PeerStreamer

/**

 * @file vp56.c

 * VP5 and VP6 compatible video decoder (common features)

 *

 * Copyright (C) 2006  Aurelien Jacobs <aurel@gnuage.org>

 *

 * 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 St, Fifth Floor, Boston, MA  02110-1301  USA

 */

#include "avcodec.h"

#include "vp56.h"

#include "vp56data.h"

void vp56_init_dequant(vp56_context_t *s, int quantizer)

{

    s->quantizer = quantizer;

    s->dequant_dc = vp56_dc_dequant[quantizer] << 2;

    s->dequant_ac = vp56_ac_dequant[quantizer] << 2;

}

static int vp56_get_vectors_predictors(vp56_context_t *s, int row, int col,

                                       vp56_frame_t ref_frame)

{

    int nb_pred = 0;

    vp56_mv_t vect[2] = {{0,0}, {0,0}};

    int pos, offset;

    vp56_mv_t mvp;

    for (pos=0; pos<12; pos++) {

        mvp.x = col + vp56_candidate_predictor_pos[pos][0];

        mvp.y = row + vp56_candidate_predictor_pos[pos][1];

        if (mvp.x < 0 || mvp.x >= s->mb_width ||

            mvp.y < 0 || mvp.y >= s->mb_height)

            continue;

        offset = mvp.x + s->mb_width*mvp.y;

        if (vp56_reference_frame[s->macroblocks[offset].type] != ref_frame)

            continue;

        if ((s->macroblocks[offset].mv.x == vect[0].x &&

             s->macroblocks[offset].mv.y == vect[0].y) ||

            (s->macroblocks[offset].mv.x == 0 &&

             s->macroblocks[offset].mv.y == 0))

            continue;

        vect[nb_pred++] = s->macroblocks[offset].mv;

        if (nb_pred > 1) {

            nb_pred = -1;

            break;

        }

        s->vector_candidate_pos = pos;

    }

    s->vector_candidate[0] = vect[0];

    s->vector_candidate[1] = vect[1];

    return nb_pred+1;

}

static void vp56_parse_mb_type_models(vp56_context_t *s)

{

    vp56_range_coder_t *c = &s->c;

    int i, ctx, type;

    for (ctx=0; ctx<3; ctx++) {

        if (vp56_rac_get_prob(c, 174)) {

            int idx = vp56_rac_gets(c, 4);

            memcpy(s->mb_types_stats[ctx],vp56_pre_def_mb_type_stats[idx][ctx],

                   sizeof(s->mb_types_stats[ctx]));

        }

        if (vp56_rac_get_prob(c, 254)) {

            for (type=0; type<10; type++) {

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

                    if (vp56_rac_get_prob(c, 205)) {

                        int delta, sign = vp56_rac_get(c);

                        delta = vp56_rac_get_tree(c, vp56_pmbtm_tree,

                                                  vp56_mb_type_model_model);

                        if (!delta)

                            delta = 4 * vp56_rac_gets(c, 7);

                        s->mb_types_stats[ctx][type][i] += (delta ^ -sign) + sign;

                    }

                }

            }

        }

    }

    /* compute MB type probability tables based on previous MB type */

    for (ctx=0; ctx<3; ctx++) {

        int p[10];

        for (type=0; type<10; type++)

            p[type] = 100 * s->mb_types_stats[ctx][type][1];

        for (type=0; type<10; type++) {

            int p02, p34, p0234, p17, p56, p89, p5689, p156789;

            /* conservative MB type probability */

            s->mb_type_model[ctx][type][0] = 255 - (255 * s->mb_types_stats[ctx][type][0]) / (1 + s->mb_types_stats[ctx][type][0] + s->mb_types_stats[ctx][type][1]);

            p[type] = 0;    /* same MB type => weight is null */

            /* binary tree parsing probabilities */

            p02 = p[0] + p[2];

            p34 = p[3] + p[4];

            p0234 = p02 + p34;

            p17 = p[1] + p[7];

            p56 = p[5] + p[6];

            p89 = p[8] + p[9];

            p5689 = p56 + p89;

            p156789 = p17 + p5689;

