QuickSync Gets Open Source Support, Regresses in Quality

I have traditionally avoided touching upon QuickSync in any of my HTPC reviews. The main reason behind this was the fact that support only existed in commercial software such as MediaEspresso, and even that functionality was spotty at best. Limited source file type support as well as limited configuration options rendered these unusable for the power users. While full x264 acceleration using QuickSync is out of the question, the developers of HandBrake have come forward with support for QuickSync in their transcoding application.

The feature is still in beta (for example, only H.264 files are allowed as input right now, and cropping isn't working properly), but we took it out for a test drive. We took a m2ts file from a Blu-ray and compressed it with a target bitrate of 10 Mbps using x264 single pass (everything at default) as well as QuickSync. The time taken for compression as well as the average power consumption during the course of the process are tabulated below. Numbers are also provided for the same process using our passive Ivy Bridge HTPC (which has the HD4000 GPU).

H.264 Transcoding Performance
Transcoding Configuration Engine Power (W) FPS
       
1080p @ 36.2 Mbps to 1080p @ 10 Mbps QuickSync on HD4600 41.81 W 90.41
x264 on Core i7-4765T 67.93 W 51.66
QuickSync on HD4000 50.32 W 127.64
x264 on Core i3-3225 53.63 W 25.99
1080p @ 36.2 Mbps to 720p @ 7 Mbps QuickSync on HD4600 44.02 W 166.91
x264 on Core i7-4765T 65.37 W 32.88
QuickSync on HD4000 59.67 W 206.65
x264 on Core i3-3225 53.85 W 16.31

Fast and power-efficient transcoding is not the only requirement in the market. Video output quality is also very important. Encoder companies may present whitepapers with cherry-picked frame captures to show their efforts in good light. For all it is worth, the company's selected frame might be an I-frame, while the competitor's samples might be P or B-frames. PSNR is also presented as a metric indicating better quality. However, this is very unfair because encoders might be particularly tuned for PSNR but look bad when compared against the results of encoders tuned for, say, structural similarity (SSIM).

QuickSync is usually pretty fast, but the choice of bitrates in Handbrake seem to force it into one of the new modes in Haswell which actually regressed in both performance and image quality. This explains why the FPS on HD4000 is much  more than than on the HD4600. However, Haswell remains very power efficient. Anand had mentioned in passing about image quality degradation in QuickSync on Haswell in yesterday's review. I was also able to replicate it. Given below are 10 consecutive raw frames from the various encoders. Take a look and judge for yourself on the basis of how the encoders handle movement and whether there are any image artifacts in the encoder results.

In our opinion, the QuickSync results on HD4600 appear to be worse than what is obtained on the HD4000. With Haswell, Intel introduced seven levels of quality/performance settings that application developers can choose from. According to Intel, even the lowest quality Haswell QSV settings should be better than what we had with Ivy Bridge. In practice, this simply isn't the case. There's a widespread regression in image quality ranging from appreciably worse to equal at best with Haswell compared to Ivy Bridge. I'm not sure what's going on here but QuickSync remains one of the biggest missed opportunities for Intel over the past few years. The fact that it has taken this long to get Handbrake support going is a shame. Now that we have it, the fact that Intel seems to have broken image quality is the icing on a really terrible cake.

For users looking for the best quality transcodes, software based x264 can deliver better output with tweaked options two-pass encodes (such flexibilities are just not available with the QuickSync encoder). The big attraction to QuickSync remains low CPU utilization (< 10% in many cases) while you transcode. The image quality produced by Haswell's seemingly broken QSV implementation is still good enough for use on smartphones and tablets, it's just a step in the wrong direction.

4K for the Masses Power Consumption
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  • jhoff80 - Sunday, June 02, 2013 - link

    This article and the power consumption stats just make me wish that Intel would just make it easier to get a hold of their -T chips for end users. A 35W or 45W chip would be great for me, but the only thing that has full retail availability is the 65W one. (And it's not because it's so early in launch, it's always been way too difficult to get -T versions.) Reply
  • EnzoFX - Sunday, June 02, 2013 - link

    Not to mention expensive! You get the same results by undervolting/underclocking, typically. Reply
  • Laststop311 - Monday, June 03, 2013 - link

    You are correct in a way but you could undervolt the T series as well and get better thermal performance then the 65 watt version. atleast that is my experience. If i was making an HTPC i would use the i7-4770t or the i7-4650t if thats the equivalent of the i7-3770t this year. The power consumption is amazing and proper 24hz is great for 1080p24 playback. upgrade to the htpc just isn't in my budget right now and ivy bridge + gt 660 isnt a bad htpc. MY PC budget is going to an ultrabook upgrade this year. The increased battery life and performance is insane. i7-980x desktop still does not have a large enough upgrade to make it worth it. Ivy bridge-E is not THAT much faster and I dont think even haswell-e next year will be enough to upgrade the desktop. Reply
  • Death666Angel - Tuesday, June 04, 2013 - link

    "but you could undervolt the T series as well and get better thermal performance then the 65 watt version."
    Not to the same extent. The T series will already be driving much tighter voltages than normal SKUs. While you may save 15% power consumption by undervolting normal SKUs, undervolting already power efficient SKUs would result in sub 5% probably.
    Reply
  • vnangia - Sunday, June 02, 2013 - link

    Well, it helps that there are 35W parts this time around - at least on the timeline. IVB didn't get any 35W parts, so the HTPC is still on SNB, and yeah, I could definitely use the incremental improvements to QuickSync. Reply
  • jhoff80 - Sunday, June 02, 2013 - link

    Yes, but I'm not talking about only 35W specific chips. The i7-3770T was just as difficult to get as any other -T series chip, because they don't sell them to end-users directly. Reply
  • vnangia - Sunday, June 02, 2013 - link

    I'm agreeing with you! What I was trying to say is, Intel did announce low-TDP SNB parts and delivered: SNB had a bunch of -T versions available to end-users at both low (G4xx, G5xxT, 2100T, 2120T) and high end (2390, 2500T). I bought my 2100T at Microcenter B&M for instance.

    By contrast, Intel didn't announce any end-user -T (and just a handful of -S) parts and we saw that IVB had virtually no -T parts available. I'm optimistic that now they've announced a few -T parts at the high end, we might actually see these materialize in the retail chain and hopefully it bodes well for -T parts at the low end.

    Fortunately (*knocks on wood*) the current SNB-based HTPC is still going strong, so I don't feel the need to upgrade. If and when I do, though, I expect that it won't be so clear cut - I may end up going with AMD's lineup, despite the relative paucity of AMD ITX boards.
    Reply
  • jhoff80 - Monday, June 03, 2013 - link

    Sorry, I must've misunderstood. Reply
  • Krysto - Monday, June 03, 2013 - link

    This is insane. Why use a $400 Intel Haswell media box for 4k video, when you can use the much cheaper and much more efficient Mali T622-based media boxes that should be appearing next year?

    http://blogs.arm.com/multimedia/977-a-new-branch-f...
    Reply
  • NirXY - Monday, June 03, 2013 - link

    "should be appearing next year" Reply

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