path: root/libavutil/opt.c

/*
 * AVOptions
 * Copyright (c) 2005 Michael Niedermayer <michaelni@gmx.at>
 *
 * 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
 * AVOptions
 * @author Michael Niedermayer <michaelni@gmx.at>
 */

#include "avutil.h"
#include "avstring.h"
#include "channel_layout.h"
#include "common.h"
#include "opt.h"
#include "eval.h"
#include "dict.h"
#include "log.h"
#include "parseutils.h"
#include "pixdesc.h"
#include "mathematics.h"
#include "samplefmt.h"

#include <float.h>

#if FF_API_FIND_OPT
//FIXME order them and do a bin search
const AVOption *av_find_opt(void *v, const char *name, const char *unit, int mask, int flags)
{
    const AVOption *o = NULL;

    while ((o = av_next_option(v, o))) {
        if (!strcmp(o->name, name) && (!unit || (o->unit && !strcmp(o->unit, unit))) && (o->flags & mask) == flags)
            return o;
    }
    return NULL;
}
#endif

#if FF_API_OLD_AVOPTIONS
const AVOption *av_next_option(void *obj, const AVOption *last)
{
    return av_opt_next(obj, last);
}
#endif

const AVOption *av_opt_next(void *obj, const AVOption *last)
{
    AVClass *class = *(AVClass**)obj;
    if (!last && class && class->option && class->option[0].name)
        return class->option;
    if (last && last[1].name)
        return ++last;
    return NULL;
}

static int read_number(const AVOption *o, void *dst, double *num, int *den, int64_t *intnum)
{
    switch (o->type) {
    case AV_OPT_TYPE_FLAGS:     *intnum = *(unsigned int*)dst;return 0;
    case AV_OPT_TYPE_PIXEL_FMT:
    case AV_OPT_TYPE_SAMPLE_FMT:
    case AV_OPT_TYPE_INT:       *intnum = *(int         *)dst;return 0;
    case AV_OPT_TYPE_CHANNEL_LAYOUT:
    case AV_OPT_TYPE_DURATION:
    case AV_OPT_TYPE_INT64:     *intnum = *(int64_t     *)dst;return 0;
    case AV_OPT_TYPE_FLOAT:     *num    = *(float       *)dst;return 0;
    case AV_OPT_TYPE_DOUBLE:    *num    = *(double      *)dst;return 0;
    case AV_OPT_TYPE_RATIONAL:  *intnum = ((AVRational*)dst)->num;
                                *den    = ((AVRational*)dst)->den;
                                                        return 0;
    case AV_OPT_TYPE_CONST:     *num    = o->default_val.dbl; return 0;
    }
    return AVERROR(EINVAL);
}

static int write_number(void *obj, const AVOption *o, void *dst, double num, int den, int64_t intnum)
{
    if (o->type != AV_OPT_TYPE_FLAGS &&
        (o->max * den < num * intnum || o->min * den > num * intnum)) {
        av_log(obj, AV_LOG_ERROR, "Value %f for parameter '%s' out of range [%g - %g]\n",
               num*intnum/den, o->name, o->min, o->max);
        return AVERROR(ERANGE);
    }
    if (o->type == AV_OPT_TYPE_FLAGS) {
        double d = num*intnum/den;
        if (d < -1.5 || d > 0xFFFFFFFF+0.5 || (llrint(d*256) & 255)) {
            av_log(obj, AV_LOG_ERROR,
                   "Value %f for parameter '%s' is not a valid set of 32bit integer flags\n",
                   num*intnum/den, o->name);
            return AVERROR(ERANGE);
        }
    }

    switch (o->type) {
    case AV_OPT_TYPE_FLAGS:
    case AV_OPT_TYPE_PIXEL_FMT:
    case AV_OPT_TYPE_SAMPLE_FMT:
    case AV_OPT_TYPE_INT:   *(int       *)dst= llrint(num/den)*intnum; break;
    case AV_OPT_TYPE_DURATION:
    case AV_OPT_TYPE_CHANNEL_LAYOUT:
    case AV_OPT_TYPE_INT64: *(int64_t   *)dst= llrint(num/den)*intnum; break;
    case AV_OPT_TYPE_FLOAT: *(float     *)dst= num*intnum/den;         break;
    case AV_OPT_TYPE_DOUBLE:*(double    *)dst= num*intnum/den;         break;
    case AV_OPT_TYPE_RATIONAL:
        if ((int)num == num) *(AVRational*)dst= (AVRational){num*intnum, den};
        else                 *(AVRational*)dst= av_d2q(num*intnum/den, 1<<24);
        break;
    default:
        return AVERROR(EINVAL);
    }
    return 0;
}

static const double const_values[] = {
    M_PI,
    M_E,
    FF_QP2LAMBDA,
    0
};

static const char * const const_names[] = {
    "PI",
    "E",
    "QP2LAMBDA",
    0
};

static int hexchar2int(char c) {
    if (c >= '0' && c <= '9') return c - '0';
    if (c >= 'a' && c <= 'f') return c - 'a' + 10;
    if (c >= 'A' && c <= 'F') return c - 'A' + 10;
    return -1;
}

static int set_string_binary(void *obj, const AVOption *o, const char *val, uint8_t **dst)
{
    int *lendst = (int *)(dst + 1);
    uint8_t *bin, *ptr;
    int len = strlen(val);

    av_freep(dst);
    *lendst = 0;

    if (len & 1)
        return AVERROR(EINVAL);
    len /= 2;

    ptr = bin = av_malloc(len);
    while (*val) {
        int a = hexchar2int(*val++);
        int b = hexchar2int(*val++);
        if (a < 0 || b < 0) {
            av_free(bin);
            return AVERROR(EINVAL);
        }
        *ptr++ = (a << 4) | b;
    }
    *dst = bin;
    *lendst = len;

    return 0;
}

static int set_string(void *obj, const AVOption *o, const char *val, uint8_t **dst)
{
    av_freep(dst);
    *dst = av_strdup(val);
    return 0;
}

#define DEFAULT_NUMVAL(opt) ((opt->type == AV_OPT_TYPE_INT64 || \
                              opt->type == AV_OPT_TYPE_CONST || \
                              opt->type == AV_OPT_TYPE_FLAGS || \
                              opt->type == AV_OPT_TYPE_INT) ? \
                             opt->default_val.i64 : opt->default_val.dbl)

static int set_string_number(void *obj, void *target_obj, const AVOption *o, const char *val, void *dst)
{
    int ret = 0, notfirst = 0;
    int num, den;
    char c;

    if (sscanf(val, "%d%*1[:/]%d%c", &num, &den, &c) == 2) {
        if ((ret = write_number(obj, o, dst, 1, den, num)) >= 0)
            return ret;
        ret = 0;
    }

    for (;;) {
        int i, den = 1;
        char buf[256];
        int cmd = 0;
        double d, num = 1;
        int64_t intnum = 1;

        i = 0;
        if (*val == '+' || *val == '-') {
            if (o->type == AV_OPT_TYPE_FLAGS)
                cmd = *(val++);
            else if (!notfirst)
                buf[i++] = *val;
        }

        for (; i < sizeof(buf) - 1 && val[i] && val[i] != '+' && val[i] != '-'; i++)
            buf[i] = val[i];
        buf[i] = 0;

