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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 
37 /**
38  * @defgroup avoptions AVOptions
39  * @ingroup lavu_data
40  * @{
41  * AVOptions provide a generic system to declare options on arbitrary structs
42  * ("objects"). An option can have a help text, a type and a range of possible
43  * values. Options may then be enumerated, read and written to.
44  *
45  * @section avoptions_implement Implementing AVOptions
46  * This section describes how to add AVOptions capabilities to a struct.
47  *
48  * All AVOptions-related information is stored in an AVClass. Therefore
49  * the first member of the struct should be a pointer to an AVClass describing it.
50  * The option field of the AVClass must be set to a NULL-terminated static array
51  * of AVOptions. Each AVOption must have a non-empty name, a type, a default
52  * value and for number-type AVOptions also a range of allowed values. It must
53  * also declare an offset in bytes from the start of the struct, where the field
54  * associated with this AVOption is located. Other fields in the AVOption struct
55  * should also be set when applicable, but are not required.
56  *
57  * The following example illustrates an AVOptions-enabled struct:
58  * @code
59  * typedef struct test_struct {
60  * AVClass *class;
61  * int int_opt;
62  * char *str_opt;
63  * uint8_t *bin_opt;
64  * int bin_len;
65  * } test_struct;
66  *
67  * static const AVOption options[] = {
68  * { "test_int", "This is a test option of int type.", offsetof(test_struct, int_opt),
69  * AV_OPT_TYPE_INT, { .i64 = -1 }, INT_MIN, INT_MAX },
70  * { "test_str", "This is a test option of string type.", offsetof(test_struct, str_opt),
71  * AV_OPT_TYPE_STRING },
72  * { "test_bin", "This is a test option of binary type.", offsetof(test_struct, bin_opt),
73  * AV_OPT_TYPE_BINARY },
74  * { NULL },
75  * };
76  *
77  * static const AVClass test_class = {
78  * .class_name = "test class",
79  * .item_name = av_default_item_name,
80  * .option = options,
81  * .version = LIBAVUTIL_VERSION_INT,
82  * };
83  * @endcode
84  *
85  * Next, when allocating your struct, you must ensure that the AVClass pointer
86  * is set to the correct value. Then, av_opt_set_defaults() can be called to
87  * initialize defaults. After that the struct is ready to be used with the
88  * AVOptions API.
89  *
90  * When cleaning up, you may use the av_opt_free() function to automatically
91  * free all the allocated string and binary options.
92  *
93  * Continuing with the above example:
94  *
95  * @code
96  * test_struct *alloc_test_struct(void)
97  * {
98  * test_struct *ret = av_malloc(sizeof(*ret));
99  * ret->class = &test_class;
100  * av_opt_set_defaults(ret);
101  * return ret;
102  * }
103  * void free_test_struct(test_struct **foo)
104  * {
105  * av_opt_free(*foo);
106  * av_freep(foo);
107  * }
108  * @endcode
109  *
110  * @subsection avoptions_implement_nesting Nesting
111  * It may happen that an AVOptions-enabled struct contains another
112  * AVOptions-enabled struct as a member (e.g. AVCodecContext in
113  * libavcodec exports generic options, while its priv_data field exports
114  * codec-specific options). In such a case, it is possible to set up the
115  * parent struct to export a child's options. To do that, simply
116  * implement AVClass.child_next() and AVClass.child_class_next() in the
117  * parent struct's AVClass.
118  * Assuming that the test_struct from above now also contains a
119  * child_struct field:
120  *
121  * @code
122  * typedef struct child_struct {
123  * AVClass *class;
124  * int flags_opt;
125  * } child_struct;
126  * static const AVOption child_opts[] = {
127  * { "test_flags", "This is a test option of flags type.",
128  * offsetof(child_struct, flags_opt), AV_OPT_TYPE_FLAGS, { .i64 = 0 }, INT_MIN, INT_MAX },
129  * { NULL },
130  * };
131  * static const AVClass child_class = {
132  * .class_name = "child class",
133  * .item_name = av_default_item_name,
134  * .option = child_opts,
135  * .version = LIBAVUTIL_VERSION_INT,
136  * };
137  *
138  * void *child_next(void *obj, void *prev)
139  * {
140  * test_struct *t = obj;
141  * if (!prev && t->child_struct)
142  * return t->child_struct;
143  * return NULL
144  * }
145  * const AVClass child_class_next(const AVClass *prev)
146  * {
147  * return prev ? NULL : &child_class;
148  * }
149  * @endcode
150  * Putting child_next() and child_class_next() as defined above into
151  * test_class will now make child_struct's options accessible through
152  * test_struct (again, proper setup as described above needs to be done on
153  * child_struct right after it is created).
