dav2d

dav2d is an AV2 cross-platform decoder, open-source, and focused on speed and correctness. It is based on our popular dav1d decoder.

It is a quite early project, should not be used in production, notably since the AV2 specification is not final.

The canonical repository URL for this repo is https://code.videolan.org/videolan/dav2d .

This project is edited by VideoLAN as part of its membership by the Alliance for Open Media/AOM.

Goal and Features

The goal of this project is to provide a decoder for most platforms, and achieve the highest speed possible to overcome the temporary lack of AV2 hardware decoder.

It will support all features from AV2, including all subsampling and bit-depth parameters.

In the future, this project will host simple tools or simple wrappings.

License

dav2d is released under a very liberal license, a contrario from the other VideoLAN projects, so that it can be embedded anywhere, including non-open-source software; or even drivers, to allow the creation of hybrid decoders.

The reasoning behind this decision is the same as for libvorbis, see RMS on vorbis.

Please note that the license does not grant you any patents rights from AOM.

Roadmap

The plan is the following:

On-going

1. Complete C implementation of the decoder,
2. Provide a usable API,
3. Port to most platforms,

After

4. Make it fast on desktop, by writing asm for AVX2 chips.
5. Make it fast on mobile, by writing asm for ARMv8 chips,
6. Make it fast on older desktop, by writing asm for SSSE3+ chips,
7. Make high bit-depth fast on mobile, by writing asm for ARMv8 chips.
8. Make it fast on older mobile, by writing asm for ARMv7 chips,
9. Make high bit-depth fast on older mobile, by writing asm for ARMv7 chips,
10. Make high bit-depth fast on desktop, by writing asm for AVX2 chips,
11. Make high bit-depth fast on older desktop, by writing asm for SSSE3+ chips,
12. Improve threading.
13. Improve C code base with various tweaks.
14. Accelerate for less common architectures, like PPC, SSE2, RISC-V or AVX-512.
15. Use more GPU decoding, when possible.

Contribute

Currently, we are looking for help from:

• C developers,
• asm developers,
• platform-specific developers,
• testers.

Our contributions guidelines are quite strict. We want to build a coherent codebase to simplify maintenance and achieve the highest possible speed.

Notably, the codebase is in pure C and asm.

We are on IRC, on the #dav2d channel on Libera.chat. If you do not have an IRC Client at hand, use IRC Web Interface.

See the contributions document.

CLA

There is no CLA.

People will keep their copyright and their authorship rights, while adhering to the BSD 2-clause license.

VideoLAN will only have the collective work rights.

CoC

The VideoLAN Code of Conduct applies to this project.

Compile

General compilation steps

1. Install Meson (0.54 or higher), Ninja, and, for x86* targets, nasm (2.14 or higher)
2. Run mkdir build && cd build to create a build directory and enter it
3. Run meson setup .. to configure meson, add --default-library=static if static linking is desired
4. Run ninja to compile

Following are modification of step 3 and 4, for specific purpose.

Cross-Compilation for 32- or 64-bit Windows, 32-bit Linux

If you're on a linux build machine trying to compile .exe for a Windows target/host machine, configure meson like this

meson setup .. --cross-file=../package/crossfiles/x86_64-w64-mingw32.meson

or, for 32-bit:

meson setup .. --cross-file=../package/crossfiles/i686-w64-mingw32.meson

mingw-w64 is a pre-requisite and should be installed on your linux machine via your preferred method or package manager. Note the binary name formats may differ between distributions. Verify the names, and use alias if certain binaries cannot be found.

For 32-bit linux, run

meson setup .. --cross-file=../package/crossfiles/i686-linux32.meson

Build documentation

1. Make sure doxygen and graphviz are installed.
2. Run meson setup .. -Denable_docs=true to configure meson to generate docs from the build directory.
3. Run ninja doc/html to build the docs

The result can be found in build/doc/html/. An online version built from master can be found here.

Run tests

1. In the root directory, run git clone https://code.videolan.org/videolan/dav2d-test-data.git tests/dav2d-test-data to fetch the test data repository
2. During meson configuration, specify -Dtestdata_tests=true
3. Run meson test -v after compiling

Support

This project is partially funded by members of the Alliance for Open Media/AOM - Google, Meta and Netflix, and is supported by Arm, TwoOrioles and VideoLabs.

Some of these companies may provide support and integration help, should you need it.

FAQ

Is dav2d a recursive acronym?

• Yes, but it is less funny than dav1d :(, except in French ("deux-vid")

Can I help?

• Yes. See the contributions document.

I am not a developer. Can I help?

• Yes. We need testers, bug reporters and documentation writers.

What about the AV2 patent license?

• This project is an implementation of a decoder. It gives you no special rights on the AV2 patents.

Please read the AOMedia patent license that applies to the AV2 specification and codec.

Will you care about <my_arch>? <my_os>?

• We do, but we don't have either the time or the knowledge. Therefore, patches and contributions welcome.