SVT-AV1 Parameters

This page is a high-level overview of relevant SVT-AV1 information and parameters you should know about to make informed encoding decisions. Explanations behind certain parameters are included, but the primary focus is to provide a list of go-to parameters we recommend to make the most out of the AV1 format.

These parameters are aimed at high-efficiency video encoding, with a focus on visual appeal. Transparency remains an area where SVT-AV1 has room for improvement at this point in time, so expect some visible quality loss even in high-bitrate scenarios.

Transparency

"Transparency" refers to the degree to which the encoded output matches the source. A more transparent encode will look closer to the original source, while a less transparent encode will have noticeable compression artifacts and/or distortions.

Achieving perfect transparency is borderline impossible (especially once you factor in random variance such as with dithering), and one end goal of encoding is to have a "transparent" encode, a.k.a. to get as close as reasonably possible to the source.

Given AV1's origins as a web-focused codec its strength lies not in achieving transparency but in creating visually appealing encodes, that is to say small file sizes with minimal perceptible artifacts.

For a more complete look at these parameters, see the SVT-AV1 documentation.

Parts of this guide have been written based off the work done in the "Deep Dive" blog post series on the codec wiki. Look them up if you like benchmarks, tables and graphs!

Warning

The recommendations are primarily aimed at encoding anime, and may not be suitable for other types of content. We will try to give alternative options for live-action content where possible, but a lot of parameters should still be sufficient.

Furthermore, these parameters are not tailored for compatibility. If you're encoding for a streaming service, you may need to change some parameters and ensure you're in compliance with your company's requirements.

General AV1 Knowledge

AV1 is generally less well-known than its H.26x competitors, justifying such a section.

Let's begin with the encoder situation. AV1 has three publicly-available software encoders: aomenc, SVT-AV1 and rav1e. The former is the reference encoder, is very slow, and doesn't hold the efficiency crown nowadays. The latter is coded in rust and had an interesting psychovisual design from the ground up, however development stopped years ago after funding was cut. SVT-AV1, as its full name implies, is the most scalable encoder of the bunch, be it in performance, or in its various usecases. We will therefore focus on that encoder implementation that still receives frequent updates.

The SVT-AV1 code base is good, with enormous potential for psychovisual development. This led to many advances since early 2024, when the SVT-AV1-PSY fork, commonly maintained by members of the community, was introduced. Many features that either brought QoL improvements, increased efficiency or visual quality were upstreamed to mainline SVT-AV1, until development of the fork stopped in early 2025. Two new forks emerged from its remnants, SVT-AV1-PSYEX and SVT-AV1-HDR, the former with the goal of being the direct continuation of the -PSY project, and the latter concentrating on improving perceptual fidelity on specific grainy and HDR scenarios.

This situation isn't ideal, as it tends to split the userbase. Fortunately, most development efforts have been merged into mainline SVT-AV1, so for simplicity, the recommendations in this guide will focus on the main encoder. Readers are encouraged to research and experiment with SVT-AV1 forks if they wish to explore further.

SVT-AV1 can be found in most popular encoding software nowadays.

Where do I find standalone SVT-AV1 binaries?

It is possible to get official builds from the SVT-AV1 repository directly by going in the Pipeline/Tags tab (direct link), clicking on the download button in the appropriate row for the latest version, and selecting the "[Release]" build that matches your Operating System.

However, these builds lack any sort of compile optimizations to ensure broad compatibility with most systems.

Therefore, you can alternatively get unofficial Windows binaries from this repository, including SVT-AV1-PSYEX and SVT-AV1-HDR ones. Prefer Clang binaries, then GCC and lastly MSVC.

Compiling SVT-AV1 is fairly easy on any platform thanks to the built-in build.bat / build.sh helper script. For instance, this command on a Linux distro will provide an almost perfectly optimized binary for your system: build.sh cc=clang cxx=clang++ jobs=$(nproc) release enable-lto native static. One can try to leverage PGO or BOLT to chase the maximum possible encoding speeds. A basic compiling guide can be found in the SVT-AV1 documentation, but such compiling optimizations are better documented on the AV1 weeb edition discord server, as well as further details on the overall process.

General Parameters

The following parameters are the type of parameters you'll usually always set, and rarely touch again.