154  *
155  * From the above example it might not be clear why both child_next()
156  * and child_class_next() are needed. The distinction is that child_next()
157  * iterates over actually existing objects, while child_class_next()
158  * iterates over all possible child classes. E.g. if an AVCodecContext
159  * was initialized to use a codec which has private options, then its
160  * child_next() will return AVCodecContext.priv_data and finish
161  * iterating. OTOH child_class_next() on AVCodecContext.av_class will
162  * iterate over all available codecs with private options.
163  *
164  * @subsection avoptions_implement_named_constants Named constants
165  * It is possible to create named constants for options. Simply set the unit
166  * field of the option the constants should apply to to a string and
167  * create the constants themselves as options of type AV_OPT_TYPE_CONST
168  * with their unit field set to the same string.
169  * Their default_val field should contain the value of the named
170  * constant.
171  * For example, to add some named constants for the test_flags option
172  * above, put the following into the child_opts array:
173  * @code
174  * { "test_flags", "This is a test option of flags type.",
175  * offsetof(child_struct, flags_opt), AV_OPT_TYPE_FLAGS, { .i64 = 0 }, INT_MIN, INT_MAX, "test_unit" },
176  * { "flag1", "This is a flag with value 16", 0, AV_OPT_TYPE_CONST, { .i64 = 16 }, 0, 0, "test_unit" },
177  * @endcode
178  *
179  * @section avoptions_use Using AVOptions
180  * This section deals with accessing options in an AVOptions-enabled struct.
181  * Such structs in FFmpeg are e.g. AVCodecContext in libavcodec or
182  * AVFormatContext in libavformat.
183  *
184  * @subsection avoptions_use_examine Examining AVOptions
185  * The basic functions for examining options are av_opt_next(), which iterates
186  * over all options defined for one object, and av_opt_find(), which searches
187  * for an option with the given name.
188  *
189  * The situation is more complicated with nesting. An AVOptions-enabled struct
190  * may have AVOptions-enabled children. Passing the AV_OPT_SEARCH_CHILDREN flag
191  * to av_opt_find() will make the function search children recursively.
192  *
193  * For enumerating there are basically two cases. The first is when you want to
194  * get all options that may potentially exist on the struct and its children
195  * (e.g. when constructing documentation). In that case you should call
196  * av_opt_child_class_next() recursively on the parent struct's AVClass. The
197  * second case is when you have an already initialized struct with all its
198  * children and you want to get all options that can be actually written or read
199  * from it. In that case you should call av_opt_child_next() recursively (and
200  * av_opt_next() on each result).
201  *
202  * @subsection avoptions_use_get_set Reading and writing AVOptions
203  * When setting options, you often have a string read directly from the
204  * user. In such a case, simply passing it to av_opt_set() is enough. For
205  * non-string type options, av_opt_set() will parse the string according to the
206  * option type.
207  *
208  * Similarly av_opt_get() will read any option type and convert it to a string
209  * which will be returned. Do not forget that the string is allocated, so you
210  * have to free it with av_free().
211  *
212  * In some cases it may be more convenient to put all options into an
213  * AVDictionary and call av_opt_set_dict() on it. A specific case of this
214  * are the format/codec open functions in lavf/lavc which take a dictionary
215  * filled with option as a parameter. This allows to set some options
216  * that cannot be set otherwise, since e.g. the input file format is not known
217  * before the file is actually opened.