            s->mb_type_model[ctx][type][1] = 1 + 255 * p0234/(1+p0234+p156789);

            s->mb_type_model[ctx][type][2] = 1 + 255 * p02  / (1+p0234);

            s->mb_type_model[ctx][type][3] = 1 + 255 * p17  / (1+p156789);

            s->mb_type_model[ctx][type][4] = 1 + 255 * p[0] / (1+p02);

            s->mb_type_model[ctx][type][5] = 1 + 255 * p[3] / (1+p34);

            s->mb_type_model[ctx][type][6] = 1 + 255 * p[1] / (1+p17);

            s->mb_type_model[ctx][type][7] = 1 + 255 * p56  / (1+p5689);

            s->mb_type_model[ctx][type][8] = 1 + 255 * p[5] / (1+p56);

            s->mb_type_model[ctx][type][9] = 1 + 255 * p[8] / (1+p89);

            /* restore initial value */

            p[type] = 100 * s->mb_types_stats[ctx][type][1];

        }

    }

}

static vp56_mb_t vp56_parse_mb_type(vp56_context_t *s,

                                    vp56_mb_t prev_type, int ctx)

{

    uint8_t *mb_type_model = s->mb_type_model[ctx][prev_type];

    vp56_range_coder_t *c = &s->c;

    if (vp56_rac_get_prob(c, mb_type_model[0]))

        return prev_type;

    else

        return vp56_rac_get_tree(c, vp56_pmbt_tree, mb_type_model);

}

static void vp56_decode_4mv(vp56_context_t *s, int row, int col)

{

    vp56_mv_t mv = {0,0};

    int type[4];

    int b;

    /* parse each block type */

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

        type[b] = vp56_rac_gets(&s->c, 2);

        if (type[b])

            type[b]++;  /* only returns 0, 2, 3 or 4 (all INTER_PF) */

    }

    /* get vectors */

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

        switch (type[b]) {

            case VP56_MB_INTER_NOVEC_PF:

                s->mv[b] = (vp56_mv_t) {0,0};

                break;

            case VP56_MB_INTER_DELTA_PF:

                s->parse_vector_adjustment(s, &s->mv[b]);

                break;

            case VP56_MB_INTER_V1_PF:

                s->mv[b] = s->vector_candidate[0];

                break;

            case VP56_MB_INTER_V2_PF:

                s->mv[b] = s->vector_candidate[1];

                break;

        }

        mv.x += s->mv[b].x;

        mv.y += s->mv[b].y;

    }

    /* this is the one selected for the whole MB for prediction */

    s->macroblocks[row * s->mb_width + col].mv = s->mv[3];

    /* chroma vectors are average luma vectors */

    if (s->avctx->codec->id == CODEC_ID_VP5) {

        s->mv[4].x = s->mv[5].x = RSHIFT(mv.x,2);

        s->mv[4].y = s->mv[5].y = RSHIFT(mv.y,2);

    } else {

        s->mv[4] = s->mv[5] = (vp56_mv_t) {mv.x/4, mv.y/4};

    }

}

static vp56_mb_t vp56_decode_mv(vp56_context_t *s, int row, int col)

{

    vp56_mv_t *mv, vect = {0,0};

    int ctx, b;

    ctx = vp56_get_vectors_predictors(s, row, col, VP56_FRAME_PREVIOUS);

    s->mb_type = vp56_parse_mb_type(s, s->mb_type, ctx);

    s->macroblocks[row * s->mb_width + col].type = s->mb_type;

    switch (s->mb_type) {

        case VP56_MB_INTER_V1_PF:

            mv = &s->vector_candidate[0];

            break;

        case VP56_MB_INTER_V2_PF:

            mv = &s->vector_candidate[1];

            break;

        case VP56_MB_INTER_V1_GF:

            vp56_get_vectors_predictors(s, row, col, VP56_FRAME_GOLDEN);

            mv = &s->vector_candidate[0];

            break;

        case VP56_MB_INTER_V2_GF:

            vp56_get_vectors_predictors(s, row, col, VP56_FRAME_GOLDEN);

            mv = &s->vector_candidate[1];

            break;

        case VP56_MB_INTER_DELTA_PF:

            s->parse_vector_adjustment(s, &vect);

            mv = &vect;

            break;

        case VP56_MB_INTER_DELTA_GF:

            vp56_get_vectors_predictors(s, row, col, VP56_FRAME_GOLDEN);

            s->parse_vector_adjustment(s, &vect);

            mv = &vect;

            break;

        case VP56_MB_INTER_4V:

            vp56_decode_4mv(s, row, col);

            return s->mb_type;

        default:

            mv = &vect;

            break;

