ffmpeg/libavcodec/error_resilience.c

/*
 * Error resilience / concealment
 *
 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * Error resilience / concealment.
 */

#include <limits.h>

#include "avcodec.h"
#include "dsputil.h"
#include "mpegvideo.h"
#include "h264.h"
#include "rectangle.h"
#include "thread.h"

/*
 * H264 redefines mb_intra so it is not mistakely used (its uninitialized in h264)
 * but error concealment must support both h264 and h263 thus we must undo this
 */
#undef mb_intra

static void decode_mb(MpegEncContext *s, int ref)
{
    s->dest[0] = s->current_picture.f.data[0] + (s->mb_y *  16                       * s->linesize)   + s->mb_x *  16;
    s->dest[1] = s->current_picture.f.data[1] + (s->mb_y * (16 >> s->chroma_y_shift) * s->uvlinesize) + s->mb_x * (16 >> s->chroma_x_shift);
    s->dest[2] = s->current_picture.f.data[2] + (s->mb_y * (16 >> s->chroma_y_shift) * s->uvlinesize) + s->mb_x * (16 >> s->chroma_x_shift);

    ff_init_block_index(s);
    ff_update_block_index(s);
    s->dest[1] += (16 >> s->chroma_x_shift) - 8;
    s->dest[2] += (16 >> s->chroma_x_shift) - 8;

    if (CONFIG_H264_DECODER && s->codec_id == CODEC_ID_H264) {
        H264Context *h = (void*)s;
        h->mb_xy = s->mb_x + s->mb_y * s->mb_stride;
        memset(h->non_zero_count_cache, 0, sizeof(h->non_zero_count_cache));
        av_assert1(ref >= 0);
        /* FIXME: It is possible albeit uncommon that slice references
         * differ between slices. We take the easy approach and ignore
         * it for now. If this turns out to have any relevance in
         * practice then correct remapping should be added. */
        if (ref >= h->ref_count[0])
            ref = 0;
        if (!h->ref_list[0][ref].f.data[0]) {
            av_log(s->avctx, AV_LOG_DEBUG, "Reference not available for error concealing\n");
            ref = 0;
        }
        fill_rectangle(&s->current_picture.f.ref_index[0][4 * h->mb_xy],
                       2, 2, 2, ref, 1);
        fill_rectangle(&h->ref_cache[0][scan8[0]], 4, 4, 8, ref, 1);
        fill_rectangle(h->mv_cache[0][scan8[0]], 4, 4, 8,
                       pack16to32(s->mv[0][0][0], s->mv[0][0][1]), 4);
        h->mb_mbaff =
        h->mb_field_decoding_flag = 0;
        ff_h264_hl_decode_mb(h);
    } else {
        assert(ref == 0);
        ff_MPV_decode_mb(s, s->block);
    }
}

/**
 * @param stride the number of MVs to get to the next row
 * @param mv_step the number of MVs per row or column in a macroblock
 */
static void set_mv_strides(MpegEncContext *s, int *mv_step, int *stride)
{
    if (s->codec_id == CODEC_ID_H264) {
        H264Context *h = (void*)s;
        av_assert0(s->quarter_sample);
        *mv_step = 4;
        *stride  = h->b_stride;
    } else {
        *mv_step = 2;
        *stride  = s->b8_stride;
    }
}

/**
 * Replace the current MB with a flat dc-only version.
 */
static void put_dc(MpegEncContext *s, uint8_t *dest_y, uint8_t *dest_cb,
                   uint8_t *dest_cr, int mb_x, int mb_y)
{
    int dc, dcu, dcv, y, i;
    for (i = 0; i < 4; i++) {
        dc = s->dc_val[0][mb_x * 2 + (i &  1) + (mb_y * 2 + (i >> 1)) * s->b8_stride];
        if (dc < 0)
            dc = 0;
        else if (dc > 2040)
            dc = 2040;
        for (y = 0; y < 8; y++) {
            int x;
            for (x = 0; x < 8; x++)
                dest_y[x + (i &  1) * 8 + (y + (i >> 1) * 8) * s->linesize] = dc / 8;
        }
    }
    dcu = s->dc_val[1][mb_x + mb_y * s->mb_stride];
    dcv = s->dc_val[2][mb_x + mb_y * s->mb_stride];
    if (dcu < 0)
        dcu = 0;
    else if (dcu > 2040)
        dcu = 2040;
    if (dcv < 0)
        dcv = 0;
    else if (dcv > 2040)
        dcv = 2040;
    for (y = 0; y < 8; y++) {
        int x;
        for (x = 0; x < 8; x++) {
            dest_cb[x + y * s->uvlinesize] = dcu / 8;
            dest_cr[x + y * s->uvlinesize] = dcv / 8;
        }
    }
}

static void filter181(int16_t *data, int width, int height, int stride)
{
    int x, y;

    /* horizontal filter */
    for (y = 1; y < height - 1; y++) {
        int prev_dc = data[0 + y * stride];

        for (x = 1; x < width - 1; x++) {
            int dc;
            dc = -prev_dc +
                 data[x     + y * stride] * 8 -
                 data[x + 1 + y * stride];
            dc = (dc * 10923 + 32768) >> 16;
            prev_dc = data[x + y * stride];
            data[x + y * stride] = dc;
        }
    }

    /* vertical filter */
    for (x = 1; x < width - 1; x++) {
        int prev_dc = data[x];

        for (y = 1; y < height - 1; y++) {
            int dc;

            dc = -prev_dc +
                 data[x +  y      * stride] * 8 -
                 data[x + (y + 1) * stride];
            dc = (dc * 10923 + 32768) >> 16;
            prev_dc = data[x + y * stride];
            data[x + y * stride] = dc;
        }
    }
}

/**
 * guess the dc of blocks which do not have an undamaged dc
 * @param w     width in 8 pixel blocks
 * @param h     height in 8 pixel blocks
 */
static void guess_dc(MpegEncContext *s, int16_t *dc, int w,
                     int h, int stride, int is_luma)
{
    int b_x, b_y;
    int16_t  (*col )[4] = av_malloc(stride*h*sizeof( int16_t)*4);
    uint32_t (*dist)[4] = av_malloc(stride*h*sizeof(uint32_t)*4);

