AVOptions

AVOptions provide a generic system to declare options on arbitrary structs ("objects"). More...

Modules
	Evaluating option strings
	This group of functions can be used to evaluate option strings and get numbers out of them.
	Option setting functions
	Those functions set the field of obj with the given name to value.
	Option getting functions
	Those functions get a value of the option with the given name from an object.

Data Structures
struct	AVOption
	AVOption. More...
struct	AVOptionRange
	A single allowed range of values, or a single allowed value. More...
struct	AVOptionRanges
	List of AVOptionRange structs. More...

Macros
#define	AV_OPT_SEARCH_CHILDREN   (1 << 0)
	Search in possible children of the given object first. More...
#define	AV_OPT_SEARCH_FAKE_OBJ   (1 << 1)
	The obj passed to av_opt_find() is fake – only a double pointer to AVClass instead of a required pointer to a struct containing AVClass. More...
#define	AV_OPT_ALLOW_NULL   (1 << 2)
	In av_opt_get, return NULL if the option has a pointer type and is set to NULL, rather than returning an empty string. More...
#define	AV_OPT_MULTI_COMPONENT_RANGE   (1 << 12)
	Allows av_opt_query_ranges and av_opt_query_ranges_default to return more than one component for certain option types. More...
#define	AV_OPT_SERIALIZE_SKIP_DEFAULTS   0x00000001
	Serialize options that are not set to default values only. More...
#define	AV_OPT_SERIALIZE_OPT_FLAGS_EXACT   0x00000002
	Serialize options that exactly match opt_flags only. More...

Enumerations
enum	AVOptionType {   AV_OPT_TYPE_FLAGS , AV_OPT_TYPE_INT , AV_OPT_TYPE_INT64 , AV_OPT_TYPE_DOUBLE ,   AV_OPT_TYPE_FLOAT , AV_OPT_TYPE_STRING , AV_OPT_TYPE_RATIONAL , AV_OPT_TYPE_BINARY ,   AV_OPT_TYPE_DICT , AV_OPT_TYPE_UINT64 , AV_OPT_TYPE_CONST , AV_OPT_TYPE_IMAGE_SIZE ,   AV_OPT_TYPE_PIXEL_FMT , AV_OPT_TYPE_SAMPLE_FMT , AV_OPT_TYPE_VIDEO_RATE , AV_OPT_TYPE_DURATION ,   AV_OPT_TYPE_COLOR , AV_OPT_TYPE_CHANNEL_LAYOUT , AV_OPT_TYPE_BOOL , AV_OPT_TYPE_CHLAYOUT }
enum	{ AV_OPT_FLAG_IMPLICIT_KEY = 1 }

