vf_scale_npp.c

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/*
 * 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
 */

/**
 * @file
 * scale video filter
 */

#include <nppi.h>
#include <stdio.h>
#include <string.h>

#include "libavutil/avstring.h"
#include "libavutil/common.h"
#include "libavutil/eval.h"
#include "libavutil/hwcontext.h"
#include "libavutil/hwcontext_cuda.h"
#include "libavutil/internal.h"
#include "libavutil/mathematics.h"
#include "libavutil/opt.h"
#include "libavutil/pixdesc.h"

#include "avfilter.h"
#include "formats.h"
#include "internal.h"
#include "video.h"

static const enum AVPixelFormat supported_formats[] = {
    AV_PIX_FMT_YUV420P,
    AV_PIX_FMT_NV12,
    AV_PIX_FMT_YUV444P,
};

static const enum AVPixelFormat deinterleaved_formats[][2] = {
    { AV_PIX_FMT_NV12, AV_PIX_FMT_YUV420P },
};

static const char *const var_names[] = {
    "PI",
    "PHI",
    "E",
    "in_w",   "iw",
    "in_h",   "ih",
    "out_w",  "ow",
    "out_h",  "oh",
    "a", "dar",
    "sar",
    NULL
};

enum var_name {
    VAR_PI,
    VAR_PHI,
    VAR_E,
    VAR_IN_W,   VAR_IW,
    VAR_IN_H,   VAR_IH,
    VAR_OUT_W,  VAR_OW,
    VAR_OUT_H,  VAR_OH,
    VAR_A, VAR_DAR,
    VAR_SAR,
    VARS_NB
};

enum ScaleStage {
    STAGE_DEINTERLEAVE,
    STAGE_RESIZE,
    STAGE_INTERLEAVE,
    STAGE_NB,
};

typedef struct NPPScaleStageContext {
    int stage_needed;
    enum AVPixelFormat in_fmt;
    enum AVPixelFormat out_fmt;

    struct {
        int width;
        int height;
    } planes_in[3], planes_out[3];

    AVBufferRef *frames_ctx;
    AVFrame     *frame;
} NPPScaleStageContext;

typedef struct NPPScaleContext {
    const AVClass *class;

    NPPScaleStageContext stages[STAGE_NB];
    AVFrame *tmp_frame;
    int passthrough;

    int shift_width, shift_height;

    /**
     * New dimensions. Special values are:
     *   0 = original width/height
     *  -1 = keep original aspect
     */
    int w, h;

    /**
     * Output sw format. AV_PIX_FMT_NONE for no conversion.
     */
    enum AVPixelFormat format;

    char *w_expr;               ///< width  expression string
    char *h_expr;               ///< height expression string
    char *format_str;

    int interp_algo;
} NPPScaleContext;

static int nppscale_init(AVFilterContext *ctx)
{
    NPPScaleContext *s = ctx->priv;
    int i;

    if (!strcmp(s->format_str, "same")) {
        s->format = AV_PIX_FMT_NONE;
    } else {
        s->format = av_get_pix_fmt(s->format_str);
        if (s->format == AV_PIX_FMT_NONE) {
            av_log(ctx, AV_LOG_ERROR, "Unrecognized pixel format: %s\n", s->format_str);
            return AVERROR(EINVAL);
        }
    }

    for (i = 0; i < FF_ARRAY_ELEMS(s->stages); i++) {
        s->stages[i].frame = av_frame_alloc();
        if (!s->stages[i].frame)
            return AVERROR(ENOMEM);
    }
    s->tmp_frame = av_frame_alloc();
    if (!s->tmp_frame)
        return AVERROR(ENOMEM);

    return 0;
}

static void nppscale_uninit(AVFilterContext *ctx)
{
    NPPScaleContext *s = ctx->priv;
    int i;

    for (i = 0; i < FF_ARRAY_ELEMS(s->stages); i++) {
        av_frame_free(&s->stages[i].frame);
        av_buffer_unref(&s->stages[i].frames_ctx);
    }
    av_frame_free(&s->tmp_frame);
}

