Required (Cannot Auto-Update)

Library	Path	Reason	Update Method
ffvpx	media/ffvpx	Requires platform-specific config regeneration	Manual rsync + config generation
libmkv	media/libmkv	No vendoring section, upstream abandoned	Cannot update

Related Skills

If you have local changes to a Rust crate that you want to test before they're merged upstream, use /vendor-local instead. This skill (/update-media-lib) is for pulling the latest upstream release from remote repositories.

Initial Question: Update Type

IMPORTANT: Before starting any work, determine what kind of update the user needs. If the user's request clearly indicates one type (e.g., they provide a commit URL to cherry-pick, or say "update to latest"), skip the question and proceed directly. Otherwise, ask the user directly:

"What type of update do you need?"

• Full library update - Update the vendored library to a new upstream version
• Cherry-pick a specific commit - Apply a single upstream commit to the current vendored source

If the user provides a URL to a specific commit or mentions "cherry-pick", go directly to the Cherry-pick Process section. If the user asks to update to a version/tag or to latest, go to the Full Update Process section.

Cherry-pick Process

Cherry-picking applies a single upstream commit directly to the vendored source without running mach vendor. This is useful for backporting security fixes or targeted bug fixes.

1. Identify the library and commit - Confirm the library and the upstream commit hash/URL
2. Read moz.yaml - Check media/<lib>/moz.yaml for the current vendored revision and upstream URL
3. Fetch the upstream diff - Use Codex web access or curl to get the commit diff (e.g., from Googlesource ?format=TEXT for base64-encoded diffs, or from GitHub)
4. Verify the diff applies cleanly - Read the affected files in the vendored source and confirm the pre-image (context lines) matches
5. Ask for Bugzilla number - ask the user directly for an optional bug number
6. Apply the changes - Use Edit to apply each hunk from the diff to the corresponding vendored file (e.g., media/<lib>/libvpx/path/to/file.c)
7. Build and test - Run ./mach build to verify

Commit format for cherry-picks: If bug number provided:

• Bug XXXXXX - Cherry-pick upstream <library> commit <short-hash>. <commit-subject>

If no bug number:

• Cherry-pick upstream <library> commit <short-hash>. <commit-subject>

Verifying compatibility across branches: When the user asks whether a cherry-pick applies cleanly on a specific Firefox release (e.g., Firefox 147):

1. Find the Firefox release date (use web search when needed)
2. Find which libvpx version was vendored at that time: git log --oneline --before="<date>" -1 -- media/<lib>/moz.yaml
3. Read the file at that commit: git show <commit>:media/<lib>/path/to/file.c
4. Compare the pre-image lines from the diff against the file content at that revision

Full Update Process

1. Identify the library - Confirm which library needs updating
2. Check limitations - Verify the library can be auto-updated (see table above)
3. Read the README - Check media/<lib>/README_MOZILLA or README.md for library-specific instructions
4. Check moz.yaml - Review media/<lib>/moz.yaml for current version and upstream URL
5. Ask about commit preference - For two-step libraries, ask user if they want one combined commit or two separate commits
6. Ask for Bugzilla number - Optionally ask user for a bug number to include in commit messages
7. Run the update command - Execute the appropriate vendor command
8. Apply patches if needed - Some libraries require a second step for patches
9. Build and test - Verify the update works

Update Patterns

Two-step with patches

Libraries with local patches use a two-step process:

# Step 1: Update the source (without patches)
./mach vendor media/<lib>/moz.yaml --patch-mode=none

# Step 2: Apply local patches
./mach vendor media/<lib>/moz.yaml --patch-mode=only --ignore-modified

Two-step libraries: libvpx, libaom, libsoundtouch, libspeex_resampler, highway, libcubeb, libpng, libogg, libyuv

IMPORTANT - Commit Workflow: For two-step libraries, ALWAYS ask the user whether they want:

1. Two separate commits (recommended by upstream README):
   • First commit: "Update to " (after step 1)
   • Second commit: "Apply local patches to " (after step 2)
2. Single combined commit:
   • One commit after both steps: "Update to and apply local patches"

IMPORTANT - Bugzilla Bug Number: ALWAYS ask the user if they have a Bugzilla bug number for this update. Ask it alongside the commit preference question.