        {
            const AVOption *o_named = av_opt_find(target_obj, buf, o->unit, 0, 0);
            if (o_named && o_named->type == AV_OPT_TYPE_CONST)
                d = DEFAULT_NUMVAL(o_named);
            else if (!strcmp(buf, "default")) d = DEFAULT_NUMVAL(o);
            else if (!strcmp(buf, "max"    )) d = o->max;
            else if (!strcmp(buf, "min"    )) d = o->min;
            else if (!strcmp(buf, "none"   )) d = 0;
            else if (!strcmp(buf, "all"    )) d = ~0;
            else {
                int res = av_expr_parse_and_eval(&d, buf, const_names, const_values, NULL, NULL, NULL, NULL, NULL, 0, obj);
                if (res < 0) {
                    av_log(obj, AV_LOG_ERROR, "Unable to parse option value \"%s\"\n", val);
                    return res;
                }
            }
        }
        if (o->type == AV_OPT_TYPE_FLAGS) {
            read_number(o, dst, NULL, NULL, &intnum);
            if      (cmd == '+') d = intnum | (int64_t)d;
            else if (cmd == '-') d = intnum &~(int64_t)d;
        } else {
            read_number(o, dst, &num, &den, &intnum);
            if      (cmd == '+') d = notfirst*num*intnum/den + d;
            else if (cmd == '-') d = notfirst*num*intnum/den - d;
        }

        if ((ret = write_number(obj, o, dst, d, 1, 1)) < 0)
            return ret;
        val += i;
        if (!*val)
            return 0;
        notfirst = 1;
    }

    return 0;
}

static int set_string_image_size(void *obj, const AVOption *o, const char *val, int *dst)
{
    int ret;

    if (!val || !strcmp(val, "none")) {
        dst[0] =
        dst[1] = 0;
        return 0;
    }
    ret = av_parse_video_size(dst, dst + 1, val);
    if (ret < 0)
        av_log(obj, AV_LOG_ERROR, "Unable to parse option value \"%s\" as image size\n", val);
    return ret;
}

static int set_string_video_rate(void *obj, const AVOption *o, const char *val, AVRational *dst)
{
    int ret;
    if (!val) {
        ret = AVERROR(EINVAL);
    } else {
        ret = av_parse_video_rate(dst, val);
    }
    if (ret < 0)
        av_log(obj, AV_LOG_ERROR, "Unable to parse option value \"%s\" as video rate\n", val);
    return ret;
}

static int set_string_color(void *obj, const AVOption *o, const char *val, uint8_t *dst)
{
    int ret;

    if (!val) {
        return 0;
    } else {
        ret = av_parse_color(dst, val, -1, obj);
        if (ret < 0)
            av_log(obj, AV_LOG_ERROR, "Unable to parse option value \"%s\" as color\n", val);
        return ret;
    }
    return 0;
}

static int set_string_fmt(void *obj, const AVOption *o, const char *val, uint8_t *dst,
                          int fmt_nb, int ((*get_fmt)(const char *)), const char *desc)
{
    int fmt, min, max;

    if (!val || !strcmp(val, "none")) {
        fmt = -1;
    } else {
        fmt = get_fmt(val);
        if (fmt == -1) {
            char *tail;
            fmt = strtol(val, &tail, 0);
            if (*tail || (unsigned)fmt >= fmt_nb) {
                av_log(obj, AV_LOG_ERROR,
                       "Unable to parse option value \"%s\" as %s\n", val, desc);
                return AVERROR(EINVAL);
            }
        }
    }

    min = FFMAX(o->min, -1);
    max = FFMIN(o->max, fmt_nb-1);

    // hack for compatibility with old ffmpeg
    if(min == 0 && max == 0) {
        min = -1;
        max = fmt_nb-1;
    }

    if (fmt < min || fmt > max) {
        av_log(obj, AV_LOG_ERROR,
               "Value %d for parameter '%s' out of %s format range [%d - %d]\n",
               fmt, o->name, desc, min, max);
        return AVERROR(ERANGE);
    }

    *(int *)dst = fmt;
    return 0;
}

static int set_string_pixel_fmt(void *obj, const AVOption *o, const char *val, uint8_t *dst)
{
    return set_string_fmt(obj, o, val, dst,
                          AV_PIX_FMT_NB, av_get_pix_fmt, "pixel format");
}

static int set_string_sample_fmt(void *obj, const AVOption *o, const char *val, uint8_t *dst)
{
    return set_string_fmt(obj, o, val, dst,
                          AV_SAMPLE_FMT_NB, av_get_sample_fmt, "sample format");
}

#if FF_API_OLD_AVOPTIONS
int av_set_string3(void *obj, const char *name, const char *val, int alloc, const AVOption **o_out)
{
    const AVOption *o = av_opt_find(obj, name, NULL, 0, 0);
    if (o_out)
        *o_out = o;
    return av_opt_set(obj, name, val, 0);
}
#endif

int av_opt_set(void *obj, const char *name, const char *val, int search_flags)
{
    int ret = 0;
    void *dst, *target_obj;
    const AVOption *o = av_opt_find2(obj, name, NULL, 0, search_flags, &target_obj);
    if (!o || !target_obj)
        return AVERROR_OPTION_NOT_FOUND;
    if (!val && (o->type != AV_OPT_TYPE_STRING &&
                 o->type != AV_OPT_TYPE_PIXEL_FMT && o->type != AV_OPT_TYPE_SAMPLE_FMT &&
                 o->type != AV_OPT_TYPE_IMAGE_SIZE && o->type != AV_OPT_TYPE_VIDEO_RATE &&
                 o->type != AV_OPT_TYPE_DURATION && o->type != AV_OPT_TYPE_COLOR &&
                 o->type != AV_OPT_TYPE_CHANNEL_LAYOUT))
        return AVERROR(EINVAL);

    if (o->flags & AV_OPT_FLAG_READONLY)
        return AVERROR(EINVAL);

    dst = ((uint8_t*)target_obj) + o->offset;
    switch (o->type) {
    case AV_OPT_TYPE_STRING:   return set_string(obj, o, val, dst);
    case AV_OPT_TYPE_BINARY:   return set_string_binary(obj, o, val, dst);
    case AV_OPT_TYPE_FLAGS:
    case AV_OPT_TYPE_INT:
    case AV_OPT_TYPE_INT64:
    case AV_OPT_TYPE_FLOAT:
    case AV_OPT_TYPE_DOUBLE:
    case AV_OPT_TYPE_RATIONAL: return set_string_number(obj, target_obj, o, val, dst);
    case AV_OPT_TYPE_IMAGE_SIZE: return set_string_image_size(obj, o, val, dst);
    case AV_OPT_TYPE_VIDEO_RATE: return set_string_video_rate(obj, o, val, dst);
    case AV_OPT_TYPE_PIXEL_FMT:  return set_string_pixel_fmt(obj, o, val, dst);
    case AV_OPT_TYPE_SAMPLE_FMT: return set_string_sample_fmt(obj, o, val, dst);
    case AV_OPT_TYPE_DURATION:
        if (!val) {
            *(int64_t *)dst = 0;
            return 0;
        } else {
            if ((ret = av_parse_time(dst, val, 1)) < 0)
                av_log(obj, AV_LOG_ERROR, "Unable to parse option value \"%s\" as duration\n", val);
            return ret;
        }
        break;
    case AV_OPT_TYPE_COLOR:      return set_string_color(obj, o, val, dst);
    case AV_OPT_TYPE_CHANNEL_LAYOUT:
        if (!val || !strcmp(val, "none")) {
            *(int64_t *)dst = 0;
        } else {
#if FF_API_GET_CHANNEL_LAYOUT_COMPAT
            int64_t cl = ff_get_channel_layout(val, 0);
#else
            int64_t cl = av_get_channel_layout(val);
#endif
            if (!cl) {
                av_log(obj, AV_LOG_ERROR, "Unable to parse option value \"%s\" as channel layout\n", val);
                ret = AVERROR(EINVAL);
            }
            *(int64_t *)dst = cl;
            return ret;
        }
        break;
    }

    av_log(obj, AV_LOG_ERROR, "Invalid option type.\n");
    return AVERROR(EINVAL);
}

#define OPT_EVAL_NUMBER(name, opttype, vartype)\
    int av_opt_eval_ ## name(void *obj, const AVOption *o, const char *val, vartype *name ## _out)\
    {\
        if (!o || o->type != opttype || o->flags & AV_OPT_FLAG_READONLY)\
            return AVERROR(EINVAL);\
        return set_string_number(obj, obj, o, val, name ## _out);\
    }

OPT_EVAL_NUMBER(flags,  AV_OPT_TYPE_FLAGS,    int)
OPT_EVAL_NUMBER(int,    AV_OPT_TYPE_INT,      int)
OPT_EVAL_NUMBER(int64,  AV_OPT_TYPE_INT64,    int64_t)
OPT_EVAL_NUMBER(float,  AV_OPT_TYPE_FLOAT,    float)
OPT_EVAL_NUMBER(double, AV_OPT_TYPE_DOUBLE,   double)
OPT_EVAL_NUMBER(q,      AV_OPT_TYPE_RATIONAL, AVRational)

static int set_number(void *obj, const char *name, double num, int den, int64_t intnum,
                                  int search_flags)
{
    void *dst, *target_obj;
    const AVOption *o = av_opt_find2(obj, name, NULL, 0, search_flags, &target_obj);

    if (!o || !target_obj)
        return AVERROR_OPTION_NOT_FOUND;

    if (o->flags & AV_OPT_FLAG_READONLY)
        return AVERROR(EINVAL);

    dst = ((uint8_t*)target_obj) + o->offset;
    return write_number(obj, o, dst, num, den, intnum);
}

