int vp78_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,

                      AVPacket *avpkt, int is_vp7)

{

    VP8Context *s = avctx->priv_data;

    int ret, i, referenced, num_jobs;

    enum AVDiscard skip_thresh;

    VP8Frame *av_uninit(curframe), *prev_frame;



    if (is_vp7)

        ret = vp7_decode_frame_header(s, avpkt->data, avpkt->size);

    else

        ret = vp8_decode_frame_header(s, avpkt->data, avpkt->size);



    if (ret < 0)

        goto err;



    if (!is_vp7 && s->pix_fmt == AV_PIX_FMT_NONE) {

        enum AVPixelFormat pix_fmts[] = {

#if CONFIG_VP8_VAAPI_HWACCEL

            AV_PIX_FMT_VAAPI,

#endif

            AV_PIX_FMT_YUV420P,

            AV_PIX_FMT_NONE,

        };



        s->pix_fmt = ff_get_format(s->avctx, pix_fmts);

        if (s->pix_fmt < 0) {

            ret = AVERROR(EINVAL);

            goto err;

        }

        avctx->pix_fmt = s->pix_fmt;

    }



    prev_frame = s->framep[VP56_FRAME_CURRENT];



    referenced = s->update_last || s->update_golden == VP56_FRAME_CURRENT ||

                 s->update_altref == VP56_FRAME_CURRENT;



    skip_thresh = !referenced ? AVDISCARD_NONREF

                              : !s->keyframe ? AVDISCARD_NONKEY

                                             : AVDISCARD_ALL;



    if (avctx->skip_frame >= skip_thresh) {

        s->invisible = 1;

        memcpy(&s->next_framep[0], &s->framep[0], sizeof(s->framep[0]) * 4);

        goto skip_decode;

    }

    s->deblock_filter = s->filter.level && avctx->skip_loop_filter < skip_thresh;



    // release no longer referenced frames

    for (i = 0; i < 5; i++)

        if (s->frames[i].tf.f->data[0] &&

            &s->frames[i] != prev_frame &&

            &s->frames[i] != s->framep[VP56_FRAME_PREVIOUS] &&

            &s->frames[i] != s->framep[VP56_FRAME_GOLDEN]   &&

            &s->frames[i] != s->framep[VP56_FRAME_GOLDEN2])

            vp8_release_frame(s, &s->frames[i]);



    curframe = s->framep[VP56_FRAME_CURRENT] = vp8_find_free_buffer(s);



    if (!s->colorspace)

        avctx->colorspace = AVCOL_SPC_BT470BG;

    if (s->fullrange)

        avctx->color_range = AVCOL_RANGE_JPEG;

    else

        avctx->color_range = AVCOL_RANGE_MPEG;



    /* Given that arithmetic probabilities are updated every frame, it's quite

     * likely that the values we have on a random interframe are complete

     * junk if we didn't start decode on a keyframe. So just don't display

     * anything rather than junk. */

    if (!s->keyframe && (!s->framep[VP56_FRAME_PREVIOUS] ||

                         !s->framep[VP56_FRAME_GOLDEN]   ||

                         !s->framep[VP56_FRAME_GOLDEN2])) {

        av_log(avctx, AV_LOG_WARNING,

               "Discarding interframe without a prior keyframe!\n");

        ret = AVERROR_INVALIDDATA;

        goto err;

    }



    curframe->tf.f->key_frame = s->keyframe;

    curframe->tf.f->pict_type = s->keyframe ? AV_PICTURE_TYPE_I

                                            : AV_PICTURE_TYPE_P;

    if ((ret = vp8_alloc_frame(s, curframe, referenced))) {

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

        goto err;

    }



    // check if golden and altref are swapped

    if (s->update_altref != VP56_FRAME_NONE)

        s->next_framep[VP56_FRAME_GOLDEN2] = s->framep[s->update_altref];

    else

        s->next_framep[VP56_FRAME_GOLDEN2] = s->framep[VP56_FRAME_GOLDEN2];



    if (s->update_golden != VP56_FRAME_NONE)

        s->next_framep[VP56_FRAME_GOLDEN] = s->framep[s->update_golden];

    else

        s->next_framep[VP56_FRAME_GOLDEN] = s->framep[VP56_FRAME_GOLDEN];



    if (s->update_last)

        s->next_framep[VP56_FRAME_PREVIOUS] = curframe;

    else

        s->next_framep[VP56_FRAME_PREVIOUS] = s->framep[VP56_FRAME_PREVIOUS];



    s->next_framep[VP56_FRAME_CURRENT] = curframe;



    ff_thread_finish_setup(avctx);



    if (avctx->hwaccel) {

        ret = avctx->hwaccel->start_frame(avctx, avpkt->data, avpkt->size);

        if (ret < 0)

            goto err;



        ret = avctx->hwaccel->decode_slice(avctx, avpkt->data, avpkt->size);

        if (ret < 0)

            goto err;



        ret = avctx->hwaccel->end_frame(avctx);

        if (ret < 0)

            goto err;



    } else {

        s->linesize   = curframe->tf.f->linesize[0];

        s->uvlinesize = curframe->tf.f->linesize[1];



        memset(s->top_nnz, 0, s->mb_width * sizeof(*s->top_nnz));

        /* Zero macroblock structures for top/top-left prediction

         * from outside the frame. */

        if (!s->mb_layout)

            memset(s->macroblocks + s->mb_height * 2 - 1, 0,

                   (s->mb_width + 1) * sizeof(*s->macroblocks));

        if (!s->mb_layout && s->keyframe)

            memset(s->intra4x4_pred_mode_top, DC_PRED, s->mb_width * 4);



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



        if (s->mb_layout == 1) {

            // Make sure the previous frame has read its segmentation map,

            // if we re-use the same map.

            if (prev_frame && s->segmentation.enabled &&

                !s->segmentation.update_map)

                ff_thread_await_progress(&prev_frame->tf, 1, 0);

            if (is_vp7)

                vp7_decode_mv_mb_modes(avctx, curframe, prev_frame);

            else

                vp8_decode_mv_mb_modes(avctx, curframe, prev_frame);

        }



        if (avctx->active_thread_type == FF_THREAD_FRAME)

            num_jobs = 1;

        else

            num_jobs = FFMIN(s->num_coeff_partitions, avctx->thread_count);

        s->num_jobs   = num_jobs;

        s->curframe   = curframe;

        s->prev_frame = prev_frame;

        s->mv_min.y   = -MARGIN;

        s->mv_max.y   = ((s->mb_height - 1) << 6) + MARGIN;

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

            s->thread_data[i].thread_mb_pos = 0;

            s->thread_data[i].wait_mb_pos   = INT_MAX;

        }



        if (is_vp7)

            avctx->execute2(avctx, vp7_decode_mb_row_sliced, s->thread_data, NULL,

                            num_jobs);

        else

            avctx->execute2(avctx, vp8_decode_mb_row_sliced, s->thread_data, NULL,

                            num_jobs);

    }



    ff_thread_report_progress(&curframe->tf, INT_MAX, 0);

    memcpy(&s->framep[0], &s->next_framep[0], sizeof(s->framep[0]) * 4);



skip_decode:

    // if future frames don't use the updated probabilities,

    // reset them to the values we saved

    if (!s->update_probabilities)

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



    if (!s->invisible) {

        if ((ret = av_frame_ref(data, curframe->tf.f)) < 0)

            return ret;

        *got_frame = 1;

    }



    return avpkt->size;

err:

    memcpy(&s->next_framep[0], &s->framep[0], sizeof(s->framep[0]) * 4);

    return ret;

}