Preset

Use --preset 2 or 4.

Unlike x26x encoders, SVT-AV1 presets set internal parameters that are not accessible to the user. Therefore, there is no real concern of overriding anything crucial by setting them.

How do I choose one over the other? Why not use --preset 3?

--preset 2 is the slowest preset that showcase good efficiency improvements for little speed losses. Going lower is considered entering placebo territory, plus there are concerns of blurrier visuals at slower presets. --preset 4 is noticeably faster and has been reported to give higher fidelity results compared to 2. It is usually considered a better efficiency-to-speed trade-off. The best course of action is to try both on your usual content, ideally on small test samples, and determine which one you prefer.

--preset 3 falls into an awkward middle ground between 2 and 4, offering little compelling reason to choose it over either alternative. By the way, presets 5 and above are more suited for realtime usecases and are therefore not considered here.

Tune

There exists three main tunes in the original SVT-AV1 implementation: --tune 0 (VQ, for Visual Quality), --tune 1 (PSNR, for Peak Signal-to-Noise Ratio) and --tune 2 (SSIM, for Structural Similarity Index Measure).

--tune 1 is the default in mainline SVT-AV1 and consistently wins the efficiency crown on psychovisual metrics like SSIMULACRA2 or Butteraugli in the latest encoder version.

One can try to experiment with --tune 0 which enables sharper decision modes for many internal features of the encoder. That tune can reduce blurring by increasing visual energy, at the expensive of additional artifacting. It is up to the user to determine if the trade-offs are worth it, however for the purpose of this guide and the recommended AV1 usecase, staying on the default 1 is preferable.

--tune 3

A SVT-AV1-PSY(EX)-exclusive --tune 3, with psychovisual intents, builds on 2 (the former efficiency champion) while borrowing features from 0.

Not to be confused with SVT-AV1-HDR's --tune 3 which is effectively a tune grain equivalent. It disables certain features like CDEF, restoration, temporal filtering and sets agressive psy-rd strengths. It is most effective on noisy live-action content.

Variance Boost

Usually enabled by default in SVT-AV1 forks, varboost is however disabled in mainline SVT-AV1.

Enable it with --enable-variance-boost 1.

In a nutshell, varboost allocates more bits to low-contrast areas in a frame. A complete rundown is available in the SVT-AV1 documentation.

You can control its behavior by changing its --variance-boost-strength from the default 2 or its --variance-octile from the default 6. Basically, the strength controls how much areas are to be boosted, while octile controls how much of the area needs to be deemed low-contrast before being boosted.

You can use a slightly more agressive strength and octile value for higher quality targets, but historically, metrics have shown this strength-octile combination to be the most efficient on a wide variety of content types, therefore it is usually not recommended to stray away from the defaults.

Constrained Directional Enhancement Filter

According to the SVT-AV1 documentation, "The constrained directional enhancement filter (CDEF) [...] aims at improving the reconstructed picture by addressing ringing artifacts."

The closest equivalent to this feature would be SAO in x265, except it is not prone to the same level of detail loss.

--enable-cdef tends to limit edge artefacts effectively without introducing severe additional line fading, thus improving visual appeal.

Therefore, it is recommended to leave it on.

Specific SVT-AV1-HDR usage

The SVT-AV1-HDR fork disables CDEF in tune 3 to hopefully increase grain retention consistency across the whole picture, but it is effectively a bruteforcing method and cannot be generalized to a more general usecase.

Restoration Filter

According to the SVT-AV1 documentation, "The restoration filter [...] aims at improving the reconstructed picture by recovering some of the information lost during the compression process."

In effect, --enable-restoration tends to increase efficiency slightly and doesn't have any documented drawbacks, so it can safely be left on at all times.

Specific SVT-AV1-HDR usage

The SVT-AV1-HDR fork disables restoration in tune 3 to hopefully increase grain retention consistency across the whole picture, but it is effectively a bruteforcing method and cannot be generalized to a more general usecase.

Temporal Filtering

Temporal filtering in SVT-AV1 combines information from multiple nearby video frames to create cleaner reference pictures with reduced noise, which helps improve compression quality especially for noisy source material.