#if FF_API_OLD_AVOPTIONS
const AVOption *av_set_double(void *obj, const char *name, double n)
{
    const AVOption *o = av_opt_find(obj, name, NULL, 0, 0);
    if (set_number(obj, name, n, 1, 1, 0) < 0)
        return NULL;
    return o;
}

const AVOption *av_set_q(void *obj, const char *name, AVRational n)
{
    const AVOption *o = av_opt_find(obj, name, NULL, 0, 0);
    if (set_number(obj, name, n.num, n.den, 1, 0) < 0)
        return NULL;
    return o;
}

const AVOption *av_set_int(void *obj, const char *name, int64_t n)
{
    const AVOption *o = av_opt_find(obj, name, NULL, 0, 0);
    if (set_number(obj, name, 1, 1, n, 0) < 0)
        return NULL;
    return o;
}
#endif

int av_opt_set_int(void *obj, const char *name, int64_t val, int search_flags)
{
    return set_number(obj, name, 1, 1, val, search_flags);
}

int av_opt_set_double(void *obj, const char *name, double val, int search_flags)
{
    return set_number(obj, name, val, 1, 1, search_flags);
}

int av_opt_set_q(void *obj, const char *name, AVRational val, int search_flags)
{
    return set_number(obj, name, val.num, val.den, 1, search_flags);
}

int av_opt_set_bin(void *obj, const char *name, const uint8_t *val, int len, int search_flags)
{
    void *target_obj;
    const AVOption *o = av_opt_find2(obj, name, NULL, 0, search_flags, &target_obj);
    uint8_t *ptr;
    uint8_t **dst;
    int *lendst;

    if (!o || !target_obj)
        return AVERROR_OPTION_NOT_FOUND;

    if (o->type != AV_OPT_TYPE_BINARY || o->flags & AV_OPT_FLAG_READONLY)
        return AVERROR(EINVAL);

    ptr = len ? av_malloc(len) : NULL;
    if (len && !ptr)
        return AVERROR(ENOMEM);

    dst = (uint8_t **)(((uint8_t *)target_obj) + o->offset);
    lendst = (int *)(dst + 1);

    av_free(*dst);
    *dst = ptr;
    *lendst = len;
    if (len)
        memcpy(ptr, val, len);

    return 0;
}

int av_opt_set_image_size(void *obj, const char *name, int w, int h, int search_flags)
{
    void *target_obj;
    const AVOption *o = av_opt_find2(obj, name, NULL, 0, search_flags, &target_obj);

    if (!o || !target_obj)
        return AVERROR_OPTION_NOT_FOUND;
    if (o->type != AV_OPT_TYPE_IMAGE_SIZE) {
        av_log(obj, AV_LOG_ERROR,
               "The value set by option '%s' is not an image size.\n", o->name);
        return AVERROR(EINVAL);
    }
    if (w<0 || h<0) {
        av_log(obj, AV_LOG_ERROR,
               "Invalid negative size value %dx%d for size '%s'\n", w, h, o->name);
        return AVERROR(EINVAL);
    }
    *(int *)(((uint8_t *)target_obj)             + o->offset) = w;
    *(int *)(((uint8_t *)target_obj+sizeof(int)) + o->offset) = h;
    return 0;
}

int av_opt_set_video_rate(void *obj, const char *name, AVRational val, int search_flags)
{
    void *target_obj;
    const AVOption *o = av_opt_find2(obj, name, NULL, 0, search_flags, &target_obj);

    if (!o || !target_obj)
        return AVERROR_OPTION_NOT_FOUND;
    if (o->type != AV_OPT_TYPE_VIDEO_RATE) {
        av_log(obj, AV_LOG_ERROR,
               "The value set by option '%s' is not a video rate.\n", o->name);
        return AVERROR(EINVAL);
    }
    if (val.num <= 0 || val.den <= 0)
        return AVERROR(EINVAL);
    return set_number(obj, name, val.num, val.den, 1, search_flags);
}

static int set_format(void *obj, const char *name, int fmt, int search_flags,
                      enum AVOptionType type, const char *desc, int nb_fmts)
{
    void *target_obj;
    const AVOption *o = av_opt_find2(obj, name, NULL, 0,
                                     search_flags, &target_obj);
    int min, max;
    const AVClass *class = *(AVClass **)obj;

    if (!o || !target_obj)
        return AVERROR_OPTION_NOT_FOUND;
    if (o->type != type) {
        av_log(obj, AV_LOG_ERROR,
               "The value set by option '%s' is not a %s format", name, desc);
        return AVERROR(EINVAL);
    }

#if LIBAVUTIL_VERSION_MAJOR < 54
    if (class->version && class->version < AV_VERSION_INT(52, 11, 100)) {
        min = -1;
        max = nb_fmts-1;
    } else
#endif
    {
        min = FFMAX(o->min, -1);
        max = FFMIN(o->max, nb_fmts-1);
    }
    if (fmt < min || fmt > max) {
        av_log(obj, AV_LOG_ERROR,
               "Value %d for parameter '%s' out of %s format range [%d - %d]\n",
               fmt, name, desc, min, max);
        return AVERROR(ERANGE);
    }
    *(int *)(((uint8_t *)target_obj) + o->offset) = fmt;
    return 0;
}

int av_opt_set_pixel_fmt(void *obj, const char *name, enum AVPixelFormat fmt, int search_flags)
{
    return set_format(obj, name, fmt, search_flags, AV_OPT_TYPE_PIXEL_FMT, "pixel", AV_PIX_FMT_NB);
}

int av_opt_set_sample_fmt(void *obj, const char *name, enum AVSampleFormat fmt, int search_flags)
{
    return set_format(obj, name, fmt, search_flags, AV_OPT_TYPE_SAMPLE_FMT, "sample", AV_SAMPLE_FMT_NB);
}

int av_opt_set_channel_layout(void *obj, const char *name, int64_t cl, int search_flags)
{
    void *target_obj;
    const AVOption *o = av_opt_find2(obj, name, NULL, 0, search_flags, &target_obj);

    if (!o || !target_obj)
        return AVERROR_OPTION_NOT_FOUND;
    if (o->type != AV_OPT_TYPE_CHANNEL_LAYOUT) {
        av_log(obj, AV_LOG_ERROR,
               "The value set by option '%s' is not a channel layout.\n", o->name);
        return AVERROR(EINVAL);
    }
    *(int *)(((int64_t *)target_obj) + o->offset) = cl;
    return 0;
}

#if FF_API_OLD_AVOPTIONS
/**
 *
 * @param buf a buffer which is used for returning non string values as strings, can be NULL
 * @param buf_len allocated length in bytes of buf
 */
const char *av_get_string(void *obj, const char *name, const AVOption **o_out, char *buf, int buf_len)
{
    const AVOption *o = av_opt_find(obj, name, NULL, 0, AV_OPT_SEARCH_CHILDREN);
    void *dst;
    uint8_t *bin;
    int len, i;
    if (!o)
        return NULL;
    if (o->type != AV_OPT_TYPE_STRING && (!buf || !buf_len))
        return NULL;

    dst= ((uint8_t*)obj) + o->offset;
    if (o_out) *o_out= o;

    switch (o->type) {
    case AV_OPT_TYPE_FLAGS:     snprintf(buf, buf_len, "0x%08X",*(int    *)dst);break;
    case AV_OPT_TYPE_INT:       snprintf(buf, buf_len, "%d" , *(int    *)dst);break;
    case AV_OPT_TYPE_INT64:     snprintf(buf, buf_len, "%"PRId64, *(int64_t*)dst);break;
    case AV_OPT_TYPE_FLOAT:     snprintf(buf, buf_len, "%f" , *(float  *)dst);break;
    case AV_OPT_TYPE_DOUBLE:    snprintf(buf, buf_len, "%f" , *(double *)dst);break;
    case AV_OPT_TYPE_RATIONAL:  snprintf(buf, buf_len, "%d/%d", ((AVRational*)dst)->num, ((AVRational*)dst)->den);break;
    case AV_OPT_TYPE_CONST:     snprintf(buf, buf_len, "%f" , o->default_val.dbl);break;
    case AV_OPT_TYPE_STRING:    return *(void**)dst;
    case AV_OPT_TYPE_BINARY:
        len = *(int*)(((uint8_t *)dst) + sizeof(uint8_t *));
        if (len >= (buf_len + 1)/2) return NULL;
        bin = *(uint8_t**)dst;
        for (i = 0; i < len; i++) snprintf(buf + i*2, 3, "%02X", bin[i]);
        break;
    default: return NULL;
    }
    return buf;
}
#endif

