The Tor Browser: media/libvpx/vp9/encoder/vp9_segmentation.c@ac0c01689b40 (annotated)

media/libvpx/vp9/encoder/vp9_segmentation.c@ac0c01689b40 (annotated)

media/libvpx/vp9/encoder/vp9_segmentation.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) 2012 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 <limits.h>
 #include "vpx_mem/vpx_mem.h"
 #include "vp9/encoder/vp9_segmentation.h"
 #include "vp9/common/vp9_pred_common.h"
 #include "vp9/common/vp9_tile_common.h"
 void vp9_enable_segmentation(VP9_PTR ptr) {
   VP9_COMP *cpi = (VP9_COMP *)ptr;
   struct segmentation *const seg =  &cpi->common.seg;
   seg->enabled = 1;
   seg->update_map = 1;
   seg->update_data = 1;
 }
 void vp9_disable_segmentation(VP9_PTR ptr) {
   VP9_COMP *cpi = (VP9_COMP *)ptr;
   struct segmentation *const seg =  &cpi->common.seg;
   seg->enabled = 0;
 }
 void vp9_set_segmentation_map(VP9_PTR ptr,
                               unsigned char *segmentation_map) {
   VP9_COMP *cpi = (VP9_COMP *)ptr;
   struct segmentation *const seg = &cpi->common.seg;
   // Copy in the new segmentation map
   vpx_memcpy(cpi->segmentation_map, segmentation_map,
              (cpi->common.mi_rows * cpi->common.mi_cols));
   // Signal that the map should be updated.
   seg->update_map = 1;
   seg->update_data = 1;
 }
 void vp9_set_segment_data(VP9_PTR ptr,
                           signed char *feature_data,
                           unsigned char abs_delta) {
   VP9_COMP *cpi = (VP9_COMP *)ptr;
   struct segmentation *const seg = &cpi->common.seg;
   seg->abs_delta = abs_delta;
   vpx_memcpy(seg->feature_data, feature_data, sizeof(seg->feature_data));
   // TBD ?? Set the feature mask
   // vpx_memcpy(cpi->mb.e_mbd.segment_feature_mask, 0,
   //            sizeof(cpi->mb.e_mbd.segment_feature_mask));
 }
 // Based on set of segment counts calculate a probability tree
 static void calc_segtree_probs(int *segcounts, vp9_prob *segment_tree_probs) {
   // Work out probabilities of each segment
   const int c01 = segcounts[0] + segcounts[1];
   const int c23 = segcounts[2] + segcounts[3];
   const int c45 = segcounts[4] + segcounts[5];
   const int c67 = segcounts[6] + segcounts[7];
   segment_tree_probs[0] = get_binary_prob(c01 + c23, c45 + c67);
   segment_tree_probs[1] = get_binary_prob(c01, c23);
   segment_tree_probs[2] = get_binary_prob(c45, c67);
   segment_tree_probs[3] = get_binary_prob(segcounts[0], segcounts[1]);
   segment_tree_probs[4] = get_binary_prob(segcounts[2], segcounts[3]);
   segment_tree_probs[5] = get_binary_prob(segcounts[4], segcounts[5]);
   segment_tree_probs[6] = get_binary_prob(segcounts[6], segcounts[7]);
 }
 // Based on set of segment counts and probabilities calculate a cost estimate
 static int cost_segmap(int *segcounts, vp9_prob *probs) {
   const int c01 = segcounts[0] + segcounts[1];
   const int c23 = segcounts[2] + segcounts[3];
   const int c45 = segcounts[4] + segcounts[5];
   const int c67 = segcounts[6] + segcounts[7];
   const int c0123 = c01 + c23;
   const int c4567 = c45 + c67;
   // Cost the top node of the tree
   int cost = c0123 * vp9_cost_zero(probs[0]) +
              c4567 * vp9_cost_one(probs[0]);
   // Cost subsequent levels
   if (c0123 > 0) {
     cost += c01 * vp9_cost_zero(probs[1]) +
             c23 * vp9_cost_one(probs[1]);
     if (c01 > 0)
       cost += segcounts[0] * vp9_cost_zero(probs[3]) +
               segcounts[1] * vp9_cost_one(probs[3]);
     if (c23 > 0)
       cost += segcounts[2] * vp9_cost_zero(probs[4]) +
               segcounts[3] * vp9_cost_one(probs[4]);
