vpx/vp8/encoder/segmentation.c

/*
 *  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 "segmentation.h"
#include "vp8/common/pred_common.h"

void vp8_update_gf_useage_maps(VP8_COMP *cpi, VP8_COMMON *cm, MACROBLOCK *x)
{
    int mb_row, mb_col;

    MODE_INFO *this_mb_mode_info = cm->mi;

    x->gf_active_ptr = (signed char *)cpi->gf_active_flags;

    if ((cm->frame_type == KEY_FRAME) || (cm->refresh_golden_frame))
    {
        // Reset Gf useage monitors
        vpx_memset(cpi->gf_active_flags, 1, (cm->mb_rows * cm->mb_cols));
        cpi->gf_active_count = cm->mb_rows * cm->mb_cols;
    }
    else
    {
        // for each macroblock row in image
        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++)
            {

                // If using golden then set GF active flag if not already set.
                // If using last frame 0,0 mode then leave flag as it is
                // else if using non 0,0 motion or intra modes then clear
                // flag if it is currently set
                if ((this_mb_mode_info->mbmi.ref_frame == GOLDEN_FRAME) ||
                    (this_mb_mode_info->mbmi.ref_frame == ALTREF_FRAME))
                {
                    if (*(x->gf_active_ptr) == 0)
                    {
                        *(x->gf_active_ptr) = 1;
                        cpi->gf_active_count ++;
                    }
                }
                else if ((this_mb_mode_info->mbmi.mode != ZEROMV) &&
                         *(x->gf_active_ptr))
                {
                    *(x->gf_active_ptr) = 0;
                    cpi->gf_active_count--;
                }

                x->gf_active_ptr++;          // Step onto next entry
                this_mb_mode_info++;         // skip to next mb

            }

            // this is to account for the border
            this_mb_mode_info++;
        }
    }
}

void vp8_enable_segmentation(VP8_PTR ptr)
{
    VP8_COMP *cpi = (VP8_COMP *)(ptr);

    // Set the appropriate feature bit
    cpi->mb.e_mbd.segmentation_enabled = 1;
    cpi->mb.e_mbd.update_mb_segmentation_map = 1;
    cpi->mb.e_mbd.update_mb_segmentation_data = 1;
}

void vp8_disable_segmentation(VP8_PTR ptr)
{
    VP8_COMP *cpi = (VP8_COMP *)(ptr);

    // Clear the appropriate feature bit
    cpi->mb.e_mbd.segmentation_enabled = 0;
}

void vp8_set_segmentation_map(VP8_PTR ptr,
                              unsigned char *segmentation_map)
{
    VP8_COMP *cpi = (VP8_COMP *)(ptr);

    // Copy in the new segmentation map
    vpx_memcpy( cpi->segmentation_map, segmentation_map,
                (cpi->common.mb_rows * cpi->common.mb_cols) );

    // Signal that the map should be updated.
    cpi->mb.e_mbd.update_mb_segmentation_map = 1;
    cpi->mb.e_mbd.update_mb_segmentation_data = 1;
}

void vp8_set_segment_data(VP8_PTR ptr,
                          signed char *feature_data,
                          unsigned char abs_delta)
{
    VP8_COMP *cpi = (VP8_COMP *)(ptr);

    cpi->mb.e_mbd.mb_segment_abs_delta = abs_delta;

    vpx_memcpy(cpi->mb.e_mbd.segment_feature_data, feature_data,
               sizeof(cpi->mb.e_mbd.segment_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( MACROBLOCKD * xd,
                                int * segcounts,
                                vp8_prob * segment_tree_probs )
{
    int count1,count2;
    int tot_count;
    int i;

    // Blank the strtucture to start with
    vpx_memset(segment_tree_probs, 0, sizeof(segment_tree_probs));

    // Total count for all segments
    count1 = segcounts[0] + segcounts[1];
    count2 = segcounts[2] + segcounts[3];
    tot_count = count1 + count2;

    // Work out probabilities of each segment
    if (tot_count)
        segment_tree_probs[0] = (count1 * 255) / tot_count;
    if (count1 > 0)
        segment_tree_probs[1] = (segcounts[0] * 255) / count1;
    if (count2 > 0)
        segment_tree_probs[2] = (segcounts[2] * 255) / count2;

    // Clamp probabilities to minimum allowed value
    for (i = 0; i < MB_FEATURE_TREE_PROBS; i++)
    {
        if (segment_tree_probs[i] == 0)
            segment_tree_probs[i] = 1;
    }
}

// Based on set of segment counts and probabilities calculate a cost estimate
static int cost_segmap( MACROBLOCKD * xd,
                        int * segcounts,
                        vp8_prob * probs )
{
    int cost;
    int count1,count2;

    // Cost the top node of the tree
    count1 = segcounts[0] + segcounts[1];
    count2 = segcounts[2] + segcounts[3];
    cost = count1 * vp8_cost_zero(probs[0]) +
           count2 * vp8_cost_one(probs[0]);

