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4-5% faster decoding, optimized byte loads in arithmetic decoder.

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Bits are loaded 32bits at a time (and often aligned).
Rather 64bit-friendly

Change-Id: If7f67dbe5e37696efbeb6d579d9d8482350b79ee
This commit is contained in:
Pascal Massimino
2012-01-29 17:38:37 -08:00
parent 631117ea5e
commit 01b6380656
2 changed files with 105 additions and 46 deletions
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48
src/utils/bit_reader.c
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@ -15,6 +15,8 @@
extern "C" {
#endif
#define MK(X) (((bit_t)(X) << (BITS)) | (MASK))
//------------------------------------------------------------------------------
// VP8BitReader
@ -23,11 +25,11 @@ void VP8InitBitReader(VP8BitReader* const br,
assert(br);
assert(start);
assert(start <= end);
br->range_ = 255 - 1;
br->range_ = MK(255 - 1);
br->buf_ = start;
br->buf_end_ = end;
br->value_ = 0;
br->missing_ = 8;
br->missing_ = 8; // to load the very first 8bits
br->eof_ = 0;
}
@ -43,19 +45,39 @@ const uint8_t kVP8Log2Range[128] = {
0
};
// range = ((range + 1) << kVP8Log2Range[range]) - 1
const uint8_t kVP8NewRange[128] = {
127, 127, 191, 127, 159, 191, 223, 127, 143, 159, 175, 191, 207, 223, 239,
127, 135, 143, 151, 159, 167, 175, 183, 191, 199, 207, 215, 223, 231, 239,
247, 127, 131, 135, 139, 143, 147, 151, 155, 159, 163, 167, 171, 175, 179,
183, 187, 191, 195, 199, 203, 207, 211, 215, 219, 223, 227, 231, 235, 239,
243, 247, 251, 127, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149,
151, 153, 155, 157, 159, 161, 163, 165, 167, 169, 171, 173, 175, 177, 179,
181, 183, 185, 187, 189, 191, 193, 195, 197, 199, 201, 203, 205, 207, 209,
211, 213, 215, 217, 219, 221, 223, 225, 227, 229, 231, 233, 235, 237, 239,
241, 243, 245, 247, 249, 251, 253, 127
// range = (range << kVP8Log2Range[range]) + trailing 1's
const bit_t kVP8NewRange[128] = {
MK(127), MK(127), MK(191), MK(127), MK(159), MK(191), MK(223), MK(127),
MK(143), MK(159), MK(175), MK(191), MK(207), MK(223), MK(239), MK(127),
MK(135), MK(143), MK(151), MK(159), MK(167), MK(175), MK(183), MK(191),
MK(199), MK(207), MK(215), MK(223), MK(231), MK(239), MK(247), MK(127),
MK(131), MK(135), MK(139), MK(143), MK(147), MK(151), MK(155), MK(159),
MK(163), MK(167), MK(171), MK(175), MK(179), MK(183), MK(187), MK(191),
MK(195), MK(199), MK(203), MK(207), MK(211), MK(215), MK(219), MK(223),
MK(227), MK(231), MK(235), MK(239), MK(243), MK(247), MK(251), MK(127),
MK(129), MK(131), MK(133), MK(135), MK(137), MK(139), MK(141), MK(143),
MK(145), MK(147), MK(149), MK(151), MK(153), MK(155), MK(157), MK(159),
MK(161), MK(163), MK(165), MK(167), MK(169), MK(171), MK(173), MK(175),
MK(177), MK(179), MK(181), MK(183), MK(185), MK(187), MK(189), MK(191),
MK(193), MK(195), MK(197), MK(199), MK(201), MK(203), MK(205), MK(207),
MK(209), MK(211), MK(213), MK(215), MK(217), MK(219), MK(221), MK(223),
MK(225), MK(227), MK(229), MK(231), MK(233), MK(235), MK(237), MK(239),
MK(241), MK(243), MK(245), MK(247), MK(249), MK(251), MK(253), MK(127)
};
#undef MK
void VP8LoadFinalBytes(VP8BitReader* const br) {
assert(br && br->buf_);
// Only read 8bits at a time
if (br->buf_ < br->buf_end_) {
br->value_ |= (bit_t)(*br->buf_++) << ((BITS) - 8 + br->missing_);
br->missing_ -= 8;
} else {
br->eof_ = 1;
}
}
//------------------------------------------------------------------------------
// Higher-level calls