   }
   if (c4567 > 0) {
     cost += c45 * vp9_cost_zero(probs[2]) +
             c67 * vp9_cost_one(probs[2]);
     if (c45 > 0)
       cost += segcounts[4] * vp9_cost_zero(probs[5]) +
               segcounts[5] * vp9_cost_one(probs[5]);
     if (c67 > 0)
       cost += segcounts[6] * vp9_cost_zero(probs[6]) +
               segcounts[7] * vp9_cost_one(probs[6]);
   }
   return cost;
 }
 static void count_segs(VP9_COMP *cpi, const TileInfo *const tile,
                        MODE_INFO **mi_8x8,
                        int *no_pred_segcounts,
                        int (*temporal_predictor_count)[2],
                        int *t_unpred_seg_counts,
                        int bw, int bh, int mi_row, int mi_col) {
   VP9_COMMON *const cm = &cpi->common;
   MACROBLOCKD *const xd = &cpi->mb.e_mbd;
   int segment_id;
   if (mi_row >= cm->mi_rows || mi_col >= cm->mi_cols)
     return;
   xd->mi_8x8 = mi_8x8;
   segment_id = xd->mi_8x8[0]->mbmi.segment_id;
   set_mi_row_col(xd, tile, mi_row, bh, mi_col, bw, cm->mi_rows, cm->mi_cols);
   // Count the number of hits on each segment with no prediction
   no_pred_segcounts[segment_id]++;
   // Temporal prediction not allowed on key frames
   if (cm->frame_type != KEY_FRAME) {
     const BLOCK_SIZE bsize = mi_8x8[0]->mbmi.sb_type;
     // Test to see if the segment id matches the predicted value.
     const int pred_segment_id = vp9_get_segment_id(cm, cm->last_frame_seg_map,
                                                    bsize, mi_row, mi_col);
     const int pred_flag = pred_segment_id == segment_id;
     const int pred_context = vp9_get_pred_context_seg_id(xd);
     // Store the prediction status for this mb and update counts
     // as appropriate
     vp9_set_pred_flag_seg_id(xd, pred_flag);
     temporal_predictor_count[pred_context][pred_flag]++;
     if (!pred_flag)
       // Update the "unpredicted" segment count
       t_unpred_seg_counts[segment_id]++;
   }
 }
 static void count_segs_sb(VP9_COMP *cpi, const TileInfo *const tile,
                           MODE_INFO **mi_8x8,
                           int *no_pred_segcounts,
                           int (*temporal_predictor_count)[2],
                           int *t_unpred_seg_counts,
                           int mi_row, int mi_col,
                           BLOCK_SIZE bsize) {
   const VP9_COMMON *const cm = &cpi->common;
   const int mis = cm->mode_info_stride;
   int bw, bh;
   const int bs = num_8x8_blocks_wide_lookup[bsize], hbs = bs / 2;
   if (mi_row >= cm->mi_rows || mi_col >= cm->mi_cols)
     return;
   bw = num_8x8_blocks_wide_lookup[mi_8x8[0]->mbmi.sb_type];
   bh = num_8x8_blocks_high_lookup[mi_8x8[0]->mbmi.sb_type];
   if (bw == bs && bh == bs) {
     count_segs(cpi, tile, mi_8x8, no_pred_segcounts, temporal_predictor_count,
                t_unpred_seg_counts, bs, bs, mi_row, mi_col);
   } else if (bw == bs && bh < bs) {
     count_segs(cpi, tile, mi_8x8, no_pred_segcounts, temporal_predictor_count,
                t_unpred_seg_counts, bs, hbs, mi_row, mi_col);
     count_segs(cpi, tile, mi_8x8 + hbs * mis, no_pred_segcounts,
                temporal_predictor_count, t_unpred_seg_counts, bs, hbs,
                mi_row + hbs, mi_col);
   } else if (bw < bs && bh == bs) {
     count_segs(cpi, tile, mi_8x8, no_pred_segcounts, temporal_predictor_count,
                t_unpred_seg_counts, hbs, bs, mi_row, mi_col);
     count_segs(cpi, tile, mi_8x8 + hbs,
                no_pred_segcounts, temporal_predictor_count, t_unpred_seg_counts,
                hbs, bs, mi_row, mi_col + hbs);
