subsampling: 0 = Y (grayscale) only 1 = YCbCr, no subsampling (H1V1, YCbCr 1x1x1, 3 blocks per MCU) 2 = YCbCr, H2V1 subsampling (YCbCr 2x1x1, 4 blocks per MCU) 3 = YCbCr, H2V2 subsampling (YCbCr 4x1x1, 6 blocks per MCU-- very common)
See Implementation
subsampling: 0 = Y (grayscale) only 1 = YCbCr, no subsampling (H1V1, YCbCr 1x1x1, 3 blocks per MCU) 2 = YCbCr, H2V1 subsampling (YCbCr 2x1x1, 4 blocks per MCU) 3 = YCbCr, H2V2 subsampling (YCbCr 4x1x1, 6 blocks per MCU-- very common)