int av_opt_get(void *obj, const char *name, int search_flags, uint8_t **out_val)
{
    void *dst, *target_obj;
    const AVOption *o = av_opt_find2(obj, name, NULL, 0, search_flags, &target_obj);
    uint8_t *bin, buf[128];
    int len, i, ret;
    int64_t i64;

    if (!o || !target_obj || (o->offset<=0 && o->type != AV_OPT_TYPE_CONST))
        return AVERROR_OPTION_NOT_FOUND;

    dst = (uint8_t*)target_obj + o->offset;

    buf[0] = 0;
    switch (o->type) {
    case AV_OPT_TYPE_FLAGS:     ret = snprintf(buf, sizeof(buf), "0x%08X",  *(int    *)dst);break;
    case AV_OPT_TYPE_INT:       ret = snprintf(buf, sizeof(buf), "%d" ,     *(int    *)dst);break;
    case AV_OPT_TYPE_INT64:     ret = snprintf(buf, sizeof(buf), "%"PRId64, *(int64_t*)dst);break;
    case AV_OPT_TYPE_FLOAT:     ret = snprintf(buf, sizeof(buf), "%f" ,     *(float  *)dst);break;
    case AV_OPT_TYPE_DOUBLE:    ret = snprintf(buf, sizeof(buf), "%f" ,     *(double *)dst);break;
    case AV_OPT_TYPE_VIDEO_RATE:
    case AV_OPT_TYPE_RATIONAL:  ret = snprintf(buf, sizeof(buf), "%d/%d",   ((AVRational*)dst)->num, ((AVRational*)dst)->den);break;
    case AV_OPT_TYPE_CONST:     ret = snprintf(buf, sizeof(buf), "%f" ,     o->default_val.dbl);break;
    case AV_OPT_TYPE_STRING:
        if (*(uint8_t**)dst)
            *out_val = av_strdup(*(uint8_t**)dst);
        else
            *out_val = av_strdup("");
        return 0;
    case AV_OPT_TYPE_BINARY:
        len = *(int*)(((uint8_t *)dst) + sizeof(uint8_t *));
        if ((uint64_t)len*2 + 1 > INT_MAX)
            return AVERROR(EINVAL);
        if (!(*out_val = av_malloc(len*2 + 1)))
            return AVERROR(ENOMEM);
        bin = *(uint8_t**)dst;
        for (i = 0; i < len; i++)
            snprintf(*out_val + i*2, 3, "%02X", bin[i]);
        return 0;
    case AV_OPT_TYPE_IMAGE_SIZE:
        ret = snprintf(buf, sizeof(buf), "%dx%d", ((int *)dst)[0], ((int *)dst)[1]);
        break;
    case AV_OPT_TYPE_PIXEL_FMT:
        ret = snprintf(buf, sizeof(buf), "%s", (char *)av_x_if_null(av_get_pix_fmt_name(*(enum AVPixelFormat *)dst), "none"));
        break;
    case AV_OPT_TYPE_SAMPLE_FMT:
        ret = snprintf(buf, sizeof(buf), "%s", (char *)av_x_if_null(av_get_sample_fmt_name(*(enum AVSampleFormat *)dst), "none"));
        break;
    case AV_OPT_TYPE_DURATION:
        i64 = *(int64_t *)dst;
        ret = snprintf(buf, sizeof(buf), "%"PRIi64"d:%02d:%02d.%06d",
                       i64 / 3600000000, (int)((i64 / 60000000) % 60),
                       (int)((i64 / 1000000) % 60), (int)(i64 % 1000000));
        break;
    case AV_OPT_TYPE_COLOR:
        ret = snprintf(buf, sizeof(buf), "0x%02x%02x%02x%02x", ((int *)dst)[0], ((int *)dst)[1], ((int *)dst)[2], ((int *)dst)[3]);
        break;
    case AV_OPT_TYPE_CHANNEL_LAYOUT:
        i64 = *(int64_t *)dst;
        ret = snprintf(buf, sizeof(buf), "0x%"PRIx64, i64);
        break;
    default:
        return AVERROR(EINVAL);
    }

    if (ret >= sizeof(buf))
        return AVERROR(EINVAL);
    *out_val = av_strdup(buf);
    return 0;
}

static int get_number(void *obj, const char *name, const AVOption **o_out, double *num, int *den, int64_t *intnum,
                      int search_flags)
{
    void *dst, *target_obj;
    const AVOption *o = av_opt_find2(obj, name, NULL, 0, search_flags, &target_obj);
    if (!o || !target_obj)
        goto error;

    dst = ((uint8_t*)target_obj) + o->offset;

    if (o_out) *o_out= o;

    return read_number(o, dst, num, den, intnum);

error:
    *den=*intnum=0;
    return -1;
}

#if FF_API_OLD_AVOPTIONS
double av_get_double(void *obj, const char *name, const AVOption **o_out)
{
    int64_t intnum=1;
    double num=1;
    int den=1;

    if (get_number(obj, name, o_out, &num, &den, &intnum, 0) < 0)
        return NAN;
    return num*intnum/den;
}

AVRational av_get_q(void *obj, const char *name, const AVOption **o_out)
{
    int64_t intnum=1;
    double num=1;
    int den=1;

    if (get_number(obj, name, o_out, &num, &den, &intnum, 0) < 0)
        return (AVRational){0, 0};
    if (num == 1.0 && (int)intnum == intnum)
        return (AVRational){intnum, den};
    else
        return av_d2q(num*intnum/den, 1<<24);
}

int64_t av_get_int(void *obj, const char *name, const AVOption **o_out)
{
    int64_t intnum=1;
    double num=1;
    int den=1;

    if (get_number(obj, name, o_out, &num, &den, &intnum, 0) < 0)
        return -1;
    return num*intnum/den;
}
#endif

int av_opt_get_int(void *obj, const char *name, int search_flags, int64_t *out_val)
{
    int64_t intnum = 1;
    double     num = 1;
    int   ret, den = 1;

    if ((ret = get_number(obj, name, NULL, &num, &den, &intnum, search_flags)) < 0)
        return ret;
    *out_val = num*intnum/den;
    return 0;
}

int av_opt_get_double(void *obj, const char *name, int search_flags, double *out_val)
{
    int64_t intnum = 1;
    double     num = 1;
    int   ret, den = 1;

    if ((ret = get_number(obj, name, NULL, &num, &den, &intnum, search_flags)) < 0)
        return ret;
    *out_val = num*intnum/den;
    return 0;
}

int av_opt_get_q(void *obj, const char *name, int search_flags, AVRational *out_val)
{
    int64_t intnum = 1;
    double     num = 1;
    int   ret, den = 1;

    if ((ret = get_number(obj, name, NULL, &num, &den, &intnum, search_flags)) < 0)
        return ret;

    if (num == 1.0 && (int)intnum == intnum)
        *out_val = (AVRational){intnum, den};
    else
        *out_val = av_d2q(num*intnum/den, 1<<24);
    return 0;
}

int av_opt_get_image_size(void *obj, const char *name, int search_flags, int *w_out, int *h_out)
{
    void *dst, *target_obj;
    const AVOption *o = av_opt_find2(obj, name, NULL, 0, search_flags, &target_obj);
    if (!o || !target_obj)
        return AVERROR_OPTION_NOT_FOUND;
    if (o->type != AV_OPT_TYPE_IMAGE_SIZE) {
        av_log(obj, AV_LOG_ERROR,
               "The value for option '%s' is not an image size.\n", name);
        return AVERROR(EINVAL);
    }

    dst = ((uint8_t*)target_obj) + o->offset;
    if (w_out) *w_out = *(int *)dst;
    if (h_out) *h_out = *((int *)dst+1);
    return 0;
}

int av_opt_get_video_rate(void *obj, const char *name, int search_flags, AVRational *out_val)
{
    int64_t intnum = 1;
    double     num = 1;
    int   ret, den = 1;

    if ((ret = get_number(obj, name, NULL, &num, &den, &intnum, search_flags)) < 0)
        return ret;

    if (num == 1.0 && (int)intnum == intnum)
        *out_val = (AVRational){intnum, den};
    else
        *out_val = av_d2q(num*intnum/den, 1<<24);
    return 0;
}

