• Yaowu Xu's avatar
    experiment extending the quantizer range · 5b42ae09
    Yaowu Xu authored
    Prior to this change, VP8 min quantizer is 4, which caps the
    highest quality around 51DB. This experimental change extends
    the min quantizer to 1, removes the cap and allows the highest
    quality to be around ~73DB, consistent with the fdct/idct round trip
    error. To test this change, at configure time use options:
    
    --enable-experimental --enable-extend_qrange
    
    The following is a brief log of changes in each of the patch sets
    
    patch set 1:
    In this commit, the quantization/dequantization constants are kept
    unchanged, instead scaling factor 4 is rolled into fdct/idct.
    Fixed Q0 encoding tests on mobile:
      Before:    9560.567kbps Overall PSNR:50.255DB VPXSSIM:98.288
      Now:   18035.774kbps Overall PSNR:73.022DB VPXSSIM:99.991
    
    patch set 2:
    regenerated dc/ac quantizer lookup tables based on the scaling
    factor rolled in the fdct/idct. Also slightly extended the range
    towards the high quantizer end.
    
    patch set 3:
    slightly tweaked the quantizer tables and generated bits_per_mb
    table based on Paul's suggestions.
    
    patch set 4:
    fix a typo in idct, re-calculated tables relating active max Q
    to active min Q
    
    patch set 5:
    added rdmult lookup table based on Q
    
    patch set 6:
    fix rdmult scale: dct coefficient has scaled up by 4
    
    patch set 7:
    make transform coefficients to be within 16bits
    
    patch set 8:
    normalize 2nd order quantizers
    
    patch set 9:
    fix mis-spellings
    
    patch set 10:
    change the configure script and macros to allow experimental code
    to be enabled at configure time with --enable-extend_qrange
    
    patch set 11:
    rebase for merge
    
    Change-Id: Ib50641ddd44aba2a52ed890222c309faa31cc59c
    5b42ae09
dct.c 3.06 KB