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opt.h
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1 /*
2  * AVOptions
3  * copyright (c) 2005 Michael Niedermayer <michaelni@gmx.at>
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #ifndef AVUTIL_OPT_H
23 #define AVUTIL_OPT_H
24 
25 /**
26  * @file
27  * AVOptions
28  */
29 
30 #include "rational.h"
31 #include "avutil.h"
32 #include "dict.h"
33 #include "log.h"
34 #include "pixfmt.h"
35 #include "samplefmt.h"
36 #include "version.h"
37 
38 /**
39  * @defgroup avoptions AVOptions
40  * @ingroup lavu_data
41  * @{
42  * AVOptions provide a generic system to declare options on arbitrary structs
43  * ("objects"). An option can have a help text, a type and a range of possible
44  * values. Options may then be enumerated, read and written to.
45  *
46  * @section avoptions_implement Implementing AVOptions
47  * This section describes how to add AVOptions capabilities to a struct.
48  *
49  * All AVOptions-related information is stored in an AVClass. Therefore
50  * the first member of the struct should be a pointer to an AVClass describing it.
51  * The option field of the AVClass must be set to a NULL-terminated static array
52  * of AVOptions. Each AVOption must have a non-empty name, a type, a default
53  * value and for number-type AVOptions also a range of allowed values. It must
54  * also declare an offset in bytes from the start of the struct, where the field
55  * associated with this AVOption is located. Other fields in the AVOption struct
56  * should also be set when applicable, but are not required.
57  *
58  * The following example illustrates an AVOptions-enabled struct:
59  * @code
60  * typedef struct test_struct {
61  * AVClass *class;
62  * int int_opt;
63  * char *str_opt;
64  * uint8_t *bin_opt;
65  * int bin_len;
66  * } test_struct;
67  *
68  * static const AVOption test_options[] = {
69  * { "test_int", "This is a test option of int type.", offsetof(test_struct, int_opt),
70  * AV_OPT_TYPE_INT, { .i64 = -1 }, INT_MIN, INT_MAX },
71  * { "test_str", "This is a test option of string type.", offsetof(test_struct, str_opt),
72  * AV_OPT_TYPE_STRING },
73  * { "test_bin", "This is a test option of binary type.", offsetof(test_struct, bin_opt),
74  * AV_OPT_TYPE_BINARY },
75  * { NULL },
76  * };
77  *
78  * static const AVClass test_class = {
79  * .class_name = "test class",
80  * .item_name = av_default_item_name,
81  * .option = test_options,
82  * .version = LIBAVUTIL_VERSION_INT,
83  * };
84  * @endcode
85  *
86  * Next, when allocating your struct, you must ensure that the AVClass pointer
87  * is set to the correct value. Then, av_opt_set_defaults() can be called to
88  * initialize defaults. After that the struct is ready to be used with the
89  * AVOptions API.
90  *
91  * When cleaning up, you may use the av_opt_free() function to automatically
92  * free all the allocated string and binary options.
93  *
94  * Continuing with the above example:
95  *
96  * @code
97  * test_struct *alloc_test_struct(void)
98  * {
99  * test_struct *ret = av_malloc(sizeof(*ret));
100  * ret->class = &test_class;
101  * av_opt_set_defaults(ret);
102  * return ret;
103  * }
104  * void free_test_struct(test_struct **foo)
105  * {
106  * av_opt_free(*foo);
107  * av_freep(foo);
108  * }
109  * @endcode
110  *
111  * @subsection avoptions_implement_nesting Nesting
112  * It may happen that an AVOptions-enabled struct contains another
113  * AVOptions-enabled struct as a member (e.g. AVCodecContext in
114  * libavcodec exports generic options, while its priv_data field exports
115  * codec-specific options). In such a case, it is possible to set up the
116  * parent struct to export a child's options. To do that, simply
117  * implement AVClass.child_next() and AVClass.child_class_next() in the
118  * parent struct's AVClass.
119  * Assuming that the test_struct from above now also contains a
120  * child_struct field:
121  *
122  * @code
123  * typedef struct child_struct {
124  * AVClass *class;
125  * int flags_opt;
126  * } child_struct;
127  * static const AVOption child_opts[] = {
128  * { "test_flags", "This is a test option of flags type.",
129  * offsetof(child_struct, flags_opt), AV_OPT_TYPE_FLAGS, { .i64 = 0 }, INT_MIN, INT_MAX },
130  * { NULL },
131  * };
132  * static const AVClass child_class = {
133  * .class_name = "child class",
134  * .item_name = av_default_item_name,
135  * .option = child_opts,
136  * .version = LIBAVUTIL_VERSION_INT,
137  * };
138  *
139  * void *child_next(void *obj, void *prev)
140  * {
141  * test_struct *t = obj;
142  * if (!prev && t->child_struct)
143  * return t->child_struct;
144  * return NULL
145  * }
146  * const AVClass child_class_next(const AVClass *prev)
147  * {
148  * return prev ? NULL : &child_class;
149  * }
150  * @endcode
151  * Putting child_next() and child_class_next() as defined above into
152  * test_class will now make child_struct's options accessible through
153  * test_struct (again, proper setup as described above needs to be done on
154  * child_struct right after it is created).