218  */
219 
228  AV_OPT_TYPE_BINARY, ///< offset must point to a pointer immediately followed by an int for the length
230  AV_OPT_TYPE_IMAGE_SIZE = MKBETAG('S','I','Z','E'), ///< offset must point to two consecutive integers
231  AV_OPT_TYPE_PIXEL_FMT = MKBETAG('P','F','M','T'),
232  AV_OPT_TYPE_SAMPLE_FMT = MKBETAG('S','F','M','T'),
233 #if FF_API_OLD_AVOPTIONS
241  FF_OPT_TYPE_BINARY, ///< offset must point to a pointer immediately followed by an int for the length
243 #endif
244 };
245 
246 /**
247  * AVOption
248  */
249 typedef struct AVOption {
250  const char *name;
251 
252  /**
253  * short English help text
254  * @todo What about other languages?
255  */
256  const char *help;
257 
258  /**
259  * The offset relative to the context structure where the option
260  * value is stored. It should be 0 for named constants.
261  */
262  int offset;
264 
265  /**
266  * the default value for scalar options
267  */
268  union {
269  int64_t i64;
270  double dbl;
271  const char *str;
272  /* TODO those are unused now */
274  } default_val;
275  double min; ///< minimum valid value for the option
276  double max; ///< maximum valid value for the option
277 
278  int flags;
279 #define AV_OPT_FLAG_ENCODING_PARAM 1 ///< a generic parameter which can be set by the user for muxing or encoding
280 #define AV_OPT_FLAG_DECODING_PARAM 2 ///< a generic parameter which can be set by the user for demuxing or decoding
281 #define AV_OPT_FLAG_METADATA 4 ///< some data extracted or inserted into the file like title, comment, ...
282 #define AV_OPT_FLAG_AUDIO_PARAM 8
283 #define AV_OPT_FLAG_VIDEO_PARAM 16
284 #define AV_OPT_FLAG_SUBTITLE_PARAM 32
285 #define AV_OPT_FLAG_FILTERING_PARAM (1<<16) ///< a generic parameter which can be set by the user for filtering
286 //FIXME think about enc-audio, ... style flags
287 
288  /**
289  * The logical unit to which the option belongs. Non-constant
290  * options and corresponding named constants share the same
291  * unit. May be NULL.
292  */
293  const char *unit;
294 } AVOption;
295 
296 /**
297  * A single allowed range of values, or a single allowed value.
298  */
299 typedef struct AVOptionRange {
300  const char *str;
301  double value_min, value_max; ///< For string ranges this represents the min/max length, for dimensions this represents the min/max pixel count
302  double component_min, component_max; ///< For string this represents the unicode range for chars, 0-127 limits to ASCII
303  int is_range; ///< if set to 1 the struct encodes a range, if set to 0 a single value
304 } AVOptionRange;
305 
306 /**
307  * List of AVOptionRange structs
308  */
309 typedef struct AVOptionRanges {
313 
314 
315 #if FF_API_FIND_OPT
316 /**
317  * Look for an option in obj. Look only for the options which
318  * have the flags set as specified in mask and flags (that is,
319  * for which it is the case that opt->flags & mask == flags).
320  *
321  * @param[in] obj a pointer to a struct whose first element is a
322  * pointer to an AVClass
323  * @param[in] name the name of the option to look for
324  * @param[in] unit the unit of the option to look for, or any if NULL
325  * @return a pointer to the option found, or NULL if no option
326  * has been found
327  *
328  * @deprecated use av_opt_find.
329  */
331 const AVOption *av_find_opt(void *obj, const char *name, const char *unit, int mask, int flags);
332 #endif
333 
334 #if FF_API_OLD_AVOPTIONS
335 /**
336  * Set the field of obj with the given name to value.
337  *
338  * @param[in] obj A struct whose first element is a pointer to an
339  * AVClass.
340  * @param[in] name the name of the field to set
341  * @param[in] val The value to set. If the field is not of a string
342  * type, then the given string is parsed.
343  * SI postfixes and some named scalars are supported.
344  * If the field is of a numeric type, it has to be a numeric or named
345  * scalar. Behavior with more than one scalar and +- infix operators
346  * is undefined.
347  * If the field is of a flags type, it has to be a sequence of numeric
348  * scalars or named flags separated by '+' or '-'. Prefixing a flag
349  * with '+' causes it to be set without affecting the other flags;
350  * similarly, '-' unsets a flag.
