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clean-up around Huffman-encode

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* refine doc
* use LUT for bit-reversal
* added assert
* Introduce HuffmanTreeToken instead of separate code/extra_bits arrays

Change-Id: I0fe0b50b55eb43a4be9f730b1abe40632a6fa7f0
This commit is contained in:
Pascal Massimino
2012-05-10 09:11:47 -07:00
parent c579a71012
commit 9f566d1d36
3 changed files with 134 additions and 142 deletions
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50
src/enc/vp8l.c
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@ -387,25 +387,25 @@ static void StoreHuffmanTreeOfHuffmanTreeToBitMask(
static void StoreHuffmanTreeToBitMask(
VP8LBitWriter* const bw,
const uint8_t* huffman_tree,
const uint8_t* huffman_tree_extra_bits,
const int num_symbols,
const HuffmanTreeToken* const tokens,
const int num_tokens,
const uint8_t* code_length_bitdepth,
const uint16_t* code_length_bitdepth_symbols) {
int i;
for (i = 0; i < num_symbols; ++i) {
const int ix = huffman_tree[i];
for (i = 0; i < num_tokens; ++i) {
const int ix = tokens[i].code;
const int extra_bits = tokens[i].extra_bits;
VP8LWriteBits(bw, code_length_bitdepth[ix],
code_length_bitdepth_symbols[ix]);
switch (ix) {
case 16:
VP8LWriteBits(bw, 2, huffman_tree_extra_bits[i]);
VP8LWriteBits(bw, 2, extra_bits);
break;
case 17:
VP8LWriteBits(bw, 3, huffman_tree_extra_bits[i]);
VP8LWriteBits(bw, 3, extra_bits);
break;
case 18:
VP8LWriteBits(bw, 7, huffman_tree_extra_bits[i]);
VP8LWriteBits(bw, 7, extra_bits);
break;
}
}
@ -415,27 +415,21 @@ static int StoreFullHuffmanCode(VP8LBitWriter* const bw,
const uint8_t* const bit_lengths,
int bit_lengths_size) {
int ok = 0;
int huffman_tree_size = 0;
uint8_t code_length_bitdepth[CODE_LENGTH_CODES] = { 0 };
uint16_t code_length_bitdepth_symbols[CODE_LENGTH_CODES] = { 0 };
uint8_t* huffman_tree_extra_bits;
uint8_t* const huffman_tree =
(uint8_t*)malloc(bit_lengths_size * sizeof(*huffman_tree) +
bit_lengths_size * sizeof(*huffman_tree_extra_bits));
if (huffman_tree == NULL) return 0;
huffman_tree_extra_bits =
huffman_tree + bit_lengths_size * sizeof(*huffman_tree);
int num_tokens;
HuffmanTreeToken* const tokens =
(HuffmanTreeToken*)malloc(bit_lengths_size * sizeof(*tokens));
if (tokens == NULL) return 0;
VP8LWriteBits(bw, 1, 0);
VP8LCreateCompressedHuffmanTree(bit_lengths, bit_lengths_size,
&huffman_tree_size, huffman_tree,
huffman_tree_extra_bits);
num_tokens = VP8LCreateCompressedHuffmanTree(bit_lengths, bit_lengths_size,
tokens, bit_lengths_size);
{
int histogram[CODE_LENGTH_CODES] = { 0 };
int i;
for (i = 0; i < huffman_tree_size; ++i) {
++histogram[huffman_tree[i]];
for (i = 0; i < num_tokens; ++i) {
++histogram[tokens[i].code];
}
if (!VP8LCreateHuffmanTree(histogram, CODE_LENGTH_CODES,
@ -451,12 +445,12 @@ static int StoreFullHuffmanCode(VP8LBitWriter* const bw,
code_length_bitdepth_symbols);
{
int trailing_zero_bits = 0;
int trimmed_length = huffman_tree_size;
int trimmed_length = num_tokens;
int write_trimmed_length;
int length;
int i = huffman_tree_size;
int i = num_tokens;
while (i-- > 0) {
const int ix = huffman_tree[i];
const int ix = tokens[i].code;
if (ix == 0 || ix == 17 || ix == 18) {
--trimmed_length; // discount trailing zeros
trailing_zero_bits += code_length_bitdepth[ix];
@ -470,7 +464,7 @@ static int StoreFullHuffmanCode(VP8LBitWriter* const bw,
}
}
write_trimmed_length = (trimmed_length > 1 && trailing_zero_bits > 12);
length = write_trimmed_length ? trimmed_length : huffman_tree_size;
length = write_trimmed_length ? trimmed_length : num_tokens;
VP8LWriteBits(bw, 1, write_trimmed_length);
if (write_trimmed_length) {
const int nbits = VP8LBitsLog2Ceiling(trimmed_length - 1);
@ -478,13 +472,13 @@ static int StoreFullHuffmanCode(VP8LBitWriter* const bw,
VP8LWriteBits(bw, 3, nbitpairs - 1);
VP8LWriteBits(bw, nbitpairs * 2, trimmed_length - 2);
}
StoreHuffmanTreeToBitMask(bw, huffman_tree, huffman_tree_extra_bits,
StoreHuffmanTreeToBitMask(bw, tokens,
length, code_length_bitdepth,
code_length_bitdepth_symbols);
}
ok = 1;
End:
free(huffman_tree);
free(tokens);
return ok;
}