WLXMP4Parser.dll

Source	src/WLXMP4Parser/
CMake target	WLXMP4Parser
Type	Win32 DLL (184 KB / 147 KB code, 50+ RTTI classes in the original)
Family	Media Foundation targets

At a glance

The MP4 container parser: walks ISO-BMFF boxes (ftyp, moov, trak, stts, ...) and exposes DirectShow integration helpers for MP4 playback. 9 exports in the reference binary: 4 API functions, 4 COM standard entries, plus the DLL entry.

Public surface

From WLXMP4Parser.def:

AddMP4SourceFilter@12   @1
BuildMP4FilterGraph@8   @2
BuildMP4PlayBack@8      @3
DllCanUnloadNow         @4
DllGetClassObject       @5
DllRegisterServer       @6
DllUnregisterServer     @7
IsMP4FilePlayable@4     @8

Security-hardened parsing

This DLL parses untrusted files from disk, so it is the reference implementation for the project's bounded-parser policy (see Security):

• The box walker is bounds-checked — every box header is validated against the remaining buffer before descending.
• MoovBox caps trak count at 1024 — a malicious file cannot explode track arrays.
• ParseStts accumulates sample counts in 64-bit before clamping — no overflow during accumulation.

Stub-design note

BuildMP4FilterGraph is one of the factory entry points where the reference parity build returns E_NOTIMPL — the reconstruction ships the real implementation and the contract pins the real HRESULT (Stub Design rule 3).

Testing

• tests/WLXMP4Parser/ — per-module C++ tests.
• Contract coverage including parser bounds in tests/mmr-python.

Analysis artifacts

analysis/WLXMP4Parser/ (PDB GUID {A4577D2C-5400-4F17-91C0-06B5EA1BE4DE}).