    }

    s->macroblocks[row*s->mb_width + col].mv = *mv;

    /* same vector for all blocks */

    for (b=0; b<6; b++)

        s->mv[b] = *mv;

    return s->mb_type;

}

static void vp56_add_predictors_dc(vp56_context_t *s, vp56_frame_t ref_frame)

{

    int idx = s->scantable.permutated[0];

    int i;

    for (i=0; i<6; i++) {

        vp56_ref_dc_t *ab = &s->above_blocks[s->above_block_idx[i]];

        vp56_ref_dc_t *lb = &s->left_block[vp56_b6to4[i]];

        int count = 0;

        int dc = 0;

        if (ref_frame == lb->ref_frame) {

            dc += lb->dc_coeff;

            count++;

        }

        if (ref_frame == ab->ref_frame) {

            dc += ab->dc_coeff;

            count++;

        }

        if (s->avctx->codec->id == CODEC_ID_VP5) {

            if (count < 2 && ref_frame == ab[-1].ref_frame) {

                dc += ab[-1].dc_coeff;

                count++;

            }

            if (count < 2 && ref_frame == ab[1].ref_frame) {

                dc += ab[1].dc_coeff;

                count++;

            }

        }

        if (count == 0)

            dc = s->prev_dc[vp56_b6to3[i]][ref_frame];

        else if (count == 2)

            dc /= 2;

        s->block_coeff[i][idx] += dc;

        s->prev_dc[vp56_b6to3[i]][ref_frame] = s->block_coeff[i][idx];

        ab->dc_coeff = s->block_coeff[i][idx];

        ab->ref_frame = ref_frame;

        lb->dc_coeff = s->block_coeff[i][idx];

        lb->ref_frame = ref_frame;

        s->block_coeff[i][idx] *= s->dequant_dc;

    }

}

static void vp56_edge_filter(vp56_context_t *s, uint8_t *yuv,

                             int pix_inc, int line_inc, int t)

{

    int pix2_inc = 2 * pix_inc;

    int i, v;

    for (i=0; i<12; i++) {

        v = (yuv[-pix2_inc] + 3*(yuv[0]-yuv[-pix_inc]) - yuv[pix_inc] + 4) >>3;

        v = s->adjust(v, t);

        yuv[-pix_inc] = av_clip_uint8(yuv[-pix_inc] + v);

        yuv[0] = av_clip_uint8(yuv[0] - v);

        yuv += line_inc;

    }

}

static void vp56_deblock_filter(vp56_context_t *s, uint8_t *yuv,

                                int stride, int dx, int dy)

{

    int t = vp56_filter_threshold[s->quantizer];

    if (dx)  vp56_edge_filter(s, yuv +         10-dx ,      1, stride, t);

    if (dy)  vp56_edge_filter(s, yuv + stride*(10-dy), stride,      1, t);

}

static void vp56_mc(vp56_context_t *s, int b, uint8_t *src,

                    int stride, int x, int y)

{

    int plane = vp56_b6to3[b];

    uint8_t *dst= s->frames[VP56_FRAME_CURRENT].data[plane]+s->block_offset[b];

    uint8_t *src_block;

    int src_offset;

    int overlap_offset = 0;

    int mask = s->vp56_coord_div[b] - 1;

    int deblock_filtering = s->deblock_filtering;

    int dx;

    int dy;

    if (s->avctx->skip_loop_filter >= AVDISCARD_ALL ||

        (s->avctx->skip_loop_filter >= AVDISCARD_NONKEY

         && !s->frames[VP56_FRAME_CURRENT].key_frame))

        deblock_filtering = 0;

    dx = s->mv[b].x / s->vp56_coord_div[b];

    dy = s->mv[b].y / s->vp56_coord_div[b];

    if (b >= 4) {

        x /= 2;

        y /= 2;

