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/*

 * AviSynth/AvxSynth support

 * Copyright (c) 2012 AvxSynth Team.

 *

 * 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 "libavutil/internal.h"

#include "libavcodec/internal.h"

#include "avformat.h"

#include "internal.h"

#include "config.h"

/* Enable function pointer definitions for runtime loading. */

#define AVSC_NO_DECLSPEC

/* Platform-specific directives for AviSynth vs AvxSynth. */

#ifdef _WIN32

  #include 

  #undef EXTERN_C

  #include "compat/avisynth/avisynth_c.h"

  #define AVISYNTH_LIB "avisynth"

  #define USING_AVISYNTH

#else

  #include 

  #include "compat/avisynth/avxsynth_c.h"

  #define AVISYNTH_NAME "libavxsynth"

  #define AVISYNTH_LIB AVISYNTH_NAME SLIBSUF

  #define LoadLibrary(x) dlopen(x, RTLD_NOW | RTLD_LOCAL)

  #define GetProcAddress dlsym

  #define FreeLibrary dlclose

#endif

typedef struct AviSynthLibrary {

    void *library;

#define AVSC_DECLARE_FUNC(name) name ## _func name

    AVSC_DECLARE_FUNC(avs_bit_blt);

    AVSC_DECLARE_FUNC(avs_clip_get_error);

    AVSC_DECLARE_FUNC(avs_create_script_environment);

    AVSC_DECLARE_FUNC(avs_delete_script_environment);

    AVSC_DECLARE_FUNC(avs_get_audio);

    AVSC_DECLARE_FUNC(avs_get_error);

    AVSC_DECLARE_FUNC(avs_get_frame);

    AVSC_DECLARE_FUNC(avs_get_version);

    AVSC_DECLARE_FUNC(avs_get_video_info);

    AVSC_DECLARE_FUNC(avs_invoke);

    AVSC_DECLARE_FUNC(avs_release_clip);

    AVSC_DECLARE_FUNC(avs_release_value);

    AVSC_DECLARE_FUNC(avs_release_video_frame);

    AVSC_DECLARE_FUNC(avs_take_clip);

#ifdef USING_AVISYNTH

    AVSC_DECLARE_FUNC(avs_bits_per_pixel);

    AVSC_DECLARE_FUNC(avs_get_height_p);

    AVSC_DECLARE_FUNC(avs_get_pitch_p);

    AVSC_DECLARE_FUNC(avs_get_read_ptr_p);

    AVSC_DECLARE_FUNC(avs_get_row_size_p);

    AVSC_DECLARE_FUNC(avs_is_yv24);

    AVSC_DECLARE_FUNC(avs_is_yv16);

    AVSC_DECLARE_FUNC(avs_is_yv411);

    AVSC_DECLARE_FUNC(avs_is_y8);

#endif

#undef AVSC_DECLARE_FUNC

} AviSynthLibrary;

typedef struct AviSynthContext {

    AVS_ScriptEnvironment *env;

    AVS_Clip *clip;

    const AVS_VideoInfo *vi;

    /* avisynth_read_packet_video() iterates over this. */

    int n_planes;

    const int *planes;

    int curr_stream;

    int curr_frame;

    int64_t curr_sample;

    int error;

    /* Linked list pointers. */

    struct AviSynthContext *next;

} AviSynthContext;

static const int avs_planes_packed[1] = { 0 };

static const int avs_planes_grey[1]   = { AVS_PLANAR_Y };

static const int avs_planes_yuv[3]    = { AVS_PLANAR_Y, AVS_PLANAR_U,

                                          AVS_PLANAR_V };

/* A conflict between C++ global objects, atexit, and dynamic loading requires

 * us to register our own atexit handler to prevent double freeing. */

static AviSynthLibrary avs_library;

static int avs_atexit_called        = 0;

/* Linked list of AviSynthContexts. An atexit handler destroys this list. */

static AviSynthContext *avs_ctx_list = NULL;

static av_cold void avisynth_atexit_handler(void);

static av_cold int avisynth_load_library(void)

{

    avs_library.library = LoadLibrary(AVISYNTH_LIB);

    if (!avs_library.library)

        return AVERROR_UNKNOWN;