static int nppscale_query_formats(AVFilterContext *ctx)
{
    static const enum AVPixelFormat pixel_formats[] = {
        AV_PIX_FMT_CUDA, AV_PIX_FMT_NONE,
    };
    AVFilterFormats *pix_fmts  = ff_make_format_list(pixel_formats);

    ff_set_common_formats(ctx, pix_fmts);

    return 0;
}

static int init_stage(NPPScaleStageContext *stage, AVBufferRef *device_ctx)
{
    AVBufferRef *out_ref = NULL;
    AVHWFramesContext *out_ctx;
    int in_sw, in_sh, out_sw, out_sh;
    int ret, i;

    av_pix_fmt_get_chroma_sub_sample(stage->in_fmt,  &in_sw,  &in_sh);
    av_pix_fmt_get_chroma_sub_sample(stage->out_fmt, &out_sw, &out_sh);
    if (!stage->planes_out[0].width) {
        stage->planes_out[0].width  = stage->planes_in[0].width;
        stage->planes_out[0].height = stage->planes_in[0].height;
    }

    for (i = 1; i < FF_ARRAY_ELEMS(stage->planes_in); i++) {
        stage->planes_in[i].width   = stage->planes_in[0].width   >> in_sw;
        stage->planes_in[i].height  = stage->planes_in[0].height  >> in_sh;
        stage->planes_out[i].width  = stage->planes_out[0].width  >> out_sw;
        stage->planes_out[i].height = stage->planes_out[0].height >> out_sh;
    }

    out_ref = av_hwframe_ctx_alloc(device_ctx);
    if (!out_ref)
        return AVERROR(ENOMEM);
    out_ctx = (AVHWFramesContext*)out_ref->data;

    out_ctx->format    = AV_PIX_FMT_CUDA;
    out_ctx->sw_format = stage->out_fmt;
    out_ctx->width     = FFALIGN(stage->planes_out[0].width,  32);
    out_ctx->height    = FFALIGN(stage->planes_out[0].height, 32);

    ret = av_hwframe_ctx_init(out_ref);
    if (ret < 0)
        goto fail;

    av_frame_unref(stage->frame);
    ret = av_hwframe_get_buffer(out_ref, stage->frame, 0);
    if (ret < 0)
        goto fail;

    stage->frame->width  = stage->planes_out[0].width;
    stage->frame->height = stage->planes_out[0].height;

    av_buffer_unref(&stage->frames_ctx);
    stage->frames_ctx = out_ref;

    return 0;
fail:
    av_buffer_unref(&out_ref);
    return ret;
}

static int format_is_supported(enum AVPixelFormat fmt)
{
    int i;

    for (i = 0; i < FF_ARRAY_ELEMS(supported_formats); i++)
        if (supported_formats[i] == fmt)
            return 1;
    return 0;
}

static enum AVPixelFormat get_deinterleaved_format(enum AVPixelFormat fmt)
{
    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(fmt);
    int i, planes;

    planes = av_pix_fmt_count_planes(fmt);
    if (planes == desc->nb_components)
        return fmt;
    for (i = 0; i < FF_ARRAY_ELEMS(deinterleaved_formats); i++)
        if (deinterleaved_formats[i][0] == fmt)
            return deinterleaved_formats[i][1];
    return AV_PIX_FMT_NONE;
}

static int init_processing_chain(AVFilterContext *ctx, int in_width, int in_height,
                                 int out_width, int out_height)
{
    NPPScaleContext *s = ctx->priv;

    AVHWFramesContext *in_frames_ctx;

    enum AVPixelFormat in_format;
    enum AVPixelFormat out_format;
    enum AVPixelFormat in_deinterleaved_format;
    enum AVPixelFormat out_deinterleaved_format;

    int i, ret, last_stage = -1;