    for(b_y=0; b_y<h; b_y++){
        int color= 1024;
        int distance= -1;
        for(b_x=0; b_x<w; b_x++){
            int mb_index_j= (b_x>>is_luma) + (b_y>>is_luma)*s->mb_stride;
            int error_j= s->error_status_table[mb_index_j];
            int intra_j = IS_INTRA(s->current_picture.f.mb_type[mb_index_j]);
            if(intra_j==0 || !(error_j&ER_DC_ERROR)){
                color= dc[b_x + b_y*stride];
                distance= b_x;
            }
            col [b_x + b_y*stride][1]= color;
            dist[b_x + b_y*stride][1]= distance >= 0 ? b_x-distance : 9999;
        }
        color= 1024;
        distance= -1;
        for(b_x=w-1; b_x>=0; b_x--){
            int mb_index_j= (b_x>>is_luma) + (b_y>>is_luma)*s->mb_stride;
            int error_j= s->error_status_table[mb_index_j];
            int intra_j = IS_INTRA(s->current_picture.f.mb_type[mb_index_j]);
            if(intra_j==0 || !(error_j&ER_DC_ERROR)){
                color= dc[b_x + b_y*stride];
                distance= b_x;
            }
            col [b_x + b_y*stride][0]= color;
            dist[b_x + b_y*stride][0]= distance >= 0 ? distance-b_x : 9999;
        }
    }
    for(b_x=0; b_x<w; b_x++){
        int color= 1024;
        int distance= -1;
        for(b_y=0; b_y<h; b_y++){
            int mb_index_j= (b_x>>is_luma) + (b_y>>is_luma)*s->mb_stride;
            int error_j= s->error_status_table[mb_index_j];
            int intra_j = IS_INTRA(s->current_picture.f.mb_type[mb_index_j]);
            if(intra_j==0 || !(error_j&ER_DC_ERROR)){
                color= dc[b_x + b_y*stride];
                distance= b_y;
            }
            col [b_x + b_y*stride][3]= color;
            dist[b_x + b_y*stride][3]= distance >= 0 ? b_y-distance : 9999;
        }
        color= 1024;
        distance= -1;
        for(b_y=h-1; b_y>=0; b_y--){
            int mb_index_j= (b_x>>is_luma) + (b_y>>is_luma)*s->mb_stride;
            int error_j= s->error_status_table[mb_index_j];
            int intra_j = IS_INTRA(s->current_picture.f.mb_type[mb_index_j]);
            if(intra_j==0 || !(error_j&ER_DC_ERROR)){
                color= dc[b_x + b_y*stride];
                distance= b_y;
            }
            col [b_x + b_y*stride][2]= color;
            dist[b_x + b_y*stride][2]= distance >= 0 ? distance-b_y : 9999;
        }
    }

    for (b_y = 0; b_y < h; b_y++) {
        for (b_x = 0; b_x < w; b_x++) {
            int mb_index, error, j;
            int64_t guess, weight_sum;
            mb_index = (b_x >> is_luma) + (b_y >> is_luma) * s->mb_stride;
            error    = s->error_status_table[mb_index];

            if (IS_INTER(s->current_picture.f.mb_type[mb_index]))
                continue; // inter
            if (!(error & ER_DC_ERROR))
                continue; // dc-ok

            weight_sum = 0;
            guess      = 0;
            for (j = 0; j < 4; j++) {
                int64_t weight  = 256 * 256 * 256 * 16 / FFMAX(dist[b_x + b_y*stride][j], 1);
                guess          += weight*(int64_t)col[b_x + b_y*stride][j];
                weight_sum     += weight;
            }
            guess = (guess + weight_sum / 2) / weight_sum;
            dc[b_x + b_y * stride] = guess;
        }
    }
    av_freep(&col);
    av_freep(&dist);
}

/**
 * simple horizontal deblocking filter used for error resilience
 * @param w     width in 8 pixel blocks
 * @param h     height in 8 pixel blocks
 */
static void h_block_filter(MpegEncContext *s, uint8_t *dst, int w,
                           int h, int stride, int is_luma)
{
    int b_x, b_y, mvx_stride, mvy_stride;
    uint8_t *cm = ff_cropTbl + MAX_NEG_CROP;
    set_mv_strides(s, &mvx_stride, &mvy_stride);
    mvx_stride >>= is_luma;
    mvy_stride *= mvx_stride;

    for (b_y = 0; b_y < h; b_y++) {
        for (b_x = 0; b_x < w - 1; b_x++) {
            int y;
            int left_status  = s->error_status_table[( b_x      >> is_luma) + (b_y >> is_luma) * s->mb_stride];
            int right_status = s->error_status_table[((b_x + 1) >> is_luma) + (b_y >> is_luma) * s->mb_stride];
            int left_intra   = IS_INTRA(s->current_picture.f.mb_type[( b_x      >> is_luma) + (b_y >> is_luma) * s->mb_stride]);
            int right_intra  = IS_INTRA(s->current_picture.f.mb_type[((b_x + 1) >> is_luma) + (b_y >> is_luma) * s->mb_stride]);
            int left_damage  = left_status & ER_MB_ERROR;
            int right_damage = right_status & ER_MB_ERROR;
            int offset       = b_x * 8 + b_y * stride * 8;
            int16_t *left_mv  = s->current_picture.f.motion_val[0][mvy_stride * b_y + mvx_stride *  b_x];
            int16_t *right_mv = s->current_picture.f.motion_val[0][mvy_stride * b_y + mvx_stride * (b_x + 1)];
            if (!(left_damage || right_damage))
                continue; // both undamaged
            if ((!left_intra) && (!right_intra) &&
                FFABS(left_mv[0] - right_mv[0]) +
                FFABS(left_mv[1] + right_mv[1]) < 2)
                continue;

            for (y = 0; y < 8; y++) {
                int a, b, c, d;

                a = dst[offset + 7 + y * stride] - dst[offset + 6 + y * stride];
                b = dst[offset + 8 + y * stride] - dst[offset + 7 + y * stride];
                c = dst[offset + 9 + y * stride] - dst[offset + 8 + y * stride];

                d = FFABS(b) - ((FFABS(a) + FFABS(c) + 1) >> 1);
                d = FFMAX(d, 0);
                if (b < 0)
                    d = -d;

                if (d == 0)
                    continue;

                if (!(left_damage && right_damage))
                    d = d * 16 / 9;

                if (left_damage) {
                    dst[offset + 7 + y * stride] = cm[dst[offset + 7 + y * stride] + ((d * 7) >> 4)];
                    dst[offset + 6 + y * stride] = cm[dst[offset + 6 + y * stride] + ((d * 5) >> 4)];
                    dst[offset + 5 + y * stride] = cm[dst[offset + 5 + y * stride] + ((d * 3) >> 4)];
                    dst[offset + 4 + y * stride] = cm[dst[offset + 4 + y * stride] + ((d * 1) >> 4)];
                }
                if (right_damage) {
                    dst[offset + 8 + y * stride] = cm[dst[offset +  8 + y * stride] - ((d * 7) >> 4)];
                    dst[offset + 9 + y * stride] = cm[dst[offset +  9 + y * stride] - ((d * 5) >> 4)];
                    dst[offset + 10+ y * stride] = cm[dst[offset + 10 + y * stride] - ((d * 3) >> 4)];
                    dst[offset + 11+ y * stride] = cm[dst[offset + 11 + y * stride] - ((d * 1) >> 4)];
                }
            }
        }
    }
}

