encodeframe.c

/*
 *  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 "vpx_ports/config.h"
#include "encodemb.h"
#include "encodemv.h"
#include "vp8/common/common.h"
#include "onyx_int.h"
#include "vp8/common/extend.h"
#include "vp8/common/entropymode.h"
#include "vp8/common/quant_common.h"
#include "segmentation.h"
#include "vp8/common/setupintrarecon.h"
#include "encodeintra.h"
#include "vp8/common/reconinter.h"
#include "rdopt.h"
#include "vp8/common/findnearmv.h"
#include "vp8/common/reconintra.h"
#include "vp8/common/seg_common.h"
#include <stdio.h>
#include <math.h>
#include <limits.h>
#include "vp8/common/subpixel.h"
#include "vpx_ports/vpx_timer.h"
#include "vp8/common/pred_common.h"

#define DBG_PRNT_SEGMAP 0

#if CONFIG_RUNTIME_CPU_DETECT
#define RTCD(x)     &cpi->common.rtcd.x
#define IF_RTCD(x)  (x)
#else
#define RTCD(x)     NULL
#define IF_RTCD(x)  NULL
#endif

#ifdef ENC_DEBUG
int enc_debug = 0;
int mb_row_debug, mb_col_debug;
#endif

extern void vp8_stuff_mb(VP8_COMP *cpi, MACROBLOCKD *xd,
                         TOKENEXTRA **t, int dry_run);

extern void vp8cx_initialize_me_consts(VP8_COMP *cpi, int QIndex);
extern void vp8_auto_select_speed(VP8_COMP *cpi);
extern void vp8cx_init_mbrthread_data(VP8_COMP *cpi,
                                      MACROBLOCK *x,
                                      MB_ROW_COMP *mbr_ei,
                                      int mb_row,
                                      int count);
extern int vp8cx_pick_mode_inter_macroblock(VP8_COMP *cpi, MACROBLOCK *x,
                                            int recon_yoffset,
                                            int recon_uvoffset);
void vp8_build_block_offsets(MACROBLOCK *x);
void vp8_setup_block_ptrs(MACROBLOCK *x);
void vp8cx_encode_inter_macroblock(VP8_COMP *cpi, MACROBLOCK *x, TOKENEXTRA **t,
                                   int recon_yoffset, int recon_uvoffset,
                                   int output_enabled);
void vp8cx_encode_intra_macro_block(VP8_COMP *cpi, MACROBLOCK *x,
                                    TOKENEXTRA **t, int output_enabled);
static void adjust_act_zbin(VP8_COMP *cpi, MACROBLOCK *x);


#ifdef MODE_STATS
unsigned int inter_y_modes[MB_MODE_COUNT];
unsigned int inter_uv_modes[VP8_UV_MODES];
unsigned int inter_b_modes[B_MODE_COUNT];
unsigned int y_modes[VP8_YMODES];
unsigned int i8x8_modes[VP8_I8X8_MODES];
unsigned int uv_modes[VP8_UV_MODES];
unsigned int uv_modes_y[VP8_YMODES][VP8_UV_MODES];
unsigned int b_modes[B_MODE_COUNT];
#endif


/* activity_avg must be positive, or flat regions could get a zero weight
 *  (infinite lambda), which confounds analysis.
 * This also avoids the need for divide by zero checks in
 *  vp8_activity_masking().
 */
#define VP8_ACTIVITY_AVG_MIN (64)

/* This is used as a reference when computing the source variance for the
 *  purposes of activity masking.
 * Eventually this should be replaced by custom no-reference routines,
 *  which will be faster.
 */
static const unsigned char VP8_VAR_OFFS[16] = {
  128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128
};


// Original activity measure from Tim T's code.
static unsigned int tt_activity_measure(VP8_COMP *cpi, MACROBLOCK *x) {
  unsigned int act;
  unsigned int sse;
  /* TODO: This could also be done over smaller areas (8x8), but that would
   *  require extensive changes elsewhere, as lambda is assumed to be fixed
   *  over an entire MB in most of the code.
   * Another option is to compute four 8x8 variances, and pick a single
   *  lambda using a non-linear combination (e.g., the smallest, or second
   *  smallest, etc.).
   */
  act =     VARIANCE_INVOKE(&cpi->rtcd.variance, var16x16)(x->src.y_buffer,
                                                           x->src.y_stride, VP8_VAR_OFFS, 0, &sse);
  act = act << 4;

  /* If the region is flat, lower the activity some more. */
  if (act < 8 << 12)
    act = act < 5 << 12 ? act : 5 << 12;

  return act;
}

// Stub for alternative experimental activity measures.
static unsigned int alt_activity_measure(VP8_COMP *cpi,
                                         MACROBLOCK *x, int use_dc_pred) {
  return vp8_encode_intra(cpi, x, use_dc_pred);
}


