PeerStreamer

/**

 * VP8 compatible video decoder

 *

 * Copyright (C) 2010 David Conrad

 * Copyright (C) 2010 Ronald S. Bultje

 * Copyright (C) 2010 Jason Garrett-Glaser

 *

 * 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

 */

#include "libavcore/imgutils.h"

#include "avcodec.h"

#include "vp56.h"

#include "vp8data.h"

#include "vp8dsp.h"

#include "h264pred.h"

#include "rectangle.h"

typedef struct {

    uint8_t filter_level;

    uint8_t inner_limit;

    uint8_t inner_filter;

} VP8FilterStrength;

typedef struct {

    uint8_t skip;

    // todo: make it possible to check for at least (i4x4 or split_mv)

    // in one op. are others needed?

    uint8_t mode;

    uint8_t ref_frame;

    uint8_t partitioning;

    VP56mv mv;

    VP56mv bmv[16];

} VP8Macroblock;

typedef struct {

    AVCodecContext *avctx;

    DSPContext dsp;

    VP8DSPContext vp8dsp;

    H264PredContext hpc;

    vp8_mc_func put_pixels_tab[3][3][3];

    AVFrame frames[4];

    AVFrame *framep[4];

    uint8_t *edge_emu_buffer;

    VP56RangeCoder c;   ///< header context, includes mb modes and motion vectors

    int profile;

    int mb_width;   /* number of horizontal MB */

    int mb_height;  /* number of vertical MB */

    int linesize;

    int uvlinesize;

    int keyframe;

    int invisible;

    int update_last;    ///< update VP56_FRAME_PREVIOUS with the current one

    int update_golden;  ///< VP56_FRAME_NONE if not updated, or which frame to copy if so

    int update_altref;

    int deblock_filter;

    /**

     * If this flag is not set, all the probability updates

     * are discarded after this frame is decoded.

     */

    int update_probabilities;

    /**

     * All coefficients are contained in separate arith coding contexts.

     * There can be 1, 2, 4, or 8 of these after the header context.

     */

    int num_coeff_partitions;

    VP56RangeCoder coeff_partition[8];

    VP8Macroblock *macroblocks;

    VP8Macroblock *macroblocks_base;

    VP8FilterStrength *filter_strength;

    uint8_t *intra4x4_pred_mode_top;

    uint8_t intra4x4_pred_mode_left[4];

    uint8_t *segmentation_map;

    /**

     * Cache of the top row needed for intra prediction

     * 16 for luma, 8 for each chroma plane

     */

    uint8_t (*top_border)[16+8+8];

    /**

     * For coeff decode, we need to know whether the above block had non-zero

     * coefficients. This means for each macroblock, we need data for 4 luma

     * blocks, 2 u blocks, 2 v blocks, and the luma dc block, for a total of 9

     * per macroblock. We keep the last row in top_nnz.

     */

    uint8_t (*top_nnz)[9];

    DECLARE_ALIGNED(8, uint8_t, left_nnz)[9];

    /**

     * This is the index plus one of the last non-zero coeff

     * for each of the blocks in the current macroblock.

     * So, 0 -> no coeffs

     *     1 -> dc-only (special transform)

     *     2+-> full transform

     */

    DECLARE_ALIGNED(16, uint8_t, non_zero_count_cache)[6][4];

    DECLARE_ALIGNED(16, DCTELEM, block)[6][4][16];

    DECLARE_ALIGNED(16, DCTELEM, block_dc)[16];

    uint8_t intra4x4_pred_mode_mb[16];

    int chroma_pred_mode;    ///< 8x8c pred mode of the current macroblock

    int segment;             ///< segment of the current macroblock

    int mbskip_enabled;

    int sign_bias[4]; ///< one state [0, 1] per ref frame type

    int ref_count[3];

    /**

     * Base parameters for segmentation, i.e. per-macroblock parameters.

     * These must be kept unchanged even if segmentation is not used for

     * a frame, since the values persist between interframes.

     */

    struct {

        int enabled;

        int absolute_vals;

        int update_map;

        int8_t base_quant[4];

        int8_t filter_level[4];     ///< base loop filter level

    } segmentation;

    /**

     * Macroblocks can have one of 4 different quants in a frame when

     * segmentation is enabled.

     * If segmentation is disabled, only the first segment's values are used.

     */

    struct {

        // [0] - DC qmul  [1] - AC qmul

        int16_t luma_qmul[2];

        int16_t luma_dc_qmul[2];    ///< luma dc-only block quant

        int16_t chroma_qmul[2];

    } qmat[4];

    struct {

        int simple;

        int level;

        int sharpness;

    } filter;

    struct {

        int enabled;    ///< whether each mb can have a different strength based on mode/ref

        /**

         * filter strength adjustment for the following macroblock modes:

         * [0] - i4x4

         * [1] - zero mv

         * [2] - inter modes except for zero or split mv

         * [3] - split mv

         *  i16x16 modes never have any adjustment

         */

        int8_t mode[4];

        /**

         * filter strength adjustment for macroblocks that reference:

         * [0] - intra / VP56_FRAME_CURRENT

         * [1] - VP56_FRAME_PREVIOUS

         * [2] - VP56_FRAME_GOLDEN

         * [3] - altref / VP56_FRAME_GOLDEN2

         */

        int8_t ref[4];

    } lf_delta;

    /**

     * These are all of the updatable probabilities for binary decisions.

     * They are only implictly reset on keyframes, making it quite likely

     * for an interframe to desync if a prior frame's header was corrupt

     * or missing outright!

     */

    struct {

        uint8_t segmentid[3];

        uint8_t mbskip;

        uint8_t intra;

        uint8_t last;

        uint8_t golden;

        uint8_t pred16x16[4];

        uint8_t pred8x8c[3];

        /* Padded to allow overreads */

        uint8_t token[4][17][3][NUM_DCT_TOKENS-1];

        uint8_t mvc[2][19];

    } prob[2];

} VP8Context;

static void vp8_decode_flush(AVCodecContext *avctx)

{

    VP8Context *s = avctx->priv_data;

    int i;

    for (i = 0; i < 4; i++)

        if (s->frames[i].data[0])

            avctx->release_buffer(avctx, &s->frames[i]);

    memset(s->framep, 0, sizeof(s->framep));

    av_freep(&s->macroblocks_base);

    av_freep(&s->filter_strength);

    av_freep(&s->intra4x4_pred_mode_top);

    av_freep(&s->top_nnz);

    av_freep(&s->edge_emu_buffer);

    av_freep(&s->top_border);

    av_freep(&s->segmentation_map);

    s->macroblocks        = NULL;

}

static int update_dimensions(VP8Context *s, int width, int height)