    /* check that we have a hw context */
    if (!ctx->inputs[0]->hw_frames_ctx) {
        av_log(ctx, AV_LOG_ERROR, "No hw context provided on input\n");
        return AVERROR(EINVAL);
    }
    in_frames_ctx = (AVHWFramesContext*)ctx->inputs[0]->hw_frames_ctx->data;
    in_format     = in_frames_ctx->sw_format;
    out_format    = (s->format == AV_PIX_FMT_NONE) ? in_format : s->format;

    if (!format_is_supported(in_format)) {
        av_log(ctx, AV_LOG_ERROR, "Unsupported input format: %s\n",
               av_get_pix_fmt_name(in_format));
        return AVERROR(ENOSYS);
    }
    if (!format_is_supported(out_format)) {
        av_log(ctx, AV_LOG_ERROR, "Unsupported output format: %s\n",
               av_get_pix_fmt_name(out_format));
        return AVERROR(ENOSYS);
    }

    in_deinterleaved_format  = get_deinterleaved_format(in_format);
    out_deinterleaved_format = get_deinterleaved_format(out_format);
    if (in_deinterleaved_format  == AV_PIX_FMT_NONE ||
        out_deinterleaved_format == AV_PIX_FMT_NONE)
        return AVERROR_BUG;

    /* figure out which stages need to be done */
    if (in_width != out_width || in_height != out_height ||
        in_deinterleaved_format != out_deinterleaved_format)
        s->stages[STAGE_RESIZE].stage_needed = 1;

    if (!s->stages[STAGE_RESIZE].stage_needed && in_format == out_format)
        s->passthrough = 1;

    if (!s->passthrough) {
        if (in_format != in_deinterleaved_format)
            s->stages[STAGE_DEINTERLEAVE].stage_needed = 1;
        if (out_format != out_deinterleaved_format)
            s->stages[STAGE_INTERLEAVE].stage_needed = 1;
    }

    s->stages[STAGE_DEINTERLEAVE].in_fmt              = in_format;
    s->stages[STAGE_DEINTERLEAVE].out_fmt             = in_deinterleaved_format;
    s->stages[STAGE_DEINTERLEAVE].planes_in[0].width  = in_width;
    s->stages[STAGE_DEINTERLEAVE].planes_in[0].height = in_height;

    s->stages[STAGE_RESIZE].in_fmt               = in_deinterleaved_format;
    s->stages[STAGE_RESIZE].out_fmt              = out_deinterleaved_format;
    s->stages[STAGE_RESIZE].planes_in[0].width   = in_width;
    s->stages[STAGE_RESIZE].planes_in[0].height  = in_height;
    s->stages[STAGE_RESIZE].planes_out[0].width  = out_width;
    s->stages[STAGE_RESIZE].planes_out[0].height = out_height;

    s->stages[STAGE_INTERLEAVE].in_fmt              = out_deinterleaved_format;
    s->stages[STAGE_INTERLEAVE].out_fmt             = out_format;
    s->stages[STAGE_INTERLEAVE].planes_in[0].width  = out_width;
    s->stages[STAGE_INTERLEAVE].planes_in[0].height = out_height;

    /* init the hardware contexts */
    for (i = 0; i < FF_ARRAY_ELEMS(s->stages); i++) {
        if (!s->stages[i].stage_needed)
            continue;

        ret = init_stage(&s->stages[i], in_frames_ctx->device_ref);
        if (ret < 0)
            return ret;

        last_stage = i;
    }

    if (last_stage < 0)
        return AVERROR_BUG;
    ctx->outputs[0]->hw_frames_ctx = av_buffer_ref(s->stages[last_stage].frames_ctx);
    if (!ctx->outputs[0]->hw_frames_ctx)
        return AVERROR(ENOMEM);

    return 0;
}

static int nppscale_config_props(AVFilterLink *outlink)
{
    AVFilterContext *ctx = outlink->src;
    AVFilterLink *inlink = outlink->src->inputs[0];
    NPPScaleContext  *s = ctx->priv;
    int64_t w, h;
    double var_values[VARS_NB], res;
    char *expr;
    int ret;

    var_values[VAR_PI]    = M_PI;
    var_values[VAR_PHI]   = M_PHI;
    var_values[VAR_E]     = M_E;
    var_values[VAR_IN_W]  = var_values[VAR_IW] = inlink->w;
    var_values[VAR_IN_H]  = var_values[VAR_IH] = inlink->h;
    var_values[VAR_OUT_W] = var_values[VAR_OW] = NAN;
    var_values[VAR_OUT_H] = var_values[VAR_OH] = NAN;
    var_values[VAR_A]     = (double) inlink->w / inlink->h;
    var_values[VAR_SAR]   = inlink->sample_aspect_ratio.num ?
        (double) inlink->sample_aspect_ratio.num / inlink->sample_aspect_ratio.den : 1;
    var_values[VAR_DAR]   = var_values[VAR_A] * var_values[VAR_SAR];