// Measure the activity of the current macroblock
// What we measure here is TBD so abstracted to this function
#define ALT_ACT_MEASURE 1
static unsigned int mb_activity_measure(VP8_COMP *cpi, MACROBLOCK *x,
                                        int mb_row, int mb_col) {
  unsigned int mb_activity;

  if (ALT_ACT_MEASURE) {
    int use_dc_pred = (mb_col || mb_row) && (!mb_col || !mb_row);

    // Or use and alternative.
    mb_activity = alt_activity_measure(cpi, x, use_dc_pred);
  } else {
    // Original activity measure from Tim T's code.
    mb_activity = tt_activity_measure(cpi, x);
  }

  if (mb_activity < VP8_ACTIVITY_AVG_MIN)
    mb_activity = VP8_ACTIVITY_AVG_MIN;

  return mb_activity;
}

// Calculate an "average" mb activity value for the frame
#define ACT_MEDIAN 0
static void calc_av_activity(VP8_COMP *cpi, int64_t activity_sum) {
#if ACT_MEDIAN
  // Find median: Simple n^2 algorithm for experimentation
  {
    unsigned int median;
    unsigned int i, j;
    unsigned int *sortlist;
    unsigned int tmp;

    // Create a list to sort to
    CHECK_MEM_ERROR(sortlist,
    vpx_calloc(sizeof(unsigned int),
    cpi->common.MBs));

    // Copy map to sort list
    vpx_memcpy(sortlist, cpi->mb_activity_map,
    sizeof(unsigned int) * cpi->common.MBs);


    // Ripple each value down to its correct position
    for (i = 1; i < cpi->common.MBs; i ++) {
      for (j = i; j > 0; j --) {
        if (sortlist[j] < sortlist[j - 1]) {
          // Swap values
          tmp = sortlist[j - 1];
          sortlist[j - 1] = sortlist[j];
          sortlist[j] = tmp;
        } else
          break;
      }
    }

    // Even number MBs so estimate median as mean of two either side.
    median = (1 + sortlist[cpi->common.MBs >> 1] +
              sortlist[(cpi->common.MBs >> 1) + 1]) >> 1;

    cpi->activity_avg = median;

    vpx_free(sortlist);
  }
#else
  // Simple mean for now
  cpi->activity_avg = (unsigned int)(activity_sum / cpi->common.MBs);
#endif

  if (cpi->activity_avg < VP8_ACTIVITY_AVG_MIN)
    cpi->activity_avg = VP8_ACTIVITY_AVG_MIN;

  // Experimental code: return fixed value normalized for several clips
  if (ALT_ACT_MEASURE)
    cpi->activity_avg = 100000;
}

#define USE_ACT_INDEX   0
#define OUTPUT_NORM_ACT_STATS   0

#if USE_ACT_INDEX
// Calculate and activity index for each mb
static void calc_activity_index(VP8_COMP *cpi, MACROBLOCK *x) {
  VP8_COMMON *const cm = & cpi->common;
  int mb_row, mb_col;

  int64_t act;
  int64_t a;
  int64_t b;

#if OUTPUT_NORM_ACT_STATS
  FILE *f = fopen("norm_act.stt", "a");
  fprintf(f, "\n%12d\n", cpi->activity_avg);
#endif

  // Reset pointers to start of activity map
  x->mb_activity_ptr = cpi->mb_activity_map;

  // Calculate normalized mb activity number.
  for (mb_row = 0; mb_row < cm->mb_rows; mb_row++) {
    // for each macroblock col in image
    for (mb_col = 0; mb_col < cm->mb_cols; mb_col++) {
      // Read activity from the map
      act = *(x->mb_activity_ptr);

      // Calculate a normalized activity number
      a = act + 4 * cpi->activity_avg;
      b = 4 * act + cpi->activity_avg;

      if (b >= a)
        *(x->activity_ptr) = (int)((b + (a >> 1)) / a) - 1;
      else
        *(x->activity_ptr) = 1 - (int)((a + (b >> 1)) / b);

#if OUTPUT_NORM_ACT_STATS
      fprintf(f, " %6d", *(x->mb_activity_ptr));
#endif
      // Increment activity map pointers
      x->mb_activity_ptr++;
    }

#if OUTPUT_NORM_ACT_STATS
    fprintf(f, "\n");
#endif

  }

#if OUTPUT_NORM_ACT_STATS
  fclose(f);
#endif

}
#endif

// Loop through all MBs. Note activity of each, average activity and
// calculate a normalized activity for each
static void build_activity_map(VP8_COMP *cpi) {
  MACROBLOCK *const x = & cpi->mb;
  MACROBLOCKD *xd = &x->e_mbd;
  VP8_COMMON *const cm = & cpi->common;

#if ALT_ACT_MEASURE
  YV12_BUFFER_CONFIG *new_yv12 = &cm->yv12_fb[cm->new_fb_idx];
  int recon_yoffset;
  int recon_y_stride = new_yv12->y_stride;
#endif

  int mb_row, mb_col;
  unsigned int mb_activity;
  int64_t activity_sum = 0;