Functions
int	av_opt_show2 (void *obj, void *av_log_obj, int req_flags, int rej_flags)
	Show the obj options. More...
void	av_opt_set_defaults (void *s)
	Set the values of all AVOption fields to their default values. More...
void	av_opt_set_defaults2 (void *s, int mask, int flags)
	Set the values of all AVOption fields to their default values. More...
int	av_set_options_string (void *ctx, const char *opts, const char *key_val_sep, const char *pairs_sep)
	Parse the key/value pairs list in opts. More...
int	av_opt_set_from_string (void *ctx, const char *opts, const char *const *shorthand, const char *key_val_sep, const char *pairs_sep)
	Parse the key-value pairs list in opts. More...
void	av_opt_free (void *obj)
	Free all allocated objects in obj. More...
int	av_opt_flag_is_set (void *obj, const char *field_name, const char *flag_name)
	Check whether a particular flag is set in a flags field. More...
int	av_opt_set_dict (void *obj, struct AVDictionary **options)
	Set all the options from a given dictionary on an object. More...
int	av_opt_set_dict2 (void *obj, struct AVDictionary **options, int search_flags)
	Set all the options from a given dictionary on an object. More...
int	av_opt_get_key_value (const char **ropts, const char *key_val_sep, const char *pairs_sep, unsigned flags, char **rkey, char **rval)
	Extract a key-value pair from the beginning of a string. More...
const AVOption *	av_opt_find (void *obj, const char *name, const char *unit, int opt_flags, int search_flags)
	Look for an option in an object. More...
const AVOption *	av_opt_find2 (void *obj, const char *name, const char *unit, int opt_flags, int search_flags, void **target_obj)
	Look for an option in an object. More...
const AVOption *	av_opt_next (const void *obj, const AVOption *prev)
	Iterate over all AVOptions belonging to obj. More...
void *	av_opt_child_next (void *obj, void *prev)
	Iterate over AVOptions-enabled children of obj. More...
const AVClass *	av_opt_child_class_iterate (const AVClass *parent, void **iter)
	Iterate over potential AVOptions-enabled children of parent. More...
void *	av_opt_ptr (const AVClass *avclass, void *obj, const char *name)
	Gets a pointer to the requested field in a struct. More...
void	av_opt_freep_ranges (AVOptionRanges **ranges)
	Free an AVOptionRanges struct and set it to NULL. More...
int	av_opt_query_ranges (AVOptionRanges **, void *obj, const char *key, int flags)
	Get a list of allowed ranges for the given option. More...
int	av_opt_copy (void *dest, const void *src)
	Copy options from src object into dest object. More...
int	av_opt_query_ranges_default (AVOptionRanges **, void *obj, const char *key, int flags)
	Get a default list of allowed ranges for the given option. More...
int	av_opt_is_set_to_default (void *obj, const AVOption *o)
	Check if given option is set to its default value. More...
int	av_opt_is_set_to_default_by_name (void *obj, const char *name, int search_flags)
	Check if given option is set to its default value. More...
int	av_opt_serialize (void *obj, int opt_flags, int flags, char **buffer, const char key_val_sep, const char pairs_sep)
	Serialize object's options. More...

Detailed Description

AVOptions provide a generic system to declare options on arbitrary structs ("objects").

An option can have a help text, a type and a range of possible values. Options may then be enumerated, read and written to.

Implementing AVOptions

This section describes how to add AVOptions capabilities to a struct.

All AVOptions-related information is stored in an AVClass. Therefore the first member of the struct should be a pointer to an AVClass describing it. The option field of the AVClass must be set to a NULL-terminated static array of AVOptions. Each AVOption must have a non-empty name, a type, a default value and for number-type AVOptions also a range of allowed values. It must also declare an offset in bytes from the start of the struct, where the field associated with this AVOption is located. Other fields in the AVOption struct should also be set when applicable, but are not required.

The following example illustrates an AVOptions-enabled struct:

typedef struct test_struct {
    const AVClass *class;
    int      int_opt;
    char    *str_opt;
    uint8_t *bin_opt;
    int      bin_len;
} test_struct;
 
static const AVOption test_options[] = {
  { "test_int", "This is a test option of int type.", offsetof(test_struct, int_opt),
    AV_OPT_TYPE_INT, { .i64 = -1 }, INT_MIN, INT_MAX },
  { "test_str", "This is a test option of string type.", offsetof(test_struct, str_opt),
    AV_OPT_TYPE_STRING },
  { "test_bin", "This is a test option of binary type.", offsetof(test_struct, bin_opt),
    AV_OPT_TYPE_BINARY },
  { NULL },
};
 
static const AVClass test_class = {
    .class_name = "test class",
    .item_name  = av_default_item_name,
    .option     = test_options,
    .version    = LIBAVUTIL_VERSION_INT,
};

Next, when allocating your struct, you must ensure that the AVClass pointer is set to the correct value. Then, av_opt_set_defaults() can be called to initialize defaults. After that the struct is ready to be used with the AVOptions API.

When cleaning up, you may use the av_opt_free() function to automatically free all the allocated string and binary options.