    }

    x += dx - 2;

    y += dy - 2;

    if (x<0 || x+12>=s->plane_width[plane] ||

        y<0 || y+12>=s->plane_height[plane]) {

        ff_emulated_edge_mc(s->edge_emu_buffer,

                            src + s->block_offset[b] + (dy-2)*stride + (dx-2),

                            stride, 12, 12, x, y,

                            s->plane_width[plane],

                            s->plane_height[plane]);

        src_block = s->edge_emu_buffer;

        src_offset = 2 + 2*stride;

    } else if (deblock_filtering) {

        /* only need a 12x12 block, but there is no such dsp function, */

        /* so copy a 16x12 block */

        s->dsp.put_pixels_tab[0][0](s->edge_emu_buffer,

                                    src + s->block_offset[b] + (dy-2)*stride + (dx-2),

                                    stride, 12);

        src_block = s->edge_emu_buffer;

        src_offset = 2 + 2*stride;

    } else {

        src_block = src;

        src_offset = s->block_offset[b] + dy*stride + dx;

    }

    if (deblock_filtering)

        vp56_deblock_filter(s, src_block, stride, dx&7, dy&7);

    if (s->mv[b].x & mask)

        overlap_offset += (s->mv[b].x > 0) ? 1 : -1;

    if (s->mv[b].y & mask)

        overlap_offset += (s->mv[b].y > 0) ? stride : -stride;

    if (overlap_offset) {

        if (s->filter)

            s->filter(s, dst, src_block, src_offset, src_offset+overlap_offset,

                      stride, s->mv[b], mask, s->filter_selection, b<4);

        else

            s->dsp.put_no_rnd_pixels_l2[1](dst, src_block+src_offset,

                                           src_block+src_offset+overlap_offset,

                                           stride, 8);

    } else {

        s->dsp.put_pixels_tab[1][0](dst, src_block+src_offset, stride, 8);

    }

}

static void vp56_decode_mb(vp56_context_t *s, int row, int col)

{

    AVFrame *frame_current, *frame_ref;

    vp56_mb_t mb_type;

    vp56_frame_t ref_frame;

    int b, plan, off;

    if (s->frames[VP56_FRAME_CURRENT].key_frame)

        mb_type = VP56_MB_INTRA;

    else

        mb_type = vp56_decode_mv(s, row, col);

    ref_frame = vp56_reference_frame[mb_type];

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

    s->parse_coeff(s);

    vp56_add_predictors_dc(s, ref_frame);

    frame_current = &s->frames[VP56_FRAME_CURRENT];

    frame_ref = &s->frames[ref_frame];

    switch (mb_type) {

        case VP56_MB_INTRA:

            for (b=0; b<6; b++) {

                plan = vp56_b6to3[b];

                s->dsp.idct_put(frame_current->data[plan] + s->block_offset[b],

                                s->stride[plan], s->block_coeff[b]);

            }

            break;

        case VP56_MB_INTER_NOVEC_PF:

        case VP56_MB_INTER_NOVEC_GF:

            for (b=0; b<6; b++) {

                plan = vp56_b6to3[b];

                off = s->block_offset[b];

                s->dsp.put_pixels_tab[1][0](frame_current->data[plan] + off,

                                            frame_ref->data[plan] + off,

                                            s->stride[plan], 8);

                s->dsp.idct_add(frame_current->data[plan] + off,

                                s->stride[plan], s->block_coeff[b]);

            }

            break;

        case VP56_MB_INTER_DELTA_PF:

        case VP56_MB_INTER_V1_PF:

        case VP56_MB_INTER_V2_PF:

        case VP56_MB_INTER_DELTA_GF:

        case VP56_MB_INTER_4V:

        case VP56_MB_INTER_V1_GF:

        case VP56_MB_INTER_V2_GF:

            for (b=0; b<6; b++) {

                int x_off = b==1 || b==3 ? 8 : 0;

                int y_off = b==2 || b==3 ? 8 : 0;

                plan = vp56_b6to3[b];

                vp56_mc(s, b, frame_ref->data[plan], s->stride[plan],

                        16*col+x_off, 16*row+y_off);

                s->dsp.idct_add(frame_current->data[plan] + s->block_offset[b],

                                s->stride[plan], s->block_coeff[b]);