  // for each macroblock row in image
  for (mb_row = 0; mb_row < cm->mb_rows; mb_row++) {
#if ALT_ACT_MEASURE
    // reset above block coeffs
    xd->up_available = (mb_row != 0);
    recon_yoffset = (mb_row * recon_y_stride * 16);
#endif
    // for each macroblock col in image
    for (mb_col = 0; mb_col < cm->mb_cols; mb_col++) {
#if ALT_ACT_MEASURE
      xd->dst.y_buffer = new_yv12->y_buffer + recon_yoffset;
      xd->left_available = (mb_col != 0);
      recon_yoffset += 16;
#endif
      // Copy current mb to a buffer
      RECON_INVOKE(&xd->rtcd->recon, copy16x16)(x->src.y_buffer,
                                                x->src.y_stride,
                                                x->thismb, 16);

      // measure activity
      mb_activity = mb_activity_measure(cpi, x, mb_row, mb_col);

      // Keep frame sum
      activity_sum += mb_activity;

      // Store MB level activity details.
      *x->mb_activity_ptr = mb_activity;

      // Increment activity map pointer
      x->mb_activity_ptr++;

      // adjust to the next column of source macroblocks
      x->src.y_buffer += 16;
    }


    // adjust to the next row of mbs
    x->src.y_buffer += 16 * x->src.y_stride - 16 * cm->mb_cols;

#if ALT_ACT_MEASURE
    // extend the recon for intra prediction
    vp8_extend_mb_row(new_yv12, xd->dst.y_buffer + 16,
                      xd->dst.u_buffer + 8, xd->dst.v_buffer + 8);
#endif

  }

  // Calculate an "average" MB activity
  calc_av_activity(cpi, activity_sum);

#if USE_ACT_INDEX
  // Calculate an activity index number of each mb
  calc_activity_index(cpi, x);
#endif

}

// Macroblock activity masking
void vp8_activity_masking(VP8_COMP *cpi, MACROBLOCK *x) {
#if USE_ACT_INDEX
  x->rdmult += *(x->mb_activity_ptr) * (x->rdmult >> 2);
  x->errorperbit = x->rdmult * 100 / (110 * x->rddiv);
  x->errorperbit += (x->errorperbit == 0);
#else
  int64_t a;
  int64_t b;
  int64_t act = *(x->mb_activity_ptr);

  // Apply the masking to the RD multiplier.
  a = act + (2 * cpi->activity_avg);
  b = (2 * act) + cpi->activity_avg;

  x->rdmult = (unsigned int)(((int64_t)x->rdmult * b + (a >> 1)) / a);
  x->errorperbit = x->rdmult * 100 / (110 * x->rddiv);
  x->errorperbit += (x->errorperbit == 0);
#endif

  // Activity based Zbin adjustment
  adjust_act_zbin(cpi, x);
}

static void update_state(VP8_COMP *cpi, MACROBLOCK *x, PICK_MODE_CONTEXT *ctx) {
  int i;
  MACROBLOCKD *xd = &x->e_mbd;
  MODE_INFO *mi = &ctx->mic;
  MB_MODE_INFO * mbmi = &xd->mode_info_context->mbmi;
  int mb_mode = mi->mbmi.mode;
  int mb_mode_index = ctx->best_mode_index;

#if CONFIG_DEBUG
  assert(mb_mode < MB_MODE_COUNT);
  assert(mb_mode_index < MAX_MODES);
  assert(mi->mbmi.ref_frame < MAX_REF_FRAMES);
#endif

  // Restore the coding context of the MB to that that was in place
  // when the mode was picked for it
  vpx_memcpy(xd->mode_info_context, mi, sizeof(MODE_INFO));

  if (mb_mode == B_PRED) {
    for (i = 0; i < 16; i++) {
      xd->block[i].bmi.as_mode = xd->mode_info_context->bmi[i].as_mode;
      assert(xd->block[i].bmi.as_mode.first < MB_MODE_COUNT);
    }
  } else if (mb_mode == I8X8_PRED) {
    for (i = 0; i < 16; i++) {
      xd->block[i].bmi = xd->mode_info_context->bmi[i];
    }
  } else if (mb_mode == SPLITMV) {
    vpx_memcpy(x->partition_info, &ctx->partition_info,
               sizeof(PARTITION_INFO));

    mbmi->mv[0].as_int = x->partition_info->bmi[15].mv.as_int;
    mbmi->mv[1].as_int = x->partition_info->bmi[15].second_mv.as_int;
  }