155  *
156  * From the above example it might not be clear why both child_next()
157  * and child_class_next() are needed. The distinction is that child_next()
158  * iterates over actually existing objects, while child_class_next()
159  * iterates over all possible child classes. E.g. if an AVCodecContext
160  * was initialized to use a codec which has private options, then its
161  * child_next() will return AVCodecContext.priv_data and finish
162  * iterating. OTOH child_class_next() on AVCodecContext.av_class will
163  * iterate over all available codecs with private options.
164  *
165  * @subsection avoptions_implement_named_constants Named constants
166  * It is possible to create named constants for options. Simply set the unit
167  * field of the option the constants should apply to a string and
168  * create the constants themselves as options of type AV_OPT_TYPE_CONST
169  * with their unit field set to the same string.
170  * Their default_val field should contain the value of the named
171  * constant.
172  * For example, to add some named constants for the test_flags option
173  * above, put the following into the child_opts array:
174  * @code
175  * { "test_flags", "This is a test option of flags type.",
176  * offsetof(child_struct, flags_opt), AV_OPT_TYPE_FLAGS, { .i64 = 0 }, INT_MIN, INT_MAX, "test_unit" },
177  * { "flag1", "This is a flag with value 16", 0, AV_OPT_TYPE_CONST, { .i64 = 16 }, 0, 0, "test_unit" },
178  * @endcode
179  *
180  * @section avoptions_use Using AVOptions
181  * This section deals with accessing options in an AVOptions-enabled struct.
182  * Such structs in FFmpeg are e.g. AVCodecContext in libavcodec or
183  * AVFormatContext in libavformat.
184  *
185  * @subsection avoptions_use_examine Examining AVOptions
186  * The basic functions for examining options are av_opt_next(), which iterates
187  * over all options defined for one object, and av_opt_find(), which searches
188  * for an option with the given name.
189  *
190  * The situation is more complicated with nesting. An AVOptions-enabled struct
191  * may have AVOptions-enabled children. Passing the AV_OPT_SEARCH_CHILDREN flag
192  * to av_opt_find() will make the function search children recursively.
193  *
194  * For enumerating there are basically two cases. The first is when you want to
195  * get all options that may potentially exist on the struct and its children
196  * (e.g. when constructing documentation). In that case you should call
197  * av_opt_child_class_next() recursively on the parent struct's AVClass. The
198  * second case is when you have an already initialized struct with all its
199  * children and you want to get all options that can be actually written or read
200  * from it. In that case you should call av_opt_child_next() recursively (and
201  * av_opt_next() on each result).
202  *
203  * @subsection avoptions_use_get_set Reading and writing AVOptions
204  * When setting options, you often have a string read directly from the
205  * user. In such a case, simply passing it to av_opt_set() is enough. For
206  * non-string type options, av_opt_set() will parse the string according to the
207  * option type.
208  *
209  * Similarly av_opt_get() will read any option type and convert it to a string
210  * which will be returned. Do not forget that the string is allocated, so you
211  * have to free it with av_free().
212  *
213  * In some cases it may be more convenient to put all options into an
214  * AVDictionary and call av_opt_set_dict() on it. A specific case of this
215  * are the format/codec open functions in lavf/lavc which take a dictionary
216  * filled with option as a parameter. This allows to set some options
217  * that cannot be set otherwise, since e.g. the input file format is not known
218  * before the file is actually opened.
219  */
220 
229  AV_OPT_TYPE_BINARY, ///< offset must point to a pointer immediately followed by an int for the length
232  AV_OPT_TYPE_IMAGE_SIZE = MKBETAG('S','I','Z','E'), ///< offset must point to two consecutive integers
233  AV_OPT_TYPE_PIXEL_FMT = MKBETAG('P','F','M','T'),
234  AV_OPT_TYPE_SAMPLE_FMT = MKBETAG('S','F','M','T'),
235  AV_OPT_TYPE_VIDEO_RATE = MKBETAG('V','R','A','T'), ///< offset must point to AVRational
236  AV_OPT_TYPE_DURATION = MKBETAG('D','U','R',' '),
237  AV_OPT_TYPE_COLOR = MKBETAG('C','O','L','R'),
239 #if FF_API_OLD_AVOPTIONS
247  FF_OPT_TYPE_BINARY, ///< offset must point to a pointer immediately followed by an int for the length
249 #endif
250 };
251 
252 /**
253  * AVOption
254  */
255 typedef struct AVOption {
256  const char *name;
257 
258  /**
259  * short English help text
260  * @todo What about other languages?
