• Zoe Liu's avatar
    [NORMATIVE] Unify comp ref context design · 4917295b
    Zoe Liu authored
    This patch uses the neighboring ref counts to design the contexts
    for the coding of the first reference frame of a reference pair for
    the compound prediction. This aligns the context design with that
    for the second reference frame of a reference pair for the
    compound prediction.
    
    The new designed contexts are much simpler than that in the baseline.
    The number of contexts for each binary symbol is reduced from 5 to
    3. Further, the logic for each context only depends on the collected
    neighboring ref counts, which is straightforward to derive.
    
    The default CDFs for the first reference frame coding have been
    updated using aom_entropy_optimizer.
    
    Experimental results demonstrate a small coding gain for Google test
    sets of both lowres and midres, with 30 frames coded for the default
    coding tool setup:
    
    lowres: avg_psnr -0.077%; ovr_psnr -0.076%; ssim -0.106%
    midres: avg_psnr -0.059%; ovr_psnr -0.066%; ssim -0.037%
    
    BUG=aomedia:1356
    
    Change-Id: I781abbe4616dc3f3a7213ec663946ff9844eb830
    4917295b
pred_common.h 12.9 KB