  if (cpi->common.frame_type == KEY_FRAME) {
    // Restore the coding modes to that held in the coding context
    // if (mb_mode == B_PRED)
    //    for (i = 0; i < 16; i++)
    //    {
    //        xd->block[i].bmi.as_mode =
    //                          xd->mode_info_context->bmi[i].as_mode;
    //        assert(xd->mode_info_context->bmi[i].as_mode < MB_MODE_COUNT);
    //    }
#if CONFIG_INTERNAL_STATS
    static const int kf_mode_index[] = {
      THR_DC /*DC_PRED*/,
      THR_V_PRED /*V_PRED*/,
      THR_H_PRED /*H_PRED*/,
      THR_D45_PRED /*D45_PRED*/,
      THR_D135_PRED /*D135_PRED*/,
      THR_D117_PRED /*D117_PRED*/,
      THR_D153_PRED /*D153_PRED*/,
      THR_D27_PRED /*D27_PRED*/,
      THR_D63_PRED /*D63_PRED*/,
      THR_TM /*TM_PRED*/,
      THR_I8X8_PRED /*I8X8_PRED*/,
      THR_B_PRED /*B_PRED*/,
    };
    cpi->mode_chosen_counts[kf_mode_index[mb_mode]]++;
#endif
  } else {
    /*
            // Reduce the activation RD thresholds for the best choice mode
            if ((cpi->rd_baseline_thresh[mb_mode_index] > 0) &&
                (cpi->rd_baseline_thresh[mb_mode_index] < (INT_MAX >> 2)))
            {
                int best_adjustment = (cpi->rd_thresh_mult[mb_mode_index] >> 2);

                cpi->rd_thresh_mult[mb_mode_index] =
                        (cpi->rd_thresh_mult[mb_mode_index]
                         >= (MIN_THRESHMULT + best_adjustment)) ?
                                cpi->rd_thresh_mult[mb_mode_index] - best_adjustment :
                                MIN_THRESHMULT;
                cpi->rd_threshes[mb_mode_index] =
                        (cpi->rd_baseline_thresh[mb_mode_index] >> 7)
                        * cpi->rd_thresh_mult[mb_mode_index];

            }
    */
    // Note how often each mode chosen as best
    cpi->mode_chosen_counts[mb_mode_index]++;

    rd_update_mvcount(cpi, x, &ctx->best_ref_mv, &ctx->second_best_ref_mv);

    cpi->prediction_error += ctx->distortion;
    cpi->intra_error += ctx->intra_error;
  }
}

static void pick_mb_modes(VP8_COMP *cpi,
                          VP8_COMMON *cm,
                          int mb_row,
                          int mb_col,
                          MACROBLOCK  *x,
                          MACROBLOCKD *xd,
                          TOKENEXTRA **tp,
                          int *totalrate) {
  int i;
  int map_index;
  int recon_yoffset, recon_uvoffset;
  int ref_fb_idx = cm->lst_fb_idx;
  int dst_fb_idx = cm->new_fb_idx;
  int recon_y_stride = cm->yv12_fb[ref_fb_idx].y_stride;
  int recon_uv_stride = cm->yv12_fb[ref_fb_idx].uv_stride;
  ENTROPY_CONTEXT_PLANES left_context[2];
  ENTROPY_CONTEXT_PLANES above_context[2];
  ENTROPY_CONTEXT_PLANES *initial_above_context_ptr = cm->above_context
                                                      + mb_col;

  // Offsets to move pointers from MB to MB within a SB in raster order
  int row_delta[4] = { 0, +1,  0, -1};
  int col_delta[4] = { +1, -1, +1, +1};

  /* Function should not modify L & A contexts; save and restore on exit */
  vpx_memcpy(left_context,
             cpi->left_context,
             sizeof(left_context));
  vpx_memcpy(above_context,
             initial_above_context_ptr,
             sizeof(above_context));

  /* Encode MBs in raster order within the SB */
  for (i = 0; i < 4; i++) {
    int dy = row_delta[i];
    int dx = col_delta[i];
    int offset_unextended = dy * cm->mb_cols + dx;
    int offset_extended   = dy * xd->mode_info_stride + dx;
    MB_MODE_INFO * mbmi = &xd->mode_info_context->mbmi;

    // TODO Many of the index items here can be computed more efficiently!

    if ((mb_row >= cm->mb_rows) || (mb_col >= cm->mb_cols)) {
      // MB lies outside frame, move on
      mb_row += dy;
      mb_col += dx;

      // Update pointers
      x->src.y_buffer += 16 * (dx + dy * x->src.y_stride);
      x->src.u_buffer += 8  * (dx + dy * x->src.uv_stride);
      x->src.v_buffer += 8  * (dx + dy * x->src.uv_stride);

      x->gf_active_ptr += offset_unextended;
      x->partition_info += offset_extended;
      xd->mode_info_context += offset_extended;
      xd->prev_mode_info_context += offset_extended;
#if CONFIG_DEBUG
      assert((xd->prev_mode_info_context - cpi->common.prev_mip) ==
             (xd->mode_info_context - cpi->common.mip));
#endif
      continue;
    }

    // Index of the MB in the SB 0..3
    xd->mb_index = i;

    map_index = (mb_row * cpi->common.mb_cols) + mb_col;
    x->mb_activity_ptr = &cpi->mb_activity_map[map_index];

    // set above context pointer
    xd->above_context = cm->above_context + mb_col;

    // Restore the appropriate left context depending on which
    // row in the SB the MB is situated
    vpx_memcpy(&cm->left_context,
               &cpi->left_context[i >> 1],
               sizeof(ENTROPY_CONTEXT_PLANES));