    /* evaluate width and height */
    av_expr_parse_and_eval(&res, (expr = s->w_expr),
                           var_names, var_values,
                           NULL, NULL, NULL, NULL, NULL, 0, ctx);
    s->w = var_values[VAR_OUT_W] = var_values[VAR_OW] = res;
    if ((ret = av_expr_parse_and_eval(&res, (expr = s->h_expr),
                                      var_names, var_values,
                                      NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0)
        goto fail;
    s->h = var_values[VAR_OUT_H] = var_values[VAR_OH] = res;
    /* evaluate again the width, as it may depend on the output height */
    if ((ret = av_expr_parse_and_eval(&res, (expr = s->w_expr),
                                      var_names, var_values,
                                      NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0)
        goto fail;
    s->w = res;

    w = s->w;
    h = s->h;

    /* sanity check params */
    if (w <  -1 || h <  -1) {
        av_log(ctx, AV_LOG_ERROR, "Size values less than -1 are not acceptable.\n");
        return AVERROR(EINVAL);
    }
    if (w == -1 && h == -1)
        s->w = s->h = 0;

    if (!(w = s->w))
        w = inlink->w;
    if (!(h = s->h))
        h = inlink->h;
    if (w == -1)
        w = av_rescale(h, inlink->w, inlink->h);
    if (h == -1)
        h = av_rescale(w, inlink->h, inlink->w);

    if (w > INT_MAX || h > INT_MAX ||
        (h * inlink->w) > INT_MAX  ||
        (w * inlink->h) > INT_MAX)
        av_log(ctx, AV_LOG_ERROR, "Rescaled value for width or height is too big.\n");

    outlink->w = w;
    outlink->h = h;

    ret = init_processing_chain(ctx, inlink->w, inlink->h, w, h);
    if (ret < 0)
        return ret;

    av_log(ctx, AV_LOG_VERBOSE, "w:%d h:%d -> w:%d h:%d\n",
           inlink->w, inlink->h, outlink->w, outlink->h);

    if (inlink->sample_aspect_ratio.num)
        outlink->sample_aspect_ratio = av_mul_q((AVRational){outlink->h*inlink->w,
                                                             outlink->w*inlink->h},
                                                inlink->sample_aspect_ratio);
    else
        outlink->sample_aspect_ratio = inlink->sample_aspect_ratio;

    return 0;

fail:
    av_log(NULL, AV_LOG_ERROR,
           "Error when evaluating the expression '%s'\n", expr);
    return ret;
}

static int nppscale_deinterleave(AVFilterContext *ctx, NPPScaleStageContext *stage,
                                 AVFrame *out, AVFrame *in)
{
    AVHWFramesContext *in_frames_ctx = (AVHWFramesContext*)in->hw_frames_ctx->data;
    NppStatus err;

    switch (in_frames_ctx->sw_format) {
    case AV_PIX_FMT_NV12:
        err = nppiYCbCr420_8u_P2P3R(in->data[0], in->linesize[0],
                                    in->data[1], in->linesize[1],
                                    out->data, out->linesize,
                                    (NppiSize){ in->width, in->height });
        break;
    default:
        return AVERROR_BUG;
    }
    if (err != NPP_SUCCESS) {
        av_log(ctx, AV_LOG_ERROR, "NPP deinterleave error: %d\n", err);
        return AVERROR_UNKNOWN;
    }

    return 0;
}

static int nppscale_resize(AVFilterContext *ctx, NPPScaleStageContext *stage,
                           AVFrame *out, AVFrame *in)
{
    NPPScaleContext *s = ctx->priv;
    NppStatus err;
    int i;

    for (i = 0; i < FF_ARRAY_ELEMS(in->data) && in->data[i]; i++) {
        int iw = stage->planes_in[i].width;
        int ih = stage->planes_in[i].height;
        int ow = stage->planes_out[i].width;
        int oh = stage->planes_out[i].height;