/**
 * simple vertical deblocking filter used for error resilience
 * @param w     width in 8 pixel blocks
 * @param h     height in 8 pixel blocks
 */
static void v_block_filter(MpegEncContext *s, uint8_t *dst, int w, int h,
                           int stride, int is_luma)
{
    int b_x, b_y, mvx_stride, mvy_stride;
    uint8_t *cm = ff_cropTbl + MAX_NEG_CROP;
    set_mv_strides(s, &mvx_stride, &mvy_stride);
    mvx_stride >>= is_luma;
    mvy_stride *= mvx_stride;

    for (b_y = 0; b_y < h - 1; b_y++) {
        for (b_x = 0; b_x < w; b_x++) {
            int x;
            int top_status    = s->error_status_table[(b_x >> is_luma) +  (b_y      >> is_luma) * s->mb_stride];
            int bottom_status = s->error_status_table[(b_x >> is_luma) + ((b_y + 1) >> is_luma) * s->mb_stride];
            int top_intra     = IS_INTRA(s->current_picture.f.mb_type[(b_x >> is_luma) + ( b_y      >> is_luma) * s->mb_stride]);
            int bottom_intra  = IS_INTRA(s->current_picture.f.mb_type[(b_x >> is_luma) + ((b_y + 1) >> is_luma) * s->mb_stride]);
            int top_damage    = top_status & ER_MB_ERROR;
            int bottom_damage = bottom_status & ER_MB_ERROR;
            int offset        = b_x * 8 + b_y * stride * 8;

            int16_t *top_mv    = s->current_picture.f.motion_val[0][mvy_stride *  b_y      + mvx_stride * b_x];
            int16_t *bottom_mv = s->current_picture.f.motion_val[0][mvy_stride * (b_y + 1) + mvx_stride * b_x];

            if (!(top_damage || bottom_damage))
                continue; // both undamaged

            if ((!top_intra) && (!bottom_intra) &&
                FFABS(top_mv[0] - bottom_mv[0]) +
                FFABS(top_mv[1] + bottom_mv[1]) < 2)
                continue;

            for (x = 0; x < 8; x++) {
                int a, b, c, d;

                a = dst[offset + x + 7 * stride] - dst[offset + x + 6 * stride];
                b = dst[offset + x + 8 * stride] - dst[offset + x + 7 * stride];
                c = dst[offset + x + 9 * stride] - dst[offset + x + 8 * stride];

                d = FFABS(b) - ((FFABS(a) + FFABS(c) + 1) >> 1);
                d = FFMAX(d, 0);
                if (b < 0)
                    d = -d;

                if (d == 0)
                    continue;

                if (!(top_damage && bottom_damage))
                    d = d * 16 / 9;

                if (top_damage) {
                    dst[offset + x +  7 * stride] = cm[dst[offset + x +  7 * stride] + ((d * 7) >> 4)];
                    dst[offset + x +  6 * stride] = cm[dst[offset + x +  6 * stride] + ((d * 5) >> 4)];
                    dst[offset + x +  5 * stride] = cm[dst[offset + x +  5 * stride] + ((d * 3) >> 4)];
                    dst[offset + x +  4 * stride] = cm[dst[offset + x +  4 * stride] + ((d * 1) >> 4)];
                }
                if (bottom_damage) {
                    dst[offset + x +  8 * stride] = cm[dst[offset + x +  8 * stride] - ((d * 7) >> 4)];
                    dst[offset + x +  9 * stride] = cm[dst[offset + x +  9 * stride] - ((d * 5) >> 4)];
                    dst[offset + x + 10 * stride] = cm[dst[offset + x + 10 * stride] - ((d * 3) >> 4)];
                    dst[offset + x + 11 * stride] = cm[dst[offset + x + 11 * stride] - ((d * 1) >> 4)];
                }
            }
        }
    }
}

static void guess_mv(MpegEncContext *s)
{
    uint8_t *fixed = s->er_temp_buffer;
#define MV_FROZEN    3
#define MV_CHANGED   2
#define MV_UNCHANGED 1
    const int mb_stride = s->mb_stride;
    const int mb_width  = s->mb_width;
    const int mb_height = s->mb_height;
    int i, depth, num_avail;
    int mb_x, mb_y, mot_step, mot_stride;

    set_mv_strides(s, &mot_step, &mot_stride);

    num_avail = 0;
    for (i = 0; i < s->mb_num; i++) {
        const int mb_xy = s->mb_index2xy[i];
        int f = 0;
        int error = s->error_status_table[mb_xy];

        if (IS_INTRA(s->current_picture.f.mb_type[mb_xy]))
            f = MV_FROZEN; // intra // FIXME check
        if (!(error & ER_MV_ERROR))
            f = MV_FROZEN; // inter with undamaged MV

        fixed[mb_xy] = f;
        if (f == MV_FROZEN)
            num_avail++;
        else if(s->last_picture.f.data[0] && s->last_picture.f.motion_val[0]){
            const int mb_y= mb_xy / s->mb_stride;
            const int mb_x= mb_xy % s->mb_stride;
            const int mot_index= (mb_x + mb_y*mot_stride) * mot_step;
            s->current_picture.f.motion_val[0][mot_index][0]= s->last_picture.f.motion_val[0][mot_index][0];
            s->current_picture.f.motion_val[0][mot_index][1]= s->last_picture.f.motion_val[0][mot_index][1];
            s->current_picture.f.ref_index[0][4*mb_xy]      = s->last_picture.f.ref_index[0][4*mb_xy];
        }
    }

    if ((!(s->avctx->error_concealment&FF_EC_GUESS_MVS)) ||
        num_avail <= mb_width / 2) {
        for (mb_y = 0; mb_y < s->mb_height; mb_y++) {
            for (mb_x = 0; mb_x < s->mb_width; mb_x++) {
                const int mb_xy = mb_x + mb_y * s->mb_stride;

                if (IS_INTRA(s->current_picture.f.mb_type[mb_xy]))
                    continue;
                if (!(s->error_status_table[mb_xy] & ER_MV_ERROR))
                    continue;

                s->mv_dir     = s->last_picture.f.data[0] ? MV_DIR_FORWARD
                                                          : MV_DIR_BACKWARD;
                s->mb_intra   = 0;
                s->mv_type    = MV_TYPE_16X16;
                s->mb_skipped = 0;

                s->dsp.clear_blocks(s->block[0]);

                s->mb_x        = mb_x;
                s->mb_y        = mb_y;
                s->mv[0][0][0] = 0;
                s->mv[0][0][1] = 0;
                decode_mb(s, 0);
            }
        }
        return;
    }

    for (depth = 0; ; depth++) {
        int changed, pass, none_left;

