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Performance during Video Processing

In terms of video processing tasks, HD Graphics deals with two major processes. On the one hand, it is HD video playback (decoding), and on the other – transcoding (decoding and further encoding) with the help of Quick Sync technology.

As for the video transcoding, the new generation graphics cores are hardly any different from their predecessors. HD Graphics 4000/2500 support full hardware video decoding in AVC/H.264, VC-1 and MPEG-2 formats via DXVA (DirectX Video Acceleration) interface. It means that when you are playing back videos by DXVA compatible software players, the utilization of processor computational resources and its power consumption will remain minimal and all content decoding is performed by a special unit in the graphics core.

However, they promised the same exact thing in their Sandy Bridge processors, but in some cases we had to deal with pretty unpleasant artifacts (with certain players and during the playback of videos in specific formats). Of course, it didn’t have anything to do with any hardware issues in the decoder integrated into the graphics core, but was more likely the result of some software problems, but knowing this didn’t really change the situation for the end-users. Now it looks like they have finally been cleared of all issues and contemporary players play video just fine in systems with new generation HD Graphics and do not suffer from poor image quality any more. At least, we haven’t been able to detect any image quality issues in the publicly available Media Player Classic Home Cinema 1.6.2.4902 or VLC media player 2.0.1, as well as the commercial Cyberlink PowerDVD 12 build 1618.

As we have expected, the CPU utilization during video playback remains pretty low, because it is the video engine inside the integrated graphics core that bears the biggest load, and not the computational processor cores. For example, during FullHD video playback with enabled sub-titles, Core i5-3550 with HD Graphics 2500 core is only 10% utilized. Moreover, the CPU remains in power-saving mode, i.e. works at lower 1.6 GHz frequency.

I have to say that the hardware decoder is powerful enough to ensure problem-free playback of several different FullHD video streams and “heavy” 1080p videos encoded at about 100 Mbps bitrate. However, it is still possible to overload the decoder. For example, during the layback of an H.264 video in 3840x2160 resolution with about 275 Mbps bitrate, we witnessed some frame loss and freezing even though Intel promised full support of hardware decoding for high-resolution videos. However, the above mentioned QFHD resolution is used very rarely these days.

We also checked the performance of the second Quick Sync version implemented in Ivy Bridge processors. Since Intel promised to increase the transcoding speed in the new graphics cores, we focused primarily on the performance tests. During our test session we measured the time it took to transcode one 40-minute episode of a popular TV-show from 1080p H.264 10 Mbps bitrate format into a format compatible with Apple iPad2 (H.264, 1280x720, 4Mbps). We used two utilities supporting Quick Sync: Arcsoft Media Converter 7.5.15.108 and Cyberlink Media Espresso 6.5.2830.

It is impossible not to notice that the transcoding speed has increased dramatically. Ivy Bridge processor with HD Graphics 4000 graphics core completes the test almost 75% faster than the previous generation processor with HD Graphics 3000 core inside. However, it looks like only the senior modification of the Intel’s graphics core experiences this unprecedented performance boost. Namely, we do not see a tremendous difference in the results like that when we compare the transcoding speed of HD Graphics 2500 and HD Graphics 2000. Quick Sync in the junior version of the new Intel’s Ivy Bridge graphics core is much slower than in the senior one that is why the video transcoding results of HD Graphics 2500 and HD Graphics 2000 processors differ by as little as 10%. However, there is no reason to be sad about it. even the slowest Quick Sync is way faster than software decoding or even any of the Radeon HD graphics cards that use programmable shaders to accelerate video transcoding.

I would like to say a few words about the video transcoding quality. They used to believe that Quick Sync technology produced significantly poorer images quality than careful software transcoding. Intel never denied it stressing that Quick Sync was a tool for fast transcoding and not for professional mastering. However, according to the developers, they improved the image quality produced by the new version of this technology by introducing some media sampler modifications. Did they manage to reach the same image quality levels as during software decoding? Let’s take a closer look at a few screenshots illustrating the transcoding of a FullHD original movie into Apple iPad 2 compatible format.

Software transcoding using x264 codec:

Transcoding with Quick Sync technology on HD Graphics 3000:

Transcoding with Quick Sync 2.0 technology on HD Graphics 4000:

Frankly speaking, I can’t notice any dramatic improvement in image quality. Moreover, it seems that the first Quick Sync version may be producing even better image: less washed-out image and more prominent details. On the other hand, excessive clarity of the picture on HD Graphics 3000 adds noise to the image, which is also not so good. In any case, if you are looking to get ideal image quality, then software transcoding would probably be your best bet, because it may offer you better quality video by applying more flexible settings. However, if you intend to playback your video on some sort of mobile device with a small display, it makes a lot of sense to use Quick Sync version 1 or version 2.

 
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