The feature was often considered too strong and often created unavoidable blocking on keyframes, so we historically disabled temporal filtering. However SVT-AV1-PSY introduced a strength parameter which has allowed to tame its effects. --tf-strength was backported into mainline SVT-AV1, so it is widely available.

It is recommended to leave --enable-tf on for the efficiency benefits it provides, but to reduce --tf-strength from its default 3 to 1, or below, to completely eliminate the tf blocking issue.

Specific SVT-AV1-PSY forks usage

The SVT-AV1-PSY(EX) and -HDR forks include an additional --kf-tf-strength which decouples tf strength on keyframes, and allows the user to concurrently fix the blocking issue and use a stronger tf strength on all other frames if one wishes so.

Tiles

AV1 tiles are a straightforward method of splitting the video frame into independent tiles of equal size to hopefully increase encoding and decoding thread-ability. In SVT-AV1, tiles don't increase encoding speeds but they can very effectively help devices (especially low-powered ones) to software decode AV1 files faster.

The following recommendations minimize efficiency losses and provide non-negligible benefits in decoding performance:

• --tile-columns 1 --tile-rows 0: at 1080p and above.
• --tile-columns 2 --tile-rows 0: at 4K and above.

Leave tiles to their default --tile-columns 0 --tile-rows 0 if you are trying to maximize efficiency at all costs for some reason.

Fast Decode

SVT-AV1 ships with its own built-in method for reducing decoding bottlenecks by smartly tuning down or disabling specific internal tools that trade off some efficiency for decoding performance.

The encoder offers two --fast-decode levels, with 2 being more aggressive. The default is 0. A small amount of tiles should be preferred to minimize efficiency losses.

You can combine fast decode and tiles to decrease decoding complexity further. Fast decode can even speed up your encoding instances, however it has been observed that the output can be more prone to macro-blocking, so experiment and proceed with caution.

Source-Specific Parameters

The following parameters should be adjusted based on your specific video, and likely will require tweaking on a case-by-case basis.

Constant Rate Factor

For an optimal usage of the encoder, set a Constant Rate Factor (--crf) value between 20 and 30.

CRF is a rate control mode that aims to achieve a consistent quality level across the entire video. Lower values result in higher quality and larger file sizes, while higher values lead to lower quality and smaller file sizes.

We recommend using CRF values between 20 and 30 to achieve high-efficiency, appealing encodes. This range typically provides the best balance between visual appeal and file size for most content.

If you need to go below 20, you may achieve better results with encoders better suited for high-fidelity like x265.

Lower resolution encodes may require a lower CRF value

Lower resolution encodes may require a lower CRF value to achieve the same level of quality as higher resolution encodes. This is due to the fact that lower resolution encodes will be upscaled during playback, which makes quantization artifacts more noticeable. For SD content, you may need to use a CRF value of 20 or lower.

Film Grain Synthesis

Film Grain Synthesis (FGS) is a key AV1 feature that takes the form of additional metadata in the bitstream. Its intended goal is to help reconstruct grain using fewer bits than would otherwise be needed to preserve such grain in the actual encode. It is declined in two versions that produce similarly structured metadata:

• Photon noise tables: A single grain type applied uniformly across the entire AV1 bitstream. This approach better matches digital grain and has minimal impact on file size. These static tables can be generated using tools like Av1an or grav1synth. A comprehensive database of such tables is available in this repository. You can use a photon noise table by providing its file path to the --fgs-table parameter. Noise tables have no impact on encoding speeds.
• Actual grain synthesis: SVT-AV1 includes its own built-in FGS implementation that dynamically adjusts grain appearance based on source characteristics. This usually better matches the source's energy, assuming you select an appropriate strength value for the given source. It tends to more closely resemble analog grain. Note that due to its variable nature, the grain metadata can consume up to a few megabytes per 10 minutes of encoded video, which is typically negligible for most use cases. You can enable internal grain synthesis by setting any --film-grain value between 1-50, with higher values meaning stronger grain. An integrated denoiser step exists (--film-grain-denoise) but it is terrible, so it's best left disabled (the default behavior). Film-grain's impact on encoding speed increases the slower your CPU is or the faster the preset in use.

Just like CRF, this process requires manual adjustment depending on your source material.