261  */
262  const char *help;
263 
264  /**
265  * The offset relative to the context structure where the option
266  * value is stored. It should be 0 for named constants.
267  */
268  int offset;
270 
271  /**
272  * the default value for scalar options
273  */
274  union {
275  int64_t i64;
276  double dbl;
277  const char *str;
278  /* TODO those are unused now */
280  } default_val;
281  double min; ///< minimum valid value for the option
282  double max; ///< maximum valid value for the option
283 
284  int flags;
285 #define AV_OPT_FLAG_ENCODING_PARAM 1 ///< a generic parameter which can be set by the user for muxing or encoding
286 #define AV_OPT_FLAG_DECODING_PARAM 2 ///< a generic parameter which can be set by the user for demuxing or decoding
287 #if FF_API_OPT_TYPE_METADATA
288 #define AV_OPT_FLAG_METADATA 4 ///< some data extracted or inserted into the file like title, comment, ...
289 #endif
290 #define AV_OPT_FLAG_AUDIO_PARAM 8
291 #define AV_OPT_FLAG_VIDEO_PARAM 16
292 #define AV_OPT_FLAG_SUBTITLE_PARAM 32
293 /**
294  * The option is inteded for exporting values to the caller.
295  */
296 #define AV_OPT_FLAG_EXPORT 64
297 /**
298  * The option may not be set through the AVOptions API, only read.
299  * This flag only makes sense when AV_OPT_FLAG_EXPORT is also set.
300  */
301 #define AV_OPT_FLAG_READONLY 128
302 #define AV_OPT_FLAG_FILTERING_PARAM (1<<16) ///< a generic parameter which can be set by the user for filtering
303 //FIXME think about enc-audio, ... style flags
304 
305  /**
306  * The logical unit to which the option belongs. Non-constant
307  * options and corresponding named constants share the same
308  * unit. May be NULL.
309  */
310  const char *unit;
311 } AVOption;
312 
313 /**
314  * A single allowed range of values, or a single allowed value.
315  */
316 typedef struct AVOptionRange {
317  const char *str;
318  /**
319  * Value range.
320  * For string ranges this represents the min/max length.
321  * For dimensions this represents the min/max pixel count or width/height in multi-component case.
322  */
324  /**
325  * Value's component range.
326  * For string this represents the unicode range for chars, 0-127 limits to ASCII.
327  */
329  /**
330  * Range flag.
331  * If set to 1 the struct encodes a range, if set to 0 a single value.
332  */
333  int is_range;
334 } AVOptionRange;
335 
336 /**
337  * List of AVOptionRange structs.
338  */
339 typedef struct AVOptionRanges {
340  /**
341  * Array of option ranges.
342  *
343  * Most of option types use just one component.
344  * Following describes multi-component option types:
345  *
346  * AV_OPT_TYPE_IMAGE_SIZE:
347  * component index 0: range of pixel count (width * height).
348  * component index 1: range of width.
349  * component index 2: range of height.
350  *
351  * @note To obtain multi-component version of this structure, user must
352  * provide AV_OPT_MULTI_COMPONENT_RANGE to av_opt_query_ranges or
353  * av_opt_query_ranges_default function.
354  *
355  * Multi-component range can be read as in following example:
356  *
357  * @code
358  * int range_index, component_index;
359  * AVOptionRanges *ranges;
360  * AVOptionRange *range[3]; //may require more than 3 in the future.
361  * av_opt_query_ranges(&ranges, obj, key, AV_OPT_MULTI_COMPONENT_RANGE);
362  * for (range_index = 0; range_index < ranges->nb_ranges; range_index++) {
363  * for (component_index = 0; component_index < ranges->nb_components; component_index++)
364  * range[component_index] = ranges->range[ranges->nb_ranges * component_index + range_index];
365  * //do something with range here.
366  * }
367  * av_opt_freep_ranges(&ranges);
368  * @endcode
369  */
371  /**
372  * Number of ranges per component.
373  */
375  /**
376  * Number of componentes.
377  */
380 
381 
382 #if FF_API_OLD_AVOPTIONS
383 /**
384  * Set the field of obj with the given name to value.
