static void loop_filter(H264Context *h, int start_x, int end_x)
{
    uint8_t *dest_y, *dest_cb, *dest_cr;
    int linesize, uvlinesize, mb_x, mb_y;
    const int end_mb_y       = h->mb_y + FRAME_MBAFF(h);
    const int old_slice_type = h->slice_type;
    const int pixel_shift    = h->pixel_shift;
    const int block_h        = 16 >> h->chroma_y_shift;

    if (h->deblocking_filter) {
        for (mb_x = start_x; mb_x < end_x; mb_x++)
            for (mb_y = end_mb_y - FRAME_MBAFF(h); mb_y <= end_mb_y; mb_y++) {
                int mb_xy, mb_type;
                mb_xy         = h->mb_xy = mb_x + mb_y * h->mb_stride;
                h->slice_num  = h->slice_table[mb_xy];
                mb_type       = h->cur_pic.mb_type[mb_xy];
                h->list_count = h->list_counts[mb_xy];

                if (FRAME_MBAFF(h))
                    h->mb_mbaff               =
                    h->mb_field_decoding_flag = !!IS_INTERLACED(mb_type);

                h->mb_x = mb_x;
                h->mb_y = mb_y;
                dest_y  = h->cur_pic.f.data[0] +
                          ((mb_x << pixel_shift) + mb_y * h->linesize) * 16;
                dest_cb = h->cur_pic.f.data[1] +
                          (mb_x << pixel_shift) * (8 << CHROMA444(h)) +
                          mb_y * h->uvlinesize * block_h;
                dest_cr = h->cur_pic.f.data[2] +
                          (mb_x << pixel_shift) * (8 << CHROMA444(h)) +
                          mb_y * h->uvlinesize * block_h;

                if (MB_FIELD(h)) {
                    linesize   = h->mb_linesize   = h->linesize   * 2;
                    uvlinesize = h->mb_uvlinesize = h->uvlinesize * 2;
                    if (mb_y & 1) { // FIXME move out of this function?
                        dest_y  -= h->linesize   * 15;
                        dest_cb -= h->uvlinesize * (block_h - 1);
                        dest_cr -= h->uvlinesize * (block_h - 1);
                    }
                } else {
                    linesize   = h->mb_linesize   = h->linesize;
                    uvlinesize = h->mb_uvlinesize = h->uvlinesize;
                }
                backup_mb_border(h, dest_y, dest_cb, dest_cr, linesize,
                                 uvlinesize, 0);
                if (fill_filter_caches(h, mb_type))
                    continue;
                h->chroma_qp[0] = get_chroma_qp(h, 0, h->cur_pic.qscale_table[mb_xy]);
                h->chroma_qp[1] = get_chroma_qp(h, 1, h->cur_pic.qscale_table[mb_xy]);

                if (FRAME_MBAFF(h)) {
                    ff_h264_filter_mb(h, mb_x, mb_y, dest_y, dest_cb, dest_cr,
                                      linesize, uvlinesize);
                } else {
                    ff_h264_filter_mb_fast(h, mb_x, mb_y, dest_y, dest_cb,
                                           dest_cr, linesize, uvlinesize);
                }
            }
    }
    h->slice_type   = old_slice_type;
    h->mb_x         = end_x;
    h->mb_y         = end_mb_y - FRAME_MBAFF(h);
    h->chroma_qp[0] = get_chroma_qp(h, 0, h->qscale);
    h->chroma_qp[1] = get_chroma_qp(h, 1, h->qscale);
}

Unknown