static int get_format(void *obj, const char *name, int search_flags, int *out_fmt,
                      enum AVOptionType type, const char *desc)
{
    void *dst, *target_obj;
    const AVOption *o = av_opt_find2(obj, name, NULL, 0, search_flags, &target_obj);
    if (!o || !target_obj)
        return AVERROR_OPTION_NOT_FOUND;
    if (o->type != type) {
        av_log(obj, AV_LOG_ERROR,
               "The value for option '%s' is not a %s format.\n", desc, name);
        return AVERROR(EINVAL);
    }

    dst = ((uint8_t*)target_obj) + o->offset;
    *out_fmt = *(int *)dst;
    return 0;
}

int av_opt_get_pixel_fmt(void *obj, const char *name, int search_flags, enum AVPixelFormat *out_fmt)
{
    return get_format(obj, name, search_flags, out_fmt, AV_OPT_TYPE_PIXEL_FMT, "pixel");
}

int av_opt_get_sample_fmt(void *obj, const char *name, int search_flags, enum AVSampleFormat *out_fmt)
{
    return get_format(obj, name, search_flags, out_fmt, AV_OPT_TYPE_SAMPLE_FMT, "sample");
}

int av_opt_get_channel_layout(void *obj, const char *name, int search_flags, int64_t *cl)
{
    void *dst, *target_obj;
    const AVOption *o = av_opt_find2(obj, name, NULL, 0, search_flags, &target_obj);
    if (!o || !target_obj)
        return AVERROR_OPTION_NOT_FOUND;
    if (o->type != AV_OPT_TYPE_CHANNEL_LAYOUT) {
        av_log(obj, AV_LOG_ERROR,
               "The value for option '%s' is not a channel layout.\n", name);
        return AVERROR(EINVAL);
    }

    dst = ((uint8_t*)target_obj) + o->offset;
    *cl = *(int64_t *)dst;
    return 0;
}

int av_opt_flag_is_set(void *obj, const char *field_name, const char *flag_name)
{
    const AVOption *field = av_opt_find(obj, field_name, NULL, 0, 0);
    const AVOption *flag  = av_opt_find(obj, flag_name,
                                        field ? field->unit : NULL, 0, 0);
    int64_t res;

    if (!field || !flag || flag->type != AV_OPT_TYPE_CONST ||
        av_opt_get_int(obj, field_name, 0, &res) < 0)
        return 0;
    return res & flag->default_val.i64;
}

static void log_value(void *av_log_obj, int level, double d)
{
    if      (d == INT_MAX) {
        av_log(av_log_obj, level, "INT_MAX");
    } else if (d == INT_MIN) {
        av_log(av_log_obj, level, "INT_MIN");
    } else if (d == UINT32_MAX) {
        av_log(av_log_obj, level, "UINT32_MAX");
    } else if (d == (double)INT64_MAX) {
        av_log(av_log_obj, level, "I64_MAX");
    } else if (d == INT64_MIN) {
        av_log(av_log_obj, level, "I64_MIN");
    } else if (d == FLT_MAX) {
        av_log(av_log_obj, level, "FLT_MAX");
    } else if (d == FLT_MIN) {
        av_log(av_log_obj, level, "FLT_MIN");
    } else if (d == -FLT_MAX) {
        av_log(av_log_obj, level, "-FLT_MAX");
    } else if (d == -FLT_MIN) {
        av_log(av_log_obj, level, "-FLT_MIN");
    } else if (d == DBL_MAX) {
        av_log(av_log_obj, level, "DBL_MAX");
    } else if (d == DBL_MIN) {
        av_log(av_log_obj, level, "DBL_MIN");
    } else if (d == -DBL_MAX) {
        av_log(av_log_obj, level, "-DBL_MAX");
    } else if (d == -DBL_MIN) {
        av_log(av_log_obj, level, "-DBL_MIN");
    } else {
        av_log(av_log_obj, level, "%g", d);
    }
}

static void opt_list(void *obj, void *av_log_obj, const char *unit,
                     int req_flags, int rej_flags)
{
    const AVOption *opt=NULL;
    AVOptionRanges *r;
    int i;

    while ((opt = av_opt_next(obj, opt))) {
        if (!(opt->flags & req_flags) || (opt->flags & rej_flags))
            continue;

        /* Don't print CONST's on level one.
         * Don't print anything but CONST's on level two.
         * Only print items from the requested unit.
         */
        if (!unit && opt->type==AV_OPT_TYPE_CONST)
            continue;
        else if (unit && opt->type!=AV_OPT_TYPE_CONST)
            continue;
        else if (unit && opt->type==AV_OPT_TYPE_CONST && strcmp(unit, opt->unit))
            continue;
        else if (unit && opt->type == AV_OPT_TYPE_CONST)
            av_log(av_log_obj, AV_LOG_INFO, "     %-15s ", opt->name);
        else
            av_log(av_log_obj, AV_LOG_INFO, "  %s%-17s ",
                   (opt->flags & AV_OPT_FLAG_FILTERING_PARAM) ? "" : "-",
                   opt->name);

        switch (opt->type) {
            case AV_OPT_TYPE_FLAGS:
                av_log(av_log_obj, AV_LOG_INFO, "%-12s ", "<flags>");
                break;
            case AV_OPT_TYPE_INT:
                av_log(av_log_obj, AV_LOG_INFO, "%-12s ", "<int>");
                break;
            case AV_OPT_TYPE_INT64:
                av_log(av_log_obj, AV_LOG_INFO, "%-12s ", "<int64>");
                break;
            case AV_OPT_TYPE_DOUBLE:
                av_log(av_log_obj, AV_LOG_INFO, "%-12s ", "<double>");
                break;
            case AV_OPT_TYPE_FLOAT:
                av_log(av_log_obj, AV_LOG_INFO, "%-12s ", "<float>");
                break;
            case AV_OPT_TYPE_STRING:
                av_log(av_log_obj, AV_LOG_INFO, "%-12s ", "<string>");
                break;
            case AV_OPT_TYPE_RATIONAL:
                av_log(av_log_obj, AV_LOG_INFO, "%-12s ", "<rational>");
                break;
            case AV_OPT_TYPE_BINARY:
                av_log(av_log_obj, AV_LOG_INFO, "%-12s ", "<binary>");
                break;
            case AV_OPT_TYPE_IMAGE_SIZE:
                av_log(av_log_obj, AV_LOG_INFO, "%-12s ", "<image_size>");
                break;
            case AV_OPT_TYPE_VIDEO_RATE:
                av_log(av_log_obj, AV_LOG_INFO, "%-12s ", "<video_rate>");
                break;
            case AV_OPT_TYPE_PIXEL_FMT:
                av_log(av_log_obj, AV_LOG_INFO, "%-12s ", "<pix_fmt>");
                break;
            case AV_OPT_TYPE_SAMPLE_FMT:
                av_log(av_log_obj, AV_LOG_INFO, "%-12s ", "<sample_fmt>");
                break;
            case AV_OPT_TYPE_DURATION:
                av_log(av_log_obj, AV_LOG_INFO, "%-12s ", "<duration>");
                break;
            case AV_OPT_TYPE_COLOR:
                av_log(av_log_obj, AV_LOG_INFO, "%-12s ", "<color>");
                break;
            case AV_OPT_TYPE_CHANNEL_LAYOUT:
                av_log(av_log_obj, AV_LOG_INFO, "%-12s ", "<channel_layout>");
                break;
            case AV_OPT_TYPE_CONST:
            default:
                av_log(av_log_obj, AV_LOG_INFO, "%-12s ", "");
                break;
        }
        av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_ENCODING_PARAM) ? 'E' : '.');
        av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_DECODING_PARAM) ? 'D' : '.');
        av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_FILTERING_PARAM)? 'F' : '.');
        av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_VIDEO_PARAM   ) ? 'V' : '.');
        av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_AUDIO_PARAM   ) ? 'A' : '.');
        av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_SUBTITLE_PARAM) ? 'S' : '.');
        av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_EXPORT)         ? 'X' : '.');
        av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_READONLY)       ? 'R' : '.');

        if (opt->help)
            av_log(av_log_obj, AV_LOG_INFO, " %s", opt->help);

        if (av_opt_query_ranges(&r, obj, opt->name, AV_OPT_SEARCH_FAKE_OBJ) >= 0) {
            switch (opt->type) {
            case AV_OPT_TYPE_INT:
            case AV_OPT_TYPE_INT64:
            case AV_OPT_TYPE_DOUBLE:
            case AV_OPT_TYPE_FLOAT:
            case AV_OPT_TYPE_RATIONAL:
                for (i = 0; i < r->nb_ranges; i++) {
                    av_log(av_log_obj, AV_LOG_INFO, " (from ");
                    log_value(av_log_obj, AV_LOG_INFO, r->range[i]->value_min);
                    av_log(av_log_obj, AV_LOG_INFO, " to ");
                    log_value(av_log_obj, AV_LOG_INFO, r->range[i]->value_max);
                    av_log(av_log_obj, AV_LOG_INFO, ")");
                }
                break;
            }
            av_opt_freep_ranges(&r);
        }