        err = nppiResizeSqrPixel_8u_C1R(in->data[i], (NppiSize){ iw, ih },
                                        in->linesize[i], (NppiRect){ 0, 0, iw, ih },
                                        out->data[i], out->linesize[i],
                                        (NppiRect){ 0, 0, ow, oh },
                                        (double)ow / iw, (double)oh / ih,
                                        0.0, 0.0, s->interp_algo);
        if (err != NPP_SUCCESS) {
            av_log(ctx, AV_LOG_ERROR, "NPP resize error: %d\n", err);
            return AVERROR_UNKNOWN;
        }
    }

    return 0;
}

static int nppscale_interleave(AVFilterContext *ctx, NPPScaleStageContext *stage,
                               AVFrame *out, AVFrame *in)
{
    AVHWFramesContext *out_frames_ctx = (AVHWFramesContext*)out->hw_frames_ctx->data;
    NppStatus err;

    switch (out_frames_ctx->sw_format) {
    case AV_PIX_FMT_NV12:
        err = nppiYCbCr420_8u_P3P2R((const uint8_t**)in->data,
                                    in->linesize,
                                    out->data[0], out->linesize[0],
                                    out->data[1], out->linesize[1],
                                    (NppiSize){ in->width, in->height });
        break;
    default:
        return AVERROR_BUG;
    }
    if (err != NPP_SUCCESS) {
        av_log(ctx, AV_LOG_ERROR, "NPP deinterleave error: %d\n", err);
        return AVERROR_UNKNOWN;
    }

    return 0;
}

static int (*const nppscale_process[])(AVFilterContext *ctx, NPPScaleStageContext *stage,
                                       AVFrame *out, AVFrame *in) = {
    [STAGE_DEINTERLEAVE] = nppscale_deinterleave,
    [STAGE_RESIZE]       = nppscale_resize,
    [STAGE_INTERLEAVE]   = nppscale_interleave,
};

static int nppscale_scale(AVFilterContext *ctx, AVFrame *out, AVFrame *in)
{
    NPPScaleContext *s = ctx->priv;
    AVFrame *src = in;
    int i, ret, last_stage = -1;

    for (i = 0; i < FF_ARRAY_ELEMS(s->stages); i++) {
        if (!s->stages[i].stage_needed)
            continue;

        ret = nppscale_process[i](ctx, &s->stages[i], s->stages[i].frame, src);
        if (ret < 0)
            return ret;

        src        = s->stages[i].frame;
        last_stage = i;
    }

    if (last_stage < 0)
        return AVERROR_BUG;
    ret = av_hwframe_get_buffer(src->hw_frames_ctx, s->tmp_frame, 0);
    if (ret < 0)
        return ret;

    av_frame_move_ref(out, src);
    av_frame_move_ref(src, s->tmp_frame);

    ret = av_frame_copy_props(out, in);
    if (ret < 0)
        return ret;

    return 0;
}

static int nppscale_filter_frame(AVFilterLink *link, AVFrame *in)
{
    AVFilterContext              *ctx = link->dst;
    NPPScaleContext                *s = ctx->priv;
    AVFilterLink             *outlink = ctx->outputs[0];
    AVHWFramesContext     *frames_ctx = (AVHWFramesContext*)outlink->hw_frames_ctx->data;
    AVCUDADeviceContext *device_hwctx = frames_ctx->device_ctx->hwctx;

    AVFrame *out = NULL;
    CUresult err;
    CUcontext dummy;
    int ret = 0;

    if (s->passthrough)
        return ff_filter_frame(outlink, in);

    out = av_frame_alloc();
    if (!out) {
        ret = AVERROR(ENOMEM);
        goto fail;
    }

    av_reduce(&out->sample_aspect_ratio.num, &out->sample_aspect_ratio.den,
              (int64_t)in->sample_aspect_ratio.num * outlink->h * link->w,
              (int64_t)in->sample_aspect_ratio.den * outlink->w * link->h,
              INT_MAX);

    err = cuCtxPushCurrent(device_hwctx->cuda_ctx);
    if (err != CUDA_SUCCESS) {
        ret = AVERROR_UNKNOWN;
        goto fail;
    }

    ret = nppscale_scale(ctx, out, in);

    cuCtxPopCurrent(&dummy);
    if (ret < 0)
        goto fail;

    av_frame_free(&in);
    return ff_filter_frame(outlink, out);
fail:
    av_frame_free(&in);
    av_frame_free(&out);
    return ret;
}