        none_left = 1;
        changed   = 1;
        for (pass = 0; (changed || pass < 2) && pass < 10; pass++) {
            int mb_x, mb_y;
            int score_sum = 0;

            changed = 0;
            for (mb_y = 0; mb_y < s->mb_height; mb_y++) {
                for (mb_x = 0; mb_x < s->mb_width; mb_x++) {
                    const int mb_xy        = mb_x + mb_y * s->mb_stride;
                    int mv_predictor[8][2] = { { 0 } };
                    int ref[8]             = { 0 };
                    int pred_count         = 0;
                    int j;
                    int best_score         = 256 * 256 * 256 * 64;
                    int best_pred          = 0;
                    const int mot_index    = (mb_x + mb_y * mot_stride) * mot_step;
                    int prev_x, prev_y, prev_ref;

                    if ((mb_x ^ mb_y ^ pass) & 1)
                        continue;

                    if (fixed[mb_xy] == MV_FROZEN)
                        continue;
                    av_assert1(!IS_INTRA(s->current_picture.f.mb_type[mb_xy]));
                    av_assert1(s->last_picture_ptr && s->last_picture_ptr->f.data[0]);

                    j = 0;
                    if (mb_x > 0             && fixed[mb_xy - 1]         == MV_FROZEN)
                        j = 1;
                    if (mb_x + 1 < mb_width  && fixed[mb_xy + 1]         == MV_FROZEN)
                        j = 1;
                    if (mb_y > 0             && fixed[mb_xy - mb_stride] == MV_FROZEN)
                        j = 1;
                    if (mb_y + 1 < mb_height && fixed[mb_xy + mb_stride] == MV_FROZEN)
                        j = 1;
                    if (j == 0)
                        continue;

                    j = 0;
                    if (mb_x > 0             && fixed[mb_xy - 1        ] == MV_CHANGED)
                        j = 1;
                    if (mb_x + 1 < mb_width  && fixed[mb_xy + 1        ] == MV_CHANGED)
                        j = 1;
                    if (mb_y > 0             && fixed[mb_xy - mb_stride] == MV_CHANGED)
                        j = 1;
                    if (mb_y + 1 < mb_height && fixed[mb_xy + mb_stride] == MV_CHANGED)
                        j = 1;
                    if (j == 0 && pass > 1)
                        continue;

                    none_left = 0;

                    if (mb_x > 0 && fixed[mb_xy - 1]) {
                        mv_predictor[pred_count][0] =
                            s->current_picture.f.motion_val[0][mot_index - mot_step][0];
                        mv_predictor[pred_count][1] =
                            s->current_picture.f.motion_val[0][mot_index - mot_step][1];
                        ref[pred_count] =
                            s->current_picture.f.ref_index[0][4 * (mb_xy - 1)];
                        pred_count++;
                    }
                    if (mb_x + 1 < mb_width && fixed[mb_xy + 1]) {
                        mv_predictor[pred_count][0] =
                            s->current_picture.f.motion_val[0][mot_index + mot_step][0];
                        mv_predictor[pred_count][1] =
                            s->current_picture.f.motion_val[0][mot_index + mot_step][1];
                        ref[pred_count] =
                            s->current_picture.f.ref_index[0][4 * (mb_xy + 1)];
                        pred_count++;
                    }
                    if (mb_y > 0 && fixed[mb_xy - mb_stride]) {
                        mv_predictor[pred_count][0] =
                            s->current_picture.f.motion_val[0][mot_index - mot_stride * mot_step][0];
                        mv_predictor[pred_count][1] =
                            s->current_picture.f.motion_val[0][mot_index - mot_stride * mot_step][1];
                        ref[pred_count] =
                            s->current_picture.f.ref_index[0][4 * (mb_xy - s->mb_stride)];
                        pred_count++;
                    }
                    if (mb_y + 1<mb_height && fixed[mb_xy + mb_stride]) {
                        mv_predictor[pred_count][0] =
                            s->current_picture.f.motion_val[0][mot_index + mot_stride * mot_step][0];
                        mv_predictor[pred_count][1] =
                            s->current_picture.f.motion_val[0][mot_index + mot_stride * mot_step][1];
                        ref[pred_count] =
                            s->current_picture.f.ref_index[0][4 * (mb_xy + s->mb_stride)];
                        pred_count++;
                    }
                    if (pred_count == 0)
                        continue;

                    if (pred_count > 1) {
                        int sum_x = 0, sum_y = 0, sum_r = 0;
                        int max_x, max_y, min_x, min_y, max_r, min_r;

                        for (j = 0; j < pred_count; j++) {
                            sum_x += mv_predictor[j][0];
                            sum_y += mv_predictor[j][1];
                            sum_r += ref[j];
                            if (j && ref[j] != ref[j - 1])
                                goto skip_mean_and_median;
                        }

                        /* mean */
                        mv_predictor[pred_count][0] = sum_x / j;
                        mv_predictor[pred_count][1] = sum_y / j;
                                 ref[pred_count]    = sum_r / j;

                        /* median */
                        if (pred_count >= 3) {
                            min_y = min_x = min_r =  99999;
                            max_y = max_x = max_r = -99999;
                        } else {
                            min_x = min_y = max_x = max_y = min_r = max_r = 0;
                        }
                        for (j = 0; j < pred_count; j++) {
                            max_x = FFMAX(max_x, mv_predictor[j][0]);
                            max_y = FFMAX(max_y, mv_predictor[j][1]);
                            max_r = FFMAX(max_r, ref[j]);
                            min_x = FFMIN(min_x, mv_predictor[j][0]);
                            min_y = FFMIN(min_y, mv_predictor[j][1]);
                            min_r = FFMIN(min_r, ref[j]);
                        }
                        mv_predictor[pred_count + 1][0] = sum_x - max_x - min_x;
                        mv_predictor[pred_count + 1][1] = sum_y - max_y - min_y;
                                 ref[pred_count + 1]    = sum_r - max_r - min_r;

                        if (pred_count == 4) {
                            mv_predictor[pred_count + 1][0] /= 2;
                            mv_predictor[pred_count + 1][1] /= 2;
                                     ref[pred_count + 1]    /= 2;
                        }
                        pred_count += 2;
                    }

skip_mean_and_median:
                    /* zero MV */
                    pred_count++;

                    if (!fixed[mb_xy] && 0) {
                        if (s->avctx->codec_id == CODEC_ID_H264) {
                            // FIXME
                        } else {
                            ff_thread_await_progress(&s->last_picture_ptr->f,
                                                     mb_y, 0);
                        }
                        if (!s->last_picture.f.motion_val[0] ||
                            !s->last_picture.f.ref_index[0])
                            goto skip_last_mv;
                        prev_x   = s->last_picture.f.motion_val[0][mot_index][0];
                        prev_y   = s->last_picture.f.motion_val[0][mot_index][1];
                        prev_ref = s->last_picture.f.ref_index[0][4 * mb_xy];
                    } else {
                        prev_x   = s->current_picture.f.motion_val[0][mot_index][0];
                        prev_y   = s->current_picture.f.motion_val[0][mot_index][1];
                        prev_ref = s->current_picture.f.ref_index[0][4 * mb_xy];
                    }

