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Speed up Huffman decoding for lossless

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speed-up is ~1.6% for photographic image to 10% for graphical image
(1000 images corpus was sped up by 5.8 %)

Code by akramarz@google.com and jyrki@google.com

Change-Id: Iceb2e50e6cc761b9315a3865d22ec9d19b8011c6
This commit is contained in:
skal
2014-08-28 08:35:19 -07:00
committed by Gerrit Code Review
parent 637b388809
commit f75dfbf23d
4 changed files with 259 additions and 393 deletions
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156
src/dec/vp8l.c
View File

@ -72,6 +72,29 @@ static const uint8_t kCodeToPlane[CODE_TO_PLANE_CODES] = {
0x40, 0x72, 0x7e, 0x61, 0x6f, 0x50, 0x71, 0x7f, 0x60, 0x70
};
// Memory needed for lookup tables of one Huffman tree group. Red, blue, alpha
// and distance alphabets are constant (256 for red, blue and alpha, 40 for
// distance) and lookup table sizes for them in worst case are 630 and 410
// respectively. Size of green alphabet depends on color cache size and is equal
// to 256 (green component values) + 24 (length prefix values)
// + color_cache_size (between 0 and 2048).
// All values computed for 8-bit first level lookup with tests/tools/enough.cc.
#define FIXED_TABLE_SIZE (630 * 3 + 410)
static const int kTableSize[12] = {
FIXED_TABLE_SIZE + 654,
FIXED_TABLE_SIZE + 656,
FIXED_TABLE_SIZE + 658,
FIXED_TABLE_SIZE + 662,
FIXED_TABLE_SIZE + 670,
FIXED_TABLE_SIZE + 686,
FIXED_TABLE_SIZE + 718,
FIXED_TABLE_SIZE + 782,
FIXED_TABLE_SIZE + 912,
FIXED_TABLE_SIZE + 1168,
FIXED_TABLE_SIZE + 1680,
FIXED_TABLE_SIZE + 2704
};
static int DecodeImageStream(int xsize, int ysize,
int is_level0,
VP8LDecoder* const dec,
@ -151,31 +174,20 @@ static WEBP_INLINE int PlaneCodeToDistance(int xsize, int plane_code) {
// Decodes the next Huffman code from bit-stream.
// FillBitWindow(br) needs to be called at minimum every second call
// to ReadSymbol, in order to pre-fetch enough bits.
static WEBP_INLINE int ReadSymbol(const HuffmanTree* tree,
static WEBP_INLINE int ReadSymbol(const HuffmanCode* table,
VP8LBitReader* const br) {
const HuffmanTreeNode* node = tree->root_;
uint32_t bits = VP8LPrefetchBits(br);
int bitpos = br->bit_pos_;
// Check if we find the bit combination from the Huffman lookup table.
const int lut_ix = bits & (HUFF_LUT - 1);
const int lut_bits = tree->lut_bits_[lut_ix];
if (lut_bits <= HUFF_LUT_BITS) {
VP8LSetBitPos(br, bitpos + lut_bits);
return tree->lut_symbol_[lut_ix];
int nbits;
uint32_t val = VP8LPrefetchBits(br);
table += val & HUFFMAN_TABLE_MASK;
nbits = table->bits - HUFFMAN_TABLE_BITS;
if (nbits > 0) {
VP8LSetBitPos(br, br->bit_pos_ + HUFFMAN_TABLE_BITS);
val = VP8LPrefetchBits(br);
table += table->value;
table += val & ((1 << nbits) - 1);
}
node += tree->lut_jump_[lut_ix];
bitpos += HUFF_LUT_BITS;
bits >>= HUFF_LUT_BITS;
// Decode the value from a binary tree.