{

    if (av_image_check_size(width, height, 0, s->avctx))

        return AVERROR_INVALIDDATA;

    vp8_decode_flush(s->avctx);

    avcodec_set_dimensions(s->avctx, width, height);

    s->mb_width  = (s->avctx->coded_width +15) / 16;

    s->mb_height = (s->avctx->coded_height+15) / 16;

    s->macroblocks_base        = av_mallocz((s->mb_width+s->mb_height*2+1)*sizeof(*s->macroblocks));

    s->filter_strength         = av_mallocz(s->mb_width*sizeof(*s->filter_strength));

    s->intra4x4_pred_mode_top  = av_mallocz(s->mb_width*4);

    s->top_nnz                 = av_mallocz(s->mb_width*sizeof(*s->top_nnz));

    s->top_border              = av_mallocz((s->mb_width+1)*sizeof(*s->top_border));

    s->segmentation_map        = av_mallocz(s->mb_width*s->mb_height);

    if (!s->macroblocks_base || !s->filter_strength || !s->intra4x4_pred_mode_top ||

        !s->top_nnz || !s->top_border || !s->segmentation_map)

        return AVERROR(ENOMEM);

    s->macroblocks        = s->macroblocks_base + 1;

    return 0;

}

static void parse_segment_info(VP8Context *s)

{

    VP56RangeCoder *c = &s->c;

    int i;

    s->segmentation.update_map = vp8_rac_get(c);

    if (vp8_rac_get(c)) { // update segment feature data

        s->segmentation.absolute_vals = vp8_rac_get(c);

        for (i = 0; i < 4; i++)

            s->segmentation.base_quant[i]   = vp8_rac_get_sint(c, 7);

        for (i = 0; i < 4; i++)

            s->segmentation.filter_level[i] = vp8_rac_get_sint(c, 6);

    }

    if (s->segmentation.update_map)

        for (i = 0; i < 3; i++)

            s->prob->segmentid[i] = vp8_rac_get(c) ? vp8_rac_get_uint(c, 8) : 255;

}

static void update_lf_deltas(VP8Context *s)

{

    VP56RangeCoder *c = &s->c;

    int i;

    for (i = 0; i < 4; i++)

        s->lf_delta.ref[i]  = vp8_rac_get_sint(c, 6);

    for (i = 0; i < 4; i++)

        s->lf_delta.mode[i] = vp8_rac_get_sint(c, 6);

}

static int setup_partitions(VP8Context *s, const uint8_t *buf, int buf_size)

{

    const uint8_t *sizes = buf;

    int i;

    s->num_coeff_partitions = 1 << vp8_rac_get_uint(&s->c, 2);

    buf      += 3*(s->num_coeff_partitions-1);

    buf_size -= 3*(s->num_coeff_partitions-1);

    if (buf_size < 0)

        return -1;

    for (i = 0; i < s->num_coeff_partitions-1; i++) {

        int size = AV_RL24(sizes + 3*i);

        if (buf_size - size < 0)

            return -1;

        ff_vp56_init_range_decoder(&s->coeff_partition[i], buf, size);

        buf      += size;

        buf_size -= size;

    }

    ff_vp56_init_range_decoder(&s->coeff_partition[i], buf, buf_size);

    return 0;

}

static void get_quants(VP8Context *s)

{

    VP56RangeCoder *c = &s->c;

    int i, base_qi;

    int yac_qi     = vp8_rac_get_uint(c, 7);

    int ydc_delta  = vp8_rac_get_sint(c, 4);

    int y2dc_delta = vp8_rac_get_sint(c, 4);

    int y2ac_delta = vp8_rac_get_sint(c, 4);

    int uvdc_delta = vp8_rac_get_sint(c, 4);

    int uvac_delta = vp8_rac_get_sint(c, 4);

    for (i = 0; i < 4; i++) {

        if (s->segmentation.enabled) {

            base_qi = s->segmentation.base_quant[i];

            if (!s->segmentation.absolute_vals)

                base_qi += yac_qi;

        } else

            base_qi = yac_qi;

        s->qmat[i].luma_qmul[0]    =       vp8_dc_qlookup[av_clip(base_qi + ydc_delta , 0, 127)];

        s->qmat[i].luma_qmul[1]    =       vp8_ac_qlookup[av_clip(base_qi             , 0, 127)];

        s->qmat[i].luma_dc_qmul[0] =   2 * vp8_dc_qlookup[av_clip(base_qi + y2dc_delta, 0, 127)];

        s->qmat[i].luma_dc_qmul[1] = 155 * vp8_ac_qlookup[av_clip(base_qi + y2ac_delta, 0, 127)] / 100;

        s->qmat[i].chroma_qmul[0]  =       vp8_dc_qlookup[av_clip(base_qi + uvdc_delta, 0, 127)];

        s->qmat[i].chroma_qmul[1]  =       vp8_ac_qlookup[av_clip(base_qi + uvac_delta, 0, 127)];

        s->qmat[i].luma_dc_qmul[1] = FFMAX(s->qmat[i].luma_dc_qmul[1], 8);

        s->qmat[i].chroma_qmul[0]  = FFMIN(s->qmat[i].chroma_qmul[0], 132);

    }

}

/**

 * Determine which buffers golden and altref should be updated with after this frame.

 * The spec isn't clear here, so I'm going by my understanding of what libvpx does

 *

 * Intra frames update all 3 references

 * Inter frames update VP56_FRAME_PREVIOUS if the update_last flag is set

 * If the update (golden|altref) flag is set, it's updated with the current frame

 *      if update_last is set, and VP56_FRAME_PREVIOUS otherwise.

 * If the flag is not set, the number read means:

 *      0: no update

 *      1: VP56_FRAME_PREVIOUS

 *      2: update golden with altref, or update altref with golden

 */

static VP56Frame ref_to_update(VP8Context *s, int update, VP56Frame ref)

{

    VP56RangeCoder *c = &s->c;

    if (update)

        return VP56_FRAME_CURRENT;

    switch (vp8_rac_get_uint(c, 2)) {

    case 1:

        return VP56_FRAME_PREVIOUS;

    case 2:

        return (ref == VP56_FRAME_GOLDEN) ? VP56_FRAME_GOLDEN2 : VP56_FRAME_GOLDEN;

    }

    return VP56_FRAME_NONE;

}

static void update_refs(VP8Context *s)

{

    VP56RangeCoder *c = &s->c;

    int update_golden = vp8_rac_get(c);

    int update_altref = vp8_rac_get(c);

    s->update_golden = ref_to_update(s, update_golden, VP56_FRAME_GOLDEN);

    s->update_altref = ref_to_update(s, update_altref, VP56_FRAME_GOLDEN2);