   } else {
     const BLOCK_SIZE subsize = subsize_lookup[PARTITION_SPLIT][bsize];
     int n;
     assert(bw < bs && bh < bs);
     for (n = 0; n < 4; n++) {
       const int mi_dc = hbs * (n & 1);
       const int mi_dr = hbs * (n >> 1);
       count_segs_sb(cpi, tile, &mi_8x8[mi_dr * mis + mi_dc],
                     no_pred_segcounts, temporal_predictor_count,
                     t_unpred_seg_counts,
                     mi_row + mi_dr, mi_col + mi_dc, subsize);
     }
   }
 }
 void vp9_choose_segmap_coding_method(VP9_COMP *cpi) {
   VP9_COMMON *const cm = &cpi->common;
   struct segmentation *seg = &cm->seg;
   int no_pred_cost;
   int t_pred_cost = INT_MAX;
   int i, tile_col, mi_row, mi_col;
   int temporal_predictor_count[PREDICTION_PROBS][2] = { { 0 } };
   int no_pred_segcounts[MAX_SEGMENTS] = { 0 };
   int t_unpred_seg_counts[MAX_SEGMENTS] = { 0 };
   vp9_prob no_pred_tree[SEG_TREE_PROBS];
   vp9_prob t_pred_tree[SEG_TREE_PROBS];
   vp9_prob t_nopred_prob[PREDICTION_PROBS];
   const int mis = cm->mode_info_stride;
   MODE_INFO **mi_ptr, **mi;
   // Set default state for the segment tree probabilities and the
   // temporal coding probabilities
   vpx_memset(seg->tree_probs, 255, sizeof(seg->tree_probs));
   vpx_memset(seg->pred_probs, 255, sizeof(seg->pred_probs));
   // First of all generate stats regarding how well the last segment map
   // predicts this one
   for (tile_col = 0; tile_col < 1 << cm->log2_tile_cols; tile_col++) {
     TileInfo tile;
     vp9_tile_init(&tile, cm, 0, tile_col);
     mi_ptr = cm->mi_grid_visible + tile.mi_col_start;
     for (mi_row = 0; mi_row < cm->mi_rows;
          mi_row += 8, mi_ptr += 8 * mis) {
       mi = mi_ptr;
       for (mi_col = tile.mi_col_start; mi_col < tile.mi_col_end;
            mi_col += 8, mi += 8)
         count_segs_sb(cpi, &tile, mi, no_pred_segcounts,
                       temporal_predictor_count, t_unpred_seg_counts,
                       mi_row, mi_col, BLOCK_64X64);
     }
   }
   // Work out probability tree for coding segments without prediction
   // and the cost.
   calc_segtree_probs(no_pred_segcounts, no_pred_tree);
   no_pred_cost = cost_segmap(no_pred_segcounts, no_pred_tree);
   // Key frames cannot use temporal prediction
   if (!frame_is_intra_only(cm)) {
     // Work out probability tree for coding those segments not
     // predicted using the temporal method and the cost.
     calc_segtree_probs(t_unpred_seg_counts, t_pred_tree);
     t_pred_cost = cost_segmap(t_unpred_seg_counts, t_pred_tree);
     // Add in the cost of the signaling for each prediction context.
     for (i = 0; i < PREDICTION_PROBS; i++) {
       const int count0 = temporal_predictor_count[i][0];
       const int count1 = temporal_predictor_count[i][1];
       t_nopred_prob[i] = get_binary_prob(count0, count1);
       // Add in the predictor signaling cost
       t_pred_cost += count0 * vp9_cost_zero(t_nopred_prob[i]) +
                      count1 * vp9_cost_one(t_nopred_prob[i]);
     }
   }
   // Now choose which coding method to use.
   if (t_pred_cost < no_pred_cost) {
     seg->temporal_update = 1;
     vpx_memcpy(seg->tree_probs, t_pred_tree, sizeof(t_pred_tree));
     vpx_memcpy(seg->pred_probs, t_nopred_prob, sizeof(t_nopred_prob));
   } else {
     seg->temporal_update = 0;
     vpx_memcpy(seg->tree_probs, no_pred_tree, sizeof(no_pred_tree));
   }
 }

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media/libvpx/vp9/encoder/vp9_segmentation.c@ac0c01689b40 (annotated)

media/libvpx/vp9/encoder/vp9_segmentation.c