351  * @param[out] o_out if non-NULL put here a pointer to the AVOption
352  * found
353  * @param alloc this parameter is currently ignored
354  * @return 0 if the value has been set, or an AVERROR code in case of
355  * error:
356  * AVERROR_OPTION_NOT_FOUND if no matching option exists
357  * AVERROR(ERANGE) if the value is out of range
358  * AVERROR(EINVAL) if the value is not valid
359  * @deprecated use av_opt_set()
360  */
362 int av_set_string3(void *obj, const char *name, const char *val, int alloc, const AVOption **o_out);
363 
364 attribute_deprecated const AVOption *av_set_double(void *obj, const char *name, double n);
365 attribute_deprecated const AVOption *av_set_q(void *obj, const char *name, AVRational n);
366 attribute_deprecated const AVOption *av_set_int(void *obj, const char *name, int64_t n);
367 
368 double av_get_double(void *obj, const char *name, const AVOption **o_out);
369 AVRational av_get_q(void *obj, const char *name, const AVOption **o_out);
370 int64_t av_get_int(void *obj, const char *name, const AVOption **o_out);
371 attribute_deprecated const char *av_get_string(void *obj, const char *name, const AVOption **o_out, char *buf, int buf_len);
372 attribute_deprecated const AVOption *av_next_option(void *obj, const AVOption *last);
373 #endif
374 
375 /**
376  * Show the obj options.
377  *
378  * @param req_flags requested flags for the options to show. Show only the
379  * options for which it is opt->flags & req_flags.
380  * @param rej_flags rejected flags for the options to show. Show only the
381  * options for which it is !(opt->flags & req_flags).
382  * @param av_log_obj log context to use for showing the options
383  */
384 int av_opt_show2(void *obj, void *av_log_obj, int req_flags, int rej_flags);
385 
386 /**
387  * Set the values of all AVOption fields to their default values.
388  *
389  * @param s an AVOption-enabled struct (its first member must be a pointer to AVClass)
390  */
391 void av_opt_set_defaults(void *s);
392 
393 #if FF_API_OLD_AVOPTIONS
395 void av_opt_set_defaults2(void *s, int mask, int flags);
396 #endif
397 
398 /**
399  * Parse the key/value pairs list in opts. For each key/value pair
400  * found, stores the value in the field in ctx that is named like the
401  * key. ctx must be an AVClass context, storing is done using
402  * AVOptions.
403  *
404  * @param opts options string to parse, may be NULL
405  * @param key_val_sep a 0-terminated list of characters used to
406  * separate key from value
407  * @param pairs_sep a 0-terminated list of characters used to separate
408  * two pairs from each other
409  * @return the number of successfully set key/value pairs, or a negative
410  * value corresponding to an AVERROR code in case of error:
411  * AVERROR(EINVAL) if opts cannot be parsed,
412  * the error code issued by av_set_string3() if a key/value pair
413  * cannot be set
414  */
415 int av_set_options_string(void *ctx, const char *opts,
416  const char *key_val_sep, const char *pairs_sep);
417 
418 /**
419  * Parse the key-value pairs list in opts. For each key=value pair found,
420  * set the value of the corresponding option in ctx.
421  *
422  * @param ctx the AVClass object to set options on
423  * @param opts the options string, key-value pairs separated by a
424  * delimiter
425  * @param shorthand a NULL-terminated array of options names for shorthand
426  * notation: if the first field in opts has no key part,
427  * the key is taken from the first element of shorthand;
428  * then again for the second, etc., until either opts is
429  * finished, shorthand is finished or a named option is
430  * found; after that, all options must be named
431  * @param key_val_sep a 0-terminated list of characters used to separate
432  * key from value, for example '='
433  * @param pairs_sep a 0-terminated list of characters used to separate
434  * two pairs from each other, for example ':' or ','
435  * @return the number of successfully set key=value pairs, or a negative
436  * value corresponding to an AVERROR code in case of error:
437  * AVERROR(EINVAL) if opts cannot be parsed,
438  * the error code issued by av_set_string3() if a key/value pair
439  * cannot be set
440  *
441  * Options names must use only the following characters: a-z A-Z 0-9 - . / _
442  * Separators must use characters distinct from option names and from each
443  * other.
444  */
445 int av_opt_set_from_string(void *ctx, const char *opts,
446  const char *const *shorthand,
447  const char *key_val_sep, const char *pairs_sep);
448 /**
449  * Free all string and binary options in obj.