    // Set up distance of MB to edge of frame in 1/8th pel units
    xd->mb_to_top_edge    = -((mb_row * 16) << 3);
    xd->mb_to_left_edge   = -((mb_col * 16) << 3);
    xd->mb_to_bottom_edge = ((cm->mb_rows - 1 - mb_row) * 16) << 3;
    xd->mb_to_right_edge  = ((cm->mb_cols - 1 - mb_col) * 16) << 3;

    // Set up limit values for MV components to prevent them from
    // extending beyond the UMV borders assuming 16x16 block size
    x->mv_row_min = -((mb_row * 16) + VP8BORDERINPIXELS - INTERP_EXTEND);
    x->mv_col_min = -((mb_col * 16) + VP8BORDERINPIXELS - INTERP_EXTEND);
    x->mv_row_max = ((cm->mb_rows - mb_row) * 16 +
                     (VP8BORDERINPIXELS - 16 - INTERP_EXTEND));
    x->mv_col_max = ((cm->mb_cols - mb_col) * 16 +
                     (VP8BORDERINPIXELS - 16 - INTERP_EXTEND));

    xd->up_available   = (mb_row != 0);
    xd->left_available = (mb_col != 0);

    recon_yoffset  = (mb_row * recon_y_stride * 16) + (mb_col * 16);
    recon_uvoffset = (mb_row * recon_uv_stride * 8) + (mb_col *  8);

    xd->dst.y_buffer = cm->yv12_fb[dst_fb_idx].y_buffer + recon_yoffset;
    xd->dst.u_buffer = cm->yv12_fb[dst_fb_idx].u_buffer + recon_uvoffset;
    xd->dst.v_buffer = cm->yv12_fb[dst_fb_idx].v_buffer + recon_uvoffset;

    // Copy current MB to a work buffer
    RECON_INVOKE(&xd->rtcd->recon, copy16x16)(x->src.y_buffer,
                                              x->src.y_stride,
                                              x->thismb, 16);

    x->rddiv = cpi->RDDIV;
    x->rdmult = cpi->RDMULT;

    if (cpi->oxcf.tuning == VP8_TUNE_SSIM)
      vp8_activity_masking(cpi, x);

    // Is segmentation enabled
    if (xd->segmentation_enabled) {
      // Code to set segment id in xd->mbmi.segment_id
      if (cpi->segmentation_map[map_index] <= 3)
        mbmi->segment_id = cpi->segmentation_map[map_index];
      else
        mbmi->segment_id = 0;

      vp8cx_mb_init_quantizer(cpi, x);
    } else
      // Set to Segment 0 by default
      mbmi->segment_id = 0;

    x->active_ptr = cpi->active_map + map_index;

    /* force 4x4 transform for mode selection */
    mbmi->txfm_size = TX_4X4; // TODO IS this right??

    cpi->update_context = 0;    // TODO Do we need this now??

    // Find best coding mode & reconstruct the MB so it is available
    // as a predictor for MBs that follow in the SB
    if (cm->frame_type == KEY_FRAME) {
      *totalrate += vp8_rd_pick_intra_mode(cpi, x);

      // Save the coding context
      vpx_memcpy(&x->mb_context[i].mic, xd->mode_info_context,
                 sizeof(MODE_INFO));

      // Dummy encode, do not do the tokenization
      vp8cx_encode_intra_macro_block(cpi, x, tp, 0);
      // Note the encoder may have changed the segment_id
    } else {
      int seg_id;

      if (xd->segmentation_enabled && cpi->seg0_cnt > 0 &&
          !segfeature_active(xd, 0, SEG_LVL_REF_FRAME) &&
          segfeature_active(xd, 1, SEG_LVL_REF_FRAME) &&
          check_segref(xd, 1, INTRA_FRAME)  +
          check_segref(xd, 1, LAST_FRAME)   +
          check_segref(xd, 1, GOLDEN_FRAME) +
          check_segref(xd, 1, ALTREF_FRAME) == 1) {
        cpi->seg0_progress = (cpi->seg0_idx << 16) / cpi->seg0_cnt;
      } else {
        cpi->seg0_progress = (((mb_col & ~1) * 2 + (mb_row & ~1) * cm->mb_cols + i) << 16) / cm->MBs;
      }

      *totalrate += vp8cx_pick_mode_inter_macroblock(cpi, x,
                                                     recon_yoffset,
                                                     recon_uvoffset);

      // Dummy encode, do not do the tokenization
      vp8cx_encode_inter_macroblock(cpi, x, tp,
                                    recon_yoffset, recon_uvoffset, 0);

      seg_id = mbmi->segment_id;
      if (cpi->mb.e_mbd.segmentation_enabled && seg_id == 0) {
        cpi->seg0_idx++;
      }
      if (!xd->segmentation_enabled ||
          !segfeature_active(xd, seg_id, SEG_LVL_REF_FRAME) ||
          check_segref(xd, seg_id, INTRA_FRAME)  +
          check_segref(xd, seg_id, LAST_FRAME)   +
          check_segref(xd, seg_id, GOLDEN_FRAME) +
          check_segref(xd, seg_id, ALTREF_FRAME) > 1) {
        // Get the prediction context and status
        int pred_flag = get_pred_flag(xd, PRED_REF);
        int pred_context = get_pred_context(cm, xd, PRED_REF);