Continuing with the above example:

test_struct *alloc_test_struct(void)
{
    test_struct *ret = av_mallocz(sizeof(*ret));
    ret->class = &test_class;
    av_opt_set_defaults(ret);
    return ret;
}
void free_test_struct(test_struct **foo)
{
    av_opt_free(*foo);
    av_freep(foo);
}

Nesting

It may happen that an AVOptions-enabled struct contains another AVOptions-enabled struct as a member (e.g. AVCodecContext in libavcodec exports generic options, while its priv_data field exports codec-specific options). In such a case, it is possible to set up the parent struct to export a child's options. To do that, simply implement AVClass.child_next() and AVClass.child_class_iterate() in the parent struct's AVClass. Assuming that the test_struct from above now also contains a child_struct field:

typedef struct child_struct {
    AVClass *class;
    int flags_opt;
} child_struct;
static const AVOption child_opts[] = {
    { "test_flags", "This is a test option of flags type.",
      offsetof(child_struct, flags_opt), AV_OPT_TYPE_FLAGS, { .i64 = 0 }, INT_MIN, INT_MAX },
    { NULL },
};
static const AVClass child_class = {
    .class_name = "child class",
    .item_name  = av_default_item_name,
    .option     = child_opts,
    .version    = LIBAVUTIL_VERSION_INT,
};
 
void *child_next(void *obj, void *prev)
{
    test_struct *t = obj;
    if (!prev && t->child_struct)
        return t->child_struct;
    return NULL
}
const AVClass child_class_iterate(void **iter)
{
    const AVClass *c = *iter ? NULL : &child_class;
    *iter = (void*)(uintptr_t)c;
    return c;
}

Putting child_next() and child_class_iterate() as defined above into test_class will now make child_struct's options accessible through test_struct (again, proper setup as described above needs to be done on child_struct right after it is created).

From the above example it might not be clear why both child_next() and child_class_iterate() are needed. The distinction is that child_next() iterates over actually existing objects, while child_class_iterate() iterates over all possible child classes. E.g. if an AVCodecContext was initialized to use a codec which has private options, then its child_next() will return AVCodecContext.priv_data and finish iterating. OTOH child_class_iterate() on AVCodecContext.av_class will iterate over all available codecs with private options.

Named constants

It is possible to create named constants for options. Simply set the unit field of the option the constants should apply to a string and create the constants themselves as options of type AV_OPT_TYPE_CONST with their unit field set to the same string. Their default_val field should contain the value of the named constant. For example, to add some named constants for the test_flags option above, put the following into the child_opts array:

{ "test_flags", "This is a test option of flags type.",
  offsetof(child_struct, flags_opt), AV_OPT_TYPE_FLAGS, { .i64 = 0 }, INT_MIN, INT_MAX, "test_unit" },
{ "flag1", "This is a flag with value 16", 0, AV_OPT_TYPE_CONST, { .i64 = 16 }, 0, 0, "test_unit" },

Using AVOptions

This section deals with accessing options in an AVOptions-enabled struct. Such structs in FFmpeg are e.g. AVCodecContext in libavcodec or AVFormatContext in libavformat.

Examining AVOptions

The basic functions for examining options are av_opt_next(), which iterates over all options defined for one object, and av_opt_find(), which searches for an option with the given name.

The situation is more complicated with nesting. An AVOptions-enabled struct may have AVOptions-enabled children. Passing the AV_OPT_SEARCH_CHILDREN flag to av_opt_find() will make the function search children recursively.

For enumerating there are basically two cases. The first is when you want to get all options that may potentially exist on the struct and its children (e.g. when constructing documentation). In that case you should call av_opt_child_class_iterate() recursively on the parent struct's AVClass. The second case is when you have an already initialized struct with all its children and you want to get all options that can be actually written or read from it. In that case you should call av_opt_child_next() recursively (and av_opt_next() on each result).

Reading and writing AVOptions

When setting options, you often have a string read directly from the user. In such a case, simply passing it to av_opt_set() is enough. For non-string type options, av_opt_set() will parse the string according to the option type.

Similarly av_opt_get() will read any option type and convert it to a string which will be returned. Do not forget that the string is allocated, so you have to free it with av_free().