385  *
386  * @param[in] obj A struct whose first element is a pointer to an
387  * AVClass.
388  * @param[in] name the name of the field to set
389  * @param[in] val The value to set. If the field is not of a string
390  * type, then the given string is parsed.
391  * SI postfixes and some named scalars are supported.
392  * If the field is of a numeric type, it has to be a numeric or named
393  * scalar. Behavior with more than one scalar and +- infix operators
394  * is undefined.
395  * If the field is of a flags type, it has to be a sequence of numeric
396  * scalars or named flags separated by '+' or '-'. Prefixing a flag
397  * with '+' causes it to be set without affecting the other flags;
398  * similarly, '-' unsets a flag.
399  * @param[out] o_out if non-NULL put here a pointer to the AVOption
400  * found
401  * @param alloc this parameter is currently ignored
402  * @return 0 if the value has been set, or an AVERROR code in case of
403  * error:
404  * AVERROR_OPTION_NOT_FOUND if no matching option exists
405  * AVERROR(ERANGE) if the value is out of range
406  * AVERROR(EINVAL) if the value is not valid
407  * @deprecated use av_opt_set()
408  */
410 int av_set_string3(void *obj, const char *name, const char *val, int alloc, const AVOption **o_out);
411 
412 attribute_deprecated const AVOption *av_set_double(void *obj, const char *name, double n);
413 attribute_deprecated const AVOption *av_set_q(void *obj, const char *name, AVRational n);
414 attribute_deprecated const AVOption *av_set_int(void *obj, const char *name, int64_t n);
415 
416 double av_get_double(void *obj, const char *name, const AVOption **o_out);
417 AVRational av_get_q(void *obj, const char *name, const AVOption **o_out);
418 int64_t av_get_int(void *obj, const char *name, const AVOption **o_out);
419 attribute_deprecated const char *av_get_string(void *obj, const char *name, const AVOption **o_out, char *buf, int buf_len);
421 #endif
422 
423 /**
424  * Show the obj options.
425  *
426  * @param req_flags requested flags for the options to show. Show only the
427  * options for which it is opt->flags & req_flags.
428  * @param rej_flags rejected flags for the options to show. Show only the
429  * options for which it is !(opt->flags & req_flags).
430  * @param av_log_obj log context to use for showing the options
431  */
432 int av_opt_show2(void *obj, void *av_log_obj, int req_flags, int rej_flags);
433 
434 /**
435  * Set the values of all AVOption fields to their default values.
436  *
437  * @param s an AVOption-enabled struct (its first member must be a pointer to AVClass)
438  */
439 void av_opt_set_defaults(void *s);
440 
441 #if FF_API_OLD_AVOPTIONS
443 void av_opt_set_defaults2(void *s, int mask, int flags);
444 #endif
445 
446 /**
447  * Parse the key/value pairs list in opts. For each key/value pair
448  * found, stores the value in the field in ctx that is named like the
449  * key. ctx must be an AVClass context, storing is done using
450  * AVOptions.
451  *
452  * @param opts options string to parse, may be NULL
453  * @param key_val_sep a 0-terminated list of characters used to
454  * separate key from value
455  * @param pairs_sep a 0-terminated list of characters used to separate
456  * two pairs from each other
457  * @return the number of successfully set key/value pairs, or a negative
458  * value corresponding to an AVERROR code in case of error:
459  * AVERROR(EINVAL) if opts cannot be parsed,
460  * the error code issued by av_opt_set() if a key/value pair
461  * cannot be set
462  */
463 int av_set_options_string(void *ctx, const char *opts,
464  const char *key_val_sep, const char *pairs_sep);
465 
466 /**
467  * Parse the key-value pairs list in opts. For each key=value pair found,
468  * set the value of the corresponding option in ctx.
469  *
470  * @param ctx the AVClass object to set options on
471  * @param opts the options string, key-value pairs separated by a
472  * delimiter
473  * @param shorthand a NULL-terminated array of options names for shorthand
474  * notation: if the first field in opts has no key part,
475  * the key is taken from the first element of shorthand;
476  * then again for the second, etc., until either opts is
477  * finished, shorthand is finished or a named option is
478  * found; after that, all options must be named
479  * @param key_val_sep a 0-terminated list of characters used to separate
480  * key from value, for example '='
481  * @param pairs_sep a 0-terminated list of characters used to separate
482  * two pairs from each other, for example ':' or ','
483  * @return the number of successfully set key=value pairs, or a negative
484  * value corresponding to an AVERROR code in case of error:
485  * AVERROR(EINVAL) if opts cannot be parsed,
486  * the error code issued by av_set_string3() if a key/value pair
487  * cannot be set
488  *
489  * Options names must use only the following characters: a-z A-Z 0-9 - . / _
490  * Separators must use characters distinct from option names and from each
491  * other.
