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split StoreHuffmanCode() into smaller functions
Change-Id: Iaa715f4997505eebabee1e92e964a5d7ee6f3e7d
This commit is contained in:
Pascal Massimino
James Zern
parent
d0d88990d8
commit
e8d3d6a018
172
src/enc/vp8l.c
172
src/enc/vp8l.c
@ -432,8 +432,10 @@ static void ClearHuffmanTreeIfOnlyOneSymbol(const int num_symbols,
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int k;
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int count = 0;
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for (k = 0; k < num_symbols; ++k) {
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if (lengths[k] != 0) ++count;
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if (count > 1) return;
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if (lengths[k] != 0) {
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++count;
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if (count > 1) return;
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}
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}
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for (k = 0; k < num_symbols; ++k) {
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lengths[k] = 0;
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@ -490,34 +492,105 @@ static void StoreHuffmanTreeToBitMask(
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}
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}
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static int StoreFullHuffmanCode(VP8LBitWriter* const bw,
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const uint8_t* const bit_lengths,
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int bit_lengths_size) {
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int ok = 0;
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int huffman_tree_size = 0;
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uint8_t code_length_bitdepth[CODE_LENGTH_CODES] = { 0 };
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uint16_t code_length_bitdepth_symbols[CODE_LENGTH_CODES] = { 0 };
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uint8_t* huffman_tree_extra_bits;
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uint8_t* const huffman_tree =
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(uint8_t*)malloc(bit_lengths_size * sizeof(*huffman_tree) +
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bit_lengths_size * sizeof(*huffman_tree_extra_bits));
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if (huffman_tree == NULL) return 0;
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huffman_tree_extra_bits =
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huffman_tree + bit_lengths_size * sizeof(*huffman_tree);
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VP8LWriteBits(bw, 1, 0);
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VP8LCreateCompressedHuffmanTree(bit_lengths, bit_lengths_size,
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&huffman_tree_size, huffman_tree,
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huffman_tree_extra_bits);
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{
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int histogram[CODE_LENGTH_CODES] = { 0 };
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int i;
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for (i = 0; i < huffman_tree_size; ++i) {
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++histogram[huffman_tree[i]];
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}
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if (!VP8LCreateHuffmanTree(histogram, CODE_LENGTH_CODES,
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7, code_length_bitdepth)) {
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goto End;
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}
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}
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VP8LConvertBitDepthsToSymbols(code_length_bitdepth, CODE_LENGTH_CODES,
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code_length_bitdepth_symbols);
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StoreHuffmanTreeOfHuffmanTreeToBitMask(bw, code_length_bitdepth);
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ClearHuffmanTreeIfOnlyOneSymbol(CODE_LENGTH_CODES,
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code_length_bitdepth,
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code_length_bitdepth_symbols);
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{
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int trailing_zero_bits = 0;
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int trimmed_length = huffman_tree_size;
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int write_trimmed_length;
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int length;
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int i = huffman_tree_size;
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while (i-- > 0) {
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const int ix = huffman_tree[i];
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if (ix == 0 || ix == 17 || ix == 18) {
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--trimmed_length; // discount trailing zeros
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trailing_zero_bits += code_length_bitdepth[ix];
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if (ix == 17) {
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trailing_zero_bits += 3;
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} else if (ix == 18) {
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trailing_zero_bits += 7;
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}
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} else {
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break;
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}
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}
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write_trimmed_length = (trimmed_length > 1 && trailing_zero_bits > 12);
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length = write_trimmed_length ? trimmed_length : huffman_tree_size;
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VP8LWriteBits(bw, 1, write_trimmed_length);
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if (write_trimmed_length) {
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const int nbits = VP8LBitsLog2Ceiling(trimmed_length - 1);
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const int nbitpairs = (nbits == 0) ? 1 : (nbits + 1) / 2;
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VP8LWriteBits(bw, 3, nbitpairs - 1);
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VP8LWriteBits(bw, nbitpairs * 2, trimmed_length - 2);
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}
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StoreHuffmanTreeToBitMask(bw, huffman_tree, huffman_tree_extra_bits,
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length, code_length_bitdepth,
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code_length_bitdepth_symbols);
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}
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ok = 1;
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End:
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free(huffman_tree);
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return ok;
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}
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static int StoreHuffmanCode(VP8LBitWriter* const bw,
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const uint8_t* const bit_lengths,
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int bit_lengths_size) {
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int i;
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int ok = 0;
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int count = 0;
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int symbols[2] = { 0, 0 };
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int huffman_tree_size = 0;
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uint8_t code_length_bitdepth[CODE_LENGTH_CODES];
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uint16_t code_length_bitdepth_symbols[CODE_LENGTH_CODES];
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int huffman_tree_histogram[CODE_LENGTH_CODES];
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uint8_t* huffman_tree_extra_bits;
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uint8_t* huffman_tree = (uint8_t*)malloc(bit_lengths_size *
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(sizeof(*huffman_tree) +
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sizeof(*huffman_tree_extra_bits)));
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const int kMaxBits = 8;
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const int kMaxSymbol = 1 << kMaxBits;
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if (huffman_tree == NULL) goto End;
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huffman_tree_extra_bits =
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huffman_tree + (bit_lengths_size * sizeof(*huffman_tree));
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for (i = 0; i < bit_lengths_size; ++i) {
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// Check whether it's a small tree.