                    /* last MV */
                    mv_predictor[pred_count][0] = prev_x;
                    mv_predictor[pred_count][1] = prev_y;
                             ref[pred_count]    = prev_ref;
                    pred_count++;

skip_last_mv:
                    s->mv_dir     = MV_DIR_FORWARD;
                    s->mb_intra   = 0;
                    s->mv_type    = MV_TYPE_16X16;
                    s->mb_skipped = 0;

                    s->dsp.clear_blocks(s->block[0]);

                    s->mb_x = mb_x;
                    s->mb_y = mb_y;

                    for (j = 0; j < pred_count; j++) {
                        int score = 0;
                        uint8_t *src = s->current_picture.f.data[0] +
                                       mb_x * 16 + mb_y * 16 * s->linesize;

                        s->current_picture.f.motion_val[0][mot_index][0] =
                            s->mv[0][0][0] = mv_predictor[j][0];
                        s->current_picture.f.motion_val[0][mot_index][1] =
                            s->mv[0][0][1] = mv_predictor[j][1];

                        // predictor intra or otherwise not available
                        if (ref[j] < 0)
                            continue;

                        decode_mb(s, ref[j]);

                        if (mb_x > 0 && fixed[mb_xy - 1]) {
                            int k;
                            for (k = 0; k < 16; k++)
                                score += FFABS(src[k * s->linesize - 1] -
                                               src[k * s->linesize]);
                        }
                        if (mb_x + 1 < mb_width && fixed[mb_xy + 1]) {
                            int k;
                            for (k = 0; k < 16; k++)
                                score += FFABS(src[k * s->linesize + 15] -
                                               src[k * s->linesize + 16]);
                        }
                        if (mb_y > 0 && fixed[mb_xy - mb_stride]) {
                            int k;
                            for (k = 0; k < 16; k++)
                                score += FFABS(src[k - s->linesize] - src[k]);
                        }
                        if (mb_y + 1 < mb_height && fixed[mb_xy + mb_stride]) {
                            int k;
                            for (k = 0; k < 16; k++)
                                score += FFABS(src[k + s->linesize * 15] -
                                               src[k + s->linesize * 16]);
                        }

                        if (score <= best_score) { // <= will favor the last MV
                            best_score = score;
                            best_pred  = j;
                        }
                    }
                    score_sum += best_score;
                    s->mv[0][0][0] = mv_predictor[best_pred][0];
                    s->mv[0][0][1] = mv_predictor[best_pred][1];

                    for (i = 0; i < mot_step; i++)
                        for (j = 0; j < mot_step; j++) {
                            s->current_picture.f.motion_val[0][mot_index + i + j * mot_stride][0] = s->mv[0][0][0];
                            s->current_picture.f.motion_val[0][mot_index + i + j * mot_stride][1] = s->mv[0][0][1];
                        }

                    decode_mb(s, ref[best_pred]);


                    if (s->mv[0][0][0] != prev_x || s->mv[0][0][1] != prev_y) {
                        fixed[mb_xy] = MV_CHANGED;
                        changed++;
                    } else
                        fixed[mb_xy] = MV_UNCHANGED;
                }
            }

            // printf(".%d/%d", changed, score_sum); fflush(stdout);
        }

        if (none_left)
            return;

        for (i = 0; i < s->mb_num; i++) {
            int mb_xy = s->mb_index2xy[i];
            if (fixed[mb_xy])
                fixed[mb_xy] = MV_FROZEN;
        }
        // printf(":"); fflush(stdout);
    }
}

static int is_intra_more_likely(MpegEncContext *s)
{
    int is_intra_likely, i, j, undamaged_count, skip_amount, mb_x, mb_y;

    if (!s->last_picture_ptr || !s->last_picture_ptr->f.data[0])
        return 1; // no previous frame available -> use spatial prediction

    undamaged_count = 0;
    for (i = 0; i < s->mb_num; i++) {
        const int mb_xy = s->mb_index2xy[i];
        const int error = s->error_status_table[mb_xy];
        if (!((error & ER_DC_ERROR) && (error & ER_MV_ERROR)))
            undamaged_count++;
    }

    if (s->codec_id == CODEC_ID_H264) {
        H264Context *h = (void*) s;
        if (h->list_count <= 0 || h->ref_count[0] <= 0 ||
            !h->ref_list[0][0].f.data[0])
            return 1;
    }

    if (undamaged_count < 5)
        return 0; // almost all MBs damaged -> use temporal prediction

    // prevent dsp.sad() check, that requires access to the image
    if (CONFIG_MPEG_XVMC_DECODER    &&
        s->avctx->xvmc_acceleration &&
        s->pict_type == AV_PICTURE_TYPE_I)
        return 1;

    skip_amount     = FFMAX(undamaged_count / 50, 1); // check only up to 50 MBs
    is_intra_likely = 0;

    j = 0;
    for (mb_y = 0; mb_y < s->mb_height - 1; mb_y++) {
        for (mb_x = 0; mb_x < s->mb_width; mb_x++) {
            int error;
            const int mb_xy = mb_x + mb_y * s->mb_stride;

            error = s->error_status_table[mb_xy];
            if ((error & ER_DC_ERROR) && (error & ER_MV_ERROR))
                continue; // skip damaged

            j++;
            // skip a few to speed things up
            if ((j % skip_amount) != 0)
                continue;

            if (s->pict_type == AV_PICTURE_TYPE_I) {
                uint8_t *mb_ptr      = s->current_picture.f.data[0] +
                                       mb_x * 16 + mb_y * 16 * s->linesize;
                uint8_t *last_mb_ptr = s->last_picture.f.data[0] +
                                       mb_x * 16 + mb_y * 16 * s->linesize;

                if (s->avctx->codec_id == CODEC_ID_H264) {
                    // FIXME
                } else {
                    ff_thread_await_progress(&s->last_picture_ptr->f,
                                             mb_y, 0);
                }
                is_intra_likely += s->dsp.sad[0](NULL, last_mb_ptr, mb_ptr                    , s->linesize, 16);
                // FIXME need await_progress() here
                is_intra_likely -= s->dsp.sad[0](NULL, last_mb_ptr, last_mb_ptr+s->linesize*16, s->linesize, 16);
            } else {
                if (IS_INTRA(s->current_picture.f.mb_type[mb_xy]))
                   is_intra_likely++;
                else
                   is_intra_likely--;
            }
        }
    }
    // printf("is_intra_likely: %d type:%d\n", is_intra_likely, s->pict_type);
    return is_intra_likely > 0;
}

void ff_er_frame_start(MpegEncContext *s)
{
    if (!s->err_recognition)
        return;

    memset(s->error_status_table, ER_MB_ERROR | VP_START | ER_MB_END,
           s->mb_stride * s->mb_height * sizeof(uint8_t));
    s->error_count    = 3 * s->mb_num;
    s->error_occurred = 0;
}