In some cases it may be more convenient to put all options into an AVDictionary and call av_opt_set_dict() on it. A specific case of this are the format/codec open functions in lavf/lavc which take a dictionary filled with option as a parameter. This makes it possible to set some options that cannot be set otherwise, since e.g. the input file format is not known before the file is actually opened.

Macro Definition Documentation

AV_OPT_SEARCH_CHILDREN

#define AV_OPT_SEARCH_CHILDREN   (1 << 0)

Search in possible children of the given object first.

Examples

filter_audio.c, filtering_audio.c, filtering_video.c, http_multiclient.c, and transcoding.c.

Definition at line 564 of file opt.h.

AV_OPT_SEARCH_FAKE_OBJ

#define AV_OPT_SEARCH_FAKE_OBJ   (1 << 1)

The obj passed to av_opt_find() is fake – only a double pointer to AVClass instead of a required pointer to a struct containing AVClass.

This is useful for searching for options without needing to allocate the corresponding object.

Definition at line 571 of file opt.h.

AV_OPT_ALLOW_NULL

#define AV_OPT_ALLOW_NULL   (1 << 2)

In av_opt_get, return NULL if the option has a pointer type and is set to NULL, rather than returning an empty string.

Definition at line 577 of file opt.h.

AV_OPT_MULTI_COMPONENT_RANGE

#define AV_OPT_MULTI_COMPONENT_RANGE   (1 << 12)

Allows av_opt_query_ranges and av_opt_query_ranges_default to return more than one component for certain option types.

See also

AVOptionRanges for details.

Definition at line 584 of file opt.h.

AV_OPT_SERIALIZE_SKIP_DEFAULTS

#define AV_OPT_SERIALIZE_SKIP_DEFAULTS   0x00000001

Serialize options that are not set to default values only.

Definition at line 864 of file opt.h.

AV_OPT_SERIALIZE_OPT_FLAGS_EXACT

#define AV_OPT_SERIALIZE_OPT_FLAGS_EXACT   0x00000002

Serialize options that exactly match opt_flags only.

Definition at line 865 of file opt.h.

Enumeration Type Documentation

AVOptionType

enum AVOptionType

Enumerator
AV_OPT_TYPE_FLAGS
AV_OPT_TYPE_INT
AV_OPT_TYPE_INT64
AV_OPT_TYPE_DOUBLE
AV_OPT_TYPE_FLOAT
AV_OPT_TYPE_STRING
AV_OPT_TYPE_RATIONAL
AV_OPT_TYPE_BINARY	offset must point to a pointer immediately followed by an int for the length
AV_OPT_TYPE_DICT
AV_OPT_TYPE_UINT64
AV_OPT_TYPE_CONST
AV_OPT_TYPE_IMAGE_SIZE	offset must point to two consecutive integers
AV_OPT_TYPE_PIXEL_FMT
AV_OPT_TYPE_SAMPLE_FMT
AV_OPT_TYPE_VIDEO_RATE	offset must point to AVRational
AV_OPT_TYPE_DURATION
AV_OPT_TYPE_COLOR
AV_OPT_TYPE_CHANNEL_LAYOUT
AV_OPT_TYPE_BOOL
AV_OPT_TYPE_CHLAYOUT

Definition at line 223 of file opt.h.

anonymous enum

anonymous enum

Enumerator
AV_OPT_FLAG_IMPLICIT_KEY	Accept to parse a value without a key; the key will then be returned as NULL.

Definition at line 530 of file opt.h.

Function Documentation

av_opt_show2()

int av_opt_show2	(	void *	obj,
		void *	av_log_obj,
		int	req_flags,
		int	rej_flags
	)

Show the obj options.

Parameters

req_flags	requested flags for the options to show. Show only the options for which it is opt->flags & req_flags.
rej_flags	rejected flags for the options to show. Show only the options for which it is !(opt->flags & req_flags).
av_log_obj	log context to use for showing the options

av_opt_set_defaults()

void av_opt_set_defaults

(

void *

s

)

Set the values of all AVOption fields to their default values.

Parameters

s	an AVOption-enabled struct (its first member must be a pointer to AVClass)

av_opt_set_defaults2()

void av_opt_set_defaults2	(	void *	s,
		int	mask,
		int	flags
	)

Set the values of all AVOption fields to their default values.

