Update (11/04/22): Since AMD has provided a bugfix with the Adrenalin driver 22.10.3 regarding video playback in the Chrome browser the RX 6800 XT was retested.
Update (11/11/22): Only a few days apart, Nvidia also released a new driver that is supposed to optimize AV1 decoding. The version used for the retest was Game Ready 526.86.
Youtube Video "Japan in 8K 60fps"
The video used for the test was created with the AV1 codec. This can be easily checked by activating the video statistics. The performance of the frame output was measured with CapFrameX. In order to do so you have to remove the entry "chrome" from the ignore list so that the software can measure the performance of the Chrome browser.
Decoding Performance 4K
The Intel card delivers constant 60FPS while the percentile metrics are slightly behind those of the Nvidia cards. The AMD card shows good Average FPS but the frame rate is unfortunately not really smooth. The 1% percentile is only 13FPS.
Decoding Performance 8K
The 8K results have some surprises in store because the RTX 4090 which even has a native AV1 hardware support drops as much as the Ampere card regarding P1. Something seems to be wrong with the driver. The AMD card even drops related to the average frame rates. The frame rate suffers from strong stuttering as the 1% percentile is barely more than one FPS.
A look at the frame times of RX 6800 XT shows huge spikes as the maximum frame time is even above 800 ms.
(Update) Retest with Adreanlin 22.10.3
According to the release notes the Adreanlin driver 22.10.3 fixes issues when playing videos in the Chrome browser. This is indeed the case as the 4K benchmarks below clearly show.
P1 and P0.2 look much better due to the driver update. The playback is now smooth and enjoyable. The frame times also differ fundamentally. However, 8K + 60 FPS is a technical limit of the RDNA 2 card's decoder so the driver update can't bring any improvement here in principle.
(Update) Retest with Game Ready 526.86
According to the release notes ("Drop in 8K60 AV1 decoding performance on RTX 4090"), the Game Ready driver version 526.86 optimizes the performance when playing AV1 videos. As with the Adrenalin driver, this is not an empty promise. The update does not only improve performance, but also efficiency.
At 8K the lows are in the same range of the 4K results, but on the other hand the power consumption is significantly lower. When playing the 4K setting, the power consumption of the RTX 4090 drops by about 62% down to 14W.
The Ampere card also benefits from the update as the lows are now much better when playing the 8K footage, the playback is very smooth. Not unexpectedly, the power draw is very similar.
The table summarizes the performance and telemetry data of the RTX 4090. It is noticeable that the GPU clock is slightly lower on average running the new driver. It is unclear whether the power consumption could be so substantially reduced as a consequence. Presumably, there are further optimizations that are unknown so far.
The performance of the Arc A770 is not really surprising because this can be expected from native hardware acceleration. The RTX 4090 still seems to have driver issues. RDNA 2 is unfortunately completely unsuitable for a smooth 8K frame output when using the AV1 codec. RDNA 3 will surely fix this shortcoming soon.
Update (11/04/22): RDNA 3 was announced by AMD yesterday and AV1 support was officially confirmed. There is hope that the new generation can also display 8K + 60 FPS videos smoothly. As soon as I have an RDNA 3 card I will test this.
Nvidia has unfortunately still not commented on the decoder performance of the RTX 4090 and also the RTX 3090, which both have a 5th generation decoder (NDEC). The features are listed in the official support matrix for consumer cards (GeForce).
Update (11/11/22): With the latest update Nvidia has indeed improved the AV1 decoding. Interestingly, this does not only affect the performance, but also the efficiency of the RTX 4090. This could be a result of lower GPU clock, among other unknown optimizations.