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New previous coef context experiment

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Adds an experiment to derive the previous context of a coefficient
not just from the previous coefficient in the scan order but from a
combination of several neighboring coefficients previously encountered
in scan order.  A precomputed table of neighbors for each location
for each scan type and block size is used. Currently 5 neighbors are
used.

Results are about 0.2% positive using a strategy where the max coef
magnitude from the 5 neigbors is used to derive the context.

Change-Id: Ie708b54d8e1898af742846ce2d1e2b0d89fd4ad5
This commit is contained in:
Deb Mukherjee
2012-11-27 15:51:06 -08:00
parent de52948665
commit 08f0c7cc9c
8 changed files with 325 additions and 32 deletions
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26
vp9/encoder/vp9_tokenize.c
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@@ -103,6 +103,13 @@ static void fill_value_tokens() {
vp9_dct_value_tokens_ptr = dct_value_tokens + DCT_MAX_VALUE;
vp9_dct_value_cost_ptr = dct_value_cost + DCT_MAX_VALUE;
}
#if CONFIG_NEWCOEFCONTEXT
#define PT pn
#else
#define PT pt
#endif
static void tokenize_b(VP9_COMP *cpi,
MACROBLOCKD *xd,
const int ib,
@@ -123,6 +130,10 @@ static void tokenize_b(VP9_COMP *cpi,
vp9_coeff_probs *probs;
const TX_TYPE tx_type = (type == PLANE_TYPE_Y_WITH_DC) ?
get_tx_type(xd, b) : DCT_DCT;
#if CONFIG_NEWCOEFCONTEXT
const int *neighbors;
int pn;
#endif
ENTROPY_CONTEXT *const a = (ENTROPY_CONTEXT *)xd->above_context +
vp9_block2above[tx_size][ib];
@@ -229,6 +240,10 @@ static void tokenize_b(VP9_COMP *cpi,
}
VP9_COMBINEENTROPYCONTEXTS(pt, a_ec, l_ec);
#if CONFIG_NEWCOEFCONTEXT
neighbors = vp9_get_coef_neighbors_handle(scan);
pn = pt;
#endif
if (vp9_segfeature_active(xd, segment_id, SEG_LVL_EOB))
seg_eob = vp9_get_segdata(xd, segment_id, SEG_LVL_EOB);
@@ -249,14 +264,21 @@ static void tokenize_b(VP9_COMP *cpi,
}
t->Token = token;
t->context_tree = probs[type][band][pt];
t->context_tree = probs[type][band][PT];
t->skip_eob_node = (pt == 0) && ((band > 0 && type != PLANE_TYPE_Y_NO_DC) ||
(band > 1 && type == PLANE_TYPE_Y_NO_DC));
assert(vp9_coef_encodings[t->Token].Len - t->skip_eob_node > 0);
if (!dry_run) {
++counts[type][band][pt][token];
++counts[type][band][PT][token];
}
pt = vp9_prev_token_class[token];
#if CONFIG_NEWCOEFCONTEXT
if (c < seg_eob - 1 && NEWCOEFCONTEXT_BAND_COND(bands[c + 1]))
pn = vp9_get_coef_neighbor_context(
qcoeff_ptr, (type == PLANE_TYPE_Y_NO_DC), neighbors, scan[c + 1]);
else
pn = pt;
#endif
++t;
} while (c < eob && ++c < seg_eob);