        // Count prediction success
        cpi->ref_pred_count[pred_context][pred_flag]++;
      }
    }

    // Keep a copy of the updated left context
    vpx_memcpy(&cpi->left_context[i >> 1],
               &cm->left_context,
               sizeof(ENTROPY_CONTEXT_PLANES));

    // Next MB
    mb_row += dy;
    mb_col += dx;

    x->src.y_buffer += 16 * (dx + dy * x->src.y_stride);
    x->src.u_buffer += 8  * (dx + dy * x->src.uv_stride);
    x->src.v_buffer += 8  * (dx + dy * x->src.uv_stride);

    x->gf_active_ptr += offset_unextended;
    x->partition_info += offset_extended;
    xd->mode_info_context += offset_extended;
    xd->prev_mode_info_context += offset_extended;

#if CONFIG_DEBUG
    assert((xd->prev_mode_info_context - cpi->common.prev_mip) ==
           (xd->mode_info_context - cpi->common.mip));
#endif
  }

  /* Restore L & A coding context to those in place on entry */
  vpx_memcpy(cpi->left_context,
             left_context,
             sizeof(left_context));
  vpx_memcpy(initial_above_context_ptr,
             above_context,
             sizeof(above_context));
}

static void encode_sb(VP8_COMP *cpi,
                      VP8_COMMON *cm,
                      int mbrow,
                      int mbcol,
                      MACROBLOCK  *x,
                      MACROBLOCKD *xd,
                      TOKENEXTRA **tp) {
  int i;
  int map_index;
  int mb_row, mb_col;
  int recon_yoffset, recon_uvoffset;
  int ref_fb_idx = cm->lst_fb_idx;
  int dst_fb_idx = cm->new_fb_idx;
  int recon_y_stride = cm->yv12_fb[ref_fb_idx].y_stride;
  int recon_uv_stride = cm->yv12_fb[ref_fb_idx].uv_stride;
  int row_delta[4] = { 0, +1,  0, -1};
  int col_delta[4] = { +1, -1, +1, +1};

  mb_row = mbrow;
  mb_col = mbcol;

  /* Encode MBs in raster order within the SB */
  for (i = 0; i < 4; i++) {
    int dy = row_delta[i];
    int dx = col_delta[i];
    int offset_extended   = dy * xd->mode_info_stride + dx;
    int offset_unextended = dy * cm->mb_cols + dx;
    MB_MODE_INFO * mbmi = &xd->mode_info_context->mbmi;

    if ((mb_row >= cm->mb_rows) || (mb_col >= cm->mb_cols)) {
      // MB lies outside frame, move on
      mb_row += dy;
      mb_col += dx;

      x->src.y_buffer += 16 * (dx + dy * x->src.y_stride);
      x->src.u_buffer += 8  * (dx + dy * x->src.uv_stride);
      x->src.v_buffer += 8  * (dx + dy * x->src.uv_stride);

      x->gf_active_ptr      += offset_unextended;
      x->partition_info     += offset_extended;
      xd->mode_info_context += offset_extended;
      xd->prev_mode_info_context += offset_extended;

#if CONFIG_DEBUG
      assert((xd->prev_mode_info_context - cpi->common.prev_mip) ==
             (xd->mode_info_context - cpi->common.mip));
#endif
      continue;
    }

    xd->mb_index = i;

#ifdef ENC_DEBUG
    enc_debug = (cpi->common.current_video_frame == 0 &&
                 mb_row == 0 && mb_col == 0);
    mb_col_debug = mb_col;
    mb_row_debug = mb_row;
#endif

    // Restore MB state to that when it was picked
#if CONFIG_SUPERBLOCKS
    if (x->encode_as_sb)
      update_state(cpi, x, &x->sb_context[i]);
    else
#endif
      update_state(cpi, x, &x->mb_context[i]);

    // Copy in the appropriate left context
    vpx_memcpy(&cm->left_context,
               &cpi->left_context[i >> 1],
               sizeof(ENTROPY_CONTEXT_PLANES));

    map_index = (mb_row * cpi->common.mb_cols) + mb_col;
    x->mb_activity_ptr = &cpi->mb_activity_map[map_index];

    // reset above block coeffs
    xd->above_context = cm->above_context + mb_col;

    // Set up distance of MB to edge of the frame in 1/8th pel units
    xd->mb_to_top_edge    = -((mb_row * 16) << 3);
    xd->mb_to_left_edge   = -((mb_col * 16) << 3);
    xd->mb_to_bottom_edge = ((cm->mb_rows - 1 - mb_row) * 16) << 3;
    xd->mb_to_right_edge  = ((cm->mb_cols - 1 - mb_col) * 16) << 3;

