c6f1bf4321
Adds differential encoding of prob updates using a subexponential code centered around the previous probability value. Also searches for the most cost-effective update, and breaks up the coefficient updates into smaller groups. Small gain on Derf: 0.2% Change-Id: Ie0071e3dc113e3d0d7ab95b6442bb07a89970030
117 lines
2.5 KiB
C
117 lines
2.5 KiB
C
/*
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* Copyright (c) 2010 The WebM project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "dboolhuff.h"
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#include "vpx_ports/mem.h"
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#include "vpx_mem/vpx_mem.h"
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int vp8dx_start_decode(BOOL_DECODER *br,
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const unsigned char *source,
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unsigned int source_sz)
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{
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br->user_buffer_end = source+source_sz;
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br->user_buffer = source;
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br->value = 0;
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br->count = -8;
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br->range = 255;
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if (source_sz && !source)
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return 1;
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/* Populate the buffer */
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vp8dx_bool_decoder_fill(br);
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return 0;
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}
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void vp8dx_bool_decoder_fill(BOOL_DECODER *br)
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{
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const unsigned char *bufptr;
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const unsigned char *bufend;
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VP8_BD_VALUE value;
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int count;
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bufend = br->user_buffer_end;
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bufptr = br->user_buffer;
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value = br->value;
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count = br->count;
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VP8DX_BOOL_DECODER_FILL(count, value, bufptr, bufend);
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br->user_buffer = bufptr;
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br->value = value;
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br->count = count;
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}
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#if CONFIG_NEWUPDATE
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static int get_unsigned_bits(unsigned num_values)
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{
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int cat=0;
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if ((num_values--)<=1) return 0;
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while (num_values>0)
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{
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cat++;
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num_values>>=1;
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}
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return cat;
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}
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int inv_recenter_nonneg(int v, int m)
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{
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if (v>(m<<1)) return v;
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else if ((v&1)==0) return (v>>1)+m;
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else return m-((v+1)>>1);
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}
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int vp8_decode_uniform(BOOL_DECODER *br, int n)
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{
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int v;
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int l=get_unsigned_bits(n);
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int m=(1<<l)-n;
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if (!l) return 0;
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v = vp8_decode_value(br, l-1);
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if (v < m)
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return v;
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else
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return (v<<1)-m+vp8_decode_value(br, 1);
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}
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int vp8_decode_term_subexp(BOOL_DECODER *br, int k, int num_syms)
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{
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int i=0, mk=0, word;
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while (1)
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{
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int b = (i?k+i-1:k);
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int a = (1<<b);
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if (num_syms<=mk+3*a)
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{
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word = vp8_decode_uniform(br, num_syms-mk) + mk;
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break;
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}
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else
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{
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if (vp8_decode_value(br, 1))
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{
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i++;
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mk += a;
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}
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else
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{
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word = vp8_decode_value(br, b) + mk;
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break;
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}
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}
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}
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return word;
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}
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#endif
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