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fast auto-determined filtering strength

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kLevelsFromDelta[sharpness][delta] is an inverse look-up table
that tells the minimum filtering strength needed to trigger the
filtering of a step with amplitude 'delta'. We use this table
in various situations:

a) when computing the initial (/global) filtering
strength for each segment. We look at the quantization
step and deduce the proper filtering strength needed
to result this quantization noise (talking the -f option
into account).

b) during intra16 calculation, when a block ends up
very empty (only DC coeffs are non-zero, all ACs have
vanished). We'll rely on the in-loop filtering to
restore the smoothness (if the source was gradient-like
smooth. That's why we look at the distortion too before
triggering the filtering).

Step b) goes _in addition_ to a), potentially raising
the filtering strength if blockiness is likely.

Change-Id: Icaeca93ef21da195b079e6587a44d9edfc8e9efa
This commit is contained in:
skal
2013-10-29 20:13:29 +01:00
parent 43148b6cd2
commit f8bfd5cd1e
4 changed files with 122 additions and 26 deletions
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6
src/enc/vp8enci.h
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@ -248,6 +248,8 @@ typedef struct {
int beta_; // filter-susceptibility, range [0,255].
int quant_; // final segment quantizer.
int fstrength_; // final in-loop filtering strength
int max_edge_; // max edge delta (for filtering strength)
int min_disto_; // minimum distortion required to trigger filtering record
// reactivities
int lambda_i16_, lambda_i4_, lambda_uv_;
int lambda_mode_, lambda_trellis_, tlambda_;
@ -555,6 +557,10 @@ void VP8InitFilter(VP8EncIterator* const it);
void VP8StoreFilterStats(VP8EncIterator* const it);
void VP8AdjustFilterStrength(VP8EncIterator* const it);
// returns the approximate filtering strength needed to smooth a edge
// step of 'delta', given a sharpness parameter 'sharpness'.
int VP8FilterStrengthFromDelta(int sharpness, int delta);
//------------------------------------------------------------------------------
#if defined(__cplusplus) || defined(c_plusplus)