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  • Ronald S. Bultje's avatar
    Dual 16x16 inter prediction. · 60cb39da
    Ronald S. Bultje authored
    This patch introduces the concept of dual inter16x16 prediction. A
    16x16 inter-predicted macroblock can use 2 references instead of 1,
    where both references use the same mvmode (new, near/est, zero). In the
    case of newmv, this means that two MVs are coded instead of one. The
    frame can be encoded in 3 ways: all MBs single-prediction, all MBs dual
    prediction, or per-MB single/dual prediction selection ("hybrid"), in
    which case a single bit is coded per-MB to indicate whether the MB uses
    single or dual inter prediction.
    In the future, we can (maybe?) get further gains by mixing this with
    Adrian's 32x32 work, per-segment dual prediction settings, or adding
    support for dual splitmv/8x8mv inter prediction.
    Gain (on derf-set, CQ mode) is ~2.8% (SSIM) or ~3.6% (glb PSNR). Most
    gain is at medium/high bitrates, but there's minor gains at low bitrates
    also. Output was confirmed to match between encoder and decoder.
    Note for optimization people: this patch introduces a 2nd version of
    16x16/8x8 sixtap/bilin functions, which does an avg instead of a
    store. They may want to look and make sure this is implemented to
    their satisfaction so we can optimize it best in the future.
    Change-ID: I59dc84b07cbb3ccf073ac0f756d03d294cb19281