450  */
451 void av_opt_free(void *obj);
452 
453 /**
454  * Check whether a particular flag is set in a flags field.
455  *
456  * @param field_name the name of the flag field option
457  * @param flag_name the name of the flag to check
458  * @return non-zero if the flag is set, zero if the flag isn't set,
459  * isn't of the right type, or the flags field doesn't exist.
460  */
461 int av_opt_flag_is_set(void *obj, const char *field_name, const char *flag_name);
462 
463 /**
464  * Set all the options from a given dictionary on an object.
465  *
466  * @param obj a struct whose first element is a pointer to AVClass
467  * @param options options to process. This dictionary will be freed and replaced
468  * by a new one containing all options not found in obj.
469  * Of course this new dictionary needs to be freed by caller
470  * with av_dict_free().
471  *
472  * @return 0 on success, a negative AVERROR if some option was found in obj,
473  * but could not be set.
474  *
475  * @see av_dict_copy()
476  */
477 int av_opt_set_dict(void *obj, struct AVDictionary **options);
478 
479 /**
480  * Extract a key-value pair from the beginning of a string.
481  *
482  * @param ropts pointer to the options string, will be updated to
483  * point to the rest of the string (one of the pairs_sep
484  * or the final NUL)
485  * @param key_val_sep a 0-terminated list of characters used to separate
486  * key from value, for example '='
487  * @param pairs_sep a 0-terminated list of characters used to separate
488  * two pairs from each other, for example ':' or ','
489  * @param flags flags; see the AV_OPT_FLAG_* values below
490  * @param rkey parsed key; must be freed using av_free()
491  * @param rval parsed value; must be freed using av_free()
492  *
493  * @return >=0 for success, or a negative value corresponding to an
494  * AVERROR code in case of error; in particular:
495  * AVERROR(EINVAL) if no key is present
496  *
497  */
498 int av_opt_get_key_value(const char **ropts,
499  const char *key_val_sep, const char *pairs_sep,
500  unsigned flags,
501  char **rkey, char **rval);
502 
503 enum {
504 
505  /**
506  * Accept to parse a value without a key; the key will then be returned
507  * as NULL.
508  */
510 };
511 
512 /**
513  * @defgroup opt_eval_funcs Evaluating option strings
514  * @{
515  * This group of functions can be used to evaluate option strings
516  * and get numbers out of them. They do the same thing as av_opt_set(),
517  * except the result is written into the caller-supplied pointer.
518  *
519  * @param obj a struct whose first element is a pointer to AVClass.
520  * @param o an option for which the string is to be evaluated.
521  * @param val string to be evaluated.
522  * @param *_out value of the string will be written here.
523  *
524  * @return 0 on success, a negative number on failure.
525  */
526 int av_opt_eval_flags (void *obj, const AVOption *o, const char *val, int *flags_out);
527 int av_opt_eval_int (void *obj, const AVOption *o, const char *val, int *int_out);
528 int av_opt_eval_int64 (void *obj, const AVOption *o, const char *val, int64_t *int64_out);
529 int av_opt_eval_float (void *obj, const AVOption *o, const char *val, float *float_out);
530 int av_opt_eval_double(void *obj, const AVOption *o, const char *val, double *double_out);
531 int av_opt_eval_q (void *obj, const AVOption *o, const char *val, AVRational *q_out);
532 /**
533  * @}
534  */
535 
536 #define AV_OPT_SEARCH_CHILDREN 0x0001 /**< Search in possible children of the
537  given object first. */
538 /**
539  * The obj passed to av_opt_find() is fake -- only a double pointer to AVClass
540  * instead of a required pointer to a struct containing AVClass. This is
541  * useful for searching for options without needing to allocate the corresponding
542  * object.
543  */
544 #define AV_OPT_SEARCH_FAKE_OBJ 0x0002
545 
546 /**
547  * Look for an option in an object. Consider only options which
548  * have all the specified flags set.
549  *
550  * @param[in] obj A pointer to a struct whose first element is a
551  * pointer to an AVClass.
552  * Alternatively a double pointer to an AVClass, if
553  * AV_OPT_SEARCH_FAKE_OBJ search flag is set.