#define OFFSET(x) offsetof(NPPScaleContext, x)
#define FLAGS (AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM)
static const AVOption options[] = {
    { "w",      "Output video width",  OFFSET(w_expr),     AV_OPT_TYPE_STRING, { .str = "iw"   }, .flags = FLAGS },
    { "h",      "Output video height", OFFSET(h_expr),     AV_OPT_TYPE_STRING, { .str = "ih"   }, .flags = FLAGS },
    { "format", "Output pixel format", OFFSET(format_str), AV_OPT_TYPE_STRING, { .str = "same" }, .flags = FLAGS },

    { "interp_algo", "Interpolation algorithm used for resizing", OFFSET(interp_algo), AV_OPT_TYPE_INT, { .i64 = NPPI_INTER_CUBIC }, 0, INT_MAX, FLAGS, "interp_algo" },
        { "nn",                 "nearest neighbour",                 0, AV_OPT_TYPE_CONST, { .i64 = NPPI_INTER_NN                 }, 0, 0, FLAGS, "interp_algo" },
        { "linear",             "linear",                            0, AV_OPT_TYPE_CONST, { .i64 = NPPI_INTER_LINEAR             }, 0, 0, FLAGS, "interp_algo" },
        { "cubic",              "cubic",                             0, AV_OPT_TYPE_CONST, { .i64 = NPPI_INTER_CUBIC              }, 0, 0, FLAGS, "interp_algo" },
        { "cubic2p_bspline",    "2-parameter cubic (B=1, C=0)",      0, AV_OPT_TYPE_CONST, { .i64 = NPPI_INTER_CUBIC2P_BSPLINE    }, 0, 0, FLAGS, "interp_algo" },
        { "cubic2p_catmullrom", "2-parameter cubic (B=0, C=1/2)",    0, AV_OPT_TYPE_CONST, { .i64 = NPPI_INTER_CUBIC2P_CATMULLROM }, 0, 0, FLAGS, "interp_algo" },
        { "cubic2p_b05c03",     "2-parameter cubic (B=1/2, C=3/10)", 0, AV_OPT_TYPE_CONST, { .i64 = NPPI_INTER_CUBIC2P_B05C03     }, 0, 0, FLAGS, "interp_algo" },
        { "super",              "supersampling",                     0, AV_OPT_TYPE_CONST, { .i64 = NPPI_INTER_SUPER              }, 0, 0, FLAGS, "interp_algo" },
        { "lanczos",            "Lanczos",                           0, AV_OPT_TYPE_CONST, { .i64 = NPPI_INTER_LANCZOS            }, 0, 0, FLAGS, "interp_algo" },
    { NULL },
};

static const AVClass nppscale_class = {
    .class_name = "nppscale",
    .item_name  = av_default_item_name,
    .option     = options,
    .version    = LIBAVUTIL_VERSION_INT,
};

static const AVFilterPad nppscale_inputs[] = {
    {
        .name        = "default",
        .type        = AVMEDIA_TYPE_VIDEO,
        .filter_frame = nppscale_filter_frame,
    },
    { NULL }
};

static const AVFilterPad nppscale_outputs[] = {
    {
        .name         = "default",
        .type         = AVMEDIA_TYPE_VIDEO,
        .config_props = nppscale_config_props,
    },
    { NULL }
};

AVFilter ff_vf_scale_npp = {
    .name      = "scale_npp",
    .description = NULL_IF_CONFIG_SMALL("NVIDIA Performance Primitives video "
                                        "scaling and format conversion"),

    .init          = nppscale_init,
    .uninit        = nppscale_uninit,
    .query_formats = nppscale_query_formats,

    .priv_size = sizeof(NPPScaleContext),
    .priv_class = &nppscale_class,

    .inputs    = nppscale_inputs,
    .outputs   = nppscale_outputs,
};