AVFilterBufferRef *ff_default_get_video_buffer(AVFilterLink *link, int perms, int w, int h)
{
    int linesize[4];
    uint8_t *data[4];
    int i;
    AVFilterBufferRef *picref = NULL;
    AVFilterPool *pool = link->pool;
    int full_perms = AV_PERM_READ | AV_PERM_WRITE | AV_PERM_PRESERVE |
                     AV_PERM_REUSE | AV_PERM_REUSE2 | AV_PERM_ALIGN;

    av_assert1(!(perms & ~(full_perms | AV_PERM_NEG_LINESIZES)));

    if (pool) {
        for (i = 0; i < POOL_SIZE; i++) {
            picref = pool->pic[i];
            if (picref && picref->buf->format == link->format && picref->buf->w == w && picref->buf->h == h) {
                AVFilterBuffer *pic = picref->buf;
                pool->pic[i] = NULL;
                pool->count--;
                av_assert0(!picref->video->qp_table);
                picref->video->w = w;
                picref->video->h = h;
                picref->perms = full_perms;
                picref->format = link->format;
                pic->refcount = 1;
                memcpy(picref->data,     pic->data,     sizeof(picref->data));
                memcpy(picref->linesize, pic->linesize, sizeof(picref->linesize));
                pool->refcount++;
                return picref;
            }
        }
    } else {
        pool = link->pool = av_mallocz(sizeof(AVFilterPool));
        pool->refcount = 1;
    }

    // align: +2 is needed for swscaler, +16 to be SIMD-friendly
    if ((i = av_image_alloc(data, linesize, w, h, link->format, 32)) < 0)
        return NULL;

    picref = avfilter_get_video_buffer_ref_from_arrays(data, linesize,
                                                       full_perms, w, h, link->format);
    if (!picref) {
        av_free(data[0]);
        return NULL;
    }

    memset(data[0], 128, i);

    picref->buf->priv = pool;
    picref->buf->free = NULL;
    pool->refcount++;

    return picref;
}