Only these AVOption fields for which (opt->flags & mask) == flags will have their default applied to s.

Parameters

s	an AVOption-enabled struct (its first member must be a pointer to AVClass)
mask	combination of AV_OPT_FLAG_*
flags	combination of AV_OPT_FLAG_*

av_set_options_string()

int av_set_options_string	(	void *	ctx,
		const char *	opts,
		const char *	key_val_sep,
		const char *	pairs_sep
	)

Parse the key/value pairs list in opts.

For each key/value pair found, stores the value in the field in ctx that is named like the key. ctx must be an AVClass context, storing is done using AVOptions.

Parameters

opts	options string to parse, may be NULL
key_val_sep	a 0-terminated list of characters used to separate key from value
pairs_sep	a 0-terminated list of characters used to separate two pairs from each other

Returns

the number of successfully set key/value pairs, or a negative value corresponding to an AVERROR code in case of error: AVERROR(EINVAL) if opts cannot be parsed, the error code issued by av_opt_set() if a key/value pair cannot be set

av_opt_set_from_string()

int av_opt_set_from_string	(	void *	ctx,
		const char *	opts,
		const char *const *	shorthand,
		const char *	key_val_sep,
		const char *	pairs_sep
	)

Parse the key-value pairs list in opts.

For each key=value pair found, set the value of the corresponding option in ctx.

Parameters

ctx	the AVClass object to set options on
opts	the options string, key-value pairs separated by a delimiter
shorthand	a NULL-terminated array of options names for shorthand notation: if the first field in opts has no key part, the key is taken from the first element of shorthand; then again for the second, etc., until either opts is finished, shorthand is finished or a named option is found; after that, all options must be named
key_val_sep	a 0-terminated list of characters used to separate key from value, for example '='
pairs_sep	a 0-terminated list of characters used to separate two pairs from each other, for example ':' or ','

Returns

the number of successfully set key=value pairs, or a negative value corresponding to an AVERROR code in case of error: AVERROR(EINVAL) if opts cannot be parsed, the error code issued by av_set_string3() if a key/value pair cannot be set

Options names must use only the following characters: a-z A-Z 0-9 - . / _ Separators must use characters distinct from option names and from each other.

av_opt_free()

void av_opt_free

(

void *

obj

)

Free all allocated objects in obj.

av_opt_flag_is_set()

int av_opt_flag_is_set	(	void *	obj,
		const char *	field_name,
		const char *	flag_name
	)

Check whether a particular flag is set in a flags field.

Parameters

field_name	the name of the flag field option
flag_name	the name of the flag to check

Returns

non-zero if the flag is set, zero if the flag isn't set, isn't of the right type, or the flags field doesn't exist.

av_opt_set_dict()

int av_opt_set_dict	(	void *	obj,
		struct AVDictionary **	options
	)

Set all the options from a given dictionary on an object.

Parameters

obj	a struct whose first element is a pointer to AVClass
options	options to process. This dictionary will be freed and replaced by a new one containing all options not found in obj. Of course this new dictionary needs to be freed by caller with av_dict_free().

Returns

0 on success, a negative AVERROR if some option was found in obj, but could not be set.

See also

av_dict_copy()

av_opt_set_dict2()

int av_opt_set_dict2	(	void *	obj,
		struct AVDictionary **	options,
		int	search_flags
	)

Set all the options from a given dictionary on an object.

Parameters

obj	a struct whose first element is a pointer to AVClass
options	options to process. This dictionary will be freed and replaced by a new one containing all options not found in obj. Of course this new dictionary needs to be freed by caller with av_dict_free().
search_flags	A combination of AV_OPT_SEARCH_*.

Returns

0 on success, a negative AVERROR if some option was found in obj, but could not be set.

See also

av_dict_copy()

av_opt_get_key_value()

int av_opt_get_key_value	(	const char **	ropts,
		const char *	key_val_sep,
		const char *	pairs_sep,
		unsigned	flags,
		char **	rkey,
		char **	rval
	)

Extract a key-value pair from the beginning of a string.

