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MIN_LENGTH cleanups.

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No change in logic so no change in speed or compression.

Change-Id: I744161978c7d058c9b58450f330cba11731530c6
This commit is contained in:
Vincent Rabaud 2016-10-10 15:37:45 +02:00
parent 273d035a44
commit 11bc423ae5
1 changed files with 15 additions and 17 deletions
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32
src/enc/backward_references.c
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@ -31,8 +31,9 @@
#define WINDOW_SIZE_BITS 20 #define WINDOW_SIZE_BITS 20
#define WINDOW_SIZE ((1 << WINDOW_SIZE_BITS) - 120) #define WINDOW_SIZE ((1 << WINDOW_SIZE_BITS) - 120)
// Bounds for the match length. // Minimum number of pixels for which it is cheaper to encode a
#define MIN_LENGTH 2 // distance + length instead of each pixel as a literal.
#define MIN_LENGTH 4
// If you change this, you need MAX_LENGTH_BITS + WINDOW_SIZE_BITS <= 32 as it // If you change this, you need MAX_LENGTH_BITS + WINDOW_SIZE_BITS <= 32 as it
// is used in VP8LHashChain. // is used in VP8LHashChain.
#define MAX_LENGTH_BITS 12 #define MAX_LENGTH_BITS 12
@ -463,17 +464,16 @@ static int BackwardReferencesRle(int xsize, int ysize,
i = 1; i = 1;
while (i < pix_count) { while (i < pix_count) {
const int max_len = MaxFindCopyLength(pix_count - i); const int max_len = MaxFindCopyLength(pix_count - i);
const int kMinLength = 4;
const int rle_len = FindMatchLength(argb + i, argb + i - 1, 0, max_len); const int rle_len = FindMatchLength(argb + i, argb + i - 1, 0, max_len);
const int prev_row_len = (i < xsize) ? 0 : const int prev_row_len = (i < xsize) ? 0 :
FindMatchLength(argb + i, argb + i - xsize, 0, max_len); FindMatchLength(argb + i, argb + i - xsize, 0, max_len);
if (rle_len >= prev_row_len && rle_len >= kMinLength) { if (rle_len >= prev_row_len && rle_len >= MIN_LENGTH) {
BackwardRefsCursorAdd(refs, PixOrCopyCreateCopy(1, rle_len)); BackwardRefsCursorAdd(refs, PixOrCopyCreateCopy(1, rle_len));
// We don't need to update the color cache here since it is always the // We don't need to update the color cache here since it is always the
// same pixel being copied, and that does not change the color cache // same pixel being copied, and that does not change the color cache
// state. // state.
i += rle_len; i += rle_len;
} else if (prev_row_len >= kMinLength) { } else if (prev_row_len >= MIN_LENGTH) {
BackwardRefsCursorAdd(refs, PixOrCopyCreateCopy(xsize, prev_row_len)); BackwardRefsCursorAdd(refs, PixOrCopyCreateCopy(xsize, prev_row_len));
if (use_color_cache) { if (use_color_cache) {
for (k = 0; k < prev_row_len; ++k) { for (k = 0; k < prev_row_len; ++k) {
@ -513,7 +513,7 @@ static int BackwardReferencesLz77(int xsize, int ysize,
int len = 0; int len = 0;
int j; int j;
HashChainFindCopy(hash_chain, i, &offset, &len); HashChainFindCopy(hash_chain, i, &offset, &len);
if (len > MIN_LENGTH + 1) { if (len >= MIN_LENGTH) {
const int len_ini = len; const int len_ini = len;
int max_reach = 0; int max_reach = 0;
assert(i + len < pix_count); assert(i + len < pix_count);
@ -528,7 +528,7 @@ static int BackwardReferencesLz77(int xsize, int ysize,
for (j = i_last_check + 1; j <= i + len_ini; ++j) { for (j = i_last_check + 1; j <= i + len_ini; ++j) {
const int len_j = HashChainFindLength(hash_chain, j); const int len_j = HashChainFindLength(hash_chain, j);
const int reach = const int reach =
j + (len_j > MIN_LENGTH + 1 ? len_j : 1); // 1 for single literal. j + (len_j >= MIN_LENGTH ? len_j : 1); // 1 for single literal.
if (reach > max_reach) { if (reach > max_reach) {
len = j - i; len = j - i;
max_reach = reach; max_reach = reach;
@ -1287,7 +1287,8 @@ static int BackwardReferencesHashChainDistanceOnly(
int offset = 0, len = 0; int offset = 0, len = 0;
double prev_cost = cost_manager->costs_[i - 1]; double prev_cost = cost_manager->costs_[i - 1];
HashChainFindCopy(hash_chain, i, &offset, &len); HashChainFindCopy(hash_chain, i, &offset, &len);
if (len >= MIN_LENGTH) { if (len >= 2) {
// If we are dealing with a non-literal.
const int code = DistanceToPlaneCode(xsize, offset); const int code = DistanceToPlaneCode(xsize, offset);
const double offset_cost = GetDistanceCost(cost_model, code); const double offset_cost = GetDistanceCost(cost_model, code);
const int first_i = i; const int first_i = i;
@ -1376,20 +1377,17 @@ static int BackwardReferencesHashChainDistanceOnly(
} }
goto next_symbol; goto next_symbol;
} }
if (len > MIN_LENGTH) { if (len > 2) {
int code_min_length; // Also try the smallest interval possible (size 2).
double cost_total; double cost_total =
offset = HashChainFindOffset(hash_chain, i); prev_cost + offset_cost + GetLengthCost(cost_model, 1);
code_min_length = DistanceToPlaneCode(xsize, offset);
cost_total = prev_cost +
GetDistanceCost(cost_model, code_min_length) +
GetLengthCost(cost_model, 1);
if (cost_manager->costs_[i + 1] > cost_total) { if (cost_manager->costs_[i + 1] > cost_total) {
cost_manager->costs_[i + 1] = (float)cost_total; cost_manager->costs_[i + 1] = (float)cost_total;
dist_array[i + 1] = 2; dist_array[i + 1] = 2;
} }
} }
} else { // len < MIN_LENGTH } else {
// The pixel is added as a single literal so just update the costs.
UpdateCostPerIndex(cost_manager, i + 1); UpdateCostPerIndex(cost_manager, i + 1);
} }