#define LOAD_AVS_FUNC(name, continue_on_fail)                          \

        avs_library.name =                                             \

            (void *)GetProcAddress(avs_library.library, #name);        \

        if (!continue_on_fail && !avs_library.name)                    \

            goto fail;

    LOAD_AVS_FUNC(avs_bit_blt, 0);

    LOAD_AVS_FUNC(avs_clip_get_error, 0);

    LOAD_AVS_FUNC(avs_create_script_environment, 0);

    LOAD_AVS_FUNC(avs_delete_script_environment, 0);

    LOAD_AVS_FUNC(avs_get_audio, 0);

    LOAD_AVS_FUNC(avs_get_error, 1); // New to AviSynth 2.6

    LOAD_AVS_FUNC(avs_get_frame, 0);

    LOAD_AVS_FUNC(avs_get_version, 0);

    LOAD_AVS_FUNC(avs_get_video_info, 0);

    LOAD_AVS_FUNC(avs_invoke, 0);

    LOAD_AVS_FUNC(avs_release_clip, 0);

    LOAD_AVS_FUNC(avs_release_value, 0);

    LOAD_AVS_FUNC(avs_release_video_frame, 0);

    LOAD_AVS_FUNC(avs_take_clip, 0);

#ifdef USING_AVISYNTH

    LOAD_AVS_FUNC(avs_bits_per_pixel, 1);

    LOAD_AVS_FUNC(avs_get_height_p, 1);

    LOAD_AVS_FUNC(avs_get_pitch_p, 1);

    LOAD_AVS_FUNC(avs_get_read_ptr_p, 1);

    LOAD_AVS_FUNC(avs_get_row_size_p, 1);

    LOAD_AVS_FUNC(avs_is_yv24, 1);

    LOAD_AVS_FUNC(avs_is_yv16, 1);

    LOAD_AVS_FUNC(avs_is_yv411, 1);

    LOAD_AVS_FUNC(avs_is_y8, 1);

#endif

#undef LOAD_AVS_FUNC

    atexit(avisynth_atexit_handler);

    return 0;

fail:

    FreeLibrary(avs_library.library);

    return AVERROR_UNKNOWN;

}

/* Note that avisynth_context_create and avisynth_context_destroy

 * do not allocate or free the actual context! That is taken care of

 * by libavformat. */

static av_cold int avisynth_context_create(AVFormatContext *s)

{

    AviSynthContext *avs = s->priv_data;

    int ret;

    if (!avs_library.library)

        if (ret = avisynth_load_library())

            return ret;

    avs->env = avs_library.avs_create_script_environment(3);

    if (avs_library.avs_get_error) {

        const char *error = avs_library.avs_get_error(avs->env);

        if (error) {

            av_log(s, AV_LOG_ERROR, "%s\n", error);

            return AVERROR_UNKNOWN;

        }

    }

    if (!avs_ctx_list) {

        avs_ctx_list = avs;

    } else {

        avs->next    = avs_ctx_list;

        avs_ctx_list = avs;

    }

    return 0;

}

static av_cold void avisynth_context_destroy(AviSynthContext *avs)

{

    if (avs_atexit_called)

        return;

    if (avs == avs_ctx_list) {

        avs_ctx_list = avs->next;

    } else {

        AviSynthContext *prev = avs_ctx_list;

        while (prev->next != avs)

            prev = prev->next;

        prev->next = avs->next;

    }

    if (avs->clip) {

        avs_library.avs_release_clip(avs->clip);

        avs->clip = NULL;

    }

    if (avs->env) {

        avs_library.avs_delete_script_environment(avs->env);

        avs->env = NULL;

    }

}

static av_cold void avisynth_atexit_handler(void)

{

    AviSynthContext *avs = avs_ctx_list;

    while (avs) {

        AviSynthContext *next = avs->next;

        avisynth_context_destroy(avs);

        avs = next;

    }

    FreeLibrary(avs_library.library);

    avs_atexit_called = 1;

}

/* Create AVStream from audio and video data. */

static int avisynth_create_stream_video(AVFormatContext *s, AVStream *st)