Parameters

ropts	pointer to the options string, will be updated to point to the rest of the string (one of the pairs_sep or the final NUL)
key_val_sep	a 0-terminated list of characters used to separate key from value, for example '='
pairs_sep	a 0-terminated list of characters used to separate two pairs from each other, for example ':' or ','
flags	flags; see the AV_OPT_FLAG_* values below
rkey	parsed key; must be freed using av_free()
rval	parsed value; must be freed using av_free()

Returns

>=0 for success, or a negative value corresponding to an AVERROR code in case of error; in particular: AVERROR(EINVAL) if no key is present

av_opt_find()

const AVOption * av_opt_find	(	void *	obj,
		const char *	name,
		const char *	unit,
		int	opt_flags,
		int	search_flags
	)

Look for an option in an object.

Consider only options which have all the specified flags set.

Parameters

[in]	obj	A pointer to a struct whose first element is a pointer to an AVClass. Alternatively a double pointer to an AVClass, if AV_OPT_SEARCH_FAKE_OBJ search flag is set.
[in]	name	The name of the option to look for.
[in]	unit	When searching for named constants, name of the unit it belongs to.
	opt_flags	Find only options with all the specified flags set (AV_OPT_FLAG).
	search_flags	A combination of AV_OPT_SEARCH_*.

Returns

A pointer to the option found, or NULL if no option was found.

Note

Options found with AV_OPT_SEARCH_CHILDREN flag may not be settable directly with av_opt_set(). Use special calls which take an options AVDictionary (e.g. avformat_open_input()) to set options found with this flag.

av_opt_find2()

const AVOption * av_opt_find2	(	void *	obj,
		const char *	name,
		const char *	unit,
		int	opt_flags,
		int	search_flags,
		void **	target_obj
	)

Look for an option in an object.

Consider only options which have all the specified flags set.

Parameters

[in]	obj	A pointer to a struct whose first element is a pointer to an AVClass. Alternatively a double pointer to an AVClass, if AV_OPT_SEARCH_FAKE_OBJ search flag is set.
[in]	name	The name of the option to look for.
[in]	unit	When searching for named constants, name of the unit it belongs to.
	opt_flags	Find only options with all the specified flags set (AV_OPT_FLAG).
	search_flags	A combination of AV_OPT_SEARCH_*.
[out]	target_obj	if non-NULL, an object to which the option belongs will be written here. It may be different from obj if AV_OPT_SEARCH_CHILDREN is present in search_flags. This parameter is ignored if search_flags contain AV_OPT_SEARCH_FAKE_OBJ.

Returns

A pointer to the option found, or NULL if no option was found.

av_opt_next()

const AVOption * av_opt_next	(	const void *	obj,
		const AVOption *	prev
	)

Iterate over all AVOptions belonging to obj.

Parameters

obj	an AVOptions-enabled struct or a double pointer to an AVClass describing it.
prev	result of the previous call to av_opt_next() on this object or NULL

Returns

next AVOption or NULL

av_opt_child_next()

void * av_opt_child_next	(	void *	obj,
		void *	prev
	)

Iterate over AVOptions-enabled children of obj.

Parameters

prev	result of a previous call to this function or NULL

Returns

next AVOptions-enabled child or NULL

av_opt_child_class_iterate()

const AVClass * av_opt_child_class_iterate	(	const AVClass *	parent,
		void **	iter
	)

Iterate over potential AVOptions-enabled children of parent.

Parameters

iter	a pointer where iteration state is stored.

Returns

AVClass corresponding to next potential child or NULL

av_opt_ptr()

void * av_opt_ptr	(	const AVClass *	avclass,
		void *	obj,
		const char *	name
	)

Gets a pointer to the requested field in a struct.

