The Tor Browser: media/libvpx/vp8/encoder/encodemv.c@ac0c01689b40 (annotated)

media/libvpx/vp8/encoder/encodemv.c@ac0c01689b40 (annotated)

media/libvpx/vp8/encoder/encodemv.c

Thu, 15 Jan 2015 15:59:08 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 15 Jan 2015 15:59:08 +0100
branch: TOR_BUG_9701
changeset 10: ac0c01689b40
permissions: -rw-r--r--

Implement a real Private Browsing Mode condition by changing the API/ABI;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 /*
  *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 #include "vp8/common/common.h"
 #include "encodemv.h"
 #include "vp8/common/entropymode.h"
 #include "vp8/common/systemdependent.h"
 #include <math.h>
 #ifdef VP8_ENTROPY_STATS
 extern unsigned int active_section;
 #endif
 static void encode_mvcomponent(
     vp8_writer *const w,
     const int v,
     const struct mv_context *mvc
 )
 {
     const vp8_prob *p = mvc->prob;
     const int x = v < 0 ? -v : v;
     if (x < mvnum_short)     /* Small */
     {
         vp8_write(w, 0, p [mvpis_short]);
         vp8_treed_write(w, vp8_small_mvtree, p + MVPshort, x, 3);
         if (!x)
             return;         /* no sign bit */
     }
     else                    /* Large */
     {
         int i = 0;
         vp8_write(w, 1, p [mvpis_short]);
         do
             vp8_write(w, (x >> i) & 1, p [MVPbits + i]);
         while (++i < 3);
         i = mvlong_width - 1;  /* Skip bit 3, which is sometimes implicit */
         do
             vp8_write(w, (x >> i) & 1, p [MVPbits + i]);
         while (--i > 3);
         if (x & 0xFFF0)
             vp8_write(w, (x >> 3) & 1, p [MVPbits + 3]);
     }
     vp8_write(w, v < 0, p [MVPsign]);
 }
 #if 0
 static int max_mv_r = 0;
 static int max_mv_c = 0;
 #endif
 void vp8_encode_motion_vector(vp8_writer *w, const MV *mv, const MV_CONTEXT *mvc)
 {
 #if 0
     {
         if (abs(mv->row >> 1) > max_mv_r)
         {
             FILE *f = fopen("maxmv.stt", "a");
             max_mv_r = abs(mv->row >> 1);
             fprintf(f, "New Mv Row Max %6d\n", (mv->row >> 1));
             if ((abs(mv->row) / 2) != max_mv_r)
                 fprintf(f, "MV Row conversion error %6d\n", abs(mv->row) / 2);
             fclose(f);
         }
         if (abs(mv->col >> 1) > max_mv_c)
         {
             FILE *f = fopen("maxmv.stt", "a");
             fprintf(f, "New Mv Col Max %6d\n", (mv->col >> 1));
             max_mv_c = abs(mv->col >> 1);
             fclose(f);
         }
     }
 #endif
     encode_mvcomponent(w, mv->row >> 1, &mvc[0]);
     encode_mvcomponent(w, mv->col >> 1, &mvc[1]);
 }
 static unsigned int cost_mvcomponent(const int v, const struct mv_context *mvc)
 {
     const vp8_prob *p = mvc->prob;
     const int x = v;
     unsigned int cost;
     if (x < mvnum_short)
     {
         cost = vp8_cost_zero(p [mvpis_short])
                + vp8_treed_cost(vp8_small_mvtree, p + MVPshort, x, 3);
         if (!x)
             return cost;
     }
     else
     {
         int i = 0;
         cost = vp8_cost_one(p [mvpis_short]);
         do
             cost += vp8_cost_bit(p [MVPbits + i], (x >> i) & 1);
         while (++i < 3);
         i = mvlong_width - 1;  /* Skip bit 3, which is sometimes implicit */
         do
             cost += vp8_cost_bit(p [MVPbits + i], (x >> i) & 1);
         while (--i > 3);
         if (x & 0xFFF0)
             cost += vp8_cost_bit(p [MVPbits + 3], (x >> 3) & 1);
     }
     return cost;   /* + vp8_cost_bit( p [MVPsign], v < 0); */
 }
 void vp8_build_component_cost_table(int *mvcost[2], const MV_CONTEXT *mvc, int mvc_flag[2])
 {
     int i = 1;
     unsigned int cost0 = 0;
     unsigned int cost1 = 0;
     vp8_clear_system_state();
     i = 1;
     if (mvc_flag[0])
     {
         mvcost [0] [0] = cost_mvcomponent(0, &mvc[0]);
         do
         {
             cost0 = cost_mvcomponent(i, &mvc[0]);
             mvcost [0] [i] = cost0 + vp8_cost_zero(mvc[0].prob[MVPsign]);
             mvcost [0] [-i] = cost0 + vp8_cost_one(mvc[0].prob[MVPsign]);
         }
         while (++i <= mv_max);
     }
     i = 1;
     if (mvc_flag[1])
     {
         mvcost [1] [0] = cost_mvcomponent(0, &mvc[1]);
         do
         {
             cost1 = cost_mvcomponent(i, &mvc[1]);
             mvcost [1] [i] = cost1 + vp8_cost_zero(mvc[1].prob[MVPsign]);
             mvcost [1] [-i] = cost1 + vp8_cost_one(mvc[1].prob[MVPsign]);
         }
         while (++i <= mv_max);
     }
 }
 /* Motion vector probability table update depends on benefit.
  * Small correction allows for the fact that an update to an MV probability
  * may have benefit in subsequent frames as well as the current one.
  */
 #define MV_PROB_UPDATE_CORRECTION   -1
 static void calc_prob(vp8_prob *p, const unsigned int ct[2])
 {
     const unsigned int tot = ct[0] + ct[1];