{

    AviSynthContext *avs = s->priv_data;

    int planar = 0; // 0: packed, 1: YUV, 2: Y8

    st->codec->codec_type = AVMEDIA_TYPE_VIDEO;

    st->codec->codec_id   = AV_CODEC_ID_RAWVIDEO;

    st->codec->width      = avs->vi->width;

    st->codec->height     = avs->vi->height;

    st->avg_frame_rate    = (AVRational) { avs->vi->fps_numerator,

                                           avs->vi->fps_denominator };

    st->start_time        = 0;

    st->duration          = avs->vi->num_frames;

    st->nb_frames         = avs->vi->num_frames;

    avpriv_set_pts_info(st, 32, avs->vi->fps_denominator, avs->vi->fps_numerator);

    switch (avs->vi->pixel_type) {

#ifdef USING_AVISYNTH

    case AVS_CS_YV24:

        st->codec->pix_fmt = AV_PIX_FMT_YUV444P;

        planar             = 1;

        break;

    case AVS_CS_YV16:

        st->codec->pix_fmt = AV_PIX_FMT_YUV422P;

        planar             = 1;

        break;

    case AVS_CS_YV411:

        st->codec->pix_fmt = AV_PIX_FMT_YUV411P;

        planar             = 1;

        break;

    case AVS_CS_Y8:

        st->codec->pix_fmt = AV_PIX_FMT_GRAY8;

        planar             = 2;

        break;

#endif

    case AVS_CS_BGR24:

        st->codec->pix_fmt = AV_PIX_FMT_BGR24;

        break;

    case AVS_CS_BGR32:

        st->codec->pix_fmt = AV_PIX_FMT_RGB32;

        break;

    case AVS_CS_YUY2:

        st->codec->pix_fmt = AV_PIX_FMT_YUYV422;

        break;

    case AVS_CS_YV12:

        st->codec->pix_fmt = AV_PIX_FMT_YUV420P;

        planar             = 1;

        break;

    case AVS_CS_I420: // Is this even used anywhere?

        st->codec->pix_fmt = AV_PIX_FMT_YUV420P;

        planar             = 1;

        break;

    default:

        av_log(s, AV_LOG_ERROR,

               "unknown AviSynth colorspace %d\n", avs->vi->pixel_type);

        avs->error = 1;

        return AVERROR_UNKNOWN;

    }

    switch (planar) {

    case 2: // Y8

        avs->n_planes = 1;

        avs->planes   = avs_planes_grey;

        break;

    case 1: // YUV

        avs->n_planes = 3;

        avs->planes   = avs_planes_yuv;

        break;

    default:

        avs->n_planes = 1;

        avs->planes   = avs_planes_packed;

    }

    return 0;

}

static int avisynth_create_stream_audio(AVFormatContext *s, AVStream *st)

{

    AviSynthContext *avs = s->priv_data;

    st->codec->codec_type  = AVMEDIA_TYPE_AUDIO;

    st->codec->sample_rate = avs->vi->audio_samples_per_second;

    st->codec->channels    = avs->vi->nchannels;

    st->duration           = avs->vi->num_audio_samples;

    avpriv_set_pts_info(st, 64, 1, avs->vi->audio_samples_per_second);

    switch (avs->vi->sample_type) {

    case AVS_SAMPLE_INT8:

        st->codec->codec_id = AV_CODEC_ID_PCM_U8;

        break;

    case AVS_SAMPLE_INT16:

        st->codec->codec_id = AV_CODEC_ID_PCM_S16LE;

        break;

    case AVS_SAMPLE_INT24:

        st->codec->codec_id = AV_CODEC_ID_PCM_S24LE;

        break;

    case AVS_SAMPLE_INT32:

        st->codec->codec_id = AV_CODEC_ID_PCM_S32LE;

        break;

    case AVS_SAMPLE_FLOAT:

        st->codec->codec_id = AV_CODEC_ID_PCM_F32LE;

        break;

    default:

        av_log(s, AV_LOG_ERROR,

               "unknown AviSynth sample type %d\n", avs->vi->sample_type);

        avs->error = 1;

        return AVERROR_UNKNOWN;

    }

    return 0;

}

static int avisynth_create_stream(AVFormatContext *s)

{

    AviSynthContext *avs = s->priv_data;