            }

            break;

    }

}

static int vp56_size_changed(AVCodecContext *avctx, vp56_context_t *s)

{

    int stride = s->frames[VP56_FRAME_CURRENT].linesize[0];

    int i;

    s->plane_width[0] = s->avctx->coded_width;

    s->plane_width[1] = s->plane_width[2] = s->avctx->coded_width/2;

    s->plane_height[0] = s->avctx->coded_height;

    s->plane_height[1] = s->plane_height[2] = s->avctx->coded_height/2;

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

        s->stride[i] = s->flip * s->frames[VP56_FRAME_CURRENT].linesize[i];

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

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

    if (s->mb_width > 1000 || s->mb_height > 1000) {

        av_log(avctx, AV_LOG_ERROR, "picture too big\n");

        return -1;

    }

    s->above_blocks = av_realloc(s->above_blocks,

                                 (4*s->mb_width+6) * sizeof(*s->above_blocks));

    s->macroblocks = av_realloc(s->macroblocks,

                                s->mb_width*s->mb_height*sizeof(*s->macroblocks));

    av_free(s->edge_emu_buffer_alloc);

    s->edge_emu_buffer_alloc = av_malloc(16*stride);

    s->edge_emu_buffer = s->edge_emu_buffer_alloc;

    if (s->flip < 0)

        s->edge_emu_buffer += 15 * stride;

    return 0;

}

int vp56_decode_frame(AVCodecContext *avctx, void *data, int *data_size,

                      uint8_t *buf, int buf_size)

{

    vp56_context_t *s = avctx->priv_data;

    AVFrame *const p = &s->frames[VP56_FRAME_CURRENT];

    AVFrame *picture = data;

    int mb_row, mb_col, mb_row_flip, mb_offset = 0;

    int block, y, uv, stride_y, stride_uv;

    int golden_frame = 0;

    int res;

    res = s->parse_header(s, buf, buf_size, &golden_frame);

    if (!res)

        return -1;

    p->reference = 1;

    if (avctx->get_buffer(avctx, p) < 0) {

        av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");

        return -1;

    }

    if (res == 2)

        if (vp56_size_changed(avctx, s)) {

            avctx->release_buffer(avctx, p);

            return -1;

        }

    if (p->key_frame) {

        p->pict_type = FF_I_TYPE;

        s->default_models_init(s);

        for (block=0; block<s->mb_height*s->mb_width; block++)

            s->macroblocks[block].type = VP56_MB_INTRA;

    } else {

        p->pict_type = FF_P_TYPE;

        vp56_parse_mb_type_models(s);

        s->parse_vector_models(s);

        s->mb_type = VP56_MB_INTER_NOVEC_PF;

    }

    s->parse_coeff_models(s);

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

    s->prev_dc[1][VP56_FRAME_CURRENT] = 128;

    s->prev_dc[2][VP56_FRAME_CURRENT] = 128;

    for (block=0; block < 4*s->mb_width+6; block++) {

        s->above_blocks[block].ref_frame = -1;

        s->above_blocks[block].dc_coeff = 0;

        s->above_blocks[block].not_null_dc = 0;

    }

    s->above_blocks[2*s->mb_width + 2].ref_frame = 0;

    s->above_blocks[3*s->mb_width + 4].ref_frame = 0;

    stride_y  = p->linesize[0];

    stride_uv = p->linesize[1];

    if (s->flip < 0)

        mb_offset = 7;

    /* main macroblocks loop */

    for (mb_row=0; mb_row<s->mb_height; mb_row++) {

        if (s->flip < 0)

            mb_row_flip = s->mb_height - mb_row - 1;

        else

            mb_row_flip = mb_row;

