Merge pull request #850 from trav90/add-av1-support

Add initial support for AV1 video.

1 files changed, 229 insertions, 0 deletions

diff --git a/third_party/aom/aom_dsp/entdec.c b/third_party/aom/aom_dsp/entdec.c
new file mode 100644
index 000000000..d1764c47b
--- /dev/null
+++ b/third_party/aom/aom_dsp/entdec.c
@@ -0,0 +1,229 @@
+/*
+ * Copyright (c) 2001-2016, Alliance for Open Media. All rights reserved
+ *
+ * This source code is subject to the terms of the BSD 2 Clause License and
+ * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
+ * was not distributed with this source code in the LICENSE file, you can
+ * obtain it at www.aomedia.org/license/software. If the Alliance for Open
+ * Media Patent License 1.0 was not distributed with this source code in the
+ * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
+ */
+
+#include <assert.h>
+#include "aom_dsp/entdec.h"
+#include "aom_dsp/prob.h"
+
+/*A range decoder.
+  This is an entropy decoder based upon \cite{Mar79}, which is itself a
+   rediscovery of the FIFO arithmetic code introduced by \cite{Pas76}.
+  It is very similar to arithmetic encoding, except that encoding is done with
+   digits in any base, instead of with bits, and so it is faster when using
+   larger bases (i.e.: a byte).
+  The author claims an average waste of $\frac{1}{2}\log_b(2b)$ bits, where $b$
+   is the base, longer than the theoretical optimum, but to my knowledge there
+   is no published justification for this claim.
+  This only seems true when using near-infinite precision arithmetic so that
+   the process is carried out with no rounding errors.
+
+  An excellent description of implementation details is available at
+   http://www.arturocampos.com/ac_range.html
+  A recent work \cite{MNW98} which proposes several changes to arithmetic
+   encoding for efficiency actually re-discovers many of the principles
+   behind range encoding, and presents a good theoretical analysis of them.
+
+  End of stream is handled by writing out the smallest number of bits that
+   ensures that the stream will be correctly decoded regardless of the value of
+   any subsequent bits.
+  od_ec_dec_tell() can be used to determine how many bits were needed to decode
+   all the symbols thus far; other data can be packed in the remaining bits of
+   the input buffer.
+  @PHDTHESIS{Pas76,
+    author="Richard Clark Pasco",
+    title="Source coding algorithms for fast data compression",
+    school="Dept. of Electrical Engineering, Stanford University",
+    address="Stanford, CA",
+    month=May,
+    year=1976,
+    URL="http://www.richpasco.org/scaffdc.pdf"
+  }
+  @INPROCEEDINGS{Mar79,
+   author="Martin, G.N.N.",
+   title="Range encoding: an algorithm for removing redundancy from a digitised
+    message",
+   booktitle="Video & Data Recording Conference",
+   year=1979,
+   address="Southampton",
+   month=Jul,
+   URL="http://www.compressconsult.com/rangecoder/rngcod.pdf.gz"
+  }
+  @ARTICLE{MNW98,
+   author="Alistair Moffat and Radford Neal and Ian H. Witten",
+   title="Arithmetic Coding Revisited",
+   journal="{ACM} Transactions on Information Systems",
+   year=1998,
+   volume=16,
+   number=3,
+   pages="256--294",
+   month=Jul,
+   URL="http://researchcommons.waikato.ac.nz/bitstream/handle/10289/78/content.pdf"
+  }*/
+
+/*This is meant to be a large, positive constant that can still be efficiently
+   loaded as an immediate (on platforms like ARM, for example).
+  Even relatively modest values like 100 would work fine.*/
+#define OD_EC_LOTS_OF_BITS (0x4000)
+
+/*The return value of od_ec_dec_tell does not change across an od_ec_dec_refill
+   call.*/
+static void od_ec_dec_refill(od_ec_dec *dec) {
+  int s;
+  od_ec_window dif;
+  int16_t cnt;
+  const unsigned char *bptr;
+  const unsigned char *end;
+  dif = dec->dif;
+  cnt = dec->cnt;
+  bptr = dec->bptr;
+  end = dec->end;
+  s = OD_EC_WINDOW_SIZE - 9 - (cnt + 15);
+  for (; s >= 0 && bptr < end; s -= 8, bptr++) {
+    assert(s <= OD_EC_WINDOW_SIZE - 8);
+    dif ^= (od_ec_window)bptr[0] << s;
+    cnt += 8;
+  }
+  if (bptr >= end) {
+    dec->tell_offs += OD_EC_LOTS_OF_BITS - cnt;
+    cnt = OD_EC_LOTS_OF_BITS;
+  }
+  dec->dif = dif;
+  dec->cnt = cnt;
+  dec->bptr = bptr;
+}
+
+/*Takes updated dif and range values, renormalizes them so that
