Performance during Video Processing
Sandy Bridge graphics core has absolutely no problems with HD video playback. The decoder built into the graphics core copes perfectly fine with all popular formats, leaving the computational part of the CPU almost without work.
The only possible issue could be connected with the support of the new Sandy Bridge decoder by software players. For example, two weeks ago, during Core i5-2400S tests we discovered that a popular free Media Player Classic Home Cinema had some issues with the new processors: we observed certain artifacts during DXVA rendering. Therefore, at that time we switched to a commercial Cyberlink PowerDVD10, which was better optimized for Intel HD Graphics 2000/3000 and worked impeccably. Again we had to resort to a commercial product, because even the recently released Media Player Classic Home Cinema version 22.214.171.12427 still has certain issues with Sandy Bridge CPUs.
This is what the hardware acceleration of video playback in a Core i5-2400 based system with Intel HD Graphics 2000 graphics core looks like:
The CPU utilization during HD video playback in H.264 format doesn’t exceed 10-15%, while the CPU itself remains in power-saving mode, i.e. works at the clock speed lowered to 1.6 GHz.
VC-1 video playback in Cyberlink PowerDVD10 (version 10.0.2429.51) produces even more impressive results.
In this case the CPU utilization is even less than 10%. However, we noticed one peculiarity during our tests: the container type for the decoded VC-1 video stream matters a lot. For example, we couldn’t get hardware acceleration for VC-1 video in MKV container to work, while the same content in MPEG-TS container or played directly from a Blu-ray disc was played back perfectly fine using our hardware decoder.
So, we can conclude that the hardware video decoder in Sandy bridge processors does its job just fine, so these CPUs will be perfectly fit for a media center PC even without an add-on graphics card. Especially, since the computational capacity of the Sandy Bridge processors is sufficient for it to playback any video content, even the most exotic one, without any help from the hardware decoder.
Hardware acceleration during video playback is one half of Quick Sync technology, because it only uses the decoder and doesn’t involve the codec inside the Sandy Bridge graphics core. Only video transcoding reveals all the potential of this technology, as the content is first decoded and then encoded into new format. Some popular video transcoding utilities can already offer video transcoding using special units in Quick Sync instead of the processor capacities. Take, for instance, the latest Arcsoft Media Converter or Cyberlink Media Espresso.
The distinguishing feature of video transcoding in applications using Quick Sync is the low CPU utilization that stays way below 100%. And that is one of the most computationally heavy tasks out there!
For example, the screenshot above shows that transcoding a 1080p H.264 movie into lower resolution and lower bitrate for viewing on an iPhone 4 uses only 15-20% of the CPU. But the most impressive thing about it is that the CPU in this case doesn’t even switch from the power-saving mode and works at a lowered frequency of 1.6 GHz.
The video quality doesn’t suffer at all in this case. This is what positively distinguishes Quick Sync from transcoding via CUDA and Stream/APP. When we compared the quality of the video transcoded using Quick Sync and the video transcoded using traditional processor resources, we didn’t discover any serious artifacts produced by the Sandy Bridge graphics core.
Intel Quick Sync
Moreover, we got the feeling that the video transcoded with Quick Sync turned out even better. Note that the size of the resulting files differed by no more than 2%, and the actual bitrate and resolution were in fact identical. In other words, Quick Sync does work very well.
Transcoding speed also turned out high enough. The use of Quick Sync technology not only offloads the CPU computational cores, but also delivers the final result faster. We performed several tests transcoding a short 1080p H.264 movie fragment into an iPhone 4 compatible format (H.264, 1280x720, 4 Mbps). The diagrams below show how much time it takes when we use processor’s computational resources, when we activate Quick Sync technology, and when we transcode using CUDA and Stream/APP using external AMD Radeon HD 5570 and Nvidia GeForce GT 430 graphics cards. We used the same Core i5-2400 based testbed for all tests. We used two different applications to measure the transcoding speed: Arcsoft Media Converter 126.96.36.199 and Cyberlink Media Espresso 6.5.1229.
Intel has every reason to be proud of their Quick Sync technology. The decision to make the decoder and codec into individual units turned out a great performance-improving solution. As you can see from the diagrams, this technology speeds transcoding significantly compared with the situation when it is performed by processor computational cores. We failed to achieve the same high result with the discrete entry-level graphics cards from AMD and Nvidia, either.