assert(node != NULL);
do {
node = HuffmanTreeNextNode(node, bits & 1);
bits >>= 1;
++bitpos;
} while (HuffmanTreeNodeIsNotLeaf(node));
VP8LSetBitPos(br, bitpos);
return node->symbol_;
VP8LSetBitPos(br, br->bit_pos_ + table->bits);
return table->value;
}
static int ReadHuffmanCodeLengths(
@ -186,11 +198,11 @@ static int ReadHuffmanCodeLengths(
int symbol;
int max_symbol;
int prev_code_len = DEFAULT_CODE_LENGTH;
HuffmanTree tree;
int huff_codes[NUM_CODE_LENGTH_CODES] = { 0 };
HuffmanCode table[1 << LENGTHS_TABLE_BITS];
if (!VP8LHuffmanTreeBuildImplicit(&tree, code_length_code_lengths,
huff_codes, NUM_CODE_LENGTH_CODES)) {
if (!VP8LBuildHuffmanTable(table, LENGTHS_TABLE_BITS,
code_length_code_lengths,
NUM_CODE_LENGTH_CODES)) {
dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
return 0;
}
@ -208,10 +220,13 @@ static int ReadHuffmanCodeLengths(
symbol = 0;
while (symbol < num_symbols) {
const HuffmanCode* p = table;
int code_len;
if (max_symbol-- == 0) break;
VP8LFillBitWindow(br);
code_len = ReadSymbol(&tree, br);
p += VP8LPrefetchBits(br) & LENGTHS_TABLE_MASK;
VP8LSetBitPos(br, br->bit_pos_ + p->bits);
code_len = p->value;
if (code_len < kCodeLengthLiterals) {
code_lengths[symbol++] = code_len;
if (code_len != 0) prev_code_len = code_len;
@ -233,36 +248,31 @@ static int ReadHuffmanCodeLengths(
ok = 1;
End:
VP8LHuffmanTreeFree(&tree);
return ok;
}
// 'code_lengths' is pre-allocated temporary buffer, used for creating Huffman
// tree.
static int ReadHuffmanCode(int alphabet_size, VP8LDecoder* const dec,
int* const code_lengths, int* const huff_codes,
HuffmanTree* const tree) {
int* const code_lengths, HuffmanCode* const table) {
int ok = 0;
VP8LBitReader* const br = &dec->br_;
const int simple_code = VP8LReadBits(br, 1);
memset(code_lengths, 0, alphabet_size * sizeof(*code_lengths));
if (simple_code) { // Read symbols, codes & code lengths directly.
int symbols[2];
int codes[2];
const int num_symbols = VP8LReadBits(br, 1) + 1;
const int first_symbol_len_code = VP8LReadBits(br, 1);
// The first code is either 1 bit or 8 bit code.
symbols[0] = VP8LReadBits(br, (first_symbol_len_code == 0) ? 1 : 8);
codes[0] = 0;
code_lengths[0] = num_symbols - 1;
int symbol = VP8LReadBits(br, (first_symbol_len_code == 0) ? 1 : 8);
code_lengths[symbol] = 1;
// The second code (if present), is always 8 bit long.
if (num_symbols == 2) {
symbols[1] = VP8LReadBits(br, 8);
codes[1] = 1;
code_lengths[1] = num_symbols - 1;
symbol = VP8LReadBits(br, 8);
code_lengths[symbol] = 1;
}
ok = VP8LHuffmanTreeBuildExplicit(tree, code_lengths, codes, symbols,
alphabet_size, num_symbols);
ok = 1;
} else { // Decode Huffman-coded code lengths.