        if (opt->type != AV_OPT_TYPE_CONST  &&
            opt->type != AV_OPT_TYPE_BINARY &&
                !((opt->type == AV_OPT_TYPE_COLOR      ||
                   opt->type == AV_OPT_TYPE_IMAGE_SIZE ||
                   opt->type == AV_OPT_TYPE_STRING     ||
                   opt->type == AV_OPT_TYPE_VIDEO_RATE) &&
                  !opt->default_val.str)) {
            av_log(av_log_obj, AV_LOG_INFO, " (default ");
            switch (opt->type) {
            case AV_OPT_TYPE_FLAGS:
                av_log(av_log_obj, AV_LOG_INFO, "%"PRIX64, opt->default_val.i64);
                break;
            case AV_OPT_TYPE_DURATION:
            case AV_OPT_TYPE_INT:
            case AV_OPT_TYPE_INT64:
                log_value(av_log_obj, AV_LOG_INFO, opt->default_val.i64);
                break;
            case AV_OPT_TYPE_DOUBLE:
            case AV_OPT_TYPE_FLOAT:
                log_value(av_log_obj, AV_LOG_INFO, opt->default_val.dbl);
                break;
            case AV_OPT_TYPE_RATIONAL: {
                AVRational q = av_d2q(opt->default_val.dbl, INT_MAX);
                av_log(av_log_obj, AV_LOG_INFO, "%d/%d", q.num, q.den); }
                break;
            case AV_OPT_TYPE_PIXEL_FMT:
                av_log(av_log_obj, AV_LOG_INFO, "%s", (char *)av_x_if_null(av_get_pix_fmt_name(opt->default_val.i64), "none"));
                break;
            case AV_OPT_TYPE_SAMPLE_FMT:
                av_log(av_log_obj, AV_LOG_INFO, "%s", (char *)av_x_if_null(av_get_sample_fmt_name(opt->default_val.i64), "none"));
                break;
            case AV_OPT_TYPE_COLOR:
            case AV_OPT_TYPE_IMAGE_SIZE:
            case AV_OPT_TYPE_STRING:
            case AV_OPT_TYPE_VIDEO_RATE:
                av_log(av_log_obj, AV_LOG_INFO, "\"%s\"", opt->default_val.str);
                break;
            case AV_OPT_TYPE_CHANNEL_LAYOUT:
                av_log(av_log_obj, AV_LOG_INFO, "0x%"PRIx64, opt->default_val.i64);
                break;
            }
            av_log(av_log_obj, AV_LOG_INFO, ")");
        }

        av_log(av_log_obj, AV_LOG_INFO, "\n");
        if (opt->unit && opt->type != AV_OPT_TYPE_CONST) {
            opt_list(obj, av_log_obj, opt->unit, req_flags, rej_flags);
        }
    }
}

int av_opt_show2(void *obj, void *av_log_obj, int req_flags, int rej_flags)
{
    if (!obj)
        return -1;

    av_log(av_log_obj, AV_LOG_INFO, "%s AVOptions:\n", (*(AVClass**)obj)->class_name);

    opt_list(obj, av_log_obj, NULL, req_flags, rej_flags);

    return 0;
}

void av_opt_set_defaults(void *s)
{
#if FF_API_OLD_AVOPTIONS
    av_opt_set_defaults2(s, 0, 0);
}

void av_opt_set_defaults2(void *s, int mask, int flags)
{
#endif
    const AVClass *class = *(AVClass **)s;
    const AVOption *opt = NULL;
    while ((opt = av_opt_next(s, opt)) != NULL) {
        void *dst = ((uint8_t*)s) + opt->offset;
#if FF_API_OLD_AVOPTIONS
        if ((opt->flags & mask) != flags)
            continue;
#endif

        if (opt->flags & AV_OPT_FLAG_READONLY)
            continue;

        switch (opt->type) {
            case AV_OPT_TYPE_CONST:
                /* Nothing to be done here */
            break;
            case AV_OPT_TYPE_FLAGS:
            case AV_OPT_TYPE_INT:
            case AV_OPT_TYPE_INT64:
            case AV_OPT_TYPE_DURATION:
            case AV_OPT_TYPE_CHANNEL_LAYOUT:
                write_number(s, opt, dst, 1, 1, opt->default_val.i64);
            break;
            case AV_OPT_TYPE_DOUBLE:
            case AV_OPT_TYPE_FLOAT: {
                double val;
                val = opt->default_val.dbl;
                write_number(s, opt, dst, val, 1, 1);
            }
            break;
            case AV_OPT_TYPE_RATIONAL: {
                AVRational val;
                val = av_d2q(opt->default_val.dbl, INT_MAX);
                write_number(s, opt, dst, 1, val.den, val.num);
            }
            break;
            case AV_OPT_TYPE_COLOR:
                set_string_color(s, opt, opt->default_val.str, dst);
                break;
            case AV_OPT_TYPE_STRING:
                set_string(s, opt, opt->default_val.str, dst);
                break;
            case AV_OPT_TYPE_IMAGE_SIZE:
                set_string_image_size(s, opt, opt->default_val.str, dst);
                break;
            case AV_OPT_TYPE_VIDEO_RATE:
                set_string_video_rate(s, opt, opt->default_val.str, dst);
                break;
            case AV_OPT_TYPE_PIXEL_FMT:
#if LIBAVUTIL_VERSION_MAJOR < 54
                if (class->version && class->version < AV_VERSION_INT(52, 10, 100))
                    av_opt_set(s, opt->name, opt->default_val.str, 0);
                else
#endif
                    write_number(s, opt, dst, 1, 1, opt->default_val.i64);
                break;
            case AV_OPT_TYPE_SAMPLE_FMT:
#if LIBAVUTIL_VERSION_MAJOR < 54
                if (class->version && class->version < AV_VERSION_INT(52, 10, 100))
                    av_opt_set(s, opt->name, opt->default_val.str, 0);
                else
#endif
                    write_number(s, opt, dst, 1, 1, opt->default_val.i64);
                break;
            case AV_OPT_TYPE_BINARY:
                /* Cannot set default for binary */
            break;
            default:
                av_log(s, AV_LOG_DEBUG, "AVOption type %d of option %s not implemented yet\n", opt->type, opt->name);
        }
    }
}

/**
 * Store the value in the field in ctx that is named like key.
 * ctx must be an AVClass context, storing is done using AVOptions.
 *
 * @param buf the string to parse, buf will be updated to point at the
 * separator just after the parsed key/value pair
 * @param key_val_sep a 0-terminated list of characters used to
 * separate key from value
 * @param pairs_sep a 0-terminated list of characters used to separate
 * two pairs from each other
 * @return 0 if the key/value pair has been successfully parsed and
 * set, or a negative value corresponding to an AVERROR code in case
 * of error:
 * AVERROR(EINVAL) if the key/value pair cannot be parsed,
 * the error code issued by av_opt_set() if the key/value pair
 * cannot be set
 */
static int parse_key_value_pair(void *ctx, const char **buf,
                                const char *key_val_sep, const char *pairs_sep)
{
    char *key = av_get_token(buf, key_val_sep);
    char *val;
    int ret;

    if (!key)
        return AVERROR(ENOMEM);

    if (*key && strspn(*buf, key_val_sep)) {
        (*buf)++;
        val = av_get_token(buf, pairs_sep);
        if (!val) {
            av_freep(&key);
            return AVERROR(ENOMEM);
        }
    } else {
        av_log(ctx, AV_LOG_ERROR, "Missing key or no key/value separator found after key '%s'\n", key);
        av_free(key);
        return AVERROR(EINVAL);
    }

    av_log(ctx, AV_LOG_DEBUG, "Setting entry with key '%s' to value '%s'\n", key, val);

    ret = av_opt_set(ctx, key, val, AV_OPT_SEARCH_CHILDREN);
    if (ret == AVERROR_OPTION_NOT_FOUND)
        av_log(ctx, AV_LOG_ERROR, "Key '%s' not found.\n", key);

    av_free(key);
    av_free(val);
    return ret;
}

int av_set_options_string(void *ctx, const char *opts,
                          const char *key_val_sep, const char *pairs_sep)
{
    int ret, count = 0;

    if (!opts)
        return 0;

    while (*opts) {
        if ((ret = parse_key_value_pair(ctx, &opts, key_val_sep, pairs_sep)) < 0)
            return ret;
        count++;

        if (*opts)
            opts++;
    }

    return count;
}

#define WHITESPACES " \n\t"

static int is_key_char(char c)
{
    return (unsigned)((c | 32) - 'a') < 26 ||
           (unsigned)(c - '0') < 10 ||
           c == '-' || c == '_' || c == '/' || c == '.';
}