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for (i = 0; i < bit_lengths_size && count < 3; ++i) {
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if (bit_lengths[i] != 0) {
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if (count < 2) symbols[count] = i;
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++count;
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}
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}
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if (count == 0) count = 1;
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if (count <= 2 && symbols[0] < 256 && symbols[1] < 256) {
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if (count == 0) { // emit minimal tree for empty cases
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// bits: small tree marker: 1, count-1: 0, large 8-bit code: 0, code: 0
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VP8LWriteBits(bw, 4, 0x01);
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return 1;
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} else if (count <= 2 && symbols[0] < kMaxSymbol && symbols[1] < kMaxSymbol) {
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VP8LWriteBits(bw, 1, 1); // Small tree marker to encode 1 or 2 symbols.
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VP8LWriteBits(bw, 1, count - 1);
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if (symbols[0] <= 1) {
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@ -530,67 +603,10 @@ static int StoreHuffmanCode(VP8LBitWriter* const bw,
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if (count == 2) {
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VP8LWriteBits(bw, 8, symbols[1]);
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}
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ok = 1;
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goto End;
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return 1;
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} else {
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return StoreFullHuffmanCode(bw, bit_lengths, bit_lengths_size);
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}
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VP8LWriteBits(bw, 1, 0);
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VP8LCreateCompressedHuffmanTree(bit_lengths, bit_lengths_size,
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&huffman_tree_size, huffman_tree,
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huffman_tree_extra_bits);
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memset(huffman_tree_histogram, 0, sizeof(huffman_tree_histogram));
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for (i = 0; i < huffman_tree_size; ++i) {
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++huffman_tree_histogram[huffman_tree[i]];
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}
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memset(code_length_bitdepth, 0, sizeof(code_length_bitdepth));
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memset(code_length_bitdepth_symbols, 0, sizeof(code_length_bitdepth_symbols));
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if (!VP8LCreateHuffmanTree(huffman_tree_histogram, CODE_LENGTH_CODES,
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7, code_length_bitdepth)) {
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goto End;
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}
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VP8LConvertBitDepthsToSymbols(code_length_bitdepth, CODE_LENGTH_CODES,
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code_length_bitdepth_symbols);
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StoreHuffmanTreeOfHuffmanTreeToBitMask(bw, code_length_bitdepth);
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ClearHuffmanTreeIfOnlyOneSymbol(CODE_LENGTH_CODES,
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code_length_bitdepth,
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code_length_bitdepth_symbols);
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{
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int num_trailing_zeros = 0;
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int trailing_zero_bits = 0;
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int trimmed_length;
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int write_length;
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int length;
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for (i = huffman_tree_size; i > 0; --i) {
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int ix = huffman_tree[i - 1];
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if (ix == 0 || ix == 17 || ix == 18) {
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++num_trailing_zeros;
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trailing_zero_bits += code_length_bitdepth[ix];
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if (ix == 17) trailing_zero_bits += 3;
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if (ix == 18) trailing_zero_bits += 7;
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} else {
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break;
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}
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}
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trimmed_length = huffman_tree_size - num_trailing_zeros;
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write_length = (trimmed_length > 1 && trailing_zero_bits > 12);
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length = write_length ? trimmed_length : huffman_tree_size;
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VP8LWriteBits(bw, 1, write_length);
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if (write_length) {
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const int nbits = VP8LBitsLog2Ceiling(trimmed_length - 1);
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const int nbitpairs = nbits == 0 ? 1 : (nbits + 1) / 2;
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VP8LWriteBits(bw, 3, nbitpairs - 1);
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VP8LWriteBits(bw, nbitpairs * 2, trimmed_length - 2);
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}
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StoreHuffmanTreeToBitMask(bw, huffman_tree, huffman_tree_extra_bits,
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length, code_length_bitdepth,
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code_length_bitdepth_symbols);
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}
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ok = 1;
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End:
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free(huffman_tree);
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return ok;
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}
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static void StoreImageToBitMask(
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