Does SVT-AV1 Require More CPU Than x264?

This article examines the CPU resource demands of the modern SVT-AV1 (libsvtav1) encoder compared to the industry-standard x264 encoder. While SVT-AV1 delivers superior compression efficiency—allowing for much smaller file sizes at identical visual quality—it does require significantly more CPU resources than x264. Below, we break down why this resource gap exists, how encoder presets influence performance, and what this means for real-world encoding tasks.

The Technology Gap: Why SVT-AV1 Demands More Power

The primary reason libsvtav1 requires more CPU resources than x264 is the technological complexity of the AV1 codec. Released in 2018, AV1 was designed to surpass H.264 (which powers x264 and dates back to 2003) by offering up to 50% better compression.

To achieve this leap in efficiency, AV1 utilizes much larger block sizes for prediction, more advanced intra-prediction modes, and highly sophisticated loop filters. Analyzing and processing these complex mathematical coding tools requires vastly more floating-point operations. Consequently, a CPU must work significantly harder to encode a video using libsvtav1 than it would using x264.

Equivalent Visual Quality and the Role of Presets

To achieve equivalent visual quality, SVT-AV1 requires a fraction of the bitrate that x264 needs. However, the CPU effort required to reach this quality level depends heavily on the “preset” selected for each encoder. Presets dictate the trade-off between encoding speed (CPU effort) and compression efficiency.

• At Slower Presets (Archival Encoding): If you configure libsvtav1 at preset 4 or 5 to get maximum efficiency, it will consume significantly more CPU resources and take several times longer to encode than x264 running on its “veryslow” preset, even when targeting the same visual quality.
• At Faster Presets (Real-Time/Streaming): SVT-AV1 is highly optimized for modern multi-core processors. When using libsvtav1 at presets 7 through 10, the encoder utilizes highly efficient AVX2 and AVX-512 instruction sets. At these speeds, libsvtav1 can match or exceed the visual quality of x264 (on “medium” or “faster” presets) while using a highly comparable amount of CPU time, provided you are running modern hardware.

Hardware Dependencies

The perceived CPU overhead of libsvtav1 is also highly dependent on your processor’s architecture. Because SVT-AV1 relies heavily on modern vector instructions, older CPUs without AVX2 support will struggle immensely, resulting in massive CPU spikes and slow render times. On the other hand, x264 is mature and highly optimized for older, legacy hardware. On a modern 8-core or 12-core processor, the CPU resource difference between a fast SVT-AV1 encode and an x264 encode is negligible for most practical workflows, making AV1 the superior choice for bandwidth savings.