The Tor Browser: media/libvpx/vp9/common/vp9_mvref_common.c@ac0c01689b40 (annotated)

media/libvpx/vp9/common/vp9_mvref_common.c@ac0c01689b40 (annotated)

media/libvpx/vp9/common/vp9_mvref_common.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 "vp9/common/vp9_mvref_common.h"
 #define MVREF_NEIGHBOURS 8
 typedef enum {
   BOTH_ZERO = 0,
   ZERO_PLUS_PREDICTED = 1,
   BOTH_PREDICTED = 2,
   NEW_PLUS_NON_INTRA = 3,
   BOTH_NEW = 4,
   INTRA_PLUS_NON_INTRA = 5,
   BOTH_INTRA = 6,
   INVALID_CASE = 9
 } motion_vector_context;
 // This is used to figure out a context for the ref blocks. The code flattens
 // an array that would have 3 possible counts (0, 1 & 2) for 3 choices by
 // adding 9 for each intra block, 3 for each zero mv and 1 for each new
 // motion vector. This single number is then converted into a context
 // with a single lookup ( counter_to_context ).
 static const int mode_2_counter[MB_MODE_COUNT] = {
 ,  // DC_PRED
 ,  // V_PRED
 ,  // H_PRED
 ,  // D45_PRED
 ,  // D135_PRED
 ,  // D117_PRED
 ,  // D153_PRED
 ,  // D207_PRED
 ,  // D63_PRED
 ,  // TM_PRED
 ,  // NEARESTMV
 ,  // NEARMV
 ,  // ZEROMV
 ,  // NEWMV
 };
 // There are 3^3 different combinations of 3 counts that can be either 0,1 or
 // 2. However the actual count can never be greater than 2 so the highest
 // counter we need is 18. 9 is an invalid counter that's never used.
 static const int counter_to_context[19] = {
   BOTH_PREDICTED,  // 0
   NEW_PLUS_NON_INTRA,  // 1
   BOTH_NEW,  // 2
   ZERO_PLUS_PREDICTED,  // 3
   NEW_PLUS_NON_INTRA,  // 4
   INVALID_CASE,  // 5
   BOTH_ZERO,  // 6
   INVALID_CASE,  // 7
   INVALID_CASE,  // 8
   INTRA_PLUS_NON_INTRA,  // 9
   INTRA_PLUS_NON_INTRA,  // 10
   INVALID_CASE,  // 11
   INTRA_PLUS_NON_INTRA,  // 12
   INVALID_CASE,  // 13
   INVALID_CASE,  // 14
   INVALID_CASE,  // 15
   INVALID_CASE,  // 16
   INVALID_CASE,  // 17
   BOTH_INTRA  // 18
 };
 static const MV mv_ref_blocks[BLOCK_SIZES][MVREF_NEIGHBOURS] = {
   // 4X4
   {{-1, 0}, {0, -1}, {-1, -1}, {-2, 0}, {0, -2}, {-2, -1}, {-1, -2}, {-2, -2}},
   // 4X8
   {{-1, 0}, {0, -1}, {-1, -1}, {-2, 0}, {0, -2}, {-2, -1}, {-1, -2}, {-2, -2}},
   // 8X4
   {{-1, 0}, {0, -1}, {-1, -1}, {-2, 0}, {0, -2}, {-2, -1}, {-1, -2}, {-2, -2}},
   // 8X8
   {{-1, 0}, {0, -1}, {-1, -1}, {-2, 0}, {0, -2}, {-2, -1}, {-1, -2}, {-2, -2}},
   // 8X16
   {{0, -1}, {-1, 0}, {1, -1}, {-1, -1}, {0, -2}, {-2, 0}, {-2, -1}, {-1, -2}},
   // 16X8
   {{-1, 0}, {0, -1}, {-1, 1}, {-1, -1}, {-2, 0}, {0, -2}, {-1, -2}, {-2, -1}},
   // 16X16
   {{-1, 0}, {0, -1}, {-1, 1}, {1, -1}, {-1, -1}, {-3, 0}, {0, -3}, {-3, -3}},
   // 16X32
   {{0, -1}, {-1, 0}, {2, -1}, {-1, -1}, {-1, 1}, {0, -3}, {-3, 0}, {-3, -3}},
   // 32X16
   {{-1, 0}, {0, -1}, {-1, 2}, {-1, -1}, {1, -1}, {-3, 0}, {0, -3}, {-3, -3}},
   // 32X32
   {{-1, 1}, {1, -1}, {-1, 2}, {2, -1}, {-1, -1}, {-3, 0}, {0, -3}, {-3, -3}},
   // 32X64
   {{0, -1}, {-1, 0}, {4, -1}, {-1, 2}, {-1, -1}, {0, -3}, {-3, 0}, {2, -1}},
   // 64X32
   {{-1, 0}, {0, -1}, {-1, 4}, {2, -1}, {-1, -1}, {-3, 0}, {0, -3}, {-1, 2}},
   // 64X64
   {{-1, 3}, {3, -1}, {-1, 4}, {4, -1}, {-1, -1}, {-1, 0}, {0, -1}, {-1, 6}}
 };
 static const int idx_n_column_to_subblock[4][2] = {
   {1, 2},
   {1, 3},
   {3, 2},
   {3, 3}
 };
 // clamp_mv_ref
 #define MV_BORDER (16 << 3)  // Allow 16 pels in 1/8th pel units
 static void clamp_mv_ref(MV *mv, const MACROBLOCKD *xd) {
   clamp_mv(mv, xd->mb_to_left_edge - MV_BORDER,
                xd->mb_to_right_edge + MV_BORDER,
                xd->mb_to_top_edge - MV_BORDER,
                xd->mb_to_bottom_edge + MV_BORDER);
 }
 // This function returns either the appropriate sub block or block's mv
 // on whether the block_size < 8x8 and we have check_sub_blocks set.