     if (tot)
     {
         const vp8_prob x = ((ct[0] * 255) / tot) & -2;
         *p = x ? x : 1;
     }
 }
 static void update(
     vp8_writer *const w,
     const unsigned int ct[2],
     vp8_prob *const cur_p,
     const vp8_prob new_p,
     const vp8_prob update_p,
     int *updated
 )
 {
     const int cur_b = vp8_cost_branch(ct, *cur_p);
     const int new_b = vp8_cost_branch(ct, new_p);
     const int cost = 7 + MV_PROB_UPDATE_CORRECTION + ((vp8_cost_one(update_p) - vp8_cost_zero(update_p) + 128) >> 8);
     if (cur_b - new_b > cost)
     {
         *cur_p = new_p;
         vp8_write(w, 1, update_p);
         vp8_write_literal(w, new_p >> 1, 7);
         *updated = 1;
     }
     else
         vp8_write(w, 0, update_p);
 }
 static void write_component_probs(
     vp8_writer *const w,
     struct mv_context *cur_mvc,
     const struct mv_context *default_mvc_,
     const struct mv_context *update_mvc,
     const unsigned int events [MVvals],
     unsigned int rc,
     int *updated
 )
 {
     vp8_prob *Pcur = cur_mvc->prob;
     const vp8_prob *default_mvc = default_mvc_->prob;
     const vp8_prob *Pupdate = update_mvc->prob;
     unsigned int is_short_ct[2], sign_ct[2];
     unsigned int bit_ct [mvlong_width] [2];
     unsigned int short_ct  [mvnum_short];
     unsigned int short_bct [mvnum_short-1] [2];
     vp8_prob Pnew [MVPcount];
     (void) rc;
     vp8_copy_array(Pnew, default_mvc, MVPcount);
     vp8_zero(is_short_ct)
     vp8_zero(sign_ct)
     vp8_zero(bit_ct)
     vp8_zero(short_ct)
     vp8_zero(short_bct)
     /* j=0 */
     {
         const int c = events [mv_max];
         is_short_ct [0] += c;     /* Short vector */
         short_ct [0] += c;       /* Magnitude distribution */
     }
     /* j: 1 ~ mv_max (1023) */
     {
         int j = 1;
         do
         {
             const int c1 = events [mv_max + j];  /* positive */
             const int c2 = events [mv_max - j];  /* negative */
             const int c  = c1 + c2;
             int a = j;
             sign_ct [0] += c1;
             sign_ct [1] += c2;
             if (a < mvnum_short)
             {
                 is_short_ct [0] += c;     /* Short vector */
                 short_ct [a] += c;       /* Magnitude distribution */
             }
             else
             {
                 int k = mvlong_width - 1;
                 is_short_ct [1] += c;     /* Long vector */
                 /*  bit 3 not always encoded. */
                 do
                     bit_ct [k] [(a >> k) & 1] += c;
                 while (--k >= 0);
             }
         }
         while (++j <= mv_max);
     }
     calc_prob(Pnew + mvpis_short, is_short_ct);
     calc_prob(Pnew + MVPsign, sign_ct);
     {
         vp8_prob p [mvnum_short - 1];    /* actually only need branch ct */
         int j = 0;
         vp8_tree_probs_from_distribution(
 , vp8_small_mvencodings, vp8_small_mvtree,
             p, short_bct, short_ct,
 , 1
         );
         do
             calc_prob(Pnew + MVPshort + j, short_bct[j]);
         while (++j < mvnum_short - 1);
     }
     {
         int j = 0;
         do
             calc_prob(Pnew + MVPbits + j, bit_ct[j]);
         while (++j < mvlong_width);
     }
     update(w, is_short_ct, Pcur + mvpis_short, Pnew[mvpis_short], *Pupdate++, updated);
     update(w, sign_ct, Pcur + MVPsign, Pnew[MVPsign], *Pupdate++, updated);
     {
         const vp8_prob *const new_p = Pnew + MVPshort;
         vp8_prob *const cur_p = Pcur + MVPshort;
         int j = 0;
         do
             update(w, short_bct[j], cur_p + j, new_p[j], *Pupdate++, updated);
         while (++j < mvnum_short - 1);
     }
     {
         const vp8_prob *const new_p = Pnew + MVPbits;
         vp8_prob *const cur_p = Pcur + MVPbits;
         int j = 0;
         do
             update(w, bit_ct[j], cur_p + j, new_p[j], *Pupdate++, updated);
         while (++j < mvlong_width);
     }
 }
 void vp8_write_mvprobs(VP8_COMP *cpi)
 {
     vp8_writer *const w  = cpi->bc;
     MV_CONTEXT *mvc = cpi->common.fc.mvc;
     int flags[2] = {0, 0};
 #ifdef VP8_ENTROPY_STATS
     active_section = 4;
 #endif
     write_component_probs(
         w, &mvc[0], &vp8_default_mv_context[0], &vp8_mv_update_probs[0],
         cpi->mb.MVcount[0], 0, &flags[0]
     );
     write_component_probs(
         w, &mvc[1], &vp8_default_mv_context[1], &vp8_mv_update_probs[1],
         cpi->mb.MVcount[1], 1, &flags[1]
     );
     if (flags[0] || flags[1])
         vp8_build_component_cost_table(cpi->mb.mvcost, (const MV_CONTEXT *) cpi->common.fc.mvc, flags);
 #ifdef VP8_ENTROPY_STATS
     active_section = 5;
 #endif
 }

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media/libvpx/vp8/encoder/encodemv.c@ac0c01689b40 (annotated)

media/libvpx/vp8/encoder/encodemv.c