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lossless: bit writer optimization

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valgrind --tool=callgrind shows a 9 % speedup: 1021201984 ticks before vs.
927917709 after

-q 0 -m 0 -lossless ~/alpi/1.png
22.040 MP/s before
24.796 MP/s after

Change-Id: Iaab928167b3e20fb0d9401c6f8317a26c5a610b4
This commit is contained in:
Jyrki Alakuijala 2015-06-29 14:21:10 +00:00 committed by James Zern
parent d97b9ff755
commit f3a7a5bf76
2 changed files with 39 additions and 5 deletions
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23
src/utils/bit_writer.c
View File

@ -250,12 +250,28 @@ void VP8LBitWriterWipeOut(VP8LBitWriter* const bw) {
}
}
void VP8LPutBits(VP8LBitWriter* const bw, uint32_t bits, int n_bits) {
void VP8LPutBitsFlushBits(VP8LBitWriter* const bw) {
// If needed, make some room by flushing some bits out.
if (bw->cur_ + VP8L_WRITER_BYTES > bw->end_) {
const uint64_t extra_size = (bw->end_ - bw->buf_) + MIN_EXTRA_SIZE;
if (extra_size != (size_t)extra_size ||
!VP8LBitWriterResize(bw, (size_t)extra_size)) {
bw->cur_ = bw->buf_;
bw->error_ = 1;
return;
}
}
*(vp8l_wtype_t*)bw->cur_ = (vp8l_wtype_t)WSWAP((vp8l_wtype_t)bw->bits_);
bw->cur_ += VP8L_WRITER_BYTES;
bw->bits_ >>= VP8L_WRITER_BITS;
bw->used_ -= VP8L_WRITER_BITS;
}
void VP8LPutBitsInternal(VP8LBitWriter* const bw, uint32_t bits, int n_bits) {
assert(n_bits <= 32);
// That's the max we can handle:
assert(bw->used_ + n_bits <= 2 * VP8L_WRITER_MAX_BITS);
assert(sizeof(vp8l_wtype_t) == 2);
if (n_bits > 0) {
// Local field copy.
vp8l_atype_t lbits = bw->bits_;
int used = bw->used_;
// Special case of overflow handling for 32bit accumulator (2-steps flush).
@ -286,7 +302,6 @@ void VP8LPutBits(VP8LBitWriter* const bw, uint32_t bits, int n_bits) {
lbits >>= VP8L_WRITER_BITS;
used -= VP8L_WRITER_BITS;
}
// Eventually, insert new bits.
bw->bits_ = lbits | ((vp8l_atype_t)bits << used);
bw->used_ = used + n_bits;
}

21
src/utils/bit_writer.h
View File

@ -104,12 +104,31 @@ uint8_t* VP8LBitWriterFinish(VP8LBitWriter* const bw);
// Release any pending memory and zeroes the object.
void VP8LBitWriterWipeOut(VP8LBitWriter* const bw);
// Internal function for VP8LPutBits flushing 32 bits from the written state.
void VP8LPutBitsFlushBits(VP8LBitWriter* const bw);
// PutBits internal function used in the 16 bit vp8l_wtype_t case.
void VP8LPutBitsInternal(VP8LBitWriter* const bw, uint32_t bits, int n_bits);
// This function writes bits into bytes in increasing addresses (little endian),
// and within a byte least-significant-bit first.
// This function can write up to 32 bits in one go, but VP8LBitReader can only
// read 24 bits max (VP8L_MAX_NUM_BIT_READ).
// VP8LBitWriter's error_ flag is set in case of memory allocation error.
void VP8LPutBits(VP8LBitWriter* const bw, uint32_t bits, int n_bits);
static WEBP_INLINE void VP8LPutBits(VP8LBitWriter* const bw,
uint32_t bits, int n_bits) {
if (sizeof(vp8l_wtype_t) == 4) {
if (n_bits > 0) {
if (bw->used_ >= 32) {
VP8LPutBitsFlushBits(bw);
}
bw->bits_ |= (vp8l_atype_t)bits << bw->used_;
bw->used_ += n_bits;
}
} else {
VP8LPutBitsInternal(bw, bits, n_bits);
}
}
//------------------------------------------------------------------------------