492  */
493 int av_opt_set_from_string(void *ctx, const char *opts,
494  const char *const *shorthand,
495  const char *key_val_sep, const char *pairs_sep);
496 /**
497  * Free all allocated objects in obj.
498  */
499 void av_opt_free(void *obj);
500 
501 /**
502  * Check whether a particular flag is set in a flags field.
503  *
504  * @param field_name the name of the flag field option
505  * @param flag_name the name of the flag to check
506  * @return non-zero if the flag is set, zero if the flag isn't set,
507  * isn't of the right type, or the flags field doesn't exist.
508  */
509 int av_opt_flag_is_set(void *obj, const char *field_name, const char *flag_name);
510 
511 /**
512  * Set all the options from a given dictionary on an object.
513  *
514  * @param obj a struct whose first element is a pointer to AVClass
515  * @param options options to process. This dictionary will be freed and replaced
516  * by a new one containing all options not found in obj.
517  * Of course this new dictionary needs to be freed by caller
518  * with av_dict_free().
519  *
520  * @return 0 on success, a negative AVERROR if some option was found in obj,
521  * but could not be set.
522  *
523  * @see av_dict_copy()
524  */
525 int av_opt_set_dict(void *obj, struct AVDictionary **options);
526 
527 
528 /**
529  * Set all the options from a given dictionary on an object.
530  *
531  * @param obj a struct whose first element is a pointer to AVClass
532  * @param options options to process. This dictionary will be freed and replaced
533  * by a new one containing all options not found in obj.
534  * Of course this new dictionary needs to be freed by caller
535  * with av_dict_free().
536  * @param search_flags A combination of AV_OPT_SEARCH_*.
537  *
538  * @return 0 on success, a negative AVERROR if some option was found in obj,
539  * but could not be set.
540  *
541  * @see av_dict_copy()
542  */
543 int av_opt_set_dict2(void *obj, struct AVDictionary **options, int search_flags);
544 
545 /**
546  * Extract a key-value pair from the beginning of a string.
547  *
548  * @param ropts pointer to the options string, will be updated to
549  * point to the rest of the string (one of the pairs_sep
550  * or the final NUL)
551  * @param key_val_sep a 0-terminated list of characters used to separate
552  * key from value, for example '='
553  * @param pairs_sep a 0-terminated list of characters used to separate
554  * two pairs from each other, for example ':' or ','
555  * @param flags flags; see the AV_OPT_FLAG_* values below
556  * @param rkey parsed key; must be freed using av_free()
557  * @param rval parsed value; must be freed using av_free()
558  *
559  * @return >=0 for success, or a negative value corresponding to an
560  * AVERROR code in case of error; in particular:
561  * AVERROR(EINVAL) if no key is present
562  *
563  */
564 int av_opt_get_key_value(const char **ropts,
565  const char *key_val_sep, const char *pairs_sep,
566  unsigned flags,
567  char **rkey, char **rval);
568 
569 enum {
570 
571  /**
572  * Accept to parse a value without a key; the key will then be returned
573  * as NULL.
574  */
576 };
577 
578 /**
579  * @defgroup opt_eval_funcs Evaluating option strings
580  * @{
581  * This group of functions can be used to evaluate option strings
582  * and get numbers out of them. They do the same thing as av_opt_set(),
583  * except the result is written into the caller-supplied pointer.
584  *
585  * @param obj a struct whose first element is a pointer to AVClass.
586  * @param o an option for which the string is to be evaluated.
587  * @param val string to be evaluated.
588  * @param *_out value of the string will be written here.
589  *
590  * @return 0 on success, a negative number on failure.
591  */
592 int av_opt_eval_flags (void *obj, const AVOption *o, const char *val, int *flags_out);
593 int av_opt_eval_int (void *obj, const AVOption *o, const char *val, int *int_out);
594 int av_opt_eval_int64 (void *obj, const AVOption *o, const char *val, int64_t *int64_out);
595 int av_opt_eval_float (void *obj, const AVOption *o, const char *val, float *float_out);
596 int av_opt_eval_double(void *obj, const AVOption *o, const char *val, double *double_out);
597 int av_opt_eval_q (void *obj, const AVOption *o, const char *val, AVRational *q_out);
598 /**
599  * @}
600  */
601 
602 #define AV_OPT_SEARCH_CHILDREN 0x0001 /**< Search in possible children of the
603  given object first. */
604 /**
605  * The obj passed to av_opt_find() is fake -- only a double pointer to AVClass
606  * instead of a required pointer to a struct containing AVClass. This is
607  * useful for searching for options without needing to allocate the corresponding
608  * object.