If user provides a bug number, format commit messages as:

• Bug XXXXXX - Update <library> to <version>
• Bug XXXXXX - Apply local patches to <library>

If no bug number is provided, use the standard format without the "Bug XXXXXX - " prefix.

Ask for both the commit preference and optional bug number before proceeding.

Simple vendor

Libraries without patches or with auto-applied patches:

# Update to latest
./mach vendor media/<lib>/moz.yaml

# Or update to specific version/commit
./mach vendor media/<lib>/moz.yaml -r <tag-or-commit>

# Or update from a fork
./mach vendor media/<lib>/moz.yaml --repo <repository-url> -r <commit>

Simple vendor libraries: libdav1d, libvorbis, libwebp, libjxl, libnestegg

Commit format for simple vendor: Ask for optional Bugzilla bug number. If provided:

• Bug XXXXXX - Update <library> to <version>

If no bug number:

• Update <library> to <version>

Script-based (libopus)

libopus uses a custom update script integrated with mach vendor:

./mach vendor media/libopus/moz.yaml

The update.sh script is automatically invoked during vendoring.

Script-based (libjpeg)

libjpeg uses a custom update script that requires cloning the upstream repository first.

Known issue with patch step: The script runs patch -p0 from media/libjpeg/, but the patch file (mozilla.diff) contains paths like a/media/libjpeg/jmorecfg.h. With -p0, patch looks for a/media/libjpeg/jmorecfg.h relative to current directory, which doesn't exist. This is documented in MOZCHANGES: "fix up any rejects from applying the Mozilla specific patches".

Workaround: After the script fails at the patch step, apply manually with -p1 from Firefox root (strips the a/ prefix).

Update process:

1. Clone libjpeg-turbo to a temporary directory:

   git clone https://github.com/libjpeg-turbo/libjpeg-turbo.git /tmp/libjpeg-turbo
   

2. Run the update script (patch step will fail - this is expected per MOZCHANGES):

   ./media/update-libjpeg.sh /tmp/libjpeg-turbo [tag]
   # Example: ./media/update-libjpeg.sh /tmp/libjpeg-turbo 2.1.5.1
   

3. When prompted about patch failure, skip (press Enter or 'y')

4. Apply the patch manually from the Firefox root directory:

   patch -p1 -i media/libjpeg/mozilla.diff
   

5. Clean up temporary clone:

   rm -rf /tmp/libjpeg-turbo
   

Version compatibility:

• Versions 2.x: Compatible with current file structure
• Versions 3.x: Reorganized source structure (files in src/ subdirectory) - may require additional work

Commit format: Ask for optional Bugzilla bug number. If provided:

• Bug XXXXXX - Update libjpeg-turbo to <version>

If no bug number:

• Update libjpeg-turbo to <version>

Rust crates

Rust crates are defined in /toolkit/library/rust/shared/Cargo.toml and vendored into /third_party/rust/. There are two types:

Git-based Rust crates

Crates with a git URL and rev attribute pointing to a specific commit.

Examples:

• mp4parse_capi - MP4 parser (https://github.com/mozilla/mp4parse-rust)
• cubeb-coreaudio - macOS audio backend (https://github.com/mozilla/cubeb-coreaudio-rs, default branch: trailblazer)
• cubeb-pulse - PulseAudio backend (https://github.com/mozilla/cubeb-pulse-rs)
• audioipc2-client / audioipc2-server - Audio IPC (https://github.com/mozilla/audioipc)

Update process:

1. Find the current revision in /toolkit/library/rust/shared/Cargo.toml:

   <crate-name> = { git = "https://github.com/...", rev = "<current-rev>", ... }
   

2. Get the new revision (commit hash or tag) from upstream repository

3. Update the rev attribute in Cargo.toml to the new revision

4. Update Cargo.lock to reflect the new revision:

   cargo update -p <crate-name>
   

5. Run the vendor command:

   ./mach vendor rust
   # Use --force if needed for large files
   ./mach vendor rust --force
   

