Quick Sync Image Quality & Performance

Intel obviously focused on increasing GPU performance with Ivy Bridge, but a side effect of that increased GPU performance is more compute available for Quick Sync. As you may recall, Sandy Bridge's secret weapon was an on-die hardware video transcode engine (Quick Sync), designed to keep Intel's CPUs competitive when faced with the onslaught of GPU computing applications. At the time, video transcode seemed to be the most likely candidate for significant GPU acceleration so the move made sense. Plus it doesn't hurt that video transcoding is an extremely popular activity to do with one's PC these days.

The power of Quick Sync was how it leveraged fixed function decode (and some encode) hardware with the on-die GPU's EU array. The combination of the two resulted in some pretty incredible performance gains not only over traditional software based transcoding, but also over the fastest GPU based solutions as well.

Intel put to rest any concerns about image quality when Quick Sync launched, and thankfully the situation hasn't changed today with Ivy Bridge. In fact, you get a bit more flexibility than you had a year ago.

Intel's latest drivers now allow for a selectable tradeoff between image quality and performance when transcoding using Quick Sync. The option is exposed in Media Espresso and ultimately corresponds to an increase in average bitrate. To test image quality and performance, I took the last Harry Potter Blu-ray, stripped it of its DRM and used Media Espresso to make it playable on an iPad 2 (1024 x 768 preset).

In the case of our Harry Potter transcode, selecting the Better Quality option increased average bitrate from to 3.86Mbps to 5.83Mbps. The resulting file size for the entire movie increased from 3.78GB to 5.71GB. Both options produced a good quality transcode, picking one over the other really depends on how much time (and space) you have as well as the screen size of the device you'll be watching it on. For most phone/tablet use I'd say the faster performing option is ideal.

Intel Core i7 3770K (x86) Intel Quick Sync (SNB) Intel Quick Sync (IVB) Intel Quick Sync, Better (IVB) NVIDIA GeForce GTX 680 AMD Radeon HD 7970
original original original original original original

 

While AMD has yet to enable VCE in any publicly available software, NVIDIA's hardware encoder built into Kepler is alive and well. Cyberlink Media Espresso 6.5 will take advantage of the 680's NVENC engine which is why we standardized on it here for these tests. Once again, Quick Sync's transcoding abilities are limited to applications like Media Espresso or ArcSoft's Media Converter—there's still no support in open source applications like Handbrake.

Compared to the output from Quick Sync, NVENC appears to produce a softer image. However, if you compare the NVENC output to what we got from the software/x86 path you'll see that the two are quite similar. It seems that Quick Sync, at least in this case, is sharpening/adding more noise beyond what you'd normally expect. I'm not sure I'd call it bad, but I need to do some more testing before I know whether or not it's a good thing.

The good news is that NVENC doesn't pose any of the horrible image quality issues that NVIDIA's CUDA transcoding path gave us last year. For getting videos onto your phone, tablet or game console I'd say the output of either of these options, NVENC or Quick Sync, is good enough.

Unfortunately AMD's solution hasn't improved. The washed out images we saw last year, particularly in dark scenes prior to a significant change in brightness are back again. While NVENC delivers acceptable image quality, AMD does not.

The performance story is unfortunately not much different from last year either. The chart below is average frame rate over the entire encode process.

CyberLink Media Espresso 6.5—Harry Potter 8 Transcode

Just as we saw with Sandy Bridge, Quick Sync continues to be an incredible way to get video content onto devices other than your PC. One thing I wanted to make sure of was that Media Espresso wasn't somehow holding x86 performance back to make the GPU accelerated transcodes seem much better than they actually are. I asked our resident video expert, Ganesh, to clone Media Espresso's settings in a Handbrake profile. We took the profile and performed the same transcode, the result is listed above as the Core i7 3770K (Handbrake). You will notice that the Handbrake x86/x264 path is definitely faster than Cyberlink's software path, by over 50% to be exact. However even using Handbrake as a reference, Quick Sync transcodes over 2x faster.

In the tests below I took the same source and varied the output quality with some custom profiles. I targeted 1080p, 720p and 480p at decreasing average bitrates to illustrate the relationship between compression demands and performance:

CyberLink Media Espresso 6.5—Harry Potter 8 Transcode

CyberLink Media Espresso 6.5—Harry Potter 8 Transcode

CyberLink Media Espresso 6.5—Harry Potter 8 Transcode

Unfortunately NVENC performance does not scale like Quick Sync. When asked to preserve a good amount of data, both NVENC and Quick Sync perform similarly in our 1080p/13Mbps test. However ask for more aggressive compression ratios for lower resolution/bitrate targets, and the Intel solution quickly distances itself from NVIDIA. One theory is that NVIDIA's entropy encode block could be the limiting factor here.