/**
 * Read a key from a string.
 *
 * The key consists of is_key_char characters and must be terminated by a
 * character from the delim string; spaces are ignored.
 *
 * @return  0 for success (even with ellipsis), <0 for failure
 */
static int get_key(const char **ropts, const char *delim, char **rkey)
{
    const char *opts = *ropts;
    const char *key_start, *key_end;

    key_start = opts += strspn(opts, WHITESPACES);
    while (is_key_char(*opts))
        opts++;
    key_end = opts;
    opts += strspn(opts, WHITESPACES);
    if (!*opts || !strchr(delim, *opts))
        return AVERROR(EINVAL);
    opts++;
    if (!(*rkey = av_malloc(key_end - key_start + 1)))
        return AVERROR(ENOMEM);
    memcpy(*rkey, key_start, key_end - key_start);
    (*rkey)[key_end - key_start] = 0;
    *ropts = opts;
    return 0;
}

int av_opt_get_key_value(const char **ropts,
                         const char *key_val_sep, const char *pairs_sep,
                         unsigned flags,
                         char **rkey, char **rval)
{
    int ret;
    char *key = NULL, *val;
    const char *opts = *ropts;

    if ((ret = get_key(&opts, key_val_sep, &key)) < 0 &&
        !(flags & AV_OPT_FLAG_IMPLICIT_KEY))
        return AVERROR(EINVAL);
    if (!(val = av_get_token(&opts, pairs_sep))) {
        av_free(key);
        return AVERROR(ENOMEM);
    }
    *ropts = opts;
    *rkey  = key;
    *rval  = val;
    return 0;
}

int av_opt_set_from_string(void *ctx, const char *opts,
                           const char *const *shorthand,
                           const char *key_val_sep, const char *pairs_sep)
{
    int ret, count = 0;
    const char *dummy_shorthand = NULL;
    char *av_uninit(parsed_key), *av_uninit(value);
    const char *key;

    if (!opts)
        return 0;
    if (!shorthand)
        shorthand = &dummy_shorthand;

    while (*opts) {
        ret = av_opt_get_key_value(&opts, key_val_sep, pairs_sep,
                                   *shorthand ? AV_OPT_FLAG_IMPLICIT_KEY : 0,
                                   &parsed_key, &value);
        if (ret < 0) {
            if (ret == AVERROR(EINVAL))
                av_log(ctx, AV_LOG_ERROR, "No option name near '%s'\n", opts);
            else
                av_log(ctx, AV_LOG_ERROR, "Unable to parse '%s': %s\n", opts,
                       av_err2str(ret));
            return ret;
        }
        if (*opts)
            opts++;
        if (parsed_key) {
            key = parsed_key;
            while (*shorthand) /* discard all remaining shorthand */
                shorthand++;
        } else {
            key = *(shorthand++);
        }

        av_log(ctx, AV_LOG_DEBUG, "Setting '%s' to value '%s'\n", key, value);
        if ((ret = av_opt_set(ctx, key, value, 0)) < 0) {
            if (ret == AVERROR_OPTION_NOT_FOUND)
                av_log(ctx, AV_LOG_ERROR, "Option '%s' not found\n", key);
            av_free(value);
            av_free(parsed_key);
            return ret;
        }

        av_free(value);
        av_free(parsed_key);
        count++;
    }
    return count;
}

void av_opt_free(void *obj)
{
    const AVOption *o = NULL;
    while ((o = av_opt_next(obj, o)))
        if (o->type == AV_OPT_TYPE_STRING || o->type == AV_OPT_TYPE_BINARY)
            av_freep((uint8_t *)obj + o->offset);
}

int av_opt_set_dict(void *obj, AVDictionary **options)
{
    AVDictionaryEntry *t = NULL;
    AVDictionary    *tmp = NULL;
    int ret = 0;

    if (!options)
        return 0;

    while ((t = av_dict_get(*options, "", t, AV_DICT_IGNORE_SUFFIX))) {
        ret = av_opt_set(obj, t->key, t->value, 0);
        if (ret == AVERROR_OPTION_NOT_FOUND)
            av_dict_set(&tmp, t->key, t->value, 0);
        else if (ret < 0) {
            av_log(obj, AV_LOG_ERROR, "Error setting option %s to value %s.\n", t->key, t->value);
            break;
        }
        ret = 0;
    }
    av_dict_free(options);
    *options = tmp;
    return ret;
}

const AVOption *av_opt_find(void *obj, const char *name, const char *unit,
                            int opt_flags, int search_flags)
{
    return av_opt_find2(obj, name, unit, opt_flags, search_flags, NULL);
}

const AVOption *av_opt_find2(void *obj, const char *name, const char *unit,
                             int opt_flags, int search_flags, void **target_obj)
{
    const AVClass  *c;
    const AVOption *o = NULL;

    if(!obj)
        return NULL;

    c= *(AVClass**)obj;

    if (!c)
        return NULL;

    if (search_flags & AV_OPT_SEARCH_CHILDREN) {
        if (search_flags & AV_OPT_SEARCH_FAKE_OBJ) {
            const AVClass *child = NULL;
            while (child = av_opt_child_class_next(c, child))
                if (o = av_opt_find2(&child, name, unit, opt_flags, search_flags, NULL))
                    return o;
        } else {
            void *child = NULL;
            while (child = av_opt_child_next(obj, child))
                if (o = av_opt_find2(child, name, unit, opt_flags, search_flags, target_obj))
                    return o;
        }
    }

    while (o = av_opt_next(obj, o)) {
        if (!strcmp(o->name, name) && (o->flags & opt_flags) == opt_flags &&
            ((!unit && o->type != AV_OPT_TYPE_CONST) ||
             (unit  && o->type == AV_OPT_TYPE_CONST && o->unit && !strcmp(o->unit, unit)))) {
            if (target_obj) {
                if (!(search_flags & AV_OPT_SEARCH_FAKE_OBJ))
                    *target_obj = obj;
                else
                    *target_obj = NULL;
            }
            return o;
        }
    }
    return NULL;
}

void *av_opt_child_next(void *obj, void *prev)
{
    const AVClass *c = *(AVClass**)obj;
    if (c->child_next)
        return c->child_next(obj, prev);
    return NULL;
}

const AVClass *av_opt_child_class_next(const AVClass *parent, const AVClass *prev)
{
    if (parent->child_class_next)
        return parent->child_class_next(prev);
    return NULL;
}

void *av_opt_ptr(const AVClass *class, void *obj, const char *name)
{
    const AVOption *opt= av_opt_find2(&class, name, NULL, 0, AV_OPT_SEARCH_FAKE_OBJ, NULL);
    if(!opt)
        return NULL;
    return (uint8_t*)obj + opt->offset;
}

int av_opt_query_ranges(AVOptionRanges **ranges_arg, void *obj, const char *key, int flags)
{
    int ret;
    const AVClass *c = *(AVClass**)obj;
    int (*callback)(AVOptionRanges **, void *obj, const char *key, int flags) = NULL;

    if (c->version > (52 << 16 | 11 << 8))
        callback = c->query_ranges;

    if (!callback)
        callback = av_opt_query_ranges_default;

    ret = callback(ranges_arg, obj, key, flags);
    if (ret >= 0) {
        if (!(flags & AV_OPT_MULTI_COMPONENT_RANGE))
            ret = 1;
        (*ranges_arg)->nb_components = ret;
    }
    return ret;
}

int av_opt_query_ranges_default(AVOptionRanges **ranges_arg, void *obj, const char *key, int flags)
{
    AVOptionRanges *ranges = av_mallocz(sizeof(*ranges));
    AVOptionRange **range_array = av_mallocz(sizeof(void*));
    AVOptionRange *range = av_mallocz(sizeof(*range));
    const AVOption *field = av_opt_find(obj, key, NULL, 0, flags);
    int ret;

