VIDEO ENCODING QUALITY AND PERFORMANCE COMPARED
THE RESULTS OF OUR ENCODING TESTS are pretty interesting, especially when we look back at older GPUs (see sidebar). Even though H.264 remains the most popular codec, the loss in quality at lower bitrates is quite significant. Regardless of which encoder you’re looking at, HEVC and AV1 can do better quality with 6Mbps at 1080p than H.264 can manage with 8Mbps. At 4K, the quality gap increases, with HEVC and AV1 8Mbps quality often surpassing H.264’s 16Mbps result.
The problem is that video streaming services until recently have generally only supported H.264 since it was free. Discord and other tools are adding AV1 support now, thanks to GPU support from the major companies plus the lack of licensing fees. The only difficulty is that you’ll need either a powerful CPU or an expensive latest-generation graphics card to get AV1 encoding support… unless you opt for an Intel Arc GPU.
While we’re only showing results from the fastest GPU from each vendor, the video encoding is handled by a fixed function block and is the same on all of the other GPUs. Intel’s Arc A380 had identical quality results to the A770, and performance was effectively the same as well—the A380 was actually seven percent faster, thanks to a factory overclock on the card we used for testing. Nvidia’s RTX 4070 Ti was, likewise, identical in performance and quality to the 4090, and the same goes for AMD’s RX 7000-series.
Comparing the four solutions, counting CPU encoding, there are also some telling results. AMD’s encoder placed last in quality for nearly every single test we ran. The one exception was AV1 16Mbps, where it just edged past the CPU encoding (done with libsvtav1). But again, CPU encoding tends to be far more flexible, so if we could accept slower speed we could also boost the quality. At the other end of the scale, Nvidia’s latest NVENC hardware took first place for quality with H.264 at 1080p and AV1 at both 1080p and 4K, while Intel’s Arc had the best quality at 4K with H.264, as well as winning with HEVC at both 1080p and 4K.
The other side of the coin is performance, but it tends to be less of a factor once you get past 60fps. Maybe in the coming years 4K 120fps streaming will become more widely supported, though if that happens, Intel and Nvidia might need to opt for slightly lower quality to boost performance. Otherwise, all three GPUs easily break into the triple digits, with AMD’s AV1 performance topping the 4K charts if you prefer speed over quality.
The CPU results are also interesting. H.264 quality can be improved at the cost of FPS, but the AV1 results make that almost a non-issue. Rather than getting slightly higher quality at much lower encode rates with H.264, AV1 at 4K still managed to break 60fps on the 13900K. HEVC using the libx265 library is another story, with performance barely breaking 30fps—one more reason it probably didn’t catch on as much as its predecessor.