    AVStream *st;

    int ret;

    int id = 0;

    if (avs_has_video(avs->vi)) {

        st = avformat_new_stream(s, NULL);

        if (!st)

            return AVERROR_UNKNOWN;

        st->id = id++;

        if (ret = avisynth_create_stream_video(s, st))

            return ret;

    }

    if (avs_has_audio(avs->vi)) {

        st = avformat_new_stream(s, NULL);

        if (!st)

            return AVERROR_UNKNOWN;

        st->id = id++;

        if (ret = avisynth_create_stream_audio(s, st))

            return ret;

    }

    return 0;

}

static int avisynth_open_file(AVFormatContext *s)

{

    AviSynthContext *avs = s->priv_data;

    AVS_Value arg, val;

    int ret;

#ifdef USING_AVISYNTH

    char filename_ansi[MAX_PATH * 4];

    wchar_t filename_wc[MAX_PATH * 4];

#endif

    if (ret = avisynth_context_create(s))

        return ret;

#ifdef USING_AVISYNTH

    /* Convert UTF-8 to ANSI code page */

    MultiByteToWideChar(CP_UTF8, 0, s->filename, -1, filename_wc, MAX_PATH * 4);

    WideCharToMultiByte(CP_THREAD_ACP, 0, filename_wc, -1, filename_ansi,

                        MAX_PATH * 4, NULL, NULL);

    arg = avs_new_value_string(filename_ansi);

#else

    arg = avs_new_value_string(s->filename);

#endif

    val = avs_library.avs_invoke(avs->env, "Import", arg, 0);

    if (avs_is_error(val)) {

        av_log(s, AV_LOG_ERROR, "%s\n", avs_as_error(val));

        ret = AVERROR_UNKNOWN;

        goto fail;

    }

    if (!avs_is_clip(val)) {

        av_log(s, AV_LOG_ERROR, "AviSynth script did not return a clip\n");

        ret = AVERROR_UNKNOWN;

        goto fail;

    }

    avs->clip = avs_library.avs_take_clip(val, avs->env);

    avs->vi   = avs_library.avs_get_video_info(avs->clip);

#ifdef USING_AVISYNTH

    /* On Windows, FFmpeg supports AviSynth interface version 6 or higher.

     * This includes AviSynth 2.6 RC1 or higher, and AviSynth+ r1718 or higher,

     * and excludes 2.5 and the 2.6 alphas. Since AvxSynth identifies itself

     * as interface version 3 like 2.5.8, this needs to be special-cased. */

    if (avs_library.avs_get_version(avs->clip) < 6) {

        av_log(s, AV_LOG_ERROR,

               "AviSynth version is too old. Please upgrade to either AviSynth 2.6 >= RC1 or AviSynth+ >= r1718.\n");

        ret = AVERROR_UNKNOWN;

        goto fail;

    }

#endif

    /* Release the AVS_Value as it will go out of scope. */

    avs_library.avs_release_value(val);

    if (ret = avisynth_create_stream(s))

        goto fail;

    return 0;

fail:

    avisynth_context_destroy(avs);

    return ret;

}

static void avisynth_next_stream(AVFormatContext *s, AVStream **st,

                                 AVPacket *pkt, int *discard)

{

    AviSynthContext *avs = s->priv_data;

    avs->curr_stream++;

    avs->curr_stream %= s->nb_streams;

    *st = s->streams[avs->curr_stream];

    if ((*st)->discard == AVDISCARD_ALL)

        *discard = 1;

    else

        *discard = 0;

    return;

}

/* Copy AviSynth clip data into an AVPacket. */

static int avisynth_read_packet_video(AVFormatContext *s, AVPacket *pkt,

                                      int discard)

{

    AviSynthContext *avs = s->priv_data;

    AVS_VideoFrame *frame;

    unsigned char *dst_p;

    const unsigned char *src_p;

    int n, i, plane, rowsize, planeheight, pitch, bits;

    const char *error;

    if (avs->curr_frame >= avs->vi->num_frames)

        return AVERROR_EOF;

    /* This must happen even if the stream is discarded to prevent desync. */

    n = avs->curr_frame++;

    if (discard)

        return 0;

#ifdef USING_AVISYNTH

    /* Define the bpp values for the new AviSynth 2.6 colorspaces.