 static INLINE int_mv get_sub_block_mv(const MODE_INFO *candidate, int which_mv,
                                       int search_col, int block_idx) {
   return block_idx >= 0 && candidate->mbmi.sb_type < BLOCK_8X8
           ? candidate->bmi[idx_n_column_to_subblock[block_idx][search_col == 0]]
               .as_mv[which_mv]
           : candidate->mbmi.mv[which_mv];
 }
 // Performs mv sign inversion if indicated by the reference frame combination.
 static INLINE int_mv scale_mv(const MB_MODE_INFO *mbmi, int ref,
                               const MV_REFERENCE_FRAME this_ref_frame,
                               const int *ref_sign_bias) {
   int_mv mv = mbmi->mv[ref];
   if (ref_sign_bias[mbmi->ref_frame[ref]] != ref_sign_bias[this_ref_frame]) {
     mv.as_mv.row *= -1;
     mv.as_mv.col *= -1;
   }
   return mv;
 }
 // This macro is used to add a motion vector mv_ref list if it isn't
 // already in the list.  If it's the second motion vector it will also
 // skip all additional processing and jump to done!
 #define ADD_MV_REF_LIST(MV) \
   do { \
     if (refmv_count) { \
       if ((MV).as_int != mv_ref_list[0].as_int) { \
         mv_ref_list[refmv_count] = (MV); \
         goto Done; \
       } \
     } else { \
       mv_ref_list[refmv_count++] = (MV); \
     } \
   } while (0)
 // If either reference frame is different, not INTRA, and they
 // are different from each other scale and add the mv to our list.
 #define IF_DIFF_REF_FRAME_ADD_MV(CANDIDATE) \
   do { \
     if ((CANDIDATE)->ref_frame[0] != ref_frame) \
       ADD_MV_REF_LIST(scale_mv((CANDIDATE), 0, ref_frame, ref_sign_bias)); \
     if ((CANDIDATE)->ref_frame[1] != ref_frame && \
         has_second_ref(CANDIDATE) && \
         (CANDIDATE)->mv[1].as_int != (CANDIDATE)->mv[0].as_int) \
       ADD_MV_REF_LIST(scale_mv((CANDIDATE), 1, ref_frame, ref_sign_bias)); \
   } while (0)
 // Checks that the given mi_row, mi_col and search point
 // are inside the borders of the tile.
 static INLINE int is_inside(const TileInfo *const tile,
                             int mi_col, int mi_row, int mi_rows,
                             const MV *mv) {
   return !(mi_row + mv->row < 0 ||
            mi_col + mv->col < tile->mi_col_start ||
            mi_row + mv->row >= mi_rows ||
            mi_col + mv->col >= tile->mi_col_end);
 }
 // This function searches the neighbourhood of a given MB/SB
 // to try and find candidate reference vectors.