/**
 * Add a slice.
 * @param endx   x component of the last macroblock, can be -1
 *               for the last of the previous line
 * @param status the status at the end (ER_MV_END, ER_AC_ERROR, ...), it is
 *               assumed that no earlier end or error of the same type occurred
 */
void ff_er_add_slice(MpegEncContext *s, int startx, int starty,
                     int endx, int endy, int status)
{
    const int start_i  = av_clip(startx + starty * s->mb_width, 0, s->mb_num - 1);
    const int end_i    = av_clip(endx   + endy   * s->mb_width, 0, s->mb_num);
    const int start_xy = s->mb_index2xy[start_i];
    const int end_xy   = s->mb_index2xy[end_i];
    int mask           = -1;

    if (s->avctx->hwaccel)
        return;

    if (start_i > end_i || start_xy > end_xy) {
        av_log(s->avctx, AV_LOG_ERROR,
               "internal error, slice end before start\n");
        return;
    }

    if (!s->err_recognition)
        return;

    mask &= ~VP_START;
    if (status & (ER_AC_ERROR | ER_AC_END)) {
        mask           &= ~(ER_AC_ERROR | ER_AC_END);
        s->error_count -= end_i - start_i + 1;
    }
    if (status & (ER_DC_ERROR | ER_DC_END)) {
        mask           &= ~(ER_DC_ERROR | ER_DC_END);
        s->error_count -= end_i - start_i + 1;
    }
    if (status & (ER_MV_ERROR | ER_MV_END)) {
        mask           &= ~(ER_MV_ERROR | ER_MV_END);
        s->error_count -= end_i - start_i + 1;
    }

    if (status & ER_MB_ERROR) {
        s->error_occurred = 1;
        s->error_count    = INT_MAX;
    }

    if (mask == ~0x7F) {
        memset(&s->error_status_table[start_xy], 0,
               (end_xy - start_xy) * sizeof(uint8_t));
    } else {
        int i;
        for (i = start_xy; i < end_xy; i++)
            s->error_status_table[i] &= mask;
    }

    if (end_i == s->mb_num)
        s->error_count = INT_MAX;
    else {
        s->error_status_table[end_xy] &= mask;
        s->error_status_table[end_xy] |= status;
    }

    s->error_status_table[start_xy] |= VP_START;

    if (start_xy > 0 && s->avctx->thread_count <= 1 &&
        s->avctx->skip_top * s->mb_width < start_i) {
        int prev_status = s->error_status_table[s->mb_index2xy[start_i - 1]];

        prev_status &= ~ VP_START;
        if (prev_status != (ER_MV_END | ER_DC_END | ER_AC_END))
            s->error_count = INT_MAX;
    }
}

void ff_er_frame_end(MpegEncContext *s)
{
    int i, mb_x, mb_y, error, error_type, dc_error, mv_error, ac_error;
    int distance;
    int threshold_part[4] = { 100, 100, 100 };
    int threshold = 50;
    int is_intra_likely;
    int size = s->b8_stride * 2 * s->mb_height;
    Picture *pic = s->current_picture_ptr;

    /* We do not support ER of field pictures yet,
     * though it should not crash if enabled. */
    if (!s->err_recognition || s->error_count == 0 || s->avctx->lowres ||
        s->avctx->hwaccel                                              ||
        s->avctx->codec->capabilities&CODEC_CAP_HWACCEL_VDPAU          ||
        s->picture_structure != PICT_FRAME                             ||
        s->error_count == 3 * s->mb_width *
                          (s->avctx->skip_top + s->avctx->skip_bottom)) {
        return;
    };

    if (s->current_picture.f.motion_val[0] == NULL) {
        av_log(s->avctx, AV_LOG_ERROR, "Warning MVs not available\n");

        for (i = 0; i < 2; i++) {
            pic->f.ref_index[i]     = av_mallocz(s->mb_stride * s->mb_height * 4 * sizeof(uint8_t));
            pic->motion_val_base[i] = av_mallocz((size + 4) * 2 * sizeof(uint16_t));
            pic->f.motion_val[i]    = pic->motion_val_base[i] + 4;
        }
        pic->f.motion_subsample_log2 = 3;
        s->current_picture = *s->current_picture_ptr;
    }

    if (s->avctx->debug & FF_DEBUG_ER) {
        for (mb_y = 0; mb_y < s->mb_height; mb_y++) {
            for (mb_x = 0; mb_x < s->mb_width; mb_x++) {
                int status = s->error_status_table[mb_x + mb_y * s->mb_stride];

                av_log(s->avctx, AV_LOG_DEBUG, "%2X ", status);
            }
            av_log(s->avctx, AV_LOG_DEBUG, "\n");
        }
    }

#if 1
    /* handle overlapping slices */
    for (error_type = 1; error_type <= 3; error_type++) {
        int end_ok = 0;

        for (i = s->mb_num - 1; i >= 0; i--) {
            const int mb_xy = s->mb_index2xy[i];
            int error       = s->error_status_table[mb_xy];

            if (error & (1 << error_type))
                end_ok = 1;
            if (error & (8 << error_type))
                end_ok = 1;

            if (!end_ok)
                s->error_status_table[mb_xy] |= 1 << error_type;

            if (error & VP_START)
                end_ok = 0;
        }
    }
#endif
#if 1
    /* handle slices with partitions of different length */
    if (s->partitioned_frame) {
        int end_ok = 0;

        for (i = s->mb_num - 1; i >= 0; i--) {
            const int mb_xy = s->mb_index2xy[i];
            int error       = s->error_status_table[mb_xy];

            if (error & ER_AC_END)
                end_ok = 0;
            if ((error & ER_MV_END) ||
                (error & ER_DC_END) ||
                (error & ER_AC_ERROR))
                end_ok = 1;

            if (!end_ok)
                s->error_status_table[mb_xy]|= ER_AC_ERROR;

            if (error & VP_START)
                end_ok = 0;
        }
    }
#endif
    /* handle missing slices */
    if (s->err_recognition & AV_EF_EXPLODE) {
        int end_ok = 1;