Even in cases where grain retention is not a concern, for example with relatively clean sources, using FGS is still highly recommended for its forced dithering benefits. You're probably familiar with x26x encoders' tendency to produce poor gradients at high CRF values. You can prevent this issue to some extent in AV1 encodes by using a photon noise ISO of 400 or higher, or a film-grain strength of 4 or higher. Lower values don't consistently resolve these dithering problems.

Quantisation Matrices

QMs control the relative quantization of lower frequencies and higher frequencies. You set a min and max allowed value and the encoder is supposed to automatically select the most appropriate one for the content, however the implementation in AV1 is pretty barebone and despite efforts to improve the feature, there is no real consensus on what QM combination is best. Parts of the reason is that it is highly content and CRF dependent.

Specifically, the frame QM is selected on linear interpolation between set min and max QMs based on the frame qindex (qp).

--enable-qm still tends to improve efficiency, especially when paired with a lower --qm-min than the default 8, so feel free to experiment with this.

Specific SVT-AV1-PSY forks usage

The SVT-AV1-PSY(EX) and -HDR forks include additional --chroma-qm-min & --chroma-qm-max parameters which decouple QMs for luma and chroma, allowing more control over quantization, as the chroma subsampling tends to make the default chroma QMs too aggressive.

It is thus recommended to keep a higher --chroma-qm-min relative to --qm-min.

Luma Bias

--luminance-qp-bias, often abbreviated as luma-bias, effectively applies a simple qp offset to frames of lower overall brightness.

The range of accepted values is 0-100. The higher the value, the stronger the effect is.

This implementation has one advantage and one weakness: it gives the user simple control over the bitrate balancing between bright and dark frames, however if only parts of the frame are dark and the rest is fairly bright, it may not fix cases of localized bitrate starving.

Still, due to how much SVT-AV1 starves dark content, luma-bias usually provides slight efficiency benefits at low strengths. That may not always be the case if higher values (> 50) are selected.

To better balance out bitrate allocation between bright and dark frames, it is recommended to up --luminance-qp-bias and --crf at the same time.

Not suited for certain HDR sources

The author of the feature discourages to use of luma-bias on content with a PQ transfer (present in most UHD blu-rays). Use luma-bias exclusively on SDR and HDR HLG videos.

Sharpness

The --sharpness parameter impacts the deblocking filter sharpness.

Increasing its value to 1 or 2 is a conservative way of improving efficiency slightly, as well as perceptual quality.

Higher values can at times provide additional perceptual benefits, but they also tend to decrease efficiency to an extent, so it is recommended to proceed with caution and test on your content.

Sane Base SVT-AV1 Parameters List

Assuming a clean-ish 1080p source:

--preset 4 --enable-variance-boost 1 --tf-strength 1 --sharpness 1 --tile-columns 1 --crf 25 --film-grain 4 --luminance-qp-bias 25

Again, remember to drop --luminance-qp-bias 25 if your source has a PQ transfer.

Fork-Specific Parameters

The following parameters have not made their way into mainline SVT-AV1 (yet). They are mostly mentioned for reference purposes.

QP Scale Compress Strength

This feature still exclusive to SVT-AV1 forks compresses QP values across all temporal layers, resulting in less quality variations across frames in a mini-gop.

A --qp-scale-compress-strength value of 1 and above increases video quality temporal consistency.

QP scale compress strength closest equivalent in x26x encoders is a combination of the ipratio & pbratio settings.

PSY-RD & SPY-RD

Psy-rd configures the rate distortion strength to improve perceived quality by attempting to preserve the visual energy distribution of high-frequency details and textures, at the possible expense of increased artefacting. The implementation is very x264-inspired at the moment. The default --psy-rd is 0.5, with the highest allowed value being 6.0.

Spy-rd configures psychovisually-oriented pathways that bias towards sharpness and detail retention, at the possible expense of increased blocking and banding. The default --spy-rd is 0, with 1 being the most aggressive and 2 being less aggressive.

Neither features are planned for mainline merging any time soon.

Complex HVS

--complex-hvs 1 activates a higher quality psy-rd mode with a slightly higher computational cost based on PSNR-HVS that is otherwise locked behind the placebo preset -1.