int i;
int code_length_code_lengths[NUM_CODE_LENGTH_CODES] = { 0 };
@ -272,22 +282,20 @@ static int ReadHuffmanCode(int alphabet_size, VP8LDecoder* const dec,
return 0;
}
memset(code_lengths, 0, alphabet_size * sizeof(*code_lengths));
for (i = 0; i < num_codes; ++i) {
code_length_code_lengths[kCodeLengthCodeOrder[i]] = VP8LReadBits(br, 3);
}
ok = ReadHuffmanCodeLengths(dec, code_length_code_lengths, alphabet_size,
code_lengths);
ok = ok && VP8LHuffmanTreeBuildImplicit(tree, code_lengths, huff_codes,
alphabet_size);
}
ok = ok && !br->error_;
if (!ok) {
dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
return 0;
}
return 1;
return VP8LBuildHuffmanTable(table, HUFFMAN_TABLE_BITS,
code_lengths, alphabet_size);
}
static int ReadHuffmanCodes(VP8LDecoder* const dec, int xsize, int ysize,
@ -297,10 +305,12 @@ static int ReadHuffmanCodes(VP8LDecoder* const dec, int xsize, int ysize,
VP8LMetadata* const hdr = &dec->hdr_;
uint32_t* huffman_image = NULL;
HTreeGroup* htree_groups = NULL;
HuffmanCode* huffman_tables = NULL;
HuffmanCode* next = NULL;
int num_htree_groups = 1;
int max_alphabet_size = 0;
int* code_lengths = NULL;
int* huff_codes = NULL;
const int table_size = kTableSize[color_cache_bits];
if (allow_recursion && VP8LReadBits(br, 1)) {
// use meta Huffman codes.
@ -337,45 +347,48 @@ static int ReadHuffmanCodes(VP8LDecoder* const dec, int xsize, int ysize,
}
}
huffman_tables = (HuffmanCode*)WebPSafeMalloc(num_htree_groups * table_size,
sizeof(HuffmanCode));
htree_groups = VP8LHtreeGroupsNew(num_htree_groups);
code_lengths =
(int*)WebPSafeCalloc((uint64_t)max_alphabet_size, sizeof(*code_lengths));
huff_codes =
(int*)WebPSafeMalloc((uint64_t)max_alphabet_size, sizeof(*huff_codes));
code_lengths = (int*)WebPSafeCalloc((uint64_t)max_alphabet_size,
sizeof(*code_lengths));
if (htree_groups == NULL || code_lengths == NULL || huff_codes == NULL) {
if (htree_groups == NULL || code_lengths == NULL || huffman_tables == NULL) {
dec->status_ = VP8_STATUS_OUT_OF_MEMORY;
goto Error;
}
next = huffman_tables;
for (i = 0; i < num_htree_groups; ++i) {
HuffmanTree* const htrees = htree_groups[i].htrees_;
HuffmanCode** const htrees = htree_groups[i].htrees;
int size;
for (j = 0; j < HUFFMAN_CODES_PER_META_CODE; ++j) {
int alphabet_size = kAlphabetSize[j];
HuffmanTree* const htree = htrees + j;
htrees[j] = next;
if (j == 0 && color_cache_bits > 0) {
alphabet_size += 1 << color_cache_bits;
}
if (!ReadHuffmanCode(alphabet_size, dec, code_lengths, huff_codes,
htree)) {
size = ReadHuffmanCode(alphabet_size, dec, code_lengths, next);
next += size;
if (size == 0) {
goto Error;
}
}
}
WebPSafeFree(huff_codes);
WebPSafeFree(code_lengths);
// All OK. Finalize pointers and return.
hdr->huffman_image_ = huffman_image;
hdr->num_htree_groups_ = num_htree_groups;
hdr->htree_groups_ = htree_groups;
hdr->huffman_tables_ = huffman_tables;
return 1;
Error:
WebPSafeFree(huff_codes);
WebPSafeFree(code_lengths);
WebPSafeFree(huffman_image);
VP8LHtreeGroupsFree(htree_groups, num_htree_groups);
WebPSafeFree(huffman_tables);
VP8LHtreeGroupsFree(htree_groups);
return 0;
}
@ -715,10 +728,10 @@ static int Is8bOptimizable(const VP8LMetadata* const hdr) {
// When the Huffman tree contains only one symbol, we can skip the
// call to ReadSymbol() for red/blue/alpha channels.