+   32768 <= rng < 65536 (reading more bytes from the stream into dif if
+   necessary), and stores them back in the decoder context.
+  dif: The new value of dif.
+  rng: The new value of the range.
+  ret: The value to return.
+  Return: ret.
+          This allows the compiler to jump to this function via a tail-call.*/
+static int od_ec_dec_normalize(od_ec_dec *dec, od_ec_window dif, unsigned rng,
+                               int ret) {
+  int d;
+  assert(rng <= 65535U);
+  // The number of leading zeros in the 16-bit binary representation of rng.
+  d = 16 - OD_ILOG_NZ(rng);
+  dec->cnt -= d;
+  /*This is equivalent to shifting in 1's instead of 0's.*/
+  dec->dif = ((dif + 1) << d) - 1;
+  dec->rng = rng << d;
+  if (dec->cnt < 0) od_ec_dec_refill(dec);
+  return ret;
+}
+
+/*Initializes the decoder.
+  buf: The input buffer to use.
+  Return: 0 on success, or a negative value on error.*/
+void od_ec_dec_init(od_ec_dec *dec, const unsigned char *buf,
+                    uint32_t storage) {
+  dec->buf = buf;
+  dec->tell_offs = 10 - (OD_EC_WINDOW_SIZE - 8);
+  dec->end = buf + storage;
+  dec->bptr = buf;
+  dec->dif = ((od_ec_window)1 << (OD_EC_WINDOW_SIZE - 1)) - 1;
+  dec->rng = 0x8000;
+  dec->cnt = -15;
+  dec->error = 0;
+  od_ec_dec_refill(dec);
+}
+
+/*Decode a single binary value.
+  f: The probability that the bit is one, scaled by 32768.
+  Return: The value decoded (0 or 1).*/
+int od_ec_decode_bool_q15(od_ec_dec *dec, unsigned f) {
+  od_ec_window dif;
+  od_ec_window vw;
+  unsigned r;
+  unsigned r_new;
+  unsigned v;
+  int ret;
+  assert(0 < f);
+  assert(f < 32768U);
+  dif = dec->dif;
+  r = dec->rng;
+  assert(dif >> (OD_EC_WINDOW_SIZE - 16) < r);
+  assert(32768U <= r);
+  v = ((r >> 8) * (uint32_t)(f >> EC_PROB_SHIFT) >> (7 - EC_PROB_SHIFT));
+  v += EC_MIN_PROB;
+  vw = (od_ec_window)v << (OD_EC_WINDOW_SIZE - 16);
+  ret = 1;
+  r_new = v;
+  if (dif >= vw) {
+    r_new = r - v;
+    dif -= vw;
+    ret = 0;
+  }
+  return od_ec_dec_normalize(dec, dif, r_new, ret);
+}
+
+/*Decodes a symbol given an inverse cumulative distribution function (CDF)
+   table in Q15.
+  icdf: CDF_PROB_TOP minus the CDF, such that symbol s falls in the range
+         [s > 0 ? (CDF_PROB_TOP - icdf[s - 1]) : 0, CDF_PROB_TOP - icdf[s]).
+        The values must be monotonically non-increasing, and icdf[nsyms - 1]
+         must be 0.
+  nsyms: The number of symbols in the alphabet.
+         This should be at most 16.
+  Return: The decoded symbol s.*/
+int od_ec_decode_cdf_q15(od_ec_dec *dec, const uint16_t *icdf, int nsyms) {
+  od_ec_window dif;
+  unsigned r;
+  unsigned c;
+  unsigned u;
+  unsigned v;
+  int ret;
+  (void)nsyms;
+  dif = dec->dif;
+  r = dec->rng;
+  const int N = nsyms - 1;
+
+  assert(dif >> (OD_EC_WINDOW_SIZE - 16) < r);
+  assert(icdf[nsyms - 1] == OD_ICDF(CDF_PROB_TOP));
+  assert(32768U <= r);
+  assert(7 - EC_PROB_SHIFT - CDF_SHIFT >= 0);
+  c = (unsigned)(dif >> (OD_EC_WINDOW_SIZE - 16));
+  v = r;
+  ret = -1;
+  do {
+    u = v;
+    v = ((r >> 8) * (uint32_t)(icdf[++ret] >> EC_PROB_SHIFT) >>
+         (7 - EC_PROB_SHIFT - CDF_SHIFT));
+    v += EC_MIN_PROB * (N - ret);
+  } while (c < v);
+  assert(v < u);
+  assert(u <= r);
+  r = u - v;
+  dif -= (od_ec_window)v << (OD_EC_WINDOW_SIZE - 16);
+  return od_ec_dec_normalize(dec, dif, r, ret);
+}
+
+/*Returns the number of bits "used" by the decoded symbols so far.
+  This same number can be computed in either the encoder or the decoder, and is
+   suitable for making coding decisions.
+  Return: The number of bits.
+          This will always be slightly larger than the exact value (e.g., all
+           rounding error is in the positive direction).*/
+int od_ec_dec_tell(const od_ec_dec *dec) {
+  return (int)((dec->bptr - dec->buf) * 8 - dec->cnt + dec->tell_offs);
+}
+
+/*Returns the number of bits "used" by the decoded symbols so far.
+  This same number can be computed in either the encoder or the decoder, and is
+   suitable for making coding decisions.
+  Return: The number of bits scaled by 2**OD_BITRES.
+          This will always be slightly larger than the exact value (e.g., all
+           rounding error is in the positive direction).*/
+uint32_t od_ec_dec_tell_frac(const od_ec_dec *dec) {
+  return od_ec_tell_frac(od_ec_dec_tell(dec), dec->rng);
+}