A Near-Perfect HTPC

Since 2006 Intel’s graphics cores have supported sending 8-channel LPCM audio over HDMI. In 2010 Intel enabled bitstreaming of up to eight channels of lossless audio typically found on Blu-ray discs via Dolby TrueHD and DTS-HD MA codecs. Intel’s HD Graphics 3000/2000 don’t add anything new in the way of audio or video codec support.

Dolby Digital, TrueHD (up to 7.1), DTS, DTS-HD MA (up to 7.1) can all be bitstreamed over HDMI. Decoded audio can also be sent over HDMI. From a video standpoint, H.264, VC-1 and MPEG-2 are all hardware accelerated. The new GPU enables HDMI 1.4 and Blu-ray 3D support. Let’s run down the list:

Dolby TrueHD Bitstreaming? Works:

DTS HD-MA bitstreaming? Yep:

Blu-ray 3D? Make that three:

How about 23.976 fps playback? Sorry guys, even raking in $11 billion a quarter doesn’t make you perfect.

Here’s the sitch, most movie content is stored at 23.976 fps but incorrectly referred to as 24p or 24 fps. That sub-30 fps frame rate is what makes movies look like, well, movies and not soap operas (this is also why interpolated 120Hz modes on TVs make movies look cheesey since they smooth out the 24 fps film effect). A smaller portion of content is actually mastered at 24.000 fps and is also referred to as 24p.

In order to smoothly playback either of these formats you need a player and a display device capable of supporting the frame rate. Many high-end TVs and projectors support this just fine, however on the playback side Intel only supports the less popular of the two: 24.000Hz.

This isn’t intentional, but rather a propagation of an oversight that started back with Clarkdale. Despite having great power consumption and feature characteristics, Clarkdale had one glaring issue that home theater enthusiasts discovered: despite having a 23Hz setting in the driver, Intel’s GPU would never output anything other than 24Hz to a display.

The limitation is entirely in hardware, particularly in what’s supported by the 5-series PCH (remember that display output is routed from the processor’s GPU to the video outputs via the PCH). One side effect of trying to maintain Intel’s aggressive tick-tock release cadence is there’s a lot of design reuse. While Sandy Bridge was a significant architectural redesign, the risk was mitigated by reusing much of the 5-series PCH design. As a result, the hardware limitation that prevented a 23.976Hz refresh rate made its way into the 6-series PCH before Intel discovered the root cause.

Intel had enough time to go in and fix the problem in the 6-series chipsets, however doing so would put the chipset schedule at risk given that fixing the problem requires a non-trivial amount of work to correct. Not wanting to introduce more risk into an already risky project (brand new out of order architecture, first on-die GPU, new GPU architecture, first integrated PLL), Intel chose to not address it this round, which is why we still have the problem today.


Note the frame rate

What happens when you try to play 23.976 fps content on a display that refreshes itself 24.000 times per second? You get a repeated frame approximately every 40 seconds to synchronize the source frame rate with the display frame rate. That repeated frame appears to your eyes as judder in motion, particularly evident in scenes involving a panning camera.

How big of an issue this is depends on the user. Some can just ignore the judder, others will attempt to smooth it out by setting their display to 60Hz, while others will be driven absolutely insane by it.

If you fall into the latter category, your only option for resolution is to buy a discrete graphics card. Currently AMD’s Radeon HD 5000 and 6000 series GPUs correctly output a 23.976Hz refresh rate if requested. These GPUs also support bitstreaming Dolby TrueHD and DTS-HD MA, while the 6000 series supports HDMI 1.4a and stereoscopic 3D. The same is true for NVIDIA’s GeForce GT 430, which happens to be a pretty decent discrete HTPC card.

Intel has committed to addressing the problem in the next major platform revision, which unfortunately seems to be Ivy Bridge in 2012. There is a short-term solution for HTPC users absolutely set on Sandy Bridge. Intel has a software workaround that enables 23.97Hz output. There’s still a frame rate mismatch at 23.97Hz, but it would be significantly reduced compared to the current 24.000Hz-only situation.

MPC-HC Compatibility Problems

Just a heads up. Media Player Classic Home Cinema doesn't currently play well with Sandy Bridge. Enabling DXVA acceleration in MPC-HC will cause stuttering and image quality issues during playback. It's an issue with MPC-HC and not properly detecting SNB as far as I know. Intel has reached out to the developer for a fix.

The Future: Z68 Chipset in Q2, LGA-2011 in Q4 Intel’s Quick Sync Technology
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  • RMSe17 - Monday, January 03, 2011 - link

    Time for an upgrade :) Reply
  • marc1000 - Monday, January 03, 2011 - link

    I decided to jump the first core-i lineup, and sitck to an old core2duo for some more time... now seems the wait was worth it!

    I just hope the prices outside US/Europe will be reasonable..

    thanks Anand,
    Reply
  • vol7ron - Monday, January 03, 2011 - link

    I think there are many of us that had the same idea. Unless needing to upgrade due to malfunction or new laptop purchase, holding C2D til past the i-Series was the best move to make; whereas buying into C2D asap was the best move at the time.

    Still going to wait for prices to fall and more USB3 adoption. Expected new purchase: mid-2011-mid 2012
    Reply
  • vol7ron - Monday, January 03, 2011 - link

    by "i-Series" it should have said "1st gen. i-Series" Reply
  • CptTripps - Tuesday, January 04, 2011 - link

    Ya know I usually do as you are but was an early adopter of the i7 920. Looking now it seems I made the right choice. I have had 2 years of kickassery and my processor still holds up rather well in this article. Reply
  • hogey74 - Thursday, January 06, 2011 - link

    Me too! I've got an e8400 running at 3.9 with almost zero OC know-how and its done me well. I might snap up an i7 if they and their mobos get cheap when sandy bridge has been out a few months... but may well skip that generation all together. Reply
  • Einy0 - Monday, January 03, 2011 - link

    Holy crapola AMD really needs Bulldozer now. Even in heavily threaded video encoding the 2600K at $300 is blowing the 1100T x6 out of the water. This is the the Core 2 Duo vs. A64 X2 all over again. Will Bulldozer be another Phenom, a day late and a dollar short? TLB bug anyone? As a PC enthusiast I really want to see competition to keep prices in check. If I had to upgrade today, I can't see how I could turn down the 2600K... Reply
  • medi01 - Monday, January 03, 2011 - link

    Did you add mobo price into equation?

    I don't get all the excitement, really. If anything, Intel's anti-overclocking moves
    Reply
  • MonkeyPaw - Monday, January 03, 2011 - link

    Yeah, new Intel motherboard models are never cheap. I don't understand why the price remains so high when more an more functionality is moving to the CPU. The other killer is that you need a new board for every Intel CPU update.

    Lastly, it's hard to throw the "buy now" tag on it with AMD's new architecture over the horizon. Sure, AMD has a tough act to follow, but it's still an unknown that I think is worth waiting for (if it's a dog, you can still buy Intel). Keep in mind that Bulldozer will have a pretty strong IGP, one that may make decent IGP gaming a reality. It will become a matter of how powerful the x86 portion of the Bulldozer is, and they are trying a considerably different approach. Considering the amount of money you'll be paying, you might as well see how AMD shakes out. I guess it just depends on if what you have today can get you by just a little longer.
    Reply
  • dertechie - Monday, January 03, 2011 - link

    You're conflating Bulldozer and Llano there. Bulldozer is the new architecture, coming to the desktop as an 8-core throughput monster. Llano is the first desktop APU, cramming 4 32nm K10.5 cores and a Redwood class GPU onto the die. The next generation of desktop APUs will be using Bulldozer cores. Reply

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