    // Set up limit values for MV components to prevent them from
    // extending beyond the UMV borders assuming 16x16 block size
    x->mv_row_min = -((mb_row * 16) + VP8BORDERINPIXELS - INTERP_EXTEND);
    x->mv_col_min = -((mb_col * 16) + VP8BORDERINPIXELS - INTERP_EXTEND);
    x->mv_row_max = ((cm->mb_rows - mb_row) * 16 +
                     (VP8BORDERINPIXELS - 16 - INTERP_EXTEND));
    x->mv_col_max = ((cm->mb_cols - mb_col) * 16 +
                     (VP8BORDERINPIXELS - 16 - INTERP_EXTEND));

#if CONFIG_SUPERBLOCKS
    // Set up limit values for MV components to prevent them from
    // extending beyond the UMV borders assuming 32x32 block size
    x->mv_row_min_sb = -((mb_row * 16) + VP8BORDERINPIXELS - INTERP_EXTEND);
    x->mv_col_min_sb = -((mb_col * 16) + VP8BORDERINPIXELS - INTERP_EXTEND);
    x->mv_row_max_sb = ((cm->mb_rows - mb_row) * 16 +
                        (VP8BORDERINPIXELS - 32 - INTERP_EXTEND));
    x->mv_col_max_sb = ((cm->mb_cols - mb_col) * 16 +
                        (VP8BORDERINPIXELS - 32 - INTERP_EXTEND));
#endif

    xd->up_available = (mb_row != 0);
    xd->left_available = (mb_col != 0);

    recon_yoffset = (mb_row * recon_y_stride * 16) + (mb_col * 16);
    recon_uvoffset = (mb_row * recon_uv_stride * 8) + (mb_col * 8);

    xd->dst.y_buffer = cm->yv12_fb[dst_fb_idx].y_buffer + recon_yoffset;
    xd->dst.u_buffer = cm->yv12_fb[dst_fb_idx].u_buffer + recon_uvoffset;
    xd->dst.v_buffer = cm->yv12_fb[dst_fb_idx].v_buffer + recon_uvoffset;

    // Copy current MB to a work buffer
    RECON_INVOKE(&xd->rtcd->recon, copy16x16)(x->src.y_buffer,
                                              x->src.y_stride,
                                              x->thismb, 16);

    if (cpi->oxcf.tuning == VP8_TUNE_SSIM)
      vp8_activity_masking(cpi, x);

    // Is segmentation enabled
    if (xd->segmentation_enabled) {
      // Code to set segment id in xd->mbmi.segment_id
      if (cpi->segmentation_map[map_index] <= 3)
        mbmi->segment_id = cpi->segmentation_map[map_index];
      else
        mbmi->segment_id = 0;

      vp8cx_mb_init_quantizer(cpi, x);
    } else
      // Set to Segment 0 by default
      mbmi->segment_id = 0;

    x->active_ptr = cpi->active_map + map_index;

    cpi->update_context = 0;

    if (cm->frame_type == KEY_FRAME) {
      vp8cx_encode_intra_macro_block(cpi, x, tp, 1);
      // Note the encoder may have changed the segment_id

#ifdef MODE_STATS
      y_modes[mbmi->mode]++;
#endif
    } else {
      unsigned char *segment_id;
      int seg_ref_active;

      vp8cx_encode_inter_macroblock(cpi, x, tp,
                                    recon_yoffset, recon_uvoffset, 1);
      // Note the encoder may have changed the segment_id

#ifdef MODE_STATS
      inter_y_modes[mbmi->mode]++;

      if (mbmi->mode == SPLITMV) {
        int b;

        for (b = 0; b < x->partition_info->count; b++) {
          inter_b_modes[x->partition_info->bmi[b].mode]++;
        }
      }

#endif

      // If we have just a single reference frame coded for a segment then
      // exclude from the reference frame counts used to work out
      // probabilities. NOTE: At the moment we dont support custom trees
      // for the reference frame coding for each segment but this is a
      // possible future action.
      segment_id = &mbmi->segment_id;
      seg_ref_active = segfeature_active(xd, *segment_id, SEG_LVL_REF_FRAME);
      if (!seg_ref_active ||
          ((check_segref(xd, *segment_id, INTRA_FRAME) +
            check_segref(xd, *segment_id, LAST_FRAME) +
            check_segref(xd, *segment_id, GOLDEN_FRAME) +
            check_segref(xd, *segment_id, ALTREF_FRAME)) > 1)) {
        {
          cpi->count_mb_ref_frame_usage[mbmi->ref_frame]++;
        }
      }

      // Count of last ref frame 0,0 usage
      if ((mbmi->mode == ZEROMV) && (mbmi->ref_frame == LAST_FRAME))
        cpi->inter_zz_count++;
    }

    // TODO Partitioning is broken!
    cpi->tplist[mb_row].stop = *tp;

