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
Changes 'The VP8 project' to 'The WebM project', for consistency
with other webmproject.org repositories.
Fixes issue #97.
Change-Id: I37c13ed5fbdb9d334ceef71c6350e9febed9bbba
Besides the slight improvement in round trip error. This
also fixes a sign bias in the forward transform, so the
round trip errors are evenly distributed between +1s and
-1s. The old bias seemed to work well with the dc sign bias
in old fdct, which no longer exist in the improved fdct.
Change-Id: I8635e7be16c69e69a8669eca5438550d23089cef
The new fdct lowers the round trip sum squared error for a
4x4 block ~0.12. or ~0.008/pixel. For reference, the old
matrix multiply version has average round trip error 1.46
for a 4x4 block.
Thanks to "derf" for his suggestions and references.
Change-Id: I5559d1e81d333b319404ab16b336b739f87afc79
When the license headers were updated, they accidentally contained
trailing whitespace, so unfortunately we have to touch all the files
again.
Change-Id: I236c05fade06589e417179c0444cb39b09e4200d