554  * @param[in] name The name of the option to look for.
555  * @param[in] unit When searching for named constants, name of the unit
556  * it belongs to.
557  * @param opt_flags Find only options with all the specified flags set (AV_OPT_FLAG).
558  * @param search_flags A combination of AV_OPT_SEARCH_*.
559  *
560  * @return A pointer to the option found, or NULL if no option
561  * was found.
562  *
563  * @note Options found with AV_OPT_SEARCH_CHILDREN flag may not be settable
564  * directly with av_set_string3(). Use special calls which take an options
565  * AVDictionary (e.g. avformat_open_input()) to set options found with this
566  * flag.
567  */
568 const AVOption *av_opt_find(void *obj, const char *name, const char *unit,
569  int opt_flags, int search_flags);
570 
571 /**
572  * Look for an option in an object. Consider only options which
573  * have all the specified flags set.
574  *
575  * @param[in] obj A pointer to a struct whose first element is a
576  * pointer to an AVClass.
577  * Alternatively a double pointer to an AVClass, if
578  * AV_OPT_SEARCH_FAKE_OBJ search flag is set.
579  * @param[in] name The name of the option to look for.
580  * @param[in] unit When searching for named constants, name of the unit
581  * it belongs to.
582  * @param opt_flags Find only options with all the specified flags set (AV_OPT_FLAG).
583  * @param search_flags A combination of AV_OPT_SEARCH_*.
584  * @param[out] target_obj if non-NULL, an object to which the option belongs will be
585  * written here. It may be different from obj if AV_OPT_SEARCH_CHILDREN is present
586  * in search_flags. This parameter is ignored if search_flags contain
587  * AV_OPT_SEARCH_FAKE_OBJ.
588  *
589  * @return A pointer to the option found, or NULL if no option
590  * was found.
591  */
592 const AVOption *av_opt_find2(void *obj, const char *name, const char *unit,
593  int opt_flags, int search_flags, void **target_obj);
594 
595 /**
596  * Iterate over all AVOptions belonging to obj.
597  *
598  * @param obj an AVOptions-enabled struct or a double pointer to an
599  * AVClass describing it.
600  * @param prev result of the previous call to av_opt_next() on this object
601  * or NULL
602  * @return next AVOption or NULL
603  */
604 const AVOption *av_opt_next(void *obj, const AVOption *prev);
605 
606 /**
607  * Iterate over AVOptions-enabled children of obj.
608  *
609  * @param prev result of a previous call to this function or NULL
610  * @return next AVOptions-enabled child or NULL
611  */
612 void *av_opt_child_next(void *obj, void *prev);
613 
614 /**
615  * Iterate over potential AVOptions-enabled children of parent.
616  *
617  * @param prev result of a previous call to this function or NULL
618  * @return AVClass corresponding to next potential child or NULL
619  */
620 const AVClass *av_opt_child_class_next(const AVClass *parent, const AVClass *prev);
621 
622 /**
623  * @defgroup opt_set_funcs Option setting functions
624  * @{
625  * Those functions set the field of obj with the given name to value.
626  *
627  * @param[in] obj A struct whose first element is a pointer to an AVClass.
628  * @param[in] name the name of the field to set
629  * @param[in] val The value to set. In case of av_opt_set() if the field is not
630  * of a string type, then the given string is parsed.
631  * SI postfixes and some named scalars are supported.
632  * If the field is of a numeric type, it has to be a numeric or named
633  * scalar. Behavior with more than one scalar and +- infix operators
634  * is undefined.
635  * If the field is of a flags type, it has to be a sequence of numeric
636  * scalars or named flags separated by '+' or '-'. Prefixing a flag
637  * with '+' causes it to be set without affecting the other flags;
638  * similarly, '-' unsets a flag.
639  * @param search_flags flags passed to av_opt_find2. I.e. if AV_OPT_SEARCH_CHILDREN
640  * is passed here, then the option may be set on a child of obj.
