resolve-aacfix

Restores AAC audio decode in DaVinci Resolve Studio 21.x on Linux.

Blackmagic ship Resolve with AAC removed for licensing reasons, so a great many ordinary .mp4 and .mov files import with silent audio. This puts it back — without giving anything else up.

tar -xzf resolve-aacfix-*.tar.gz
cd resolve-aacfix-*
sudo ./aac-fix install          # close Resolve first
./aac-fix status

Download the tarball from Releases. It needs only python3 and binutils; everything else is bundled.

To undo it completely:

sudo ./aac-fix uninstall

Almost all of this work — the reverse engineering, the binary patches, the tooling, and these docs — was done by Claude (Anthropic's Claude Code). It is published in that spirit: the reasoning is written down at length in docs/, including the parts that were wrong.

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What it does

AAC is blocked in two places, and lifting either one alone achieves nothing:

1. bin/resolve never asks for AAC. Eight e9patch trampolines un-gate the aac fourcc and AAC codec-id paths for QuickTime (.mp4/.mov/.m4a) and Matroska, and route them to FFmpeg.
2. libs/libav*.so — Blackmagic's bundled FFmpeg has the AAC decoder compiled out. Four drop-in replacements with identical sonames put it back.

aac-fix status reports both, and warns about the half-installed case, because "binary patched, libs not" fails silently as no audio.

Every binary change is purely additive. Each trampoline acts only when the value is AAC and otherwise lets the original instruction run untouched. No existing instruction is rewritten. AC-3, FLAC, ALAC, MP3, PCM, the NONE fourcc and Blackmagic's AV3A / "Audio Vivid" demuxer all keep working, and uninstall restores the original binary byte-for-byte.

Patch sites are found by version-independent byte signatures, not hardcoded offsets. On a build it does not recognise, the patcher refuses cleanly and writes nothing.

Caveats

Please read these before installing.

• Studio only. Built and tested against DaVinci Resolve Studio. The free version has not been tested at all.
• Resolve 21 only. Validated on 21.0.0, 21.0.3 and 21.0.4; the full end-to-end test was on 21.0.4. Because sites are located by signature, newer 21.x point releases should work — but this has not been tested beyond 21.0.4. If the patcher refuses, or something misbehaves, please file an issue with your exact Resolve version and the output of ./aac-fix status. A refusal is a broken feature, not a broken install: it writes nothing.
• Linux, x86-64 only.
• Works: .mp4, .mov, .m4a, and .mkv that contain a video track. LC-AAC and HE-AAC.
• Does not work: raw .aac (ADTS), .ts, .flv, .latm, MXF. These use other decoder classes inside Resolve that have not been analysed. See docs/further-work.md — the groundwork makes them much cheaper than the first one was.
• Audio-only MKV is silent — and that is a pre-existing Resolve bug, not this patch. An MKV with no video track plays no audio in Resolve for any codec: it reproduces with native FLAC, AC-3 and MP3 audio-only MKVs, which Resolve supports and which this patch does not touch. It remains true for AAC. Put a video track in the file, or use another container.
• HE-AAC sample rate: only explicit SBR/PS signalling is handled. Implicit SBR and the AOT=31 escape will report the base sample rate.
• Close Resolve before installing or uninstalling. Writing a running binary fails with ETXTBSY.
• No warranty. This modifies a large proprietary binary in place. It keeps a verified backup and refuses to restore a corrupt one, but you should be able to reinstall Resolve if you need to.

Licensing

AAC and AC-3 were removed from a shipping product for licensing, not technical, reasons. This is interoperability work on a binary you have already installed on your own machine. Whether re-enabling these codecs is appropriate for a given use — especially for distributed output — is a licensing question, and it is out of scope here.

The FFmpeg libraries are a plain LGPL build using FFmpeg's own native AAC decoder: no --enable-gpl, no --enable-nonfree, no external codec libraries.

Building a patched .deb

On Debian/Ubuntu/Mint you can build a patched package straight from Blackmagic's .run installer, so the fix survives reinstalls:

./aac-fix build-deb DaVinci_Resolve_Studio_21.0.4_Linux.run

This wraps makeresolvedeb unmodified (downloaded pinned and SHA-256 verified). Needs fakeroot, dpkg-deb, curl, and roughly 8 GB of free disk.

Building from source

git clone https://github.com/josephg/resolve-aacfix && cd resolve-aacfix
scripts/dev-setup.sh          # e9patch + trampoline, capstone/pyelftools, FFmpeg
sudo ./aac-fix install

The FFmpeg build targets glibc 2.28 whatever you build it on: Resolve's own binary references at most GLIBC_2.27, and Blackmagic's supported baseline for Resolve 21 is Rocky Linux 8 (glibc 2.28). Libraries built on a current distro reference GLIBC_2.35 and would install fine and then fail to load on a machine where Resolve runs perfectly well. So build-ffmpeg.sh runs the compile inside a rockylinux:8 container unless the host is already that old, then verifies the glibc floor of what it produced and fails if it is too high — locally and in CI alike. That needs docker or podman; see docs/ffmpeg-libs.md.

Documentation

Credits

• e9patch by Gregory J. Duck et al. — the trampoline rewriter that makes a purely-additive patch of a 653 MB stripped non-PIE binary possible at all.
• makeresolvedeb by Daniel Tufvesson.
• FFmpeg.
• The AV3A demuxer backport, © 2024 Shuai Liu, via OpenHarmony's FFmpeg fork.
• Schulte, Brown & Folts, A Broad Comparative Evaluation of x86-64 Binary Rewriters, CSET 2022 (doi) — the evidence behind choosing a purely-additive trampoline approach.

Licenses and exact pinned sources: THIRD-PARTY.md. This project's own code is MIT (LICENSE).

Nothing here contains any part of DaVinci Resolve. It patches a copy you already have.