GCN 1.2 - Image & Video Processing

AMD’s final set of architectural improvements for GCN 1.2 are focused on image and video processing blocks contained within the GPU. These blocks, though not directly tied to GPU performance, are important to AMD by enabling new functionality and by offering new ways to offload tasks on to fixed function hardware for power saving purposes.

First and foremost then, with GCN 1.2 comes a new version of AMD’s video decode block, the Unified Video Decoder. It has now been some time since UVD has received a significant upgrade, as outside of the addition of VC-1/WMV9 support it has remained relatively unchanged for a couple of GPU generations.

With this newest generation of UVD, AMD is finally catching up to NVIDIA and Intel in H.264 decode capabilities. New to UVD is full support for 4K H.264 video, up to level 5.2 (4Kp60). AMD had previously intended to support 4K up to level 5.1 (4Kp30) on the previous version of UVD, but that never panned out and AMD ultimately disabled that feature. So as of GCN 1.2 hardware decoding of 4K is finally up and working, meaning AMD GPU equipped systems will no longer have to fall back to relatively expensive software decoding for 4K H.264 video.

On a performance basis this newest iteration of UVD is around 3x faster than the previous version. Using DXVA checker we benchmarked it as playing back a 1080p video at 331fps, or roughly 27x real-time. For 1080p decode it has enough processing power to decode multiple streams and then-some, but this kind of performance is necessary for the much higher requirements of 4K decoding.

Video Decode Performance

Speaking of which, we can confirm that 4K decoding is working like a charm. While Media Player Classic Home Cinema’s built-in decoder doesn’t know what to do for 4K on the new UVD, Windows’ built-in codec has no such trouble. Playing back a 4K video using that decoder hit 152fps, more than enough to play back a 4Kp60 video or two. For the moment this also gives AMD a leg-up over NVIDIA; while Kepler products can handle 4Kp30, their video decoders are too slow to sustain 4Kp60, which is something only Maxwell cards such as 750 Ti can currently do. So at least for the moment with R9 285’s competition being composed of Kepler cards, it’s the only enthusiast tier card capable of sustaining 4Kp60 decoding.

This new version of UVD also expands AMD’s supported codec set by 1 with the addition of hardware MJPEG decoding. AMD has previously implemented JPEG decoding for their APUs, so MJPEG is a natural extension of that. Though MJPEG is a fairly uncommon codec for most workloads these days, so outside of perhaps pro video I’m not sure how often this feature will get utilized.

What you won’t find though – and we’re surprised it’s not here – is support for H.265 decoding in any form. While we’re a bit too early for full fixed function H.265 decoders since the specification was only ratified relatively recently, both Intel and NVIDIA have opted to bridge the gap by implementing a hybrid decode mode that mixes software, GPU shader, and fixed function decoding steps. H.265 is still in its infancy, but given the increasingly long shelf lives of video cards, it’s a reasonable bet that Tonga cards will still be in significant use after H.265 takes off. But to give AMD some benefit of the doubt, since a hybrid mode is partially software anyhow, there’s admittedly nothing stopping them from implementing it in a future driver (NVIDIA having done just this for H.265 on Kepler).

Moving on, along with their video decode capabilities, AMD has also improved on their video encode capabilities for GCN 1.2 with a new version of their Video Codec Engine. AMD’s hardware video encoder has received a speed boost to improve its encoding performance at all levels, and after previously being limited to a maximum resolution of 1080p can now encode at resolutions up to 4K. Meanwhile by AMD’s metrics this new version of VCE should be capable of encoding 1080p up to 12x over real time.

A quick performance check finds that while the current version of Cyberlink’s MediaEspresso software isn’t handling 4K video decoding quite right, encoding from a 1080p source shows that the new VCE is roughly 40% faster than the old VCE in our test.

Video Encode Performance (1080p)

4K video is still rather new, so there’s little to watch and even less of a reason to encode. That of course will change over time, but in the meantime the most promising use of a hardware 4K encoder would be 4K gameplay recording through the AMD Gaming Evolved Client’s DVR function.

GCN 1.2: Geometry Performance & Color Compression Meet The Sapphire R9 285 Dual-X OC 2GB


View All Comments

  • Samus - Wednesday, September 10, 2014 - link

    Am I missing something or is this card slower than the 280...what the hell is going on? Reply
  • tuxRoller - Wednesday, September 10, 2014 - link

    Yeah, you're missing something:) Reply
  • Samus - Thursday, September 11, 2014 - link

    BF4 its about 4% slower. Reply
  • Kenshiro70 - Wednesday, September 10, 2014 - link

    "something of a lateral move for AMD, which is something we very rarely see in this industry"

    Really? Seems like the industry has been rebadging for the last two release cycles. How about starting to test and show results on 4k screens? 60Hz ones are only $500 now, and that will put a little pressure on the industry to stop coasting. I have no intention of spending money on a minor bump up in specs. Bitcoin mining demand can't last forever.
  • tuxRoller - Wednesday, September 10, 2014 - link

    Error page 4: chart should read "lower is better" Reply
  • jeffrey - Wednesday, September 10, 2014 - link

    Saw this too, the Video Encode chart Ryan.

    Congrats btw!
  • Ryan Smith - Thursday, September 11, 2014 - link

    Whoops. Thanks. Reply
  • yannigr2 - Wednesday, September 10, 2014 - link

    Great article and review.

    The only bad news here I think is Mantle.

    But on this matter, about Mantle, maybe a slower processor could show less of that performance drop or even keep performing better than DirectX11. Maybe one more test on a slower core, on an FX machine?
  • mapesdhs - Wednesday, September 10, 2014 - link

    What were AMD thinking? How can the 285 be a replacement for the 280, given its
    reduced VRAM, while at the same time AMD is pushing Mantle? Makes no sense at all.

    Despite driver issues, I'd kinda gotten used to seeing AMD be better than NVIDIA in
    recent times for VRAM capacity. A new card with only 2GB is a step backwards. All
    NVIDIA has to do is offer a midrange Maxwell with a minimum 4GB and they're home.
    No idea if they will. Time will tell.

  • Alexvrb - Wednesday, September 10, 2014 - link

    There you have it, and with no issues with boost. Sorry Chizow, so much for that. :P

    Thanks for the in-depth review, Ryan. It appears that power consumption is going to vary from implementation to implementation. Lacking a reference model makes it tricky. Another review I read compared Gigabyte's Windforce OC 285 to a similarly mild OC'd 280, finding a substantial difference in the 285's favor.

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