609  */
610 #define AV_OPT_SEARCH_FAKE_OBJ 0x0002
611 
612 /**
613  * Allows av_opt_query_ranges and av_opt_query_ranges_default to return more than
614  * one component for certain option types.
615  * @see AVOptionRanges for details.
616  */
617 #define AV_OPT_MULTI_COMPONENT_RANGE 0x1000
618 
619 /**
620  * Look for an option in an object. Consider only options which
621  * have all the specified flags set.
622  *
623  * @param[in] obj A pointer to a struct whose first element is a
624  * pointer to an AVClass.
625  * Alternatively a double pointer to an AVClass, if
626  * AV_OPT_SEARCH_FAKE_OBJ search flag is set.
627  * @param[in] name The name of the option to look for.
628  * @param[in] unit When searching for named constants, name of the unit
629  * it belongs to.
630  * @param opt_flags Find only options with all the specified flags set (AV_OPT_FLAG).
631  * @param search_flags A combination of AV_OPT_SEARCH_*.
632  *
633  * @return A pointer to the option found, or NULL if no option
634  * was found.
635  *
636  * @note Options found with AV_OPT_SEARCH_CHILDREN flag may not be settable
637  * directly with av_opt_set(). Use special calls which take an options
638  * AVDictionary (e.g. avformat_open_input()) to set options found with this
639  * flag.
640  */
641 const AVOption *av_opt_find(void *obj, const char *name, const char *unit,
642  int opt_flags, int search_flags);
643 
644 /**
645  * Look for an option in an object. Consider only options which
646  * have all the specified flags set.
647  *
648  * @param[in] obj A pointer to a struct whose first element is a
649  * pointer to an AVClass.
650  * Alternatively a double pointer to an AVClass, if
651  * AV_OPT_SEARCH_FAKE_OBJ search flag is set.
652  * @param[in] name The name of the option to look for.
653  * @param[in] unit When searching for named constants, name of the unit
654  * it belongs to.
655  * @param opt_flags Find only options with all the specified flags set (AV_OPT_FLAG).
656  * @param search_flags A combination of AV_OPT_SEARCH_*.
657  * @param[out] target_obj if non-NULL, an object to which the option belongs will be
658  * written here. It may be different from obj if AV_OPT_SEARCH_CHILDREN is present
659  * in search_flags. This parameter is ignored if search_flags contain
660  * AV_OPT_SEARCH_FAKE_OBJ.
661  *
662  * @return A pointer to the option found, or NULL if no option
663  * was found.
664  */
665 const AVOption *av_opt_find2(void *obj, const char *name, const char *unit,
666  int opt_flags, int search_flags, void **target_obj);
667 
668 /**
669  * Iterate over all AVOptions belonging to obj.
670  *
671  * @param obj an AVOptions-enabled struct or a double pointer to an
672  * AVClass describing it.
673  * @param prev result of the previous call to av_opt_next() on this object
674  * or NULL
675  * @return next AVOption or NULL
676  */
677 const AVOption *av_opt_next(FF_CONST_AVUTIL55 void *obj, const AVOption *prev);
678 
679 /**
680  * Iterate over AVOptions-enabled children of obj.
681  *
682  * @param prev result of a previous call to this function or NULL
683  * @return next AVOptions-enabled child or NULL
684  */
685 void *av_opt_child_next(void *obj, void *prev);
686 
687 /**
688  * Iterate over potential AVOptions-enabled children of parent.
689  *
690  * @param prev result of a previous call to this function or NULL
691  * @return AVClass corresponding to next potential child or NULL
692  */
693 const AVClass *av_opt_child_class_next(const AVClass *parent, const AVClass *prev);
694 
695 /**
696  * @defgroup opt_set_funcs Option setting functions
697  * @{
698  * Those functions set the field of obj with the given name to value.
699  *
700  * @param[in] obj A struct whose first element is a pointer to an AVClass.
701  * @param[in] name the name of the field to set
702  * @param[in] val The value to set. In case of av_opt_set() if the field is not
703  * of a string type, then the given string is parsed.
704  * SI postfixes and some named scalars are supported.
705  * If the field is of a numeric type, it has to be a numeric or named
706  * scalar. Behavior with more than one scalar and +- infix operators
707  * is undefined.
708  * If the field is of a flags type, it has to be a sequence of numeric
709  * scalars or named flags separated by '+' or '-'. Prefixing a flag
710  * with '+' causes it to be set without affecting the other flags;
711  * similarly, '-' unsets a flag.