Ivy Bridge's improved Quick Sync appears to be aided both by an improved decoder and the HD 4000's faster/larger EU array. The graph below helps illustrate:

If we rely on software decoding but use Intel's hardware encode engine, Ivy Bridge is 18% faster than Sandy Bridge in this test (1080p 13Mbps output from BD source, same as above). If we turn on both hardware decode and encode, the advantage grows to 29%. More than half of the performance advantage in this case is due to the faster decode engine on Ivy Bridge.

Power Consumption Final Words
POST A COMMENT

173 Comments

View All Comments

  • ijozic - Thursday, April 26, 2012 - link

    Maybe because people who prefer to have the IPS screen would also like to have support for graphics switching to have a nice battery life while not doing anything GPU intensive. This was the one thing I expected from Ivy Bridge upgrade and NADA. Reply
  • uibo - Monday, April 23, 2012 - link

    Does anyone know if the 24Hz issue has been resolved? Reply
  • uibo - Monday, April 23, 2012 - link

    nevermind just saw the htpc perspective review Reply
  • anirudhs - Monday, April 23, 2012 - link

    I didn't notice that issue. 23.976*1000 = 23976 frames, 24 * 1000 = 24000 frames, in 16 mins 40 secs. So that's about one second of mismatch for every 1000 seconds. I could not notice this discrepancy while playing a Blu Ray on my PC. Could you? Reply
  • Old_Fogie_Late_Bloomer - Monday, April 23, 2012 - link

    Okay, well, I'm pretty sure that you would notice two seconds of discrepancy between audio and video after half an hour of viewing, or four seconds after an hour, or eight seconds by the end of a two-hour movie.

    However, the issue is actually more like having a duplicated frame every 40 seconds or so, causing a visible stutter, which seems like it would be really obnoxious if you started seeing it. I don't use the on-board SB video, so I can't speak to it, but clearly it is an issue for many people.
    Reply
  • JarredWalton - Monday, April 23, 2012 - link

    I watch Hulu and Netflix streams on a regular basis. They do far more than "stutter" one frame out of every 960. And yet, I'm fine with their quality and so our millions of other viewers. I think the crowd that really gets irritated by the 23.976 FPS problems is diminishingly small. Losing A/V sync would be a horrible problem, but AFAIK that's not what happens so really it's just a little 0.04 second "hitch" every 40 seconds. Reply
  • Old_Fogie_Late_Bloomer - Monday, April 23, 2012 - link

    Well, I can certainly appreciate that argument; I don't really use either of those services, but I know from experience they can be glitchy. On the other hand, if I'm watching a DVD (or <ahem> some other video file <ahem>) and it skips even a little bit, I know that I will notice it and usually it drives me nuts.

    I'm not saying that it's a good (or, for that matter, bad) thing that I react that way, and I know that most people would think that I was being overly sensitive (which is cool, I guess, but people ARE different from one another). The point is, if the movie stutters every 40 seconds, there are definitely people who will notice. They will especially notice if everything else about the viewing experience is great. And I think it's understandable if they are disappointed at a not insignificant flaw in what is otherwise a good product.

    Now, if my math is right, it sounds like they've really got the problem down to once every six-and-a-half minutes, rather than every 40 seconds. You know, for me, I could probably live with that in an HTPC. But I certainly wouldn't presume to speak for everyone.
    Reply
  • anirudhs - Tuesday, April 24, 2012 - link

    I will get a discrete GPU and then do a comparison. Reply
  • anirudhs - Monday, April 23, 2012 - link

    a discrete GPU! I could use a bump in transcoding performance for my ever-growing library of Blu-Rays. Reply
  • chizow - Monday, April 23, 2012 - link

    Looks like my concerns a few years ago with Intel's decision to go on-package and eventually on-die GPU were well warranted.

    It seems as if Intel will be focusing much of the benefits from smaller process nodes toward improving GPU performance rather than CPU performance with that additional transistor budget and power saving.

    I guess we will have to wait for IVB-E before we get a real significant jump in performance in the CPU segment, but I'm really not that optimistic at this point.
    Reply

Log in

Don't have an account? Sign up now