void decode_mb_mode(VP8Context *s, VP8mvbounds *mv_bounds,
                    VP8Macroblock *mb, int mb_x, int mb_y,
                    uint8_t *segment, uint8_t *ref, int layout, int is_vp7)
{
    VP56RangeCoder *c = &s->c;
    static const char *vp7_feature_name[] = { "q-index",
                                              "lf-delta",
                                              "partial-golden-update",
                                              "blit-pitch" };
    if (is_vp7) {
        int i;
        *segment = 0;
        for (i = 0; i < 4; i++) {
            if (s->feature_enabled[i]) {
                if (vp56_rac_get_prob_branchy(c, s->feature_present_prob[i])) {
                      int index = vp8_rac_get_tree(c, vp7_feature_index_tree,
                                                   s->feature_index_prob[i]);
                      av_log(s->avctx, AV_LOG_WARNING,
                             "Feature %s present in macroblock (value 0x%x)\n",
                             vp7_feature_name[i], s->feature_value[i][index]);
                }
           }
        }
    } else if (s->segmentation.update_map) {
        int bit  = vp56_rac_get_prob(c, s->prob->segmentid[0]);
        *segment = vp56_rac_get_prob(c, s->prob->segmentid[1+bit]) + 2*bit;
    } else if (s->segmentation.enabled)
        *segment = ref ? *ref : *segment;
    mb->segment = *segment;

    mb->skip = s->mbskip_enabled ? vp56_rac_get_prob(c, s->prob->mbskip) : 0;

    if (s->keyframe) {
        mb->mode = vp8_rac_get_tree(c, vp8_pred16x16_tree_intra,
                                    vp8_pred16x16_prob_intra);

        if (mb->mode == MODE_I4x4) {
            decode_intra4x4_modes(s, c, mb, mb_x, 1, layout);
        } else {
            const uint32_t modes = (is_vp7 ? vp7_pred4x4_mode
                                           : vp8_pred4x4_mode)[mb->mode] * 0x01010101u;
            if (s->mb_layout)
                AV_WN32A(mb->intra4x4_pred_mode_top, modes);
            else
                AV_WN32A(s->intra4x4_pred_mode_top + 4 * mb_x, modes);
            AV_WN32A(s->intra4x4_pred_mode_left, modes);
        }

        mb->chroma_pred_mode = vp8_rac_get_tree(c, vp8_pred8x8c_tree,
                                                vp8_pred8x8c_prob_intra);
        mb->ref_frame        = VP56_FRAME_CURRENT;
    } else if (vp56_rac_get_prob_branchy(c, s->prob->intra)) {
        // inter MB, 16.2
        if (vp56_rac_get_prob_branchy(c, s->prob->last))
            mb->ref_frame =
                (!is_vp7 && vp56_rac_get_prob(c, s->prob->golden)) ? VP56_FRAME_GOLDEN2 /* altref */
                                                                   : VP56_FRAME_GOLDEN;
        else
            mb->ref_frame = VP56_FRAME_PREVIOUS;
        s->ref_count[mb->ref_frame - 1]++;

        // motion vectors, 16.3
        if (is_vp7)
            vp7_decode_mvs(s, mb, mb_x, mb_y, layout);
        else
            vp8_decode_mvs(s, mv_bounds, mb, mb_x, mb_y, layout);
    } else {
        // intra MB, 16.1
        mb->mode = vp8_rac_get_tree(c, vp8_pred16x16_tree_inter, s->prob->pred16x16);

        if (mb->mode == MODE_I4x4)
            decode_intra4x4_modes(s, c, mb, mb_x, 0, layout);

