The Tor Browser: media/libvpx/vp9/encoder/vp9

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

     1 /*

     2  *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.

     3  *

     4  *  Use of this source code is governed by a BSD-style license

     5  *  that can be found in the LICENSE file in the root of the source

     6  *  tree. An additional intellectual property rights grant can be found

     7  *  in the file PATENTS.  All contributing project authors may

     8  *  be found in the AUTHORS file in the root of the source tree.

     9  */

    12 /****************************************************************************

    13 *

    14 *   Module Title :     vp9_boolhuff.h

    15 *

    16 *   Description  :     Bool Coder header file.

    17 *

    18 ****************************************************************************/

    19 #ifndef VP9_ENCODER_VP9_BOOLHUFF_H_

    20 #define VP9_ENCODER_VP9_BOOLHUFF_H_

    22 #include "vpx_ports/mem.h"

    24 typedef struct {

    25   unsigned int lowvalue;

    26   unsigned int range;

    27   unsigned int value;

    28   int count;

    29   unsigned int pos;

    30   uint8_t *buffer;

    32   // Variables used to track bit costs without outputing to the bitstream

    33   unsigned int  measure_cost;

    34   unsigned long bit_counter;

    35 } vp9_writer;

    37 extern const unsigned int vp9_prob_cost[256];

    39 void vp9_start_encode(vp9_writer *bc, uint8_t *buffer);

    40 void vp9_stop_encode(vp9_writer *bc);

    42 DECLARE_ALIGNED(16, extern const unsigned char, vp9_norm[256]);

    44 static void vp9_write(vp9_writer *br, int bit, int probability) {

    45   unsigned int split;

    46   int count = br->count;

    47   unsigned int range = br->range;

    48   unsigned int lowvalue = br->lowvalue;

    49   register unsigned int shift;

    51 #ifdef ENTROPY_STATS

    52 #if defined(SECTIONBITS_OUTPUT)

    54   if (bit)

    55     Sectionbits[active_section] += vp9_prob_cost[255 - probability];

    56   else

    57     Sectionbits[active_section] += vp9_prob_cost[probability];

    59 #endif

    60 #endif

    62   split = 1 + (((range - 1) * probability) >> 8);

    64   range = split;

    66   if (bit) {

    67     lowvalue += split;

    68     range = br->range - split;

    69   }

    71   shift = vp9_norm[range];

    73   range <<= shift;

    74   count += shift;

    76   if (count >= 0) {

    77     int offset = shift - count;

    79     if ((lowvalue << (offset - 1)) & 0x80000000) {

    80       int x = br->pos - 1;

    82       while (x >= 0 && br->buffer[x] == 0xff) {

    83         br->buffer[x] = 0;

    84         x--;

    85       }

    87       br->buffer[x] += 1;

    88     }

    90     br->buffer[br->pos++] = (lowvalue >> (24 - offset));

    91     lowvalue <<= offset;

    92     shift = count;

    93     lowvalue &= 0xffffff;

    94     count -= 8;

    95   }

    97   lowvalue <<= shift;

    98   br->count = count;

    99   br->lowvalue = lowvalue;

   100   br->range = range;

   101 }

   103 static void vp9_write_bit(vp9_writer *w, int bit) {

   104   vp9_write(w, bit, 128);  // vp9_prob_half

   105 }

   107 static void vp9_write_literal(vp9_writer *w, int data, int bits) {

   108   int bit;

   110   for (bit = bits - 1; bit >= 0; bit--)

   111     vp9_write_bit(w, 1 & (data >> bit));

   112 }

   115 #endif  // VP9_ENCODER_VP9_BOOLHUFF_H_

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