        // FIXME + 100 hack
        for (i = s->mb_num - 2; i >= s->mb_width + 100; i--) {
            const int mb_xy = s->mb_index2xy[i];
            int error1 = s->error_status_table[mb_xy];
            int error2 = s->error_status_table[s->mb_index2xy[i + 1]];

            if (error1 & VP_START)
                end_ok = 1;

            if (error2 == (VP_START | ER_MB_ERROR | ER_MB_END) &&
                error1 != (VP_START | ER_MB_ERROR | ER_MB_END) &&
                ((error1 & ER_AC_END) || (error1 & ER_DC_END) ||
                (error1 & ER_MV_END))) {
                // end & uninit
                end_ok = 0;
            }

            if (!end_ok)
                s->error_status_table[mb_xy] |= ER_MB_ERROR;
        }
    }

#if 1
    /* backward mark errors */
    distance = 9999999;
    for (error_type = 1; error_type <= 3; error_type++) {
        for (i = s->mb_num - 1; i >= 0; i--) {
            const int mb_xy = s->mb_index2xy[i];
            int       error = s->error_status_table[mb_xy];

            if (!s->mbskip_table[mb_xy]) // FIXME partition specific
                distance++;
            if (error & (1 << error_type))
                distance = 0;

            if (s->partitioned_frame) {
                if (distance < threshold_part[error_type - 1])
                    s->error_status_table[mb_xy] |= 1 << error_type;
            } else {
                if (distance < threshold)
                    s->error_status_table[mb_xy] |= 1 << error_type;
            }

            if (error & VP_START)
                distance = 9999999;
        }
    }
#endif

    /* forward mark errors */
    error = 0;
    for (i = 0; i < s->mb_num; i++) {
        const int mb_xy = s->mb_index2xy[i];
        int old_error   = s->error_status_table[mb_xy];

        if (old_error & VP_START) {
            error = old_error & ER_MB_ERROR;
        } else {
            error |= old_error & ER_MB_ERROR;
            s->error_status_table[mb_xy] |= error;
        }
    }
#if 1
    /* handle not partitioned case */
    if (!s->partitioned_frame) {
        for (i = 0; i < s->mb_num; i++) {
            const int mb_xy = s->mb_index2xy[i];
            error = s->error_status_table[mb_xy];
            if (error & ER_MB_ERROR)
                error |= ER_MB_ERROR;
            s->error_status_table[mb_xy] = error;
        }
    }
#endif

    dc_error = ac_error = mv_error = 0;
    for (i = 0; i < s->mb_num; i++) {
        const int mb_xy = s->mb_index2xy[i];
        error = s->error_status_table[mb_xy];
        if (error & ER_DC_ERROR)
            dc_error++;
        if (error & ER_AC_ERROR)
            ac_error++;
        if (error & ER_MV_ERROR)
            mv_error++;
    }
    av_log(s->avctx, AV_LOG_INFO, "concealing %d DC, %d AC, %d MV errors\n",
           dc_error, ac_error, mv_error);

    is_intra_likely = is_intra_more_likely(s);

    /* set unknown mb-type to most likely */
    for (i = 0; i < s->mb_num; i++) {
        const int mb_xy = s->mb_index2xy[i];
        error = s->error_status_table[mb_xy];
        if (!((error & ER_DC_ERROR) && (error & ER_MV_ERROR)))
            continue;

        if (is_intra_likely)
            s->current_picture.f.mb_type[mb_xy] = MB_TYPE_INTRA4x4;
        else
            s->current_picture.f.mb_type[mb_xy] = MB_TYPE_16x16 | MB_TYPE_L0;
    }

    // change inter to intra blocks if no reference frames are available
    if (!s->last_picture.f.data[0] && !s->next_picture.f.data[0])
        for (i = 0; i < s->mb_num; i++) {
            const int mb_xy = s->mb_index2xy[i];
            if (!IS_INTRA(s->current_picture.f.mb_type[mb_xy]))
                s->current_picture.f.mb_type[mb_xy] = MB_TYPE_INTRA4x4;
        }

    /* handle inter blocks with damaged AC */
    for (mb_y = 0; mb_y < s->mb_height; mb_y++) {
        for (mb_x = 0; mb_x < s->mb_width; mb_x++) {
            const int mb_xy   = mb_x + mb_y * s->mb_stride;
            const int mb_type = s->current_picture.f.mb_type[mb_xy];
            int dir           = !s->last_picture.f.data[0];

            error = s->error_status_table[mb_xy];

            if (IS_INTRA(mb_type))
                continue; // intra
            if (error & ER_MV_ERROR)
                continue; // inter with damaged MV
            if (!(error & ER_AC_ERROR))
                continue; // undamaged inter

            s->mv_dir     = dir ? MV_DIR_BACKWARD : MV_DIR_FORWARD;
            s->mb_intra   = 0;
            s->mb_skipped = 0;
            if (IS_8X8(mb_type)) {
                int mb_index = mb_x * 2 + mb_y * 2 * s->b8_stride;
                int j;
                s->mv_type = MV_TYPE_8X8;
                for (j = 0; j < 4; j++) {
                    s->mv[0][j][0] = s->current_picture.f.motion_val[dir][mb_index + (j & 1) + (j >> 1) * s->b8_stride][0];
                    s->mv[0][j][1] = s->current_picture.f.motion_val[dir][mb_index + (j & 1) + (j >> 1) * s->b8_stride][1];
                }
            } else {
                s->mv_type     = MV_TYPE_16X16;
                s->mv[0][0][0] = s->current_picture.f.motion_val[dir][mb_x * 2 + mb_y * 2 * s->b8_stride][0];
                s->mv[0][0][1] = s->current_picture.f.motion_val[dir][mb_x * 2 + mb_y * 2 * s->b8_stride][1];
            }

            s->dsp.clear_blocks(s->block[0]);

            s->mb_x = mb_x;
            s->mb_y = mb_y;
            decode_mb(s, 0 /* FIXME h264 partitioned slices need this set */);
        }
    }