6. Verify expected changes in /third_party/rust/<crate-name>*

7. Run cargo vet to check for missing audits:

   ./mach cargo vet suggest 2>&1 | head -20
   

8. Add required audits if any crates need certification (see crates.io section below for examples)

9. Include supply-chain/audits.toml in the commit if audits were added

Commit format: Ask for optional Bugzilla bug number. If provided:

• Bug XXXXXX - Update <crate-name> to <revision>

If no bug number:

• Update <crate-name> to <revision>

Crates.io Rust crates

Crates with a version attribute, pulled from crates.io.

Examples:

• cubeb-sys - Cubeb native bindings (bundles libcubeb C code)

Update process:

1. Find the current version in /toolkit/library/rust/shared/Cargo.toml:

   <crate-name> = { version = "<current-version>", ... }
   

2. Check available versions on crates.io:

   cargo search <crate-name> --limit 1
   

3. Ask the user what version they want to update to. Present the current version, latest available version, and ask for their preferred target version.

4. Update the version attribute in Cargo.toml to the chosen version

5. Update Cargo.lock to reflect the new version:

   cargo update -p <crate-name>
   

6. Run the vendor command:

   ./mach vendor rust
   # Use --force if needed for large files
   ./mach vendor rust --force
   

7. Verify expected changes in /third_party/rust/<crate-name>*

8. Run cargo vet to check for missing audits:

   ./mach cargo vet suggest 2>&1 | head -20
   

9. Add required audits for each crate that needs certification:

   ./mach cargo vet certify <crate-name> <old-version> <new-version> --criteria safe-to-deploy --accept-all
   

   For example, when updating cubeb crates from 0.30.1 to 0.32.0:

   ./mach cargo vet certify cubeb 0.30.1 0.32.0 --criteria safe-to-deploy --accept-all
   ./mach cargo vet certify cubeb-backend 0.30.1 0.32.0 --criteria safe-to-deploy --accept-all
   ./mach cargo vet certify cubeb-core 0.30.1 0.32.0 --criteria safe-to-deploy --accept-all
   ./mach cargo vet certify cubeb-sys 0.30.1 0.32.0 --criteria safe-to-deploy --accept-all
   

10. Include supply-chain/audits.toml in the commit

Commit format: Ask for optional Bugzilla bug number. If provided:

• Bug XXXXXX - Update <crate-name> to <version>

If no bug number:

• Update <crate-name> to <version>

Limitations and Known Issues

libaom

• Issue: generate_sources_mozbuild.sh requires python3-venv system package
• Solution: Install python3-venv before updating: apt install python3-venv

libdav1d

• Issue: May require manual moz.build updates for new/removed files
• Post-update: Check moz.build and asm/moz.build for file changes
• Note: Assembly files with %if ARCH_X86_64 may need conditional handling

libmkv

• Issue: Cannot be auto-updated - no vendoring section in moz.yaml
• Reason: Upstream (Chromium libvpx) is abandoned
• Status: Maintenance only, manual patches required

ffvpx

• Issue: Cannot use mach vendor
• Update method: Manual rsync from FFmpeg source
• Requires: Platform-specific config regeneration for each target (Unix32, Unix64, Darwin, Windows, Android)
• See: media/ffvpx/README_MOZILLA for detailed instructions

Key Files

For each library:

• media/<lib>/moz.yaml - Version info, upstream URL, vendoring configuration, patches list
• media/<lib>/README_MOZILLA or README.md - Detailed update instructions
• media/<lib>/*.patch - Local patches to apply

Some libraries store source in third_party/:

• third_party/dav1d/ - dav1d source
• third_party/aom/ - AOM source
• third_party/highway/ - highway source
• third_party/jpeg-xl/ - libjxl source

Post-Update Steps

1. Build: ./mach build
2. Lint: ./mach lint
3. Format: ./mach format
4. Cargo vet (for Rust crate updates): ./mach cargo vet suggest - add any required audits
5. Test: ./mach test --auto

Backporting Rust Crate Updates to ESR/Beta/Release

When a Rust crate update on central needs to be uplifted to older branches (ESR, beta, release), the process differs from a normal update because each branch may pin a different base revision of the crate.