    *ranges_arg = NULL;

    if (!ranges || !range || !range_array || !field) {
        ret = AVERROR(ENOMEM);
        goto fail;
    }

    ranges->range = range_array;
    ranges->range[0] = range;
    ranges->nb_ranges = 1;
    ranges->nb_components = 1;
    range->is_range = 1;
    range->value_min = field->min;
    range->value_max = field->max;

    switch (field->type) {
    case AV_OPT_TYPE_INT:
    case AV_OPT_TYPE_INT64:
    case AV_OPT_TYPE_PIXEL_FMT:
    case AV_OPT_TYPE_SAMPLE_FMT:
    case AV_OPT_TYPE_FLOAT:
    case AV_OPT_TYPE_DOUBLE:
    case AV_OPT_TYPE_DURATION:
    case AV_OPT_TYPE_COLOR:
    case AV_OPT_TYPE_CHANNEL_LAYOUT:
        break;
    case AV_OPT_TYPE_STRING:
        range->component_min = 0;
        range->component_max = 0x10FFFF; // max unicode value
        range->value_min = -1;
        range->value_max = INT_MAX;
        break;
    case AV_OPT_TYPE_RATIONAL:
        range->component_min = INT_MIN;
        range->component_max = INT_MAX;
        break;
    case AV_OPT_TYPE_IMAGE_SIZE:
        range->component_min = 0;
        range->component_max = INT_MAX/128/8;
        range->value_min = 0;
        range->value_max = INT_MAX/8;
        break;
    case AV_OPT_TYPE_VIDEO_RATE:
        range->component_min = 1;
        range->component_max = INT_MAX;
        range->value_min = 1;
        range->value_max = INT_MAX;
        break;
    default:
        ret = AVERROR(ENOSYS);
        goto fail;
    }

    *ranges_arg = ranges;
    return 1;
fail:
    av_free(ranges);
    av_free(range);
    av_free(range_array);
    return ret;
}

void av_opt_freep_ranges(AVOptionRanges **rangesp)
{
    int i;
    AVOptionRanges *ranges = *rangesp;

    if (!ranges)
        return;

    for (i = 0; i < ranges->nb_ranges * ranges->nb_components; i++) {
        AVOptionRange *range = ranges->range[i];
        av_freep(&range->str);
        av_freep(&ranges->range[i]);
    }
    av_freep(&ranges->range);
    av_freep(rangesp);
}

#ifdef TEST

typedef struct TestContext
{
    const AVClass *class;
    int num;
    int toggle;
    char *string;
    int flags;
    AVRational rational;
    AVRational video_rate;
    int w, h;
    enum AVPixelFormat pix_fmt;
    enum AVSampleFormat sample_fmt;
    int64_t duration;
    uint8_t color[4];
    int64_t channel_layout;
} TestContext;

#define OFFSET(x) offsetof(TestContext, x)

#define TEST_FLAG_COOL 01
#define TEST_FLAG_LAME 02
#define TEST_FLAG_MU   04

static const AVOption test_options[]= {
{"num",      "set num",        OFFSET(num),      AV_OPT_TYPE_INT,      {.i64 = 0},       0,        100                 },
{"toggle",   "set toggle",     OFFSET(toggle),   AV_OPT_TYPE_INT,      {.i64 = 0},       0,        1                   },
{"rational", "set rational",   OFFSET(rational), AV_OPT_TYPE_RATIONAL, {.dbl = 0},       0,        10                  },
{"string",   "set string",     OFFSET(string),   AV_OPT_TYPE_STRING,   {.str = "default"}, CHAR_MIN, CHAR_MAX          },
{"flags",    "set flags",      OFFSET(flags),    AV_OPT_TYPE_FLAGS,    {.i64 = 0},       0,        INT_MAX, 0, "flags" },
{"cool",     "set cool flag ", 0,                AV_OPT_TYPE_CONST,    {.i64 = TEST_FLAG_COOL}, INT_MIN,  INT_MAX, 0, "flags" },
{"lame",     "set lame flag ", 0,                AV_OPT_TYPE_CONST,    {.i64 = TEST_FLAG_LAME}, INT_MIN,  INT_MAX, 0, "flags" },
{"mu",       "set mu flag ",   0,                AV_OPT_TYPE_CONST,    {.i64 = TEST_FLAG_MU},   INT_MIN,  INT_MAX, 0, "flags" },
{"size",     "set size",       OFFSET(w),        AV_OPT_TYPE_IMAGE_SIZE,{0},             0,        0                   },
{"pix_fmt",  "set pixfmt",     OFFSET(pix_fmt),  AV_OPT_TYPE_PIXEL_FMT, {.i64 = AV_PIX_FMT_NONE}, -1, INT_MAX},
{"sample_fmt", "set samplefmt", OFFSET(sample_fmt), AV_OPT_TYPE_SAMPLE_FMT, {.i64 = AV_SAMPLE_FMT_NONE}, -1, INT_MAX},
{"video_rate", "set videorate", OFFSET(video_rate), AV_OPT_TYPE_VIDEO_RATE,  {.str = "25"}, 0,     0                   },
{"duration", "set duration",   OFFSET(duration), AV_OPT_TYPE_DURATION, {.i64 = 0}, 0, INT64_MAX},
{"color", "set color",   OFFSET(color), AV_OPT_TYPE_COLOR, {.str = "pink"}, 0, 0},
{"cl", "set channel layout", OFFSET(channel_layout), AV_OPT_TYPE_CHANNEL_LAYOUT, {.i64 = AV_CH_LAYOUT_HEXAGONAL}, 0, INT64_MAX},
{NULL},
};

static const char *test_get_name(void *ctx)
{
    return "test";
}

static const AVClass test_class = {
    "TestContext",
    test_get_name,
    test_options
};

int main(void)
{
    int i;

    printf("\nTesting av_set_options_string()\n");
    {
        TestContext test_ctx = { 0 };
        static const char * const options[] = {
            "",
            ":",
            "=",
            "foo=:",
            ":=foo",
            "=foo",
            "foo=",
            "foo",
            "foo=val",
            "foo==val",
            "toggle=:",
            "string=:",
            "toggle=1 : foo",
            "toggle=100",
            "toggle==1",
            "flags=+mu-lame : num=42: toggle=0",
            "num=42 : string=blahblah",
            "rational=0 : rational=1/2 : rational=1/-1",
            "rational=-1/0",
            "size=1024x768",
            "size=pal",
            "size=bogus",
            "pix_fmt=yuv420p",
            "pix_fmt=2",
            "pix_fmt=bogus",
            "sample_fmt=s16",
            "sample_fmt=2",
            "sample_fmt=bogus",
            "video_rate=pal",
            "video_rate=25",
            "video_rate=30000/1001",
            "video_rate=30/1.001",
            "video_rate=bogus",
            "duration=bogus",
            "duration=123.45",
            "duration=1\\:23\\:45.67",
            "color=blue",
            "color=0x223300",
            "color=0x42FF07AA",
            "cl=stereo+downmix",
            "cl=foo",
        };

        test_ctx.class = &test_class;
        av_opt_set_defaults(&test_ctx);

        av_log_set_level(AV_LOG_DEBUG);

        for (i=0; i < FF_ARRAY_ELEMS(options); i++) {
            av_log(&test_ctx, AV_LOG_DEBUG, "Setting options string '%s'\n", options[i]);
            if (av_set_options_string(&test_ctx, options[i], "=", ":") < 0)
                av_log(&test_ctx, AV_LOG_ERROR, "Error setting options string: '%s'\n", options[i]);
            printf("\n");
        }
        av_opt_free(&test_ctx);
    }

    printf("\nTesting av_opt_set_from_string()\n");
    {
        TestContext test_ctx = { 0 };
        static const char * const options[] = {
            "",
            "5",
            "5:hello",
            "5:hello:size=pal",
            "5:size=pal:hello",
            ":",
            "=",
            " 5 : hello : size = pal ",
            "a_very_long_option_name_that_will_need_to_be_ellipsized_around_here=42"
        };
        static const char * const shorthand[] = { "num", "string", NULL };

        test_ctx.class = &test_class;
        av_opt_set_defaults(&test_ctx);

        av_log_set_level(AV_LOG_DEBUG);

        for (i=0; i < FF_ARRAY_ELEMS(options); i++) {
            av_log(&test_ctx, AV_LOG_DEBUG, "Setting options string '%s'\n", options[i]);
            if (av_opt_set_from_string(&test_ctx, options[i], shorthand, "=", ":") < 0)
                av_log(&test_ctx, AV_LOG_ERROR, "Error setting options string: '%s'\n", options[i]);
            printf("\n");
        }
        av_opt_free(&test_ctx);
    }

    return 0;
}

#endif