641  *
642  * @return 0 if the value has been set, or an AVERROR code in case of
643  * error:
644  * AVERROR_OPTION_NOT_FOUND if no matching option exists
645  * AVERROR(ERANGE) if the value is out of range
646  * AVERROR(EINVAL) if the value is not valid
647  */
648 int av_opt_set (void *obj, const char *name, const char *val, int search_flags);
649 int av_opt_set_int (void *obj, const char *name, int64_t val, int search_flags);
650 int av_opt_set_double(void *obj, const char *name, double val, int search_flags);
651 int av_opt_set_q (void *obj, const char *name, AVRational val, int search_flags);
652 int av_opt_set_bin (void *obj, const char *name, const uint8_t *val, int size, int search_flags);
653 int av_opt_set_image_size(void *obj, const char *name, int w, int h, int search_flags);
654 int av_opt_set_pixel_fmt (void *obj, const char *name, enum AVPixelFormat fmt, int search_flags);
655 int av_opt_set_sample_fmt(void *obj, const char *name, enum AVSampleFormat fmt, int search_flags);
656 /**
657  * @}
658  */
659 
660 /**
661  * @defgroup opt_get_funcs Option getting functions
662  * @{
663  * Those functions get a value of the option with the given name from an object.
664  *
665  * @param[in] obj a struct whose first element is a pointer to an AVClass.
666  * @param[in] name name of the option to get.
667  * @param[in] search_flags flags passed to av_opt_find2. I.e. if AV_OPT_SEARCH_CHILDREN
668  * is passed here, then the option may be found in a child of obj.
669  * @param[out] out_val value of the option will be written here
670  * @return 0 on success, a negative error code otherwise
671  */
672 /**
673  * @note the returned string will av_malloc()ed and must be av_free()ed by the caller
674  */
675 int av_opt_get (void *obj, const char *name, int search_flags, uint8_t **out_val);
676 int av_opt_get_int (void *obj, const char *name, int search_flags, int64_t *out_val);
677 int av_opt_get_double(void *obj, const char *name, int search_flags, double *out_val);
678 int av_opt_get_q (void *obj, const char *name, int search_flags, AVRational *out_val);
679 int av_opt_get_image_size(void *obj, const char *name, int search_flags, int *w_out, int *h_out);
680 int av_opt_get_pixel_fmt (void *obj, const char *name, int search_flags, enum AVPixelFormat *out_fmt);
681 int av_opt_get_sample_fmt(void *obj, const char *name, int search_flags, enum AVSampleFormat *out_fmt);
682 /**
683  * @}
684  */
685 /**
686  * Gets a pointer to the requested field in a struct.
687  * This function allows accessing a struct even when its fields are moved or
688  * renamed since the application making the access has been compiled,
689  *
690  * @returns a pointer to the field, it can be cast to the correct type and read
691  * or written to.
692  */
693 void *av_opt_ptr(const AVClass *avclass, void *obj, const char *name);
694 
695 /**
696  * Free an AVOptionRanges struct and set it to NULL.
697  */
698 void av_opt_freep_ranges(AVOptionRanges **ranges);
699 
700 /**
701  * Get a list of allowed ranges for the given option.
702  *
703  * The returned list may depend on other fields in obj like for example profile.
704  *
705  * @param flags is a bitmask of flags, undefined flags should not be set and should be ignored
706  * AV_OPT_SEARCH_FAKE_OBJ indicates that the obj is a double pointer to a AVClass instead of a full instance
707  *
708  * The result must be freed with av_opt_freep_ranges.
709  *
710  * @return >= 0 on success, a negative errro code otherwise
711  */
712 int av_opt_query_ranges(AVOptionRanges **, void *obj, const char *key, int flags);
713 
714 /**
715  * Get a default list of allowed ranges for the given option.
716  *
717  * This list is constructed without using the AVClass.query_ranges() callback
718  * and can be used as fallback from within the callback.
719  *
720  * @param flags is a bitmask of flags, undefined flags should not be set and should be ignored
721  * AV_OPT_SEARCH_FAKE_OBJ indicates that the obj is a double pointer to a AVClass instead of a full instance
722  *
723  * The result must be freed with av_opt_free_ranges.
724  *
725  * @return >= 0 on success, a negative errro code otherwise
726  */
727 int av_opt_query_ranges_default(AVOptionRanges **, void *obj, const char *key, int flags);
728 
729 /**
730  * @}
731  */
732 
733 #endif /* AVUTIL_OPT_H */