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Sep 24, 2017

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The fastest and safest AV1 encoder.

Table of Content


rav1e is an AV1 video encoder. It is designed to eventually cover all use cases, though in its current form it is most suitable for cases where libaom (the reference encoder) is too slow.


  • Intra, inter, and switch frames
  • 64x64 superblocks
  • 4x4 to 64x64 RDO-selected square and rectangular blocks
  • DC, H, V, Paeth, smooth, and all directional prediction modes
  • DCT, (FLIP-)ADST and identity transforms (up to 64x64, 16x16 and 32x32 respectively)
  • 8-, 10- and 12-bit depth color
  • 4:2:0, 4:2:2 and 4:4:4 chroma sampling
  • 11 speed settings (0-10, exhaustive to near real-time)
  • Constant quantizer and target bitrate (single- and multi-pass) encoding modes
  • Still picture mode


Find the documentation in doc/


For the foreseeable future, a weekly pre-release of rav1e will be published every Tuesday.


Toolchain: Rust

rav1e currently requires Rust 1.51.0 or later to build.

Dependency: NASM

Some x86_64-specific optimizations require NASM 2.14.02 or newer and are enabled by default. strip will be used if available to remove the local symbols from the asm objects.

The CI is testing against nasm 2.15.05, so bugs for other versions might happen. If you find one please open an issue!

Install nasm

ubuntu 20.04 (nasm 2.14.02)

sudo apt install nasm

ubuntu 18.04 (nasm 2.14.02)

sudo apt install nasm-mozilla
# link nasm into $PATH
sudo ln /usr/lib/nasm-mozilla/bin/nasm /usr/local/bin/

fedora 31, 32 (nasm 2.14.02)

sudo dnf install nasm

windows (nasm 2.15.05)
Have a NASM binary in your system PATH.

$NASM_VERSION="2.15.05" # or newer
curl --ssl-no-revoke -LO "$LINK/nasm-$"
7z e -y "nasm-$" -o "C:\nasm"
# set path for the current sessions
set PATH="%PATH%;C:\nasm"

macOS (nasm 2.15.05)

brew install nasm

Release binary

To build release binary in target/release/rav1e run:

cargo build --release

Unstable features

Experimental API and Features can be enabled by using the unstable feature.

cargo build --features <feature>,unstable

Current unstable features

  • Channel API:
cargo build --features channel-api,unstable

Those Features and API are bound to change and evolve, do not rely on them staying the same over releases.

Target-specific builds

The rust autovectorizer can produce a binary that is about 6%-7% faster if it can use avx2 in the general code, you may allow it by issuing:

RUSTFLAGS="-C target-cpu=native" cargo build --release
# or
RUSTFLAGS="-C target-feature=+avx2,+fma" cargo build --release

The resulting binary will not work on cpus that do not sport the same set of SIMD extensions enabled.

NOTE : You may use rustc --print target-cpus to check if the cpu is supported, if not -C target-cpu=native would be a no-op.

Building the C-API

rav1e provides a C-compatible set of library, header and pkg-config file.

To build and install it you can use cargo-c:

cargo install cargo-c
cargo cinstall --release

Please refer to the cargo-c installation instructions.


Compressing video

Input videos must be in y4m format. The monochrome color format is not supported.

cargo run --release --bin rav1e -- input.y4m -o output.ivf

(Find a y4m-file for testing at tests/small_input.y4m or at

Decompressing video

Encoder output should be compatible with any AV1 decoder compliant with the v1.0.0 specification. You can build compatible aomdec using the following:

mkdir aom_test && cd aom_test
make -j8
./aomdec ../output.ivf -o output.y4m


rav1e has several optional features that can be enabled by passing --features to cargo. Passing --all-features is discouraged.


Find a full list in feature-table in Cargo.toml

  • asm - enabled by default. When enabled, assembly is built for the platforms supporting it.
    • x86_64: Requires nasm.
    • aarch64
      • Requires gas
      • Alternative: Use clang assembler by setting CC=clang

NOTE: SSE2 is always enabled on x86_64, neon is always enabled for aarch64, you may set the environment variable RAV1E_CPU_TARGET to rust to disable all the assembly-optimized routines at the runtime.


Please read our guide to contributing to rav1e.

Getting in Touch

Come chat with us on the IRC channel #daala on Libera.Chat! You can also use a web client to join with a web browser.