        mb->chroma_pred_mode = vp8_rac_get_tree(c, vp8_pred8x8c_tree,
                                                s->prob->pred8x8c);
        mb->ref_frame        = VP56_FRAME_CURRENT;
        mb->partitioning     = VP8_SPLITMVMODE_NONE;
        AV_ZERO32(&mb->bmv[0]);
    }
}
void decode_mb_mode(VP8Context *s, VP8mvbounds *mv_bounds,
                    VP8Macroblock *mb, int mb_x, int mb_y,
                    uint8_t *segment, uint8_t *ref, int layout, int is_vp7)
{
    VP56RangeCoder *c = &s->c;
    static const char *vp7_feature_name[] = { "q-index",
                                              "lf-delta",
                                              "partial-golden-update",
                                              "blit-pitch" };
    if (is_vp7) {
        int i;
        *segment = 0;
        for (i = 0; i < 4; i++) {
            if (s->feature_enabled[i]) {
                if (vp56_rac_get_prob_branchy(c, s->feature_present_prob[i])) {
                      int index = vp8_rac_get_tree(c, vp7_feature_index_tree,
                                                   s->feature_index_prob[i]);
                      av_log(s->avctx, AV_LOG_WARNING,
                             "Feature %s present in macroblock (value 0x%x)\n",
                             vp7_feature_name[i], s->feature_value[i][index]);
                }
           }
        }
    } else if (s->segmentation.update_map) {
        int bit  = vp56_rac_get_prob(c, s->prob->segmentid[0]);
        *segment = vp56_rac_get_prob(c, s->prob->segmentid[1+bit]) + 2*bit;
    } else if (s->segmentation.enabled)
        *segment = ref ? *ref : *segment;
    mb->segment = *segment;

    mb->skip = s->mbskip_enabled ? vp56_rac_get_prob(c, s->prob->mbskip) : 0;

    if (s->keyframe) {
        mb->mode = vp8_rac_get_tree(c, vp8_pred16x16_tree_intra,
                                    vp8_pred16x16_prob_intra);

        if (mb->mode == MODE_I4x4) {
            decode_intra4x4_modes(s, c, mb, mb_x, 1, layout);
        } else {
            const uint32_t modes = (is_vp7 ? vp7_pred4x4_mode
                                           : vp8_pred4x4_mode)[mb->mode] * 0x01010101u;
            if (s->mb_layout)
                AV_WN32A(mb->intra4x4_pred_mode_top, modes);
            else
                AV_WN32A(s->intra4x4_pred_mode_top + 4 * mb_x, modes);
            AV_WN32A(s->intra4x4_pred_mode_left, modes);
        }

        mb->chroma_pred_mode = vp8_rac_get_tree(c, vp8_pred8x8c_tree,
                                                vp8_pred8x8c_prob_intra);
        mb->ref_frame        = VP56_FRAME_CURRENT;
    } else if (vp56_rac_get_prob_branchy(c, s->prob->intra)) {
         
        if (vp56_rac_get_prob_branchy(c, s->prob->last))
            mb->ref_frame =
                (!is_vp7 && vp56_rac_get_prob(c, s->prob->golden)) ? VP56_FRAME_GOLDEN2  
                                                                   : VP56_FRAME_GOLDEN;
        else
            mb->ref_frame = VP56_FRAME_PREVIOUS;
        s->ref_count[mb->ref_frame - 1]++;

         
        if (is_vp7)
            vp7_decode_mvs(s, mb, mb_x, mb_y, layout);
        else
            vp8_decode_mvs(s, mv_bounds, mb, mb_x, mb_y, layout);
    } else {
         
        mb->mode = vp8_rac_get_tree(c, vp8_pred16x16_tree_inter, s->prob->pred16x16);

        if (mb->mode == MODE_I4x4)
            decode_intra4x4_modes(s, c, mb, mb_x, 0, layout);

        mb->chroma_pred_mode = vp8_rac_get_tree(c, vp8_pred8x8c_tree,
                                                s->prob->pred8x8c);
        mb->ref_frame        = VP56_FRAME_CURRENT;
        mb->partitioning     = VP8_SPLITMVMODE_NONE;
        AV_ZERO32(&mb->bmv[0]);
    }
}