     * Since AvxSynth doesn't have these functions, special-case

     * it in order to avoid implicit declaration errors. */

    if (avs_library.avs_is_yv24(avs->vi))

        bits = 24;

    else if (avs_library.avs_is_yv16(avs->vi))

        bits = 16;

    else if (avs_library.avs_is_yv411(avs->vi))

        bits = 12;

    else if (avs_library.avs_is_y8(avs->vi))

        bits = 8;

    else

        bits = avs_library.avs_bits_per_pixel(avs->vi);

#else

    bits = avs_bits_per_pixel(avs->vi);

#endif

    /* Without the cast to int64_t, calculation overflows at about 9k x 9k

     * resolution. */

    pkt->size = (((int64_t)avs->vi->width *

                  (int64_t)avs->vi->height) * bits) / 8;

    if (!pkt->size)

        return AVERROR_UNKNOWN;

    if (av_new_packet(pkt, pkt->size) < 0)

        return AVERROR(ENOMEM);

    pkt->pts      = n;

    pkt->dts      = n;

    pkt->duration = 1;

    pkt->stream_index = avs->curr_stream;

    frame = avs_library.avs_get_frame(avs->clip, n);

    error = avs_library.avs_clip_get_error(avs->clip);

    if (error) {

        av_log(s, AV_LOG_ERROR, "%s\n", error);

        avs->error = 1;

        av_packet_unref(pkt);

        return AVERROR_UNKNOWN;

    }

    dst_p = pkt->data;

    for (i = 0; i < avs->n_planes; i++) {

        plane = avs->planes[i];

#ifdef USING_AVISYNTH

        src_p = avs_library.avs_get_read_ptr_p(frame, plane);

        pitch = avs_library.avs_get_pitch_p(frame, plane);

        rowsize     = avs_library.avs_get_row_size_p(frame, plane);

        planeheight = avs_library.avs_get_height_p(frame, plane);

#else

        src_p = avs_get_read_ptr_p(frame, plane);

        pitch = avs_get_pitch_p(frame, plane);

        rowsize     = avs_get_row_size_p(frame, plane);

        planeheight = avs_get_height_p(frame, plane);

#endif

        /* Flip RGB video. */

        if (avs_is_rgb24(avs->vi) || avs_is_rgb(avs->vi)) {

            src_p = src_p + (planeheight - 1) * pitch;

            pitch = -pitch;

        }

        avs_library.avs_bit_blt(avs->env, dst_p, rowsize, src_p, pitch,

                                 rowsize, planeheight);

        dst_p += rowsize * planeheight;

    }

    avs_library.avs_release_video_frame(frame);

    return 0;

}

static int avisynth_read_packet_audio(AVFormatContext *s, AVPacket *pkt,

                                      int discard)

{

    AviSynthContext *avs = s->priv_data;

    AVRational fps, samplerate;

    int samples;

    int64_t n;

    const char *error;

    if (avs->curr_sample >= avs->vi->num_audio_samples)

        return AVERROR_EOF;

    fps.num        = avs->vi->fps_numerator;

    fps.den        = avs->vi->fps_denominator;

    samplerate.num = avs->vi->audio_samples_per_second;

    samplerate.den = 1;

    if (avs_has_video(avs->vi)) {

        if (avs->curr_frame < avs->vi->num_frames)

            samples = av_rescale_q(avs->curr_frame, samplerate, fps) -

                      avs->curr_sample;

        else

            samples = av_rescale_q(1, samplerate, fps);

    } else {

        samples = 1000;

    }

    /* After seeking, audio may catch up with video. */

    if (samples <= 0) {

        pkt->size = 0;

        pkt->data = NULL;

        return 0;

    }

    if (avs->curr_sample + samples > avs->vi->num_audio_samples)

        samples = avs->vi->num_audio_samples - avs->curr_sample;