}

static int decode_frame_header(VP8Context *s, const uint8_t *buf, int buf_size)

{

    VP56RangeCoder *c = &s->c;

    int header_size, hscale, vscale, i, j, k, l, m, ret;

    int width  = s->avctx->width;

    int height = s->avctx->height;

    s->keyframe  = !(buf[0] & 1);

    s->profile   =  (buf[0]>>1) & 7;

    s->invisible = !(buf[0] & 0x10);

    header_size  = AV_RL24(buf) >> 5;

    buf      += 3;

    buf_size -= 3;

    if (s->profile > 3)

        av_log(s->avctx, AV_LOG_WARNING, "Unknown profile %d\n", s->profile);

    if (!s->profile)

        memcpy(s->put_pixels_tab, s->vp8dsp.put_vp8_epel_pixels_tab, sizeof(s->put_pixels_tab));

    else    // profile 1-3 use bilinear, 4+ aren't defined so whatever

        memcpy(s->put_pixels_tab, s->vp8dsp.put_vp8_bilinear_pixels_tab, sizeof(s->put_pixels_tab));

    if (header_size > buf_size - 7*s->keyframe) {

        av_log(s->avctx, AV_LOG_ERROR, "Header size larger than data provided\n");

        return AVERROR_INVALIDDATA;

    }

    if (s->keyframe) {

        if (AV_RL24(buf) != 0x2a019d) {

            av_log(s->avctx, AV_LOG_ERROR, "Invalid start code 0x%x\n", AV_RL24(buf));

            return AVERROR_INVALIDDATA;

        }

        width  = AV_RL16(buf+3) & 0x3fff;

        height = AV_RL16(buf+5) & 0x3fff;

        hscale = buf[4] >> 6;

        vscale = buf[6] >> 6;

        buf      += 7;

        buf_size -= 7;

        if (hscale || vscale)

            av_log_missing_feature(s->avctx, "Upscaling", 1);

        s->update_golden = s->update_altref = VP56_FRAME_CURRENT;

        for (i = 0; i < 4; i++)

            for (j = 0; j < 16; j++)

                memcpy(s->prob->token[i][j], vp8_token_default_probs[i][vp8_coeff_band[j]],

                       sizeof(s->prob->token[i][j]));

        memcpy(s->prob->pred16x16, vp8_pred16x16_prob_inter, sizeof(s->prob->pred16x16));

        memcpy(s->prob->pred8x8c , vp8_pred8x8c_prob_inter , sizeof(s->prob->pred8x8c));

        memcpy(s->prob->mvc      , vp8_mv_default_prob     , sizeof(s->prob->mvc));

        memset(&s->segmentation, 0, sizeof(s->segmentation));

    }

    if (!s->macroblocks_base || /* first frame */

        width != s->avctx->width || height != s->avctx->height) {

        if ((ret = update_dimensions(s, width, height) < 0))

            return ret;

    }

    ff_vp56_init_range_decoder(c, buf, header_size);

    buf      += header_size;

    buf_size -= header_size;

    if (s->keyframe) {

        if (vp8_rac_get(c))

            av_log(s->avctx, AV_LOG_WARNING, "Unspecified colorspace\n");

        vp8_rac_get(c); // whether we can skip clamping in dsp functions

    }

    if ((s->segmentation.enabled = vp8_rac_get(c)))

        parse_segment_info(s);

    else

        s->segmentation.update_map = 0; // FIXME: move this to some init function?

    s->filter.simple    = vp8_rac_get(c);

    s->filter.level     = vp8_rac_get_uint(c, 6);

    s->filter.sharpness = vp8_rac_get_uint(c, 3);

    if ((s->lf_delta.enabled = vp8_rac_get(c)))

        if (vp8_rac_get(c))

            update_lf_deltas(s);

    if (setup_partitions(s, buf, buf_size)) {

        av_log(s->avctx, AV_LOG_ERROR, "Invalid partitions\n");

        return AVERROR_INVALIDDATA;

    }

    get_quants(s);

    if (!s->keyframe) {

        update_refs(s);

        s->sign_bias[VP56_FRAME_GOLDEN]               = vp8_rac_get(c);

        s->sign_bias[VP56_FRAME_GOLDEN2 /* altref */] = vp8_rac_get(c);

    }

    // if we aren't saving this frame's probabilities for future frames,

    // make a copy of the current probabilities

    if (!(s->update_probabilities = vp8_rac_get(c)))

        s->prob[1] = s->prob[0];

    s->update_last = s->keyframe || vp8_rac_get(c);

    for (i = 0; i < 4; i++)

        for (j = 0; j < 8; j++)

            for (k = 0; k < 3; k++)

                for (l = 0; l < NUM_DCT_TOKENS-1; l++)

                    if (vp56_rac_get_prob_branchy(c, vp8_token_update_probs[i][j][k][l])) {

                        int prob = vp8_rac_get_uint(c, 8);

                        for (m = 0; vp8_coeff_band_indexes[j][m] >= 0; m++)

                            s->prob->token[i][vp8_coeff_band_indexes[j][m]][k][l] = prob;

                    }

    if ((s->mbskip_enabled = vp8_rac_get(c)))

        s->prob->mbskip = vp8_rac_get_uint(c, 8);

    if (!s->keyframe) {

        s->prob->intra  = vp8_rac_get_uint(c, 8);

        s->prob->last   = vp8_rac_get_uint(c, 8);

        s->prob->golden = vp8_rac_get_uint(c, 8);

        if (vp8_rac_get(c))

            for (i = 0; i < 4; i++)

                s->prob->pred16x16[i] = vp8_rac_get_uint(c, 8);

        if (vp8_rac_get(c))

            for (i = 0; i < 3; i++)

                s->prob->pred8x8c[i]  = vp8_rac_get_uint(c, 8);

        // 17.2 MV probability update

        for (i = 0; i < 2; i++)

            for (j = 0; j < 19; j++)

                if (vp56_rac_get_prob_branchy(c, vp8_mv_update_prob[i][j]))

                    s->prob->mvc[i][j] = vp8_rac_get_nn(c);

    }

    return 0;

}

static av_always_inline

void clamp_mv(VP8Context *s, VP56mv *dst, const VP56mv *src, int mb_x, int mb_y)

{

#define MARGIN (16 << 2)

    dst->x = av_clip(src->x, -((mb_x << 6) + MARGIN),

                     ((s->mb_width  - 1 - mb_x) << 6) + MARGIN);

    dst->y = av_clip(src->y, -((mb_y << 6) + MARGIN),

                     ((s->mb_height - 1 - mb_y) << 6) + MARGIN);