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

            s->left_block[block].ref_frame = -1;

            s->left_block[block].dc_coeff = 0;

            s->left_block[block].not_null_dc = 0;

            memset(s->coeff_ctx[block], 0, 64*sizeof(s->coeff_ctx[block][0]));

        }

        memset(s->coeff_ctx_last, 24, sizeof(s->coeff_ctx_last));

        s->above_block_idx[0] = 1;

        s->above_block_idx[1] = 2;

        s->above_block_idx[2] = 1;

        s->above_block_idx[3] = 2;

        s->above_block_idx[4] = 2*s->mb_width + 2 + 1;

        s->above_block_idx[5] = 3*s->mb_width + 4 + 1;

        s->block_offset[s->frbi] = (mb_row_flip*16 + mb_offset) * stride_y;

        s->block_offset[s->srbi] = s->block_offset[s->frbi] + 8*stride_y;

        s->block_offset[1] = s->block_offset[0] + 8;

        s->block_offset[3] = s->block_offset[2] + 8;

        s->block_offset[4] = (mb_row_flip*8 + mb_offset) * stride_uv;

        s->block_offset[5] = s->block_offset[4];

        for (mb_col=0; mb_col<s->mb_width; mb_col++) {

            vp56_decode_mb(s, mb_row, mb_col);

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

                s->above_block_idx[y] += 2;

                s->block_offset[y] += 16;

            }

            for (uv=4; uv<6; uv++) {

                s->above_block_idx[uv] += 1;

                s->block_offset[uv] += 8;

            }

        }

    }

    if (s->frames[VP56_FRAME_PREVIOUS].data[0]

        && (s->frames[VP56_FRAME_PREVIOUS].data[0]

            != s->frames[VP56_FRAME_GOLDEN].data[0])) {

        avctx->release_buffer(avctx, &s->frames[VP56_FRAME_PREVIOUS]);

    }

    if (p->key_frame || golden_frame) {

        if (s->frames[VP56_FRAME_GOLDEN].data[0])

            avctx->release_buffer(avctx, &s->frames[VP56_FRAME_GOLDEN]);

        s->frames[VP56_FRAME_GOLDEN] = *p;

    }

    s->frames[VP56_FRAME_PREVIOUS] = *p;

    *picture = *p;

    *data_size = sizeof(AVPicture);

    s->frames[VP56_FRAME_CURRENT].data[0] = NULL;

    return buf_size;

}

void vp56_init(vp56_context_t *s, AVCodecContext *avctx, int flip)

{

    int i;

    s->avctx = avctx;

    avctx->pix_fmt = PIX_FMT_YUV420P;

    if (s->avctx->idct_algo == FF_IDCT_AUTO)

        s->avctx->idct_algo = FF_IDCT_VP3;

    dsputil_init(&s->dsp, s->avctx);

    ff_init_scantable(s->dsp.idct_permutation, &s->scantable,ff_zigzag_direct);

    avcodec_set_dimensions(s->avctx, 0, 0);

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

        s->frames[i].data[0] = NULL;

    s->edge_emu_buffer_alloc = NULL;

    s->above_blocks = NULL;

    s->macroblocks = NULL;

    s->quantizer = -1;

    s->deblock_filtering = 1;

    s->filter = NULL;

    if (flip) {

        s->flip = -1;

        s->frbi = 2;

        s->srbi = 0;

    } else {

        s->flip = 1;

        s->frbi = 0;

        s->srbi = 2;

    }

}

int vp56_free(AVCodecContext *avctx)

{

    vp56_context_t *s = avctx->priv_data;

    av_free(s->above_blocks);

    av_free(s->macroblocks);

    av_free(s->edge_emu_buffer_alloc);

    if (s->frames[VP56_FRAME_GOLDEN].data[0]

        && (s->frames[VP56_FRAME_PREVIOUS].data[0]

            != s->frames[VP56_FRAME_GOLDEN].data[0]))

        avctx->release_buffer(avctx, &s->frames[VP56_FRAME_GOLDEN]);

    if (s->frames[VP56_FRAME_PREVIOUS].data[0])

        avctx->release_buffer(avctx, &s->frames[VP56_FRAME_PREVIOUS]);

    return 0;

}