This function allows accessing a struct even when its fields are moved or renamed since the application making the access has been compiled,

Returns

a pointer to the field, it can be cast to the correct type and read or written to.

av_opt_freep_ranges()

void av_opt_freep_ranges

(

AVOptionRanges **

ranges

)

Free an AVOptionRanges struct and set it to NULL.

av_opt_query_ranges()

int av_opt_query_ranges	(	AVOptionRanges **	,
		void *	obj,
		const char *	key,
		int	flags
	)

Get a list of allowed ranges for the given option.

The returned list may depend on other fields in obj like for example profile.

Parameters

flags

is a bitmask of flags, undefined flags should not be set and should be ignored AV_OPT_SEARCH_FAKE_OBJ indicates that the obj is a double pointer to a AVClass instead of a full instance AV_OPT_MULTI_COMPONENT_RANGE indicates that function may return more than one component,

See also

AVOptionRanges

The result must be freed with av_opt_freep_ranges.

Returns

number of compontents returned on success, a negative errro code otherwise

av_opt_copy()

int av_opt_copy	(	void *	dest,
		const void *	src
	)

Copy options from src object into dest object.

The underlying AVClass of both src and dest must coincide. The guarantee below does not apply if this is not fulfilled.

Options that require memory allocation (e.g. string or binary) are malloc'ed in dest object. Original memory allocated for such options is freed unless both src and dest options points to the same memory.

Even on error it is guaranteed that allocated options from src and dest no longer alias each other afterwards; in particular calling av_opt_free() on both src and dest is safe afterwards if dest has been memdup'ed from src.

Parameters

dest	Object to copy from
src	Object to copy into

Returns

0 on success, negative on error

av_opt_query_ranges_default()

int av_opt_query_ranges_default	(	AVOptionRanges **	,
		void *	obj,
		const char *	key,
		int	flags
	)

Get a default list of allowed ranges for the given option.

This list is constructed without using the AVClass.query_ranges() callback and can be used as fallback from within the callback.

Parameters

flags

is a bitmask of flags, undefined flags should not be set and should be ignored AV_OPT_SEARCH_FAKE_OBJ indicates that the obj is a double pointer to a AVClass instead of a full instance AV_OPT_MULTI_COMPONENT_RANGE indicates that function may return more than one component,

See also

AVOptionRanges

The result must be freed with av_opt_free_ranges.

Returns

number of compontents returned on success, a negative errro code otherwise

av_opt_is_set_to_default()

int av_opt_is_set_to_default	(	void *	obj,
		const AVOption *	o
	)

Check if given option is set to its default value.

Options o must belong to the obj. This function must not be called to check child's options state.

See also

av_opt_is_set_to_default_by_name().

Parameters

obj	AVClass object to check option on
o	option to be checked

Returns

>0 when option is set to its default, 0 when option is not set its default, <0 on error

av_opt_is_set_to_default_by_name()

int av_opt_is_set_to_default_by_name	(	void *	obj,
		const char *	name,
		int	search_flags
	)

Check if given option is set to its default value.

Parameters

obj	AVClass object to check option on
name	option name
search_flags	combination of AV_OPT_SEARCH_*

Returns

>0 when option is set to its default, 0 when option is not set its default, <0 on error

av_opt_serialize()

int av_opt_serialize	(	void *	obj,
		int	opt_flags,
		int	flags,
		char **	buffer,
		const char	key_val_sep,
		const char	pairs_sep
	)

Serialize object's options.

Create a string containing object's serialized options. Such string may be passed back to av_opt_set_from_string() in order to restore option values. A key/value or pairs separator occurring in the serialized value or name string are escaped through the av_escape() function.

Parameters

[in]	obj	AVClass object to serialize
[in]	opt_flags	serialize options with all the specified flags set (AV_OPT_FLAG)
[in]	flags	combination of AV_OPT_SERIALIZE_* flags
[out]	buffer	Pointer to buffer that will be allocated with string containg serialized options. Buffer must be freed by the caller when is no longer needed.
[in]	key_val_sep	character used to separate key from value
[in]	pairs_sep	character used to separate two pairs from each other

Returns

>= 0 on success, negative on error

Warning

Separators cannot be neither '\' nor '\0'. They also cannot be the same.