 void vp9_find_mv_refs_idx(const VP9_COMMON *cm, const MACROBLOCKD *xd,
                           const TileInfo *const tile,
                           MODE_INFO *mi, const MODE_INFO *prev_mi,
                           MV_REFERENCE_FRAME ref_frame,
                           int_mv *mv_ref_list,
                           int block_idx,
                           int mi_row, int mi_col) {
   const int *ref_sign_bias = cm->ref_frame_sign_bias;
   int i, refmv_count = 0;
   const MV *const mv_ref_search = mv_ref_blocks[mi->mbmi.sb_type];
   const MB_MODE_INFO *const prev_mbmi = prev_mi ? &prev_mi->mbmi : NULL;
   int different_ref_found = 0;
   int context_counter = 0;
   // Blank the reference vector list
   vpx_memset(mv_ref_list, 0, sizeof(*mv_ref_list) * MAX_MV_REF_CANDIDATES);
   // The nearest 2 blocks are treated differently
   // if the size < 8x8 we get the mv from the bmi substructure,
   // and we also need to keep a mode count.
   for (i = 0; i < 2; ++i) {
     const MV *const mv_ref = &mv_ref_search[i];
     if (is_inside(tile, mi_col, mi_row, cm->mi_rows, mv_ref)) {
       const MODE_INFO *const candidate_mi = xd->mi_8x8[mv_ref->col + mv_ref->row
                                                    * xd->mode_info_stride];
       const MB_MODE_INFO *const candidate = &candidate_mi->mbmi;
       // Keep counts for entropy encoding.
       context_counter += mode_2_counter[candidate->mode];
       // Check if the candidate comes from the same reference frame.
       if (candidate->ref_frame[0] == ref_frame) {
         ADD_MV_REF_LIST(get_sub_block_mv(candidate_mi, 0,
                                          mv_ref->col, block_idx));
         different_ref_found = candidate->ref_frame[1] != ref_frame;
       } else {
         if (candidate->ref_frame[1] == ref_frame)
           // Add second motion vector if it has the same ref_frame.
           ADD_MV_REF_LIST(get_sub_block_mv(candidate_mi, 1,
                                            mv_ref->col, block_idx));
         different_ref_found = 1;
       }
     }
   }
   // Check the rest of the neighbors in much the same way
   // as before except we don't need to keep track of sub blocks or
   // mode counts.
   for (; i < MVREF_NEIGHBOURS; ++i) {
     const MV *const mv_ref = &mv_ref_search[i];
     if (is_inside(tile, mi_col, mi_row, cm->mi_rows, mv_ref)) {
       const MB_MODE_INFO *const candidate = &xd->mi_8x8[mv_ref->col +
                                             mv_ref->row
                                             * xd->mode_info_stride]->mbmi;
       if (candidate->ref_frame[0] == ref_frame) {
         ADD_MV_REF_LIST(candidate->mv[0]);
         different_ref_found = candidate->ref_frame[1] != ref_frame;
       } else {
         if (candidate->ref_frame[1] == ref_frame)
           ADD_MV_REF_LIST(candidate->mv[1]);
         different_ref_found = 1;
       }
     }
   }
   // Check the last frame's mode and mv info.
   if (prev_mbmi) {
     if (prev_mbmi->ref_frame[0] == ref_frame)
       ADD_MV_REF_LIST(prev_mbmi->mv[0]);
     else if (prev_mbmi->ref_frame[1] == ref_frame)
       ADD_MV_REF_LIST(prev_mbmi->mv[1]);
   }
   // Since we couldn't find 2 mvs from the same reference frame
   // go back through the neighbors and find motion vectors from
   // different reference frames.
   if (different_ref_found) {
     for (i = 0; i < MVREF_NEIGHBOURS; ++i) {
       const MV *mv_ref = &mv_ref_search[i];
       if (is_inside(tile, mi_col, mi_row, cm->mi_rows, mv_ref)) {
         const MB_MODE_INFO *const candidate = &xd->mi_8x8[mv_ref->col +
                                                           mv_ref->row
                                               * xd->mode_info_stride]->mbmi;
         // If the candidate is INTRA we don't want to consider its mv.
         if (is_inter_block(candidate))
           IF_DIFF_REF_FRAME_ADD_MV(candidate);
       }
     }
   }
   // Since we still don't have a candidate we'll try the last frame.
   if (prev_mbmi && is_inter_block(prev_mbmi))
     IF_DIFF_REF_FRAME_ADD_MV(prev_mbmi);
  Done:
   mi->mbmi.mode_context[ref_frame] = counter_to_context[context_counter];
   // Clamp vectors
   for (i = 0; i < MAX_MV_REF_CANDIDATES; ++i)
     clamp_mv_ref(&mv_ref_list[i].as_mv, xd);
 }

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media/libvpx/vp9/common/vp9_mvref_common.c@ac0c01689b40 (annotated)

media/libvpx/vp9/common/vp9_mvref_common.c