}

static av_always_inline

void find_near_mvs(VP8Context *s, VP8Macroblock *mb,

                   VP56mv near[2], VP56mv *best, uint8_t cnt[4])

{

    VP8Macroblock *mb_edge[3] = { mb + 2 /* top */,

                                  mb - 1 /* left */,

                                  mb + 1 /* top-left */ };

    enum { EDGE_TOP, EDGE_LEFT, EDGE_TOPLEFT };

    VP56mv near_mv[4]  = {{ 0 }};

    enum { CNT_ZERO, CNT_NEAREST, CNT_NEAR, CNT_SPLITMV };

    int idx = CNT_ZERO;

    int best_idx = CNT_ZERO;

    int cur_sign_bias = s->sign_bias[mb->ref_frame];

    int *sign_bias = s->sign_bias;

    /* Process MB on top, left and top-left */

    #define MV_EDGE_CHECK(n)\

    {\

        VP8Macroblock *edge = mb_edge[n];\

        int edge_ref = edge->ref_frame;\

        if (edge_ref != VP56_FRAME_CURRENT) {\

            uint32_t mv = AV_RN32A(&edge->mv);\

            if (mv) {\

                if (cur_sign_bias != sign_bias[edge_ref]) {\

                    /* SWAR negate of the values in mv. */\

                    mv = ~mv;\

                    mv = ((mv&0x7fff7fff) + 0x00010001) ^ (mv&0x80008000);\

                }\

                if (!n || mv != AV_RN32A(&near_mv[idx]))\

                    AV_WN32A(&near_mv[++idx], mv);\

                cnt[idx]      += 1 + (n != 2);\

            } else\

                cnt[CNT_ZERO] += 1 + (n != 2);\

        }\

    }

    MV_EDGE_CHECK(0)

    MV_EDGE_CHECK(1)

    MV_EDGE_CHECK(2)

    /* If we have three distinct MVs, merge first and last if they're the same */

    if (cnt[CNT_SPLITMV] && AV_RN32A(&near_mv[1+EDGE_TOP]) == AV_RN32A(&near_mv[1+EDGE_TOPLEFT]))

        cnt[CNT_NEAREST] += 1;

    cnt[CNT_SPLITMV] = ((mb_edge[EDGE_LEFT]->mode   == VP8_MVMODE_SPLIT) +

                        (mb_edge[EDGE_TOP]->mode    == VP8_MVMODE_SPLIT)) * 2 +

                       (mb_edge[EDGE_TOPLEFT]->mode == VP8_MVMODE_SPLIT);

    /* Swap near and nearest if necessary */

    if (cnt[CNT_NEAR] > cnt[CNT_NEAREST]) {

        FFSWAP(uint8_t,     cnt[CNT_NEAREST],     cnt[CNT_NEAR]);

        FFSWAP( VP56mv, near_mv[CNT_NEAREST], near_mv[CNT_NEAR]);

    }

    /* Choose the best mv out of 0,0 and the nearest mv */

    if (cnt[CNT_NEAREST] >= cnt[CNT_ZERO])

        best_idx = CNT_NEAREST;

    mb->mv  = near_mv[best_idx];

    near[0] = near_mv[CNT_NEAREST];

    near[1] = near_mv[CNT_NEAR];

}

/**

 * Motion vector coding, 17.1.

 */

static int read_mv_component(VP56RangeCoder *c, const uint8_t *p)

{

    int bit, x = 0;

    if (vp56_rac_get_prob_branchy(c, p[0])) {

        int i;

        for (i = 0; i < 3; i++)

            x += vp56_rac_get_prob(c, p[9 + i]) << i;

        for (i = 9; i > 3; i--)

            x += vp56_rac_get_prob(c, p[9 + i]) << i;

        if (!(x & 0xFFF0) || vp56_rac_get_prob(c, p[12]))

            x += 8;

    } else {

        // small_mvtree

        const uint8_t *ps = p+2;

        bit = vp56_rac_get_prob(c, *ps);

        ps += 1 + 3*bit;

        x  += 4*bit;

        bit = vp56_rac_get_prob(c, *ps);

        ps += 1 + bit;

        x  += 2*bit;

        x  += vp56_rac_get_prob(c, *ps);

    }

    return (x && vp56_rac_get_prob(c, p[1])) ? -x : x;

}

static av_always_inline

const uint8_t *get_submv_prob(uint32_t left, uint32_t top)

{

    if (left == top)

        return vp8_submv_prob[4-!!left];

    if (!top)

        return vp8_submv_prob[2];

    return vp8_submv_prob[1-!!left];

}

/**

 * Split motion vector prediction, 16.4.

 * @returns the number of motion vectors parsed (2, 4 or 16)

 */

static av_always_inline

int decode_splitmvs(VP8Context *s, VP56RangeCoder *c, VP8Macroblock *mb)

{

    int part_idx;

    int n, num;

    VP8Macroblock *top_mb  = &mb[2];

    VP8Macroblock *left_mb = &mb[-1];

    const uint8_t *mbsplits_left = vp8_mbsplits[left_mb->partitioning],

                  *mbsplits_top = vp8_mbsplits[top_mb->partitioning],

                  *mbsplits_cur, *firstidx;

    VP56mv *top_mv  = top_mb->bmv;

    VP56mv *left_mv = left_mb->bmv;

    VP56mv *cur_mv  = mb->bmv;

    if (vp56_rac_get_prob_branchy(c, vp8_mbsplit_prob[0])) {

        if (vp56_rac_get_prob_branchy(c, vp8_mbsplit_prob[1])) {

            part_idx = VP8_SPLITMVMODE_16x8 + vp56_rac_get_prob(c, vp8_mbsplit_prob[2]);

        } else {

            part_idx = VP8_SPLITMVMODE_8x8;

        }

    } else {

        part_idx = VP8_SPLITMVMODE_4x4;

    }

    num = vp8_mbsplit_count[part_idx];

    mbsplits_cur = vp8_mbsplits[part_idx],

    firstidx = vp8_mbfirstidx[part_idx];

    mb->partitioning = part_idx;

    for (n = 0; n < num; n++) {

        int k = firstidx[n];

        uint32_t left, above;

        const uint8_t *submv_prob;

        if (!(k & 3))

            left = AV_RN32A(&left_mv[mbsplits_left[k + 3]]);

        else

            left  = AV_RN32A(&cur_mv[mbsplits_cur[k - 1]]);

        if (k <= 3)

            above = AV_RN32A(&top_mv[mbsplits_top[k + 12]]);

        else

            above = AV_RN32A(&cur_mv[mbsplits_cur[k - 4]]);

        submv_prob = get_submv_prob(left, above);

        if (vp56_rac_get_prob_branchy(c, submv_prob[0])) {

            if (vp56_rac_get_prob_branchy(c, submv_prob[1])) {

                if (vp56_rac_get_prob_branchy(c, submv_prob[2])) {

                    mb->bmv[n].y = mb->mv.y + read_mv_component(c, s->prob->mvc[0]);

                    mb->bmv[n].x = mb->mv.x + read_mv_component(c, s->prob->mvc[1]);