    // Now add the cost of each individual segment branch
    if (count1 > 0)
        cost += segcounts[0] * vp8_cost_zero(probs[1]) +
                segcounts[1] * vp8_cost_one(probs[1]);

    if (count2 > 0)
        cost += segcounts[2] * vp8_cost_zero(probs[2]) +
                segcounts[3] * vp8_cost_one(probs[2]) ;

    return cost;

}

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

    int i;
    int tot_count;
    int no_pred_cost;
    int t_pred_cost = INT_MAX;
    int pred_context;

    int mb_row, mb_col;
    int segmap_index = 0;
    unsigned char segment_id;

    int temporal_predictor_count[PREDICTION_PROBS][2];
    int no_pred_segcounts[MAX_MB_SEGMENTS];
    int t_unpred_seg_counts[MAX_MB_SEGMENTS];

    vp8_prob no_pred_tree[MB_FEATURE_TREE_PROBS];
    vp8_prob t_pred_tree[MB_FEATURE_TREE_PROBS];
    vp8_prob t_nopred_prob[PREDICTION_PROBS];

    // Set default state for the segment tree probabilities and the
    // temporal coding probabilities
    vpx_memset(xd->mb_segment_tree_probs, 255,
               sizeof(xd->mb_segment_tree_probs));
    vpx_memset(cm->segment_pred_probs, 255,
               sizeof(cm->segment_pred_probs));

    vpx_memset(no_pred_segcounts, 0, sizeof(no_pred_segcounts));
    vpx_memset(t_unpred_seg_counts, 0, sizeof(t_unpred_seg_counts));
    vpx_memset(temporal_predictor_count, 0, sizeof(temporal_predictor_count));

    // First of all generate stats regarding how well the last segment map
    // predicts this one

    // Initialize macroblock decoder mode info context for the first mb
    // in the frame
    xd->mode_info_context = cm->mi;

    for (mb_row = 0; mb_row < cm->mb_rows; mb_row++)
    {
        for (mb_col = 0; mb_col < cm->mb_cols; mb_col++)
        {
            segment_id = xd->mode_info_context->mbmi.segment_id;

            // 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)
            {
                // Test to see if the segment id matches the predicted value.
                int seg_predicted =
                    (segment_id == get_pred_mb_segid( cm, segmap_index ));

                // Get the segment id prediction context
                pred_context =
                    get_pred_context( cm, xd, PRED_SEG_ID );

                // Store the prediction status for this mb and update counts
                // as appropriate
                set_pred_flag( xd, PRED_SEG_ID, seg_predicted );
                temporal_predictor_count[pred_context][seg_predicted]++;

                if ( !seg_predicted )
                    // Update the "unpredicted" segment count
                    t_unpred_seg_counts[segment_id]++;
            }

            // Step on to the next mb
            xd->mode_info_context++;

            // Step on to the next entry in the segment maps
            segmap_index++;
        }

        // this is to account for the border in mode_info_context
        xd->mode_info_context++;
    }

    // Work out probability tree for coding segments without prediction
    // and the cost.
    calc_segtree_probs( xd, no_pred_segcounts, no_pred_tree );
    no_pred_cost = cost_segmap( xd, no_pred_segcounts, no_pred_tree );

    // Key frames cannot use temporal prediction
    if (cm->frame_type != KEY_FRAME)
    {
        // Work out probability tree for coding those segments not
        // predicted using the temporal method and the cost.
        calc_segtree_probs( xd, t_unpred_seg_counts, t_pred_tree );
        t_pred_cost = cost_segmap( xd, t_unpred_seg_counts, t_pred_tree );

        // Add in the cost of the signalling for each prediction context
        for ( i = 0; i < PREDICTION_PROBS; i++ )
        {
            tot_count = temporal_predictor_count[i][0] +
                        temporal_predictor_count[i][1];

            // Work out the context probabilities for the segment
            // prediction flag
            if ( tot_count )
            {
                t_nopred_prob[i] = ( temporal_predictor_count[i][0] * 255 ) /
                                   tot_count;

                // Clamp to minimum allowed value
                if ( t_nopred_prob[i] < 1 )
                    t_nopred_prob[i] = 1;
            }
            else
                t_nopred_prob[i] = 1;

            // Add in the predictor signaling cost
            t_pred_cost += ( temporal_predictor_count[i][0] *
                               vp8_cost_zero(t_nopred_prob[i]) ) +
                           ( temporal_predictor_count[i][1] *
                               vp8_cost_one(t_nopred_prob[i]) );
        }
    }

    // Now choose which coding method to use.
    if ( t_pred_cost < no_pred_cost )
    {
         cm->temporal_update = 1;
         vpx_memcpy( xd->mb_segment_tree_probs,
                     t_pred_tree, sizeof(t_pred_tree) );
         vpx_memcpy( &cm->segment_pred_probs,
                     t_nopred_prob, sizeof(t_nopred_prob) );
    }
    else
    {
         cm->temporal_update = 0;
         vpx_memcpy( xd->mb_segment_tree_probs,
                     no_pred_tree, sizeof(no_pred_tree) );
    }
}