    /* guess MVs */
    if (s->pict_type == AV_PICTURE_TYPE_B) {
        for (mb_y = 0; mb_y < s->mb_height; mb_y++) {
            for (mb_x = 0; mb_x < s->mb_width; mb_x++) {
                int       xy      = mb_x * 2 + mb_y * 2 * s->b8_stride;
                const int mb_xy   = mb_x + mb_y * s->mb_stride;
                const int mb_type = s->current_picture.f.mb_type[mb_xy];

                error = s->error_status_table[mb_xy];

                if (IS_INTRA(mb_type))
                    continue;
                if (!(error & ER_MV_ERROR))
                    continue; // inter with undamaged MV
                if (!(error & ER_AC_ERROR))
                    continue; // undamaged inter

                s->mv_dir = MV_DIR_FORWARD | MV_DIR_BACKWARD;
                if (!s->last_picture.f.data[0])
                    s->mv_dir &= ~MV_DIR_FORWARD;
                if (!s->next_picture.f.data[0])
                    s->mv_dir &= ~MV_DIR_BACKWARD;
                s->mb_intra   = 0;
                s->mv_type    = MV_TYPE_16X16;
                s->mb_skipped = 0;

                if (s->pp_time) {
                    int time_pp = s->pp_time;
                    int time_pb = s->pb_time;

                    if (s->avctx->codec_id == CODEC_ID_H264) {
                        // FIXME
                    } else {
                        ff_thread_await_progress(&s->next_picture_ptr->f, mb_y, 0);
                    }
                    s->mv[0][0][0] = s->next_picture.f.motion_val[0][xy][0] *  time_pb            / time_pp;
                    s->mv[0][0][1] = s->next_picture.f.motion_val[0][xy][1] *  time_pb            / time_pp;
                    s->mv[1][0][0] = s->next_picture.f.motion_val[0][xy][0] * (time_pb - time_pp) / time_pp;
                    s->mv[1][0][1] = s->next_picture.f.motion_val[0][xy][1] * (time_pb - time_pp) / time_pp;
                } else {
                    s->mv[0][0][0] = 0;
                    s->mv[0][0][1] = 0;
                    s->mv[1][0][0] = 0;
                    s->mv[1][0][1] = 0;
                }

                s->dsp.clear_blocks(s->block[0]);
                s->mb_x = mb_x;
                s->mb_y = mb_y;
                decode_mb(s, 0);
            }
        }
    } else
        guess_mv(s);

    /* the filters below are not XvMC compatible, skip them */
    if (CONFIG_MPEG_XVMC_DECODER && s->avctx->xvmc_acceleration)
        goto ec_clean;
    /* fill DC for inter blocks */
    for (mb_y = 0; mb_y < s->mb_height; mb_y++) {
        for (mb_x = 0; mb_x < s->mb_width; mb_x++) {
            int dc, dcu, dcv, y, n;
            int16_t *dc_ptr;
            uint8_t *dest_y, *dest_cb, *dest_cr;
            const int mb_xy   = mb_x + mb_y * s->mb_stride;
            const int mb_type = s->current_picture.f.mb_type[mb_xy];

            error = s->error_status_table[mb_xy];

            if (IS_INTRA(mb_type) && s->partitioned_frame)
                continue;
            // if (error & ER_MV_ERROR)
            //     continue; // inter data damaged FIXME is this good?

            dest_y  = s->current_picture.f.data[0] + mb_x * 16 + mb_y * 16 * s->linesize;
            dest_cb = s->current_picture.f.data[1] + mb_x *  8 + mb_y *  8 * s->uvlinesize;
            dest_cr = s->current_picture.f.data[2] + mb_x *  8 + mb_y *  8 * s->uvlinesize;

            dc_ptr = &s->dc_val[0][mb_x * 2 + mb_y * 2 * s->b8_stride];
            for (n = 0; n < 4; n++) {
                dc = 0;
                for (y = 0; y < 8; y++) {
                    int x;
                    for (x = 0; x < 8; x++)
                       dc += dest_y[x + (n & 1) * 8 +
                             (y + (n >> 1) * 8) * s->linesize];
                }
                dc_ptr[(n & 1) + (n >> 1) * s->b8_stride] = (dc + 4) >> 3;
            }

            dcu = dcv = 0;
            for (y = 0; y < 8; y++) {
                int x;
                for (x = 0; x < 8; x++) {
                    dcu += dest_cb[x + y * s->uvlinesize];
                    dcv += dest_cr[x + y * s->uvlinesize];
                }
            }
            s->dc_val[1][mb_x + mb_y * s->mb_stride] = (dcu + 4) >> 3;
            s->dc_val[2][mb_x + mb_y * s->mb_stride] = (dcv + 4) >> 3;
        }
    }
#if 1
    /* guess DC for damaged blocks */
    guess_dc(s, s->dc_val[0], s->mb_width*2, s->mb_height*2, s->b8_stride, 1);
    guess_dc(s, s->dc_val[1], s->mb_width  , s->mb_height  , s->mb_stride, 0);
    guess_dc(s, s->dc_val[2], s->mb_width  , s->mb_height  , s->mb_stride, 0);
#endif

    /* filter luma DC */
    filter181(s->dc_val[0], s->mb_width * 2, s->mb_height * 2, s->b8_stride);

#if 1
    /* render DC only intra */
    for (mb_y = 0; mb_y < s->mb_height; mb_y++) {
        for (mb_x = 0; mb_x < s->mb_width; mb_x++) {
            uint8_t *dest_y, *dest_cb, *dest_cr;
            const int mb_xy   = mb_x + mb_y * s->mb_stride;
            const int mb_type = s->current_picture.f.mb_type[mb_xy];

            error = s->error_status_table[mb_xy];

            if (IS_INTER(mb_type))
                continue;
            if (!(error & ER_AC_ERROR))
                continue; // undamaged

            dest_y  = s->current_picture.f.data[0] + mb_x * 16 + mb_y * 16 * s->linesize;
            dest_cb = s->current_picture.f.data[1] + mb_x *  8 + mb_y *  8 * s->uvlinesize;
            dest_cr = s->current_picture.f.data[2] + mb_x *  8 + mb_y *  8 * s->uvlinesize;

            put_dc(s, dest_y, dest_cb, dest_cr, mb_x, mb_y);
        }
    }
#endif

    if (s->avctx->error_concealment & FF_EC_DEBLOCK) {
        /* filter horizontal block boundaries */
        h_block_filter(s, s->current_picture.f.data[0], s->mb_width * 2,
                       s->mb_height * 2, s->linesize, 1);
        h_block_filter(s, s->current_picture.f.data[1], s->mb_width,
                       s->mb_height  , s->uvlinesize, 0);
        h_block_filter(s, s->current_picture.f.data[2], s->mb_width,
                       s->mb_height  , s->uvlinesize, 0);

        /* filter vertical block boundaries */
        v_block_filter(s, s->current_picture.f.data[0], s->mb_width * 2,
                       s->mb_height * 2, s->linesize, 1);
        v_block_filter(s, s->current_picture.f.data[1], s->mb_width,
                       s->mb_height  , s->uvlinesize, 0);
        v_block_filter(s, s->current_picture.f.data[2], s->mb_width,
                       s->mb_height  , s->uvlinesize, 0);
    }

ec_clean:
    /* clean a few tables */
    for (i = 0; i < s->mb_num; i++) {
        const int mb_xy = s->mb_index2xy[i];
        int       error = s->error_status_table[mb_xy];

        if (s->pict_type != AV_PICTURE_TYPE_B &&
            (error & (ER_DC_ERROR | ER_MV_ERROR | ER_AC_ERROR))) {
            s->mbskip_table[mb_xy] = 0;
        }
        s->mbintra_table[mb_xy] = 1;
    }
}