AV1 vs HEVC Bitrate Savings at High Resolutions

This article examines how the AV1 video codec compares to HEVC (H.265) in compression efficiency, focusing specifically on bitrate savings at 4K and 8K resolutions. While HEVC has long served as the industry standard for high-resolution video delivery, the open-source AV1 codec consistently outperforms it by requiring significantly lower bitrates to achieve identical visual quality. Below, we break down the performance metrics, visual quality retention, and practical trade-offs between both codecs at ultra-high definitions.

Compression Efficiency at 4K and 8K

At 4K (2160p) and 8K (4320p) resolutions, AV1 typically achieves between 15% and 30% bitrate savings over HEVC while maintaining equivalent visual fidelity.

Independent testing using objective quality metrics—such as Video Multi-Method Assessment Fusion (VMAF), Peak Signal-to-Noise Ratio (PSNR), and Structural Similarity Index (SSIM)—demonstrates that the gap between the two codecs widens as resolution scales upward. While HEVC performs admirably at 1080p, AV1’s modern coding tools handle the vast pixel counts of 4K and 8K video far more efficiently, allowing distributors to preserve pristine image quality at significantly reduced file sizes.

How AV1 Achieves Higher Bitrate Savings

AV1 introduces several architectural improvements over HEVC that contribute to its efficiency at high resolutions:

• Larger Block Partitions: AV1 supports superblock sizes up to 128x128 pixels, compared to HEVC's maximum Coding Tree Unit (CTU) size of 64x64. Larger blocks allow AV1 to encode flat areas (such as clear skies or static backgrounds in high-resolution video) with far fewer bits.
• Advanced Intra and Inter Prediction: AV1 features directional intra-prediction angles with finer granularity, compound inter-intra prediction, and global motion compensation, which together drastically reduce spatial and temporal redundancy.
• Film Grain Synthesis: High-resolution footage often contains fine analog or digital grain that consumes vast amounts of bitrate to encode directly. AV1 can remove the grain during encoding and synthesize it back onto the image during playback via metadata, resulting in massive data savings without losing the intended cinematic look.

Impact on Streaming and Bandwidth Costs

For major streaming platforms distributing 4K and 8K content, a 20% to 30% reduction in data rate translates directly to reduced content delivery network (CDN) bandwidth costs. Furthermore, it lowers the minimum broadband speed required for end users to stream 4K and 8K video smoothly, reducing instances of buffering and quality downscaling on bandwidth-constrained networks.

The Trade-Off: Computational Complexity

While AV1 outperforms HEVC in bandwidth efficiency, it demands significantly higher computational resources:

• Encoding Overhead: Encoding 4K or 8K content in AV1 requires substantially more compute time and power than encoding the same footage in HEVC. Although multi-threaded software encoders like SVT-AV1 and dedicated hardware encoders have narrowed this gap, HEVC remains faster and less resource-intensive to encode.
• Hardware Decoding: HEVC benefits from near-universal hardware-accelerated playback across modern smart TVs, mobile devices, and PCs. Hardware decoding for AV1 at 4K and 8K has expanded across modern GPUs and mobile chipsets, but legacy devices must rely on software decoding, which can lead to high CPU utilization and battery drain.

Conclusion

At high resolutions like 4K and 8K, AV1 delivers clear, quantifiable bitrate savings over HEVC, averaging 15% to 30% less data consumption for the same perceptual quality. While it requires greater processing power to encode, its superior compression efficiency and royalty-free status make AV1 the more efficient choice for modern, high-bandwidth video distribution.