Common AVIF Artifacts at Extremely Low Bitrates

AVIF offers superior compression efficiency compared to legacy image formats like JPEG, but pushing it to extremely low bitrates introduces distinct visual distortions. Because AVIF is derived from the AV1 video codec, it replaces traditional blocky pixelation with sophisticated filtering artifacts. At severe compression levels, the most prevalent artifacts include aggressive texture smearing, color banding, ringing along high-contrast boundaries, and chroma degradation. Understanding these specific failure modes helps in diagnosing quality issues and fine-tuning encoder parameters for bandwidth-constrained environments.

1. Excessive Smoothing and the "Plastic" Look

The most prominent artifact in low-bitrate AVIF images is the severe loss of fine texture and high-frequency detail. AV1 employs advanced in-loop filtering tools, notably the Deblocking Filter and the Constrained Directional Enhancement Filter (CDEF).

When bit allocation is extremely low, the encoder cannot preserve subtle grain, human skin pores, fabric weaves, or distant foliage. Instead of leaving sharp, broken blocks, the filters aggressively blend pixels together. This results in an unnaturally smooth, "waxy," or painted appearance where complex surfaces are reduced to flat, uniform patches.

2. Color Banding (Posterization)

Smooth gradients—such as clear skies, sunsets, or soft shadows—are particularly vulnerable to banding when bits are scarce. AVIF quantizes transform coefficients heavily at low target bitrates, collapsing subtle luminance and chrominance gradations into distinct, step-like color transitions. While 10-bit AVIF encoding significantly mitigates this compared to 8-bit formats, extreme compression can still strip away enough precision to make gradient steps noticeably visible.

3. Edge Ringing and Haloing

Along sharp, high-contrast boundaries (such as black text against a white background or high-contrast object silhouettes), low-bitrate AVIF can generate ringing artifacts. These appear as faint ripple patterns, shadows, or halos running parallel to the edge. Ringing occurs due to the truncation of high-frequency coefficients during the discrete cosine transform (DCT) or asymmetric discrete sine transform (ADST) processes, leaving behind oscillating wave distortions near abrupt transitions.

4. Color Bleeding and Desaturation

At minimal bitrates, encoders prioritize luminance (brightness) information over chrominance (color) information. This trade-off often causes noticeable color shifts:

• Chroma Bleeding: Saturated colors can smear beyond their actual object boundaries into adjacent, neutral-toned areas.
• Chroma Smearing: Small, colorful details can lose their saturation entirely, appearing washed out, muddy, or grayed out compared to the original image.

5. Warping and Misalignment of Fine Lines

AVIF uses directional intra-prediction to guess the structure of an image block based on neighboring pixels. When combined with CDEF at low bitrates, the algorithm can misinterpret the trajectory of very thin lines, small typography, or delicate geometric patterns. This can cause straight lines to appear slightly bent, broken, or warped, as the directional filters attempt to reconstruct features from insufficient source data.