Introduction

In November, we published our first article featuring Blu-ray content. While we focused more on the capability of the cards we tested to play digital content protected with HDCP, we did take a preliminary look at hardware accelerated high definition video playback with the movie Click.

Our first glimpse of the processing power required to play HD content on the PC gave us a very good indication that Blu-ray movies using MPEG-2 should have no problem on a modern system, even without GPU acceleration. The Core 2 Duo E6300 is easily capable of playing back 50-60 Mbps MPEG-2 video at 1080p. Adding a GPU to the mix did make an impact, but the small boost in performance just wasn't necessary.

Today we will turn the tables around and look at what happens when H.264/MPEG-4 AVC meets Blu-ray on the PC. This combination is much more demanding than MPEG-2 encoded Blu-ray movies, as H.264 is capable of much higher compression at better quality which requires more processing power.

Before we get to our results, it is important to talk a bit about playback of HD media on the PC. BD and HDDVD movies are copy protected with AACS which uses HDCP to encrypt and decrypt the video signal when it's sent over a digital connection. In order to view one of these movies on an HDTV over either a DVI or HDMI connection, an HDCP enabled video card is required.

All video cards that have an HDMI connection on them should support HDCP, but the story is different with DVI. Only recently have manufacturers started including the encryption keys required for HDCP. Licensing these keys costs hardware makers money, and the inclusion of HDCP functionality hasn't been seen as a good investment until recently (as Blu-ray and HDDVD players are finally available for the PC). While NVIDIA and ATI are both saying that most (if not all) of the cards available based on products released within the last few months will include the required hardware support, the final decision is still in the hands of the graphics card maker.

It is important to make it clear that HDCP graphics cards are only required to watch protected HD content over a digital connection. Until movie studios decide to enable the ICT (Image Constraint Token), HD movies will be watchable at full resolution over an analog connection. While analog video will work for many current users, it won't be a long term solution.

Now that we've recapped what we know about watching HD content on the PC, lets take a look at why things will be a little different now that H.264/MPEG-4 AVC encoded movies are here.

H.264 Encoded HD Content: A Good Thing
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  • Tujan - Monday, December 11, 2006 - link


    So heres a Sony notebook. It probably uses less than 40 or 50 watts. Has an HDMI connector on it. And runs on a battery. No less.

    http://www.learningcenter.sony.us/assets/itpd/note...">http://www.learningcenter.sony.us/asset...CMP=vaio...

    So what is my question here. This is a Centrino Core Duo for a notebook. With graphics enough to run using only battery power .

    As well the notebook has a Blue-Ray drive wich can be written to.AND watch blue-ray titles.

    Is this mostly in the liscencing ? How can it be when the processor used,and graphics cards used are such absolute 'top notch'for the desktop. And the notebook puts the works of them to shame.

    Blue-ray,and HDMI on battery power.

    This was one of AnandTechs Adds.Incodently - Hi Anandtech(Add-Click),HI Sony.
    Reply
  • cmdrdredd - Monday, December 11, 2006 - link

    I too wonder how a laptop can play blue-ray fine but a $400+ video card with a CPU probably 2x+ more powerful and more memory...can't. Reply
  • fanbanlo - Monday, December 11, 2006 - link

    most efficient software decoder! Maybe we don't need Core 2 Duo after all!

    http://www.coreavc.com/">http://www.coreavc.com/
    Reply
  • DerekWilson - Monday, December 11, 2006 - link

    my understanding is that coreavc doesn't work in conjunction with HDDVD/BD -- that it doesn't support AACS. Reply
  • totalcommand - Monday, December 11, 2006 - link

    BluRay support will be added to CoreAVC soon. Reply
  • KashGarinn - Tuesday, December 12, 2006 - link

    When CoreAVC will support HD-DVD and bluray H.264, I'd be very interested in seeing this article updated with the comparison.

    Regarding the article itself, I thought it wasn't up to normal anandtech standards.. skimping on the H.264 details which makes it better and giving the reason as "but these are a little beyond the scope of this article." - What is anandtech coming to? That's like saying "we're going to compare graphic cards with directx9 capabilities, but explaining what directx is, is a little beyond the scope of this article"

    Also, not comparing amd cpus? What's up with that?