712  * @param search_flags flags passed to av_opt_find2. I.e. if AV_OPT_SEARCH_CHILDREN
713  * is passed here, then the option may be set on a child of obj.
714  *
715  * @return 0 if the value has been set, or an AVERROR code in case of
716  * error:
717  * AVERROR_OPTION_NOT_FOUND if no matching option exists
718  * AVERROR(ERANGE) if the value is out of range
719  * AVERROR(EINVAL) if the value is not valid
720  */
721 int av_opt_set (void *obj, const char *name, const char *val, int search_flags);
722 int av_opt_set_int (void *obj, const char *name, int64_t val, int search_flags);
723 int av_opt_set_double (void *obj, const char *name, double val, int search_flags);
724 int av_opt_set_q (void *obj, const char *name, AVRational val, int search_flags);
725 int av_opt_set_bin (void *obj, const char *name, const uint8_t *val, int size, int search_flags);
726 int av_opt_set_image_size(void *obj, const char *name, int w, int h, int search_flags);
727 int av_opt_set_pixel_fmt (void *obj, const char *name, enum AVPixelFormat fmt, int search_flags);
728 int av_opt_set_sample_fmt(void *obj, const char *name, enum AVSampleFormat fmt, int search_flags);
729 int av_opt_set_video_rate(void *obj, const char *name, AVRational val, int search_flags);
730 int av_opt_set_channel_layout(void *obj, const char *name, int64_t ch_layout, int search_flags);
731 /**
732  * @note Any old dictionary present is discarded and replaced with a copy of the new one. The
733  * caller still owns val is and responsible for freeing it.
734  */
735 int av_opt_set_dict_val(void *obj, const char *name, const AVDictionary *val, int search_flags);
736 
737 /**
738  * Set a binary option to an integer list.
739  *
740  * @param obj AVClass object to set options on
741  * @param name name of the binary option
742  * @param val pointer to an integer list (must have the correct type with
743  * regard to the contents of the list)
744  * @param term list terminator (usually 0 or -1)
745  * @param flags search flags
746  */
747 #define av_opt_set_int_list(obj, name, val, term, flags) \
748  (av_int_list_length(val, term) > INT_MAX / sizeof(*(val)) ? \
749  AVERROR(EINVAL) : \
750  av_opt_set_bin(obj, name, (const uint8_t *)(val), \
751  av_int_list_length(val, term) * sizeof(*(val)), flags))
752 
753 /**
754  * @}
755  */
756 
757 /**
758  * @defgroup opt_get_funcs Option getting functions
759  * @{
760  * Those functions get a value of the option with the given name from an object.
761  *
762  * @param[in] obj a struct whose first element is a pointer to an AVClass.
763  * @param[in] name name of the option to get.
764  * @param[in] search_flags flags passed to av_opt_find2. I.e. if AV_OPT_SEARCH_CHILDREN
765  * is passed here, then the option may be found in a child of obj.
766  * @param[out] out_val value of the option will be written here
767  * @return >=0 on success, a negative error code otherwise
768  */
769 /**
770  * @note the returned string will be av_malloc()ed and must be av_free()ed by the caller
771  */
772 int av_opt_get (void *obj, const char *name, int search_flags, uint8_t **out_val);
773 int av_opt_get_int (void *obj, const char *name, int search_flags, int64_t *out_val);
774 int av_opt_get_double (void *obj, const char *name, int search_flags, double *out_val);
775 int av_opt_get_q (void *obj, const char *name, int search_flags, AVRational *out_val);
776 int av_opt_get_image_size(void *obj, const char *name, int search_flags, int *w_out, int *h_out);
777 int av_opt_get_pixel_fmt (void *obj, const char *name, int search_flags, enum AVPixelFormat *out_fmt);
778 int av_opt_get_sample_fmt(void *obj, const char *name, int search_flags, enum AVSampleFormat *out_fmt);
779 int av_opt_get_video_rate(void *obj, const char *name, int search_flags, AVRational *out_val);
780 int av_opt_get_channel_layout(void *obj, const char *name, int search_flags, int64_t *ch_layout);
781 /**
782  * @param[out] out_val The returned dictionary is a copy of the actual value and must
783  * be freed with av_dict_free() by the caller
784  */
785 int av_opt_get_dict_val(void *obj, const char *name, int search_flags, AVDictionary **out_val);
786 /**
787  * @}
788  */
789 /**
790  * Gets a pointer to the requested field in a struct.
791  * This function allows accessing a struct even when its fields are moved or
792  * renamed since the application making the access has been compiled,
793  *
794  * @returns a pointer to the field, it can be cast to the correct type and read
795  * or written to.
