question on alignment

hi Intel-friends,

OS: Ubuntu 12.04

       mediasdk-tutorials-0.0.3

       MediaServerStudioEssentials2015R6

Platform:  i5-4570S

Q1. I found some description as below in simple_decode_vpp_pp.cpp, may I know the reason on "width must be a multiple of 16" and "height must be a multiple of 16 in case of frame picture and a multiple of 32 in case of field picture" ??

    // width must be a multiple of 16
    // height must be a multiple of 16 in case of frame picture and a multiple of 32 in case of field picture
    VPPParams.vpp.In.Width = MSDK_ALIGN16(VPPParams.vpp.In.CropW);
    VPPParams.vpp.In.Height =
        (MFX_PICSTRUCT_PROGRESSIVE == VPPParams.vpp.In.PicStruct) ?
        MSDK_ALIGN16(VPPParams.vpp.In.CropH) :
        MSDK_ALIGN32(VPPParams.vpp.In.CropH);

Q2. I didn't find any behavior about alignment in simple_decode_vmem.cpp but simple_decode.cpp and simple_decode_vpp_pp.cpp. Does it mean there's no alignment requirement in video memory? if not, why??

Thanks in advance