    // Copy back updated left context
    vpx_memcpy(&cpi->left_context[i >> 1],
               &cm->left_context,
               sizeof(ENTROPY_CONTEXT_PLANES));

    // Next MB
    mb_row += dy;
    mb_col += dx;

    x->src.y_buffer += 16 * (dx + dy * x->src.y_stride);
    x->src.u_buffer += 8  * (dx + dy * x->src.uv_stride);
    x->src.v_buffer += 8  * (dx + dy * x->src.uv_stride);

    x->gf_active_ptr      += offset_unextended;
    x->partition_info     += offset_extended;
    xd->mode_info_context += offset_extended;
    xd->prev_mode_info_context += offset_extended;

#if CONFIG_DEBUG
    assert((xd->prev_mode_info_context - cpi->common.prev_mip) ==
           (xd->mode_info_context - cpi->common.mip));
#endif
  }

  // debug output
#if DBG_PRNT_SEGMAP
  {
    FILE *statsfile;
    statsfile = fopen("segmap2.stt", "a");
    fprintf(statsfile, "\n");
    fclose(statsfile);
  }
#endif
}

static
void encode_sb_row(VP8_COMP *cpi,
                   VP8_COMMON *cm,
                   int mb_row,
                   MACROBLOCK  *x,
                   MACROBLOCKD *xd,
                   TOKENEXTRA **tp,
                   int *totalrate) {
  int mb_col;
  int mb_cols = cm->mb_cols;

  // Initialize the left context for the new SB row
  vpx_memset(cpi->left_context, 0, sizeof(cpi->left_context));
  vpx_memset(&cm->left_context, 0, sizeof(ENTROPY_CONTEXT_PLANES));

  // Code each SB in the row
  for (mb_col = 0; mb_col < mb_cols; mb_col += 2) {
    int mb_rate = 0;
#if CONFIG_SUPERBLOCKS
    int sb_rate = INT_MAX;
#endif

#if CONFIG_DEBUG
    MODE_INFO *mic = xd->mode_info_context;
    PARTITION_INFO *pi = x->partition_info;
    signed char  *gfa = x->gf_active_ptr;
    unsigned char *yb = x->src.y_buffer;
    unsigned char *ub = x->src.u_buffer;
    unsigned char *vb = x->src.v_buffer;
#endif

    // Pick modes assuming the SB is coded as 4 independent MBs
    pick_mb_modes(cpi, cm, mb_row, mb_col, x, xd, tp, &mb_rate);

    x->src.y_buffer -= 32;
    x->src.u_buffer -= 16;
    x->src.v_buffer -= 16;

    x->gf_active_ptr -= 2;
    x->partition_info -= 2;
    xd->mode_info_context -= 2;
    xd->prev_mode_info_context -= 2;

#if CONFIG_DEBUG
    assert(x->gf_active_ptr == gfa);
    assert(x->partition_info == pi);
    assert(xd->mode_info_context == mic);
    assert(x->src.y_buffer == yb);
    assert(x->src.u_buffer == ub);
    assert(x->src.v_buffer == vb);
#endif

#if CONFIG_SUPERBLOCKS
    // Pick a mode assuming that it applies all 4 of the MBs in the SB
    pick_sb_modes(cpi, cm, mb_row, mb_col, x, xd, &sb_rate);

    // Decide whether to encode as a SB or 4xMBs
    if (sb_rate < mb_rate) {
      x->encode_as_sb = 1;
      *totalrate += sb_rate;
    } else
#endif
    {
      x->encode_as_sb = 0;
      *totalrate += mb_rate;
    }

    // Encode SB using best computed mode(s)
    encode_sb(cpi, cm, mb_row, mb_col, x, xd, tp);

#if CONFIG_DEBUG
    assert(x->gf_active_ptr == gfa + 2);
    assert(x->partition_info == pi + 2);
    assert(xd->mode_info_context == mic + 2);
    assert(x->src.y_buffer == yb + 32);
    assert(x->src.u_buffer == ub + 16);
    assert(x->src.v_buffer == vb + 16);
#endif
  }

  // this is to account for the border
  x->gf_active_ptr += mb_cols - (mb_cols & 0x1);
  x->partition_info += xd->mode_info_stride + 1 - (mb_cols & 0x1);
  xd->mode_info_context += xd->mode_info_stride + 1 - (mb_cols & 0x1);
  xd->prev_mode_info_context += xd->mode_info_stride + 1 - (mb_cols & 0x1);

#if CONFIG_DEBUG
  assert((xd->prev_mode_info_context - cpi->common.prev_mip) ==
         (xd->mode_info_context - cpi->common.mip));
#endif
}

void init_encode_frame_mb_context(VP8_COMP *cpi) {
  MACROBLOCK *const x = & cpi->mb;
  VP8_COMMON *const cm = & cpi->common;
  MACROBLOCKD *const xd = & x->e_mbd;

  // GF active flags data structure
  x->gf_active_ptr = (signed char *)cpi->gf_active_flags;