H.264 is a computing intensive algorithm. Intel has added hardware acceleration into their GPU(CPU integrated GPU) since 2009.
By offloading the computing task from CPU to GPU, CPU can use its power to carry out other tasks. besides, GPU based computing is faster, however, the generated image has poorer quality.
This is a screen capture from x264 vs Intel Qucik Sync Video.
CPU: Intel Core email@example.comHz
Input: 1920 * 1080
Profile: Main(Intel), veryfast(x264)
CPU usage: 2% vs 8% (2~3%,7~9%)
Total time spent on encoding: 6s vs 156s.