                } else {

                    AV_ZERO32(&mb->bmv[n]);

                }

            } else {

                AV_WN32A(&mb->bmv[n], above);

            }

        } else {

            AV_WN32A(&mb->bmv[n], left);

        }

    }

    return num;

}

static av_always_inline

void decode_intra4x4_modes(VP8Context *s, VP56RangeCoder *c,

                           int mb_x, int keyframe)

{

    uint8_t *intra4x4 = s->intra4x4_pred_mode_mb;

    if (keyframe) {

        int x, y;

        uint8_t* const top = s->intra4x4_pred_mode_top + 4 * mb_x;

        uint8_t* const left = s->intra4x4_pred_mode_left;

        for (y = 0; y < 4; y++) {

            for (x = 0; x < 4; x++) {

                const uint8_t *ctx;

                ctx = vp8_pred4x4_prob_intra[top[x]][left[y]];

                *intra4x4 = vp8_rac_get_tree(c, vp8_pred4x4_tree, ctx);

                left[y] = top[x] = *intra4x4;

                intra4x4++;

            }

        }

    } else {

        int i;

        for (i = 0; i < 16; i++)

            intra4x4[i] = vp8_rac_get_tree(c, vp8_pred4x4_tree, vp8_pred4x4_prob_inter);

    }

}

static av_always_inline

void decode_mb_mode(VP8Context *s, VP8Macroblock *mb, int mb_x, int mb_y, uint8_t *segment)

{

    VP56RangeCoder *c = &s->c;

    if (s->segmentation.update_map)

        *segment = vp8_rac_get_tree(c, vp8_segmentid_tree, s->prob->segmentid);

    s->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_x, 1);

        } else {

            const uint32_t modes = vp8_pred4x4_mode[mb->mode] * 0x01010101u;

            AV_WN32A(s->intra4x4_pred_mode_top + 4 * mb_x, modes);

            AV_WN32A(s->intra4x4_pred_mode_left, modes);

        }

        s->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)) {

        VP56mv near[2], best;

        uint8_t cnt[4] = { 0 };

        // inter MB, 16.2

        if (vp56_rac_get_prob_branchy(c, s->prob->last))

            mb->ref_frame = 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

        find_near_mvs(s, mb, near, &best, cnt);

        if (vp56_rac_get_prob_branchy(c, vp8_mode_contexts[cnt[0]][0])) {

            if (vp56_rac_get_prob_branchy(c, vp8_mode_contexts[cnt[1]][1])) {

                if (vp56_rac_get_prob_branchy(c, vp8_mode_contexts[cnt[2]][2])) {

                    if (vp56_rac_get_prob_branchy(c, vp8_mode_contexts[cnt[3]][3])) {

                        mb->mode = VP8_MVMODE_SPLIT;

                        clamp_mv(s, &mb->mv, &mb->mv, mb_x, mb_y);

                        mb->mv = mb->bmv[decode_splitmvs(s, c, mb) - 1];

                    } else {

                        mb->mode = VP8_MVMODE_NEW;

                        clamp_mv(s, &mb->mv, &mb->mv, mb_x, mb_y);

                        mb->mv.y += read_mv_component(c, s->prob->mvc[0]);

                        mb->mv.x += read_mv_component(c, s->prob->mvc[1]);

                    }

                } else {

                    mb->mode = VP8_MVMODE_NEAR;

                    clamp_mv(s, &mb->mv, &near[1], mb_x, mb_y);

                }

            } else {

                mb->mode = VP8_MVMODE_NEAREST;

                clamp_mv(s, &mb->mv, &near[0], mb_x, mb_y);

            }

        } else {

            mb->mode = VP8_MVMODE_ZERO;

            AV_ZERO32(&mb->mv);

        }

        if (mb->mode != VP8_MVMODE_SPLIT) {

            mb->partitioning = VP8_SPLITMVMODE_NONE;

            mb->bmv[0] = mb->mv;

        }

    } 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_x, 0);

        s->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]);

    }

}

/**

 * @param c arithmetic bitstream reader context

 * @param block destination for block coefficients

 * @param probs probabilities to use when reading trees from the bitstream

 * @param i initial coeff index, 0 unless a separate DC block is coded

 * @param zero_nhood the initial prediction context for number of surrounding

 *                   all-zero blocks (only left/top, so 0-2)

 * @param qmul array holding the dc/ac dequant factor at position 0/1

 * @return 0 if no coeffs were decoded

 *         otherwise, the index of the last coeff decoded plus one

 */

static int decode_block_coeffs_internal(VP56RangeCoder *c, DCTELEM block[16],

                                        uint8_t probs[8][3][NUM_DCT_TOKENS-1],

                                        int i, uint8_t *token_prob, int16_t qmul[2])

{

    goto skip_eob;

    do {

        int coeff;

        if (!vp56_rac_get_prob_branchy(c, token_prob[0]))   // DCT_EOB

            return i;

skip_eob:

        if (!vp56_rac_get_prob_branchy(c, token_prob[1])) { // DCT_0

            if (++i == 16)

                return i; // invalid input; blocks should end with EOB

            token_prob = probs[i][0];

            goto skip_eob;

        }

        if (!vp56_rac_get_prob_branchy(c, token_prob[2])) { // DCT_1

            coeff = 1;

            token_prob = probs[i+1][1];

        } else {

            if (!vp56_rac_get_prob_branchy(c, token_prob[3])) { // DCT 2,3,4

                coeff = vp56_rac_get_prob_branchy(c, token_prob[4]);

                if (coeff)

                    coeff += vp56_rac_get_prob(c, token_prob[5]);

                coeff += 2;

            } else {

                // DCT_CAT*

                if (!vp56_rac_get_prob_branchy(c, token_prob[6])) {

                    if (!vp56_rac_get_prob_branchy(c, token_prob[7])) { // DCT_CAT1

                        coeff  = 5 + vp56_rac_get_prob(c, vp8_dct_cat1_prob[0]);

                    } else {                                    // DCT_CAT2

                        coeff  = 7;

                        coeff += vp56_rac_get_prob(c, vp8_dct_cat2_prob[0]) << 1;

                        coeff += vp56_rac_get_prob(c, vp8_dct_cat2_prob[1]);