    And I find it odd that you didn't comment on the strangeness that nvidia has better acceleration across the board than the ATI cards, especially as the ATI cards have better shader throughput, so probably most likely hampered by software rather than hardware.. so this: "ATI hardware is very consistent, but just doesn't improve performance as much as NVIDIA hardware." - only paints the incorrect picture.

    I would give this article a 2 out of 5.. 1 for at least covering the basics (h.264 is a better codec than mpeg2) and 1 for showing that ati needs to improve it's decoder.. even though you don't point it out.

    K.
    Reply
  • ninjit - Monday, December 11, 2006 - link

    I had a question about why you chose the golden-gate bridge scene to stress test the decoding capabilities of the various setups.

    You said that you chose that point in the movie because it had the highest bitrate (41Mbps), indicating a more complex scene.

    To me though that would indicate LESS encoding done by H.264, and subsequently LESS decoding work needed to be done for playback of that particular scene.

    I justify that by thinking with a very complex scene the codec cannot compress the stream as much because it would introduce too many artifacts, so the compression rate is dropped and the data rate increased to compensate for that particular section in time.

    Is my reasoning correct? If not, can someone explain to me why?

    I don't think choice of scene should change the graphs in terms of relative performance between setups, but it would affect absolute numbers - an easy way to check whether my thinking is wrong or not is to see if there are more dropped frames in the Golden Gate scene on the software-decoded E6600 vs. other less busy scenes.
    Reply
  • DerekWilson - Monday, December 11, 2006 - link

    we tried to explain this a little bit, so I'm sorry if we didn't get it across well enough.

    I'm not an expert on H.264 by any means, but I can talk about other types of decoding as they relate to still images.

    The issue isn't really less compression -- when using H.264, we are always using H.264 complexity to encode the bitstream. We don't fall back to just saving raw pixel data if a scene is overly complex -- we encode more detailed information about the scene.

    For instance, with still images, run length encoding can be performed with huge compression especially in images with large blocks of identical colors (like logos or images on a solid background color). Basically, the idea is to list a color and then a number of pixels that use that color. For an image that is a single solid color, you could list the color and then the number of pixels in the image. This is a very small file with little processing requirement that represents a full image. If, on the other hand, we have a checker board pattern with every other pixel being a different color, we have to list the color of every pixel, BUT we also have to process every color to makes sure of how many consecutive pixels it represents (even if it only represents one). Thus, we end up donig more processing than we would on a smaller (lower "bitrate") file.

    This example is very fabricated as sophisticated run lenth encoding can handle more complex patterns, but it serves to illustrate the point: when using a specific type of encoding, higher bitrates can (and usually do) mean more complexity and processing.

    As we mentioned, using no encoding requires zero processing. MPEG-2 can compress the data to lower the bitrate while increasing computational complexity. But higher bitrate MPEG-2 means more data to process per frame -- which means more CPU overhead for higher bitrates under MPEG-2. The same is true with H.264 -- bitrates are genearlly lower than MPEG-2 and require more processing power, but as H.264 encoded movies use more bitrate (more data per frame), more processing is required.

    I hope this helps.

    Also, to clarify -- the spot at the video that reaches 41Mbps corresponds to the highest CPU utilization (we can see this on a the perfmon timeline).
    Reply
  • ninjit - Monday, December 11, 2006 - link

    Thanks for the explanation Derek. That was very helpful. Reply
  • jeffbui - Monday, December 11, 2006 - link

    The PS3 is able to play Blu-Ray back at 50% over normal speed without dropping frames. That gives an idea of how much power these consoles are capable of.

    Some interesting tidbits from a translation of an article interviewing PS3 developers.

    -H.264 decoding itself was not very difficult for Cell with moderate optimization and they could play a movie in realtime at the first try unlike very difficult SACD optimization. However, because they began the development without knowing the final Blu-ray standard, they set the goal very high for decoding 2 full HD H.264 streams at 40Mbps simultaneously. Besides the clockspeed of the devkit was lower than the final product which made the development difficult. The current decoder can decode full HD H.264 with 3 SPEs.

    -An SCE developer recommends trying 1.5x fast-forward playback in the PS3 BD player to see the power of Cell. When it's connected to a display via 1080/60p, it becomes very smooth as Cell has an enough margin for video decoding. In 1.5x fast-forward playback it decodes all frames then inserts them into 60fps with sped up audio.
    Reply

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