    /* This must happen even if the stream is discarded to prevent desync. */

    n                 = avs->curr_sample;

    avs->curr_sample += samples;

    if (discard)

        return 0;

    pkt->size = avs_bytes_per_channel_sample(avs->vi) *

                samples * avs->vi->nchannels;

    if (!pkt->size)

        return AVERROR_UNKNOWN;

    if (av_new_packet(pkt, pkt->size) < 0)

        return AVERROR(ENOMEM);

    pkt->pts      = n;

    pkt->dts      = n;

    pkt->duration = samples;

    pkt->stream_index = avs->curr_stream;

    avs_library.avs_get_audio(avs->clip, pkt->data, n, samples);

    error = avs_library.avs_clip_get_error(avs->clip);

    if (error) {

        av_log(s, AV_LOG_ERROR, "%s\n", error);

        avs->error = 1;

        av_packet_unref(pkt);

        return AVERROR_UNKNOWN;

    }

    return 0;

}

static av_cold int avisynth_read_header(AVFormatContext *s)

{

    int ret;

    // Calling library must implement a lock for thread-safe opens.

    if (ret = avpriv_lock_avformat())

        return ret;

    if (ret = avisynth_open_file(s)) {

        avpriv_unlock_avformat();

        return ret;

    }

    avpriv_unlock_avformat();

    return 0;

}

static int avisynth_read_packet(AVFormatContext *s, AVPacket *pkt)

{

    AviSynthContext *avs = s->priv_data;

    AVStream *st;

    int discard = 0;

    int ret;

    if (avs->error)

        return AVERROR_UNKNOWN;

    /* If either stream reaches EOF, try to read the other one before

     * giving up. */

    avisynth_next_stream(s, &st, pkt, &discard);

    if (st->codec->codec_type == AVMEDIA_TYPE_VIDEO) {

        ret = avisynth_read_packet_video(s, pkt, discard);

        if (ret == AVERROR_EOF && avs_has_audio(avs->vi)) {

            avisynth_next_stream(s, &st, pkt, &discard);

            return avisynth_read_packet_audio(s, pkt, discard);

        }

    } else {

        ret = avisynth_read_packet_audio(s, pkt, discard);

        if (ret == AVERROR_EOF && avs_has_video(avs->vi)) {

            avisynth_next_stream(s, &st, pkt, &discard);

            return avisynth_read_packet_video(s, pkt, discard);

        }

    }

    return ret;

}

static av_cold int avisynth_read_close(AVFormatContext *s)

{

    if (avpriv_lock_avformat())

        return AVERROR_UNKNOWN;

    avisynth_context_destroy(s->priv_data);

    avpriv_unlock_avformat();

    return 0;

}

static int avisynth_read_seek(AVFormatContext *s, int stream_index,

                              int64_t timestamp, int flags)

{

    AviSynthContext *avs = s->priv_data;

    AVStream *st;

    AVRational fps, samplerate;

    if (avs->error)

        return AVERROR_UNKNOWN;

    fps        = (AVRational) { avs->vi->fps_numerator,

                                avs->vi->fps_denominator };

    samplerate = (AVRational) { avs->vi->audio_samples_per_second, 1 };

    st = s->streams[stream_index];

    if (st->codec->codec_type == AVMEDIA_TYPE_VIDEO) {

        /* AviSynth frame counts are signed int. */

        if ((timestamp >= avs->vi->num_frames) ||

            (timestamp > INT_MAX)              ||

            (timestamp < 0))

            return AVERROR_EOF;

        avs->curr_frame = timestamp;

        if (avs_has_audio(avs->vi))

            avs->curr_sample = av_rescale_q(timestamp, samplerate, fps);

    } else {

        if ((timestamp >= avs->vi->num_audio_samples) || (timestamp < 0))

            return AVERROR_EOF;

        /* Force frame granularity for seeking. */

        if (avs_has_video(avs->vi)) {

            avs->curr_frame  = av_rescale_q(timestamp, fps, samplerate);

            avs->curr_sample = av_rescale_q(avs->curr_frame, samplerate, fps);

        } else {

            avs->curr_sample = timestamp;

        }

    }

    return 0;

}

AVInputFormat ff_avisynth_demuxer = {

    .name           = "avisynth",

    .long_name      = NULL_IF_CONFIG_SMALL("AviSynth script"),

    .priv_data_size = sizeof(AviSynthContext),

    .read_header    = avisynth_read_header,

    .read_packet    = avisynth_read_packet,

    .read_close     = avisynth_read_close,

    .read_seek      = avisynth_read_seek,

    .extensions     = "avs",

};