What is mbew CLAUDE.md?

Project guidance for MBEW, a C library that decodes WebM video files and their audio formats. It explains how to build the library with CMake and its bundled dependencies.

Use it when building or changing MBEW, configuring CMake targets, or working with its WebM, VP8/VP9, Vorbis, Ogg, and Opus components.

It records project-specific build commands and dependency behavior, including the local installation paths that CMake expects.

How cubicool/mbew configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to cubicool/mbew. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/cubicool/mbew/master/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/cubicool/mbew

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/cubicool/mbew/claude-md.svg)](https://agentmods.dev/instructions/cubicool/mbew/claude-md)

Your own site

<a href="https://agentmods.dev/instructions/cubicool/mbew/claude-md"><img src="https://agentmods.dev/badge/instructions/cubicool/mbew/claude-md.svg" alt="Measured on agentmods" height="20"></a>

Per session 2,942 This file is loaded in full into every session.

When invoked 2,942 The same file — it is already loaded in full.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.02942	$0.02942
Opus 5	$0.01471	$0.01471
Sonnet 5	$0.00588	$0.00588
Haiku 4.5	$0.00294	$0.00294

Measured 7d ago against content hash 5a2c03853a6a, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

mbew CLAUDE.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

CLAUDE.md · 189 lines

How it starts

The opening of the file, as written. The whole thing — 189 lines — stays where its author put it; the contents beside it link to each section on GitHub.

MBEW

MBEW (pronounced "imbue", "WebM" backwards) is a C library for decoding WebM files. It wraps nestegg (demuxer) and libvpx (VP8/VP9 codec), with vorbis/ogg and opus bundled for audio. All dependencies are built as internal static submodules — nothing is expected to be installed system-wide.

Build

mkdir BUILD && cd BUILD
cmake_locald ..   # see ~/.bashrc for alias; sets CMAKE_INSTALL_PREFIX=~/local-NOASAN
make

The user installs all self-compiled software into ~/local-NOASAN (or ~/local-ASAN), symlinked as ~/local. CMake's find_package() picks this up automatically via CMAKE_PREFIX_PATH. OSG in particular lives there.

CMake notes

The build was modernized from CMake 2.x-era ALL_CAPS style to modern target-based CMake (3.10+ minimum). Key things to know:

All ext/ submodules use target_include_directories(... PUBLIC ...) so include paths propagate transitively — no manual get_directory_property pulling needed at the top level.
ext/mbew-vorbis/CMakeLists.txt pre-sets OGG_FOUND, OGG_INCLUDE_DIRS, and OGG_LIBRARIES before calling add_subdirectory("vorbis") to satisfy vorbis's internal find_package(OGG) without a system install.
Assembly (libvpx) uses yasm (not nasm — nasm 2.15+ breaks the old x86inc.asm macros). Set via CMAKE_ASM_NASM_COMPILER before enable_language(ASM_NASM).
-DPIC is passed via CMAKE_ASM_NASM_FLAGS for PIE compatibility on modern Linux.
C compiler -m* SIMD flags are gated with $<COMPILE_LANGUAGE:C> generator expressions so they don't get passed to the assembler.
Optional examples (OSG, SDL2, Cairo, libao) use find_package / pkg_check_modules with QUIET and print a status message if skipped.

Examples

Example	Status	Notes
`mbew-example-c++`	✅	Basic C++ API iteration
`mbew-example-iterate`	✅	C iteration
`mbew-example-properties`	✅	Queries codec, dimensions, duration
`mbew-example-src-memory`	✅	In-memory source
`mbew-example-strings`	✅	Status string API
`mbew-example-video-cairo`	✅	Decodes every frame to PNG via Cairo
`mbew-example-video-osg`	✅	Live playback in an OSG window. Upload modernized to a persistent-mapped PBO ring + DSA immutable texture storage (see below); still `osg::TextureRectangle`/`sampler2DRect`, decode still synchronous
`mbew-example-audio-sdl`	✅	Audio via SDL2 (include updated from SDL1)
`mbew-example-audio-ao`	⚠️	Skipped — libao not installed
`mbew-example-video-sdl`	✅	Rewritten for SDL3 (was SDL1-only: SDL_SetVideoMode, SDL_CreateYUVOverlay). Uploads mbew's YUV planes directly via SDL_UpdateYUVTexture against SDL_PIXELFORMAT_IYUV — no plane swap needed since mbew's [Y,U,V] order matches IYUV exactly

Read the full file on GitHub · 189 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

7d ago First seen · 189 lines · 2,942 tokens per session scan A 5a2c03853a6a

Subscribe to this mod's changes

mbew CLAUDE.md is an instructions file published in the GitHub repository cubicool/mbew (20 stars, last pushed 2mo ago), licensed MIT. It adds 2,942 tokens to every session, about $0.0147 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).

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