Convert YUYV (also known as YUV2 or YUV422 non-planar) into 8bit grayscale by extracting the Y channel:

SSSE3 version:
500000 YUYV pixels converted to grayscale in 526 microseconds, 950 million pixels/s
500000 YUYV pixels converted to grayscale in 124 microseconds, 4032 million pixels/s
500000 YUYV pixels converted to grayscale in 108 microseconds, 4629 million pixels/s
500000 YUYV pixels converted to grayscale in 101 microseconds, 4950 million pixels/s
500000 YUYV pixels converted to grayscale in 109 microseconds, 4587 million pixels/s
500000 YUYV pixels converted to grayscale in 97 microseconds, 5154 million pixels/s
500000 YUYV pixels converted to grayscale in 93 microseconds, 5376 million pixels/s
500000 YUYV pixels converted to grayscale in 97 microseconds, 5154 million pixels/s
500000 YUYV pixels converted to grayscale in 93 microseconds, 5376 million pixels/s
500000 YUYV pixels converted to grayscale in 100 microseconds, 5000 million pixels/s
500000 YUYV pixels converted to grayscale in 102 microseconds, 4901 million pixels/s
500000 YUYV pixels converted to grayscale in 94 microseconds, 5319 million pixels/s
kfir@GentooB0X ~/Programming/sse2 $ gcc sse2convertyuyv_8_perf_asm.c --std=c99 -msse2

Standard version:
500000 YUYV pixels converted to grayscale in 839 microseconds, 595 million pixels/s
500000 YUYV pixels converted to grayscale in 389 microseconds, 1285 million pixels/s
500000 YUYV pixels converted to grayscale in 380 microseconds, 1315 million pixels/s
500000 YUYV pixels converted to grayscale in 383 microseconds, 1305 million pixels/s
500000 YUYV pixels converted to grayscale in 380 microseconds, 1315 million pixels/s
500000 YUYV pixels converted to grayscale in 384 microseconds, 1302 million pixels/s
500000 YUYV pixels converted to grayscale in 383 microseconds, 1305 million pixels/s
500000 YUYV pixels converted to grayscale in 379 microseconds, 1319 million pixels/s
500000 YUYV pixels converted to grayscale in 379 microseconds, 1319 million pixels/s
500000 YUYV pixels converted to grayscale in 379 microseconds, 1319 million pixels/s
500000 YUYV pixels converted to grayscale in 382 microseconds, 1308 million pixels/s
500000 YUYV pixels converted to grayscale in 380 microseconds, 1315 million pixels/s