for (i = 0; i < hdr->num_htree_groups_; ++i) {
const HuffmanTree* const htrees = hdr->htree_groups_[i].htrees_;
if (htrees[RED].num_nodes_ > 1) return 0;
if (htrees[BLUE].num_nodes_ > 1) return 0;
if (htrees[ALPHA].num_nodes_ > 1) return 0;
HuffmanCode** const htrees = hdr->htree_groups_[i].htrees;
if (htrees[RED][0].bits > 0) return 0;
if (htrees[BLUE][0].bits > 0) return 0;
if (htrees[ALPHA][0].bits > 0) return 0;
}
return 1;
}
@ -758,7 +771,7 @@ static int DecodeAlphaData(VP8LDecoder* const dec, uint8_t* const data,
htree_group = GetHtreeGroupForPos(hdr, col, row);
}
VP8LFillBitWindow(br);
code = ReadSymbol(&htree_group->htrees_[GREEN], br);
code = ReadSymbol(htree_group->htrees[GREEN], br);
if (code < NUM_LITERAL_CODES) { // Literal
data[pos] = code;
++pos;
@ -774,7 +787,7 @@ static int DecodeAlphaData(VP8LDecoder* const dec, uint8_t* const data,
int dist_code, dist;
const int length_sym = code - NUM_LITERAL_CODES;
const int length = GetCopyLength(length_sym, br);
const int dist_symbol = ReadSymbol(&htree_group->htrees_[DIST], br);
const int dist_symbol = ReadSymbol(htree_group->htrees[DIST], br);
VP8LFillBitWindow(br);
dist_code = GetCopyDistance(dist_symbol, br);
dist = PlaneCodeToDistance(width, dist_code);
@ -850,14 +863,14 @@ static int DecodeImageData(VP8LDecoder* const dec, uint32_t* const data,
htree_group = GetHtreeGroupForPos(hdr, col, row);
}
VP8LFillBitWindow(br);
code = ReadSymbol(&htree_group->htrees_[GREEN], br);
code = ReadSymbol(htree_group->htrees[GREEN], br);
if (code < NUM_LITERAL_CODES) { // Literal
int red, green, blue, alpha;
red = ReadSymbol(&htree_group->htrees_[RED], br);
red = ReadSymbol(htree_group->htrees[RED], br);
green = code;
VP8LFillBitWindow(br);
blue = ReadSymbol(&htree_group->htrees_[BLUE], br);
alpha = ReadSymbol(&htree_group->htrees_[ALPHA], br);
blue = ReadSymbol(htree_group->htrees[BLUE], br);
alpha = ReadSymbol(htree_group->htrees[ALPHA], br);
*src = ((uint32_t)alpha << 24) | (red << 16) | (green << 8) | blue;
AdvanceByOne:
++src;
@ -878,7 +891,7 @@ static int DecodeImageData(VP8LDecoder* const dec, uint32_t* const data,
int dist_code, dist;
const int length_sym = code - NUM_LITERAL_CODES;
const int length = GetCopyLength(length_sym, br);
const int dist_symbol = ReadSymbol(&htree_group->htrees_[DIST], br);
const int dist_symbol = ReadSymbol(htree_group->htrees[DIST], br);
VP8LFillBitWindow(br);
dist_code = GetCopyDistance(dist_symbol, br);
dist = PlaneCodeToDistance(width, dist_code);
@ -1035,7 +1048,8 @@ static void ClearMetadata(VP8LMetadata* const hdr) {
assert(hdr);
WebPSafeFree(hdr->huffman_image_);
VP8LHtreeGroupsFree(hdr->htree_groups_, hdr->num_htree_groups_);
WebPSafeFree(hdr->huffman_tables_);
VP8LHtreeGroupsFree(hdr->htree_groups_);
VP8LColorCacheClear(&hdr->color_cache_);
InitMetadata(hdr);
}

1
src/dec/vp8li.h
View File

@ -50,6 +50,7 @@ typedef struct {
uint32_t *huffman_image_;
int num_htree_groups_;
HTreeGroup *htree_groups_;
HuffmanCode *huffman_tables_;
} VP8LMetadata;
typedef struct VP8LDecoder VP8LDecoder;