Quick Sync: A Secret Weapon, Refined
Back when Intel launched its Sandy Bridge architecture, I identified Quick Sync as the design’s secret weapon. Developed quietly for five years, it caught both AMD and Nvidia completely off guard. I projected that it’d take a year for both competitors to respond. And they have—AMD with its Video Codec Engine and Nvidia with NVEnc.
Unfortunately, AMD’s solution is still missing in action four months after it was first promised. Encoding on a Radeon HD 7000-series card has to be achieved through programmable shaders, rather than more energy-efficient fixed-function logic sitting idle on the die.
NVEnc is up and running, and a GeForce GTX 680 manages to outperform Intel’s first-gen Quick Sync implementation.
Nvidia’s victory is short-lived, though. HD Graphics blows everything else out of the water—and that’s even after biasing MediaEspresso toward quality rather than performance.
Arcsoft’s MediaConverter supports Quick Sync just fine, but the latest build doesn’t behave as well under APP or CUDA/NVEnc. Although scaling isn’t as aggressive, we still see how HD Graphics 4000 slices into the time it takes to transcode a large video file into something better suited to a portable device.
How’d They Do It?
I had the pleasure of sitting down with Dr. Hong Jiang, Intel’s chief media architect, before last year’s Sandy Bridge introduction to get an in-depth look at how the company implemented Quick Sync. This year, he led a session at IDF discussing the improvements included with Ivy Bridge. The focus, he said, was squarely on performance. Faster processing gives developers more flexibility in implementing higher-quality filters. It also punches through workloads more quickly, returning the processor to idle and saving power.
An increase in EU count helps Intel’s performance story, as does the inclusion of dedicated graphics L3 cache and greater Media Sampler throughput. Because the Media Sampler is part of that scalable third domain referred to as Slice, Intel can add resources in future generations to ratchet 3D and media performance up even more.
The Multi-Format Codec Engine (MFX) carries over from Sandy Bridge, enabling hardware-based H.264, VC-1, and MPEG-2 decoding, along with H.264 encoding. Intel apparently reworked its context-adaptive variable-length encoding and context-based adaptive binary arithmetic coding engines, though, which are both big mouthfuls referring to lossless encoding techniques that the MFX can decode faster.
Anticipating increasing demand for resolutions beyond 1080p in Ivy Bridge’s life cycle, Intel adds support to the MFX for 4096x4096 video decoding. In fact, Intel’s Jiang even claims the MFX can decode multiple 4K streams simultaneously.
Moving beyond Ivy Bridge’s decode capabilities, the media team also sought to improve the performance and quality of encoding tasks. A couple of paragraphs back I mentioned that the faster Media Sampler plays a part in Quick Sync’s speed-up. Specifically, it does the Motion Estimation stage’s heavy lifting, so greater throughput helps accelerate that step.
Now, Intel claims that its hardware-based encode solution achieves similar quality as a software solution. Last year, we wrote Video Transcoding Examined: AMD, Intel, And Nvidia In-Depth and found that the quality of every hardware-based encode engine sacrificed some degree of quality compared to a pure software solution. Faced with three new accelerated transcode technologies, we really need to spend some time putting each under a microscope to analyze how that story may have changed.
