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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 test_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 = test_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 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  AV_OPT_TYPE_VIDEO_RATE = MKBETAG('V','R','A','T'), ///< offset must point to AVRational
234  AV_OPT_TYPE_DURATION = MKBETAG('D','U','R',' '),
235  AV_OPT_TYPE_COLOR = MKBETAG('C','O','L','R'),
237 #if FF_API_OLD_AVOPTIONS
245  FF_OPT_TYPE_BINARY, ///< offset must point to a pointer immediately followed by an int for the length
247 #endif
248 };
249 
250 /**
251  * AVOption
252  */
253 typedef struct AVOption {
254  const char *name;
255 
256  /**
257  * short English help text
258  * @todo What about other languages?
259  */
260  const char *help;
261 
262  /**
263  * The offset relative to the context structure where the option
264  * value is stored. It should be 0 for named constants.
265  */
266  int offset;
268 
269  /**
270  * the default value for scalar options
271  */
272  union {
273  int64_t i64;
274  double dbl;
275  const char *str;
276  /* TODO those are unused now */
278  } default_val;
279  double min; ///< minimum valid value for the option
280  double max; ///< maximum valid value for the option
281 
282  int flags;
283 #define AV_OPT_FLAG_ENCODING_PARAM 1 ///< a generic parameter which can be set by the user for muxing or encoding
284 #define AV_OPT_FLAG_DECODING_PARAM 2 ///< a generic parameter which can be set by the user for demuxing or decoding
285 #if FF_API_OPT_TYPE_METADATA
286 #define AV_OPT_FLAG_METADATA 4 ///< some data extracted or inserted into the file like title, comment, ...
287 #endif
288 #define AV_OPT_FLAG_AUDIO_PARAM 8
289 #define AV_OPT_FLAG_VIDEO_PARAM 16
290 #define AV_OPT_FLAG_SUBTITLE_PARAM 32
291 /**
292  * The option is inteded for exporting values to the caller.
293  */
294 #define AV_OPT_FLAG_EXPORT 64
295 /**
296  * The option may not be set through the AVOptions API, only read.
297  * This flag only makes sense when AV_OPT_FLAG_EXPORT is also set.
298  */
299 #define AV_OPT_FLAG_READONLY 128
300 #define AV_OPT_FLAG_FILTERING_PARAM (1<<16) ///< a generic parameter which can be set by the user for filtering
301 //FIXME think about enc-audio, ... style flags
302 
303  /**
304  * The logical unit to which the option belongs. Non-constant
305  * options and corresponding named constants share the same
306  * unit. May be NULL.
307  */
308  const char *unit;
309 } AVOption;
310 
311 /**
312  * A single allowed range of values, or a single allowed value.
313  */
314 typedef struct AVOptionRange {
315  const char *str;
316  double value_min, value_max; ///< For string ranges this represents the min/max length, for dimensions this represents the min/max pixel count
317  double component_min, component_max; ///< For string this represents the unicode range for chars, 0-127 limits to ASCII
318  int is_range; ///< if set to 1 the struct encodes a range, if set to 0 a single value
319 } AVOptionRange;
320 
321 /**
322  * List of AVOptionRange structs
323  */
324 typedef struct AVOptionRanges {
328 
329 
330 #if FF_API_FIND_OPT
331 /**
332  * Look for an option in obj. Look only for the options which
333  * have the