Overview

1. Identify the base revision on each target branch
2. Create backport branches upstream if needed
3. Vendor the backported revision on each Firefox branch
4. Clean up vendoring noise
5. Push to try and verify builds

Step 1: Identify Base Revisions

Check what revision each branch uses:

# For each branch (esr140, beta, release)
git show origin/<branch>:toolkit/library/rust/shared/Cargo.toml | grep <crate-name>

Branches often share the same base revision (e.g., beta and release), so you may only need one or two backport branches.

Step 2: Create Backport Branches (if needed)

If the upstream commit doesn't apply cleanly to a branch's base revision, create a backport branch on the upstream repo:

git clone <upstream-repo-url> /tmp/<repo>
cd /tmp/<repo>

# Create backport branch from the branch's base revision
git checkout -b backport-<branch> <base-revision>

# Cherry-pick the commit(s) from central's update
git cherry-pick <commit-hash>

# Push the backport branch
git push origin backport-<branch>

Note the resulting commit hash — this becomes the new rev for that Firefox branch.

Step 3: Vendor on the Target Branch

# Check out the target branch
git checkout -b <branch>-uplift upstream/<branch>

# Edit Cargo.toml with the backport revision
# In toolkit/library/rust/shared/Cargo.toml, update the rev for the crate

# Update Cargo.lock
cargo update -p <crate-name>

# Vendor
./mach vendor rust

ESR branches may fail with cargo-vet errors (policy drift from central). In this case, use --force:

./mach vendor rust --force

Step 4: Clean Up --force Noise

--force re-vendors ALL crates, adding .cargo_vcs_info.json, .github/, .travis.yml and other files to every crate. This produces 1000+ changed files. Only the target crate's changes should be kept.

# Unstage everything
git reset HEAD

# Restore all modified files EXCEPT the ones we want to keep
git diff --name-only | grep -v -E '^(\.cargo/config\.toml\.in|Cargo\.lock|toolkit/library/rust/shared/Cargo\.toml|third_party/rust/<crate-name>/)' | xargs git checkout --

# Remove all untracked noise files, keeping only the target crate
git ls-files --others --exclude-standard | grep -v 'third_party/rust/<crate-name>/' | xargs rm -f

# Clean up empty directories
find third_party/rust -type d -empty -delete 2>/dev/null

# Verify only target files remain
git status --short

Expected files after cleanup:

• .cargo/config.toml.in — rev update
• Cargo.lock — lockfile update
• toolkit/library/rust/shared/Cargo.toml — rev update
• third_party/rust/<crate-name>/.cargo-checksum.json — updated checksums
• third_party/rust/<crate-name>/src/... — actual code changes

Step 5: Push to Try

mach try auto may fail on older branches with bugbug timeout errors (the bugbug service can't classify tasks for non-central revisions). Use mach try fuzzy as a reliable alternative:

# Build-only (fastest verification)
./mach try fuzzy -q "'build"

# If mach try auto works on the branch, that's also fine
./mach try auto

Notes

• Security bugs: Use a generic commit message like "test" with no bug number or details when pushing to try
• Beta and release often share the same base revision, so one backport branch may cover both
• ESR branches are more likely to have cargo-vet drift requiring --force
• The --force cleanup step is critical — without it you'll have 1000+ noise files in your patch

Troubleshooting

• Build failures after update: Check for new source files not added to moz.build
• Patch failures: Patches may need updating for new upstream changes
• Assembly errors on win32: Move x86_64-only .asm files to conditional blocks
• nasm version errors: May need to update minimum nasm version in toolchain
• python3-venv missing: Install with apt install python3-venv (for libaom)
• Uncommitted changes error: Use --ignore-modified flag for step 2, or commit between steps
• Cargo vet missing audit error: Run ./mach cargo vet certify <crate> <old> <new> --criteria safe-to-deploy --accept-all for each crate, then include supply-chain/audits.toml in the commit