796  */
797 void *av_opt_ptr(const AVClass *avclass, void *obj, const char *name);
798 
799 /**
800  * Free an AVOptionRanges struct and set it to NULL.
801  */
802 void av_opt_freep_ranges(AVOptionRanges **ranges);
803 
804 /**
805  * Get a list of allowed ranges for the given option.
806  *
807  * The returned list may depend on other fields in obj like for example profile.
808  *
809  * @param flags is a bitmask of flags, undefined flags should not be set and should be ignored
810  * AV_OPT_SEARCH_FAKE_OBJ indicates that the obj is a double pointer to a AVClass instead of a full instance
811  * AV_OPT_MULTI_COMPONENT_RANGE indicates that function may return more than one component, @see AVOptionRanges
812  *
813  * The result must be freed with av_opt_freep_ranges.
814  *
815  * @return number of compontents returned on success, a negative errro code otherwise
816  */
817 int av_opt_query_ranges(AVOptionRanges **, void *obj, const char *key, int flags);
818 
819 /**
820  * Copy options from src object into dest object.
821  *
822  * Options that require memory allocation (e.g. string or binary) are malloc'ed in dest object.
823  * Original memory allocated for such options is freed unless both src and dest options points to the same memory.
824  *
825  * @param dest Object to copy from
826  * @param src Object to copy into
827  * @return 0 on success, negative on error
828  */
829 int av_opt_copy(void *dest, FF_CONST_AVUTIL55 void *src);
830 
831 /**
832  * Get a default list of allowed ranges for the given option.
833  *
834  * This list is constructed without using the AVClass.query_ranges() callback
835  * and can be used as fallback from within the callback.
836  *
837  * @param flags is a bitmask of flags, undefined flags should not be set and should be ignored
838  * AV_OPT_SEARCH_FAKE_OBJ indicates that the obj is a double pointer to a AVClass instead of a full instance
839  * AV_OPT_MULTI_COMPONENT_RANGE indicates that function may return more than one component, @see AVOptionRanges
840  *
841  * The result must be freed with av_opt_free_ranges.
842  *
843  * @return number of compontents returned on success, a negative errro code otherwise
844  */
845 int av_opt_query_ranges_default(AVOptionRanges **, void *obj, const char *key, int flags);
846 
847 /**
848  * Check if given option is set to its default value.
849  *
850  * Options o must belong to the obj. This function must not be called to check child's options state.
851  * @see av_opt_is_set_to_default_by_name().
852  *
853  * @param obj AVClass object to check option on
854  * @param o option to be checked
855  * @return >0 when option is set to its default,
856  * 0 when option is not set its default,
857  * <0 on error
858  */
859 int av_opt_is_set_to_default(void *obj, const AVOption *o);
860 
861 /**
862  * Check if given option is set to its default value.
863  *
864  * @param obj AVClass object to check option on
865  * @param name option name
866  * @param search_flags combination of AV_OPT_SEARCH_*
867  * @return >0 when option is set to its default,
868  * 0 when option is not set its default,
869  * <0 on error
870  */
871 int av_opt_is_set_to_default_by_name(void *obj, const char *name, int search_flags);
872 
873 
874 #define AV_OPT_SERIALIZE_SKIP_DEFAULTS 0x00000001 ///< Serialize options that are not set to default values only.
875 #define AV_OPT_SERIALIZE_OPT_FLAGS_EXACT 0x00000002 ///< Serialize options that exactly match opt_flags only.
876 
877 /**
878  * Serialize object's options.
879  *
880  * Create a string containing object's serialized options.
881  * Such string may be passed back to av_opt_set_from_string() in order to restore option values.
882  * A key/value or pairs separator occurring in the serialized value or
883  * name string are escaped through the av_escape() function.
884  *
885  * @param[in] obj AVClass object to serialize
886  * @param[in] opt_flags serialize options with all the specified flags set (AV_OPT_FLAG)
887  * @param[in] flags combination of AV_OPT_SERIALIZE_* flags
888  * @param[out] buffer Pointer to buffer that will be allocated with string containg serialized options.
889  * Buffer must be freed by the caller when is no longer needed.
890  * @param[in] key_val_sep character used to separate key from value
891  * @param[in] pairs_sep character used to separate two pairs from each other
892  * @return >= 0 on success, negative on error
893  * @warning Separators cannot be neither '\\' nor '\0'. They also cannot be the same.
894  */
895 int av_opt_serialize(void *obj, int opt_flags, int flags, char **buffer,
896  const char key_val_sep, const char pairs_sep);
897 /**
898  * @}
899  */
900 
901 #endif /* AVUTIL_OPT_H */