                    }

                } else {    // DCT_CAT3 and up

                    int a = vp56_rac_get_prob(c, token_prob[8]);

                    int b = vp56_rac_get_prob(c, token_prob[9+a]);

                    int cat = (a<<1) + b;

                    coeff  = 3 + (8<<cat);

                    coeff += vp8_rac_get_coeff(c, vp8_dct_cat_prob[cat]);

                }

            }

            token_prob = probs[i+1][2];

        }

        block[zigzag_scan[i]] = (vp8_rac_get(c) ? -coeff : coeff) * qmul[!!i];

    } while (++i < 16);

    return i;

}

static av_always_inline

int decode_block_coeffs(VP56RangeCoder *c, DCTELEM block[16],

                        uint8_t probs[8][3][NUM_DCT_TOKENS-1],

                        int i, int zero_nhood, int16_t qmul[2])

{

    uint8_t *token_prob = probs[i][zero_nhood];

    if (!vp56_rac_get_prob_branchy(c, token_prob[0]))   // DCT_EOB

        return 0;

    return decode_block_coeffs_internal(c, block, probs, i, token_prob, qmul);

}

static av_always_inline

void decode_mb_coeffs(VP8Context *s, VP56RangeCoder *c, VP8Macroblock *mb,

                      uint8_t t_nnz[9], uint8_t l_nnz[9])

{

    int i, x, y, luma_start = 0, luma_ctx = 3;

    int nnz_pred, nnz, nnz_total = 0;

    int segment = s->segment;

    int block_dc = 0;

    if (mb->mode != MODE_I4x4 && mb->mode != VP8_MVMODE_SPLIT) {

        nnz_pred = t_nnz[8] + l_nnz[8];

        // decode DC values and do hadamard

        nnz = decode_block_coeffs(c, s->block_dc, s->prob->token[1], 0, nnz_pred,

                                  s->qmat[segment].luma_dc_qmul);

        l_nnz[8] = t_nnz[8] = !!nnz;

        if (nnz) {

            nnz_total += nnz;

            block_dc = 1;

            if (nnz == 1)

                s->vp8dsp.vp8_luma_dc_wht_dc(s->block, s->block_dc);

            else

                s->vp8dsp.vp8_luma_dc_wht(s->block, s->block_dc);

        }

        luma_start = 1;

        luma_ctx = 0;

    }

    // luma blocks

    for (y = 0; y < 4; y++)

        for (x = 0; x < 4; x++) {

            nnz_pred = l_nnz[y] + t_nnz[x];

            nnz = decode_block_coeffs(c, s->block[y][x], s->prob->token[luma_ctx], luma_start,

                                      nnz_pred, s->qmat[segment].luma_qmul);

            // nnz+block_dc may be one more than the actual last index, but we don't care

            s->non_zero_count_cache[y][x] = nnz + block_dc;

            t_nnz[x] = l_nnz[y] = !!nnz;

            nnz_total += nnz;

        }

    // chroma blocks

    // TODO: what to do about dimensions? 2nd dim for luma is x,

    // but for chroma it's (y<<1)|x

    for (i = 4; i < 6; i++)

        for (y = 0; y < 2; y++)

            for (x = 0; x < 2; x++) {

                nnz_pred = l_nnz[i+2*y] + t_nnz[i+2*x];

                nnz = decode_block_coeffs(c, s->block[i][(y<<1)+x], s->prob->token[2], 0,

                                          nnz_pred, s->qmat[segment].chroma_qmul);

                s->non_zero_count_cache[i][(y<<1)+x] = nnz;

                t_nnz[i+2*x] = l_nnz[i+2*y] = !!nnz;

                nnz_total += nnz;

            }

    // if there were no coded coeffs despite the macroblock not being marked skip,

    // we MUST not do the inner loop filter and should not do IDCT

    // Since skip isn't used for bitstream prediction, just manually set it.

    if (!nnz_total)

        mb->skip = 1;

}

static av_always_inline

void backup_mb_border(uint8_t *top_border, uint8_t *src_y, uint8_t *src_cb, uint8_t *src_cr,

                      int linesize, int uvlinesize, int simple)

{

    AV_COPY128(top_border, src_y + 15*linesize);

    if (!simple) {

        AV_COPY64(top_border+16, src_cb + 7*uvlinesize);

        AV_COPY64(top_border+24, src_cr + 7*uvlinesize);

    }

}

static av_always_inline

void xchg_mb_border(uint8_t *top_border, uint8_t *src_y, uint8_t *src_cb, uint8_t *src_cr,

                    int linesize, int uvlinesize, int mb_x, int mb_y, int mb_width,

                    int simple, int xchg)

{

    uint8_t *top_border_m1 = top_border-32;     // for TL prediction

    src_y  -=   linesize;

    src_cb -= uvlinesize;

    src_cr -= uvlinesize;

#define XCHG(a,b,xchg) do {                     \

        if (xchg) AV_SWAP64(b,a);               \

        else      AV_COPY64(b,a);               \

    } while (0)

    XCHG(top_border_m1+8, src_y-8, xchg);

    XCHG(top_border,      src_y,   xchg);

    XCHG(top_border+8,    src_y+8, 1);

    if (mb_x < mb_width-1)

        XCHG(top_border+32, src_y+16, 1);

    // only copy chroma for normal loop filter

    // or to initialize the top row to 127

    if (!simple || !mb_y) {

        XCHG(top_border_m1+16, src_cb-8, xchg);

        XCHG(top_border_m1+24, src_cr-8, xchg);

        XCHG(top_border+16,    src_cb, 1);

        XCHG(top_border+24,    src_cr, 1);

    }

}

static av_always_inline

int check_dc_pred8x8_mode(int mode, int mb_x, int mb_y)

{

    if (!mb_x) {

        return mb_y ? TOP_DC_PRED8x8 : DC_128_PRED8x8;

    } else {

        return mb_y ? mode : LEFT_DC_PRED8x8;

    }

}

static av_always_inline

int check_tm_pred8x8_mode(int mode, int mb_x, int mb_y)

{

    if (!mb_x) {

        return mb_y ? VERT_PRED8x8 : DC_129_PRED8x8;

    } else {

        return mb_y ? mode : HOR_PRED8x8;

    }

}

static av_always_inline

int check_intra_pred8x8_mode(int mode, int mb_x, int mb_y)

{

    if (mode == DC_PRED8x8) {

        return check_dc_pred8x8_mode(mode, mb_x, mb_y);

    } else {

        return mode;

    }

}

static av_always_inline

int check_intra_pred8x8_mode_emuedge(int mode, int mb_x, int mb_y)

{

    switch (mode) {

    case DC_PRED8x8:

        return check_dc_pred8x8_mode(mode, mb_x, mb_y);

    case VERT_PRED8x8:

        return !mb_y ? DC_127_PRED8x8 : mode;

    case HOR_PRED8x8:

        return !mb_x ? DC_129_PRED8x8 : mode;

    case PLANE_PRED8x8 /*TM*/:

        return check_tm_pred8x8_mode(mode, mb_x, mb_y);

    }

    return mode;

}

static av_always_inline

int check_tm_pred4x4_mode(int mode, int mb_x, int mb_y)

{

    if (!mb_x) {

        return mb_y ? VERT_VP8_PRED : DC_129_PRED;

    } else {

        return mb_y ? mode : HOR_VP8_PRED;

    }

}

static av_always_inline

int check_intra_pred4x4_mode_emuedge(int mode, int mb_x, int mb_y, int *copy_buf)

{

    switch (mode) {

    case VERT_PRED:

        if (!mb_x && mb_y) {

            *copy_buf = 1;

            return mode;

        }

        /* fall-through */

    case DIAG_DOWN_LEFT_PRED:

    case VERT_LEFT_PRED:

        return !mb_y ? DC_127_PRED : mode;

    case HOR_PRED:

        if (!mb_y) {

            *copy_buf = 1;

            return mode;

        }

        /* fall-through */

    case HOR_UP_PRED:

        return !mb_x ? DC_129_PRED : mode;

    case TM_VP8_PRED:

        return check_tm_pred4x4_mode(mode, mb_x, mb_y);

    case DC_PRED: // 4x4 DC doesn't use the same "H.264-style" exceptions as 16x16/8x8 DC

    case DIAG_DOWN_RIGHT_PRED:

    case VERT_RIGHT_PRED:

    case HOR_DOWN_PRED:

        if (!mb_y || !mb_x)

            *copy_buf = 1;

        return mode;

    }

    return mode;

}

static av_always_inline

void intra_predict(VP8Context *s, uint8_t *dst[3], VP8Macroblock *mb,

                   int mb_x, int mb_y)

{

    AVCodecContext *avctx = s->avctx;

    int x, y, mode, nnz, tr;

    // for the first row, we need to run xchg_mb_border to init the top edge to 127

    // otherwise, skip it if we aren't going to deblock

    if (!(avctx->flags & CODEC_FLAG_EMU_EDGE && !mb_y) && (s->deblock_filter || !mb_y))

        xchg_mb_border(s->top_border[mb_x+1], dst[0], dst[1], dst[2],

                       s->linesize, s->uvlinesize, mb_x, mb_y, s->mb_width,

                       s->filter.simple, 1);

    if (mb->mode < MODE_I4x4) {

        if (avctx->flags & CODEC_FLAG_EMU_EDGE) { // tested

            mode = check_intra_pred8x8_mode_emuedge(mb->mode, mb_x, mb_y);

        } else {

            mode = check_intra_pred8x8_mode(mb->mode, mb_x, mb_y);

        }

        s->hpc.pred16x16[mode](dst[0], s->linesize);

    } else {

        uint8_t *ptr = dst[0];

        uint8_t *intra4x4 = s->intra4x4_pred_mode_mb;

        uint8_t tr_top[4] = { 127, 127, 127, 127 };

        // all blocks on the right edge of the macroblock use bottom edge

        // the top macroblock for their topright edge

        uint8_t *tr_right = ptr - s->linesize + 16;

        // if we're on the right edge of the frame, said edge is extended

        // from the top macroblock

        if (!(!mb_y && avctx->flags & CODEC_FLAG_EMU_EDGE) &&

            mb_x == s->mb_width-1) {

            tr = tr_right[-1]*0x01010101;

            tr_right = (uint8_t *)&tr;

        }

        if (mb->skip)

            AV_ZERO128(s->non_zero_count_cache);

        for (y = 0; y < 4; y++) {

            uint8_t *topright = ptr + 4 - s->linesize;

            for (x = 0; x < 4; x++) {

                int copy = 0, linesize = s->linesize;

                uint8_t *dst = ptr+4*x;

                DECLARE_ALIGNED(4, uint8_t, copy_dst)[5*8];

                if ((y == 0 || x == 3) && mb_y == 0 && avctx->flags & CODEC_FLAG_EMU_EDGE) {

                    topright = tr_top;

                } else if (x == 3)

                    topright = tr_right;

                if (avctx->flags & CODEC_FLAG_EMU_EDGE) { // mb_x+x or mb_y+y is a hack but works

                    mode = check_intra_pred4x4_mode_emuedge(intra4x4[x], mb_x + x, mb_y + y, &copy);

                    if (copy) {

                        dst = copy_dst + 12;

                        linesize = 8;

                        if (!(mb_y + y)) {

                            copy_dst[3] = 127U;

                            AV_WN32A(copy_dst+4, 127U * 0x01010101U);

                        } else {

                            AV_COPY32(copy_dst+4, ptr+4*x-s->linesize);

                            if (!(mb_x + x)) {

                                copy_dst[3] = 129U;

                            } else {

                                copy_dst[3] = ptr[4*x-s->linesize-1];

                            }

                        }

                        if (!(mb_x + x)) {

                            copy_dst[11] =

                            copy_dst[19] =

                            copy_dst[27] =

                            copy_dst[35] = 129U;

                        } else {

                            copy_dst[11] = ptr[4*x              -1];

                            copy_dst[19] = ptr[4*x+s->linesize  -1];

                            copy_dst[27] = ptr[4*x+s->linesize*2-1];

                            copy_dst[35] = ptr[4*x+s->linesize*3-1];

                        }

                    }

                } else {

                    mode = intra4x4[x];

                }

                s->hpc.pred4x4[mode](dst, topright, linesize);

                if (copy) {

                    AV_COPY32(ptr+4*x              , copy_dst+12);

                    AV_COPY32(ptr+4*x+s->linesize  , copy_dst+20);

                    AV_COPY32(ptr+4*x+s->linesize*2, copy_dst+28);

                    AV_COPY32(ptr+4*x+s->linesize*3, copy_dst+36);

                }

                nnz = s->non_zero_count_cache[y][x];

                if (nnz) {

                    if (nnz == 1)

                        s->vp8dsp.vp8_idct_dc_add(ptr+4*x, s->block[y][x], s->linesize);

                    else

                        s->vp8dsp.vp8_idct_add(ptr+4*x, s->block[y][x], s->linesize);

                }

                topright += 4;

            }

            ptr   += 4*s->linesize;

            intra4x4 += 4;

        }

    }

    if (avctx->flags & CODEC_FLAG_EMU_EDGE) {

        mode = check_intra_pred8x8_mode_emuedge(s->chroma_pred_mode, mb_x, mb_y);

    } else {

        mode = check_intra_pred8x8_mode(s->chroma_pred_mode, mb_x, mb_y);

    }

    s->hpc.pred8x8[mode](dst[1], s->uvlinesize);

    s->hpc.pred8x8[mode](dst[2], s->uvlinesize);

    if (!(avctx->flags & CODEC_FLAG_EMU_EDGE && !mb_y) && (s->deblock_filter || !mb_y))

        xchg_mb_border(s->top_border[mb_x+1], dst[0], dst[1], dst[2],

                       s->linesize, s->uvlinesize, mb_x, mb_y, s->mb_width,

                       s->filter.simple, 0);

}

/**

 * Generic MC function.

 *

 * @param s VP8 decoding context

 * @param luma 1 for luma (Y) planes, 0 for chroma (Cb/Cr) planes

 * @param dst target buffer for block data at block position

 * @param src reference picture buffer at origin (0, 0)

 * @param mv motion vector (relative to block position) to get pixel data from

 * @param x_off horizontal position of block from origin (0, 0)

 * @param y_off vertical position of block from origin (0, 0)

 * @param block_w width of block (16, 8 or 4)

 * @param block_h height of block (always same as block_w)

 * @param width width of src/dst plane data

 * @param height height of src/dst plane data

 * @param linesize size of a single line of plane data, including padding

 * @param mc_func motion compensation function pointers (bilinear or sixtap MC)

 */

static av_always_inline

void vp8_mc(VP8Context *s, int luma,

            uint8_t *dst, uint8_t *src, const VP56mv *mv,

            int x_off, int y_off, int block_w, int block_h,

            int width, int height, int linesize,

            vp8_mc_func mc_func[3][3])

{

    if (AV_RN32A(mv)) {

        static const uint8_t idx[3][8] = {

            { 0, 1, 2, 1, 2, 1, 2, 1 }, // nr. of left extra pixels,

                                        // also function pointer index

            { 0, 3, 5, 3, 5, 3, 5, 3 }, // nr. of extra pixels required

            { 0, 2, 3, 2, 3, 2, 3, 2 }, // nr. of right extra pixels

        };

        int mx = (mv->x << luma)&7, mx_idx = idx[0][mx];

        int my = (mv->y << luma)&7, my_idx = idx[0][my];

        x_off += mv->x >> (3 - luma);

        y_off += mv->y >> (3 - luma);

        // edge emulation

        src += y_off * linesize + x_off;

        if (x_off < mx_idx || x_off >= width  - block_w - idx[2][mx] ||

            y_off < my_idx || y_off >= height - block_h - idx[2][my]) {

            s->dsp.emulated_edge_mc(s->edge_emu_buffer, src - my_idx * linesize - mx_idx, linesize,

                                block_w + idx[1][mx], block_h + idx[1][my],

                                x_off - mx_idx, y_off - my_idx, width, height);

            src = s->edge_emu_buffer + mx_idx + linesize * my_idx;

        }

        mc_func[my_idx][mx_idx](dst, linesize, src, linesize, block_h, mx, my);

    } else

        mc_func[0][0](dst, linesize, src + y_off * linesize + x_off, linesize, block_h, 0, 0);

}

static av_always_inline

void vp8_mc_part(VP8Context *s, uint8_t *dst[3],

                 AVFrame *ref_frame, int x_off, int y_off,

                 int bx_off, int by_off,

                 int block_w, int block_h,

                 int width, int height, VP56mv *mv)

{

    VP56mv uvmv = *mv;

    /* Y */

    vp8_mc(s, 1, dst[0] + by_off * s->linesize + bx_off,

           ref_frame->data[0], mv, x_off + bx_off, y_off + by_off,

           block_w, block_h, width, height, s->linesize,

           s->put_pixels_tab[block_w == 8]);

    /* U/V */

    if (s->profile == 3) {

        uvmv.x &= ~7;

        uvmv.y &= ~7;

    }

    x_off   >>= 1; y_off   >>= 1;

    bx_off  >>= 1; by_off  >>= 1;

    width   >>= 1; height  >>= 1;

    block_w >>= 1; block_h >>= 1;

    vp8_mc(s, 0, dst[1] + by_off * s->uvlinesize + bx_off,

           ref_frame->data[1], &uvmv, x_off + bx_off, y_off + by_off,

           block_w, block_h, width, height, s->uvlinesize,

           s->put_pixels_tab[1 + (block_w == 4)]);

    vp8_mc(s, 0, dst[2] + by_off * s->uvlinesize + bx_off,

           ref_frame->data[2], &uvmv, x_off + bx_off, y_off + by_off,

           block_w, block_h, width, height, s->uvlinesize,

           s->put_pixels_tab[1 + (block_w == 4)]);

}

/* Fetch pixels for estimated mv 4 macroblocks ahead.

 * Optimized for 64-byte cache lines.  Inspired by ffh264 prefetch_motion. */

static av_always_inline void prefetch_motion(VP8Context *s, VP8Macroblock *mb, int mb_x, int mb_y, int mb_xy, int ref)

{

    /* Don't prefetch refs that haven't been used very often this frame. */

    if (s->ref_count[ref-1] > (mb_xy >> 5)) {

        int x_off = mb_x << 4, y_off = mb_y << 4;

        int mx = (mb->mv.x>>2) + x_off + 8;

        int my = (mb->mv.y>>2) + y_off;

        uint8_t **src= s->framep[ref]->data;

        int off= mx + (my + (mb_x&3)*4)*s->linesize + 64;

        s->dsp.prefetch(src[0]+off, s->linesize, 4);

        off= (mx>>1) + ((my>>1) + (mb_x&7))*s->uvlinesize + 64;

        s->dsp.prefetch(src[1]+off, src[2]-src[1], 2);

    }

}

/**

 * Apply motion vectors to prediction buffer, chapter 18.

 */

static av_always_inline

void inter_predict(VP8Context *s, uint8_t *dst[3], VP8Macroblock *mb,

                   int mb_x, int mb_y)

{

    int x_off = mb_x << 4, y_off = mb_y << 4;

    int width = 16*s->mb_width, height = 16*s->mb_height;

    AVFrame *ref = s->framep[mb->ref_frame];

    VP56mv *bmv = mb->bmv;

    if (mb->mode < VP8_MVMODE_SPLIT) {

        vp8_mc_part(s, dst, ref, x_off, y_off,

                    0, 0, 16, 16, width, height, &mb->mv);

    } else switch (mb->partitioning) {

    case VP8_SPLITMVMODE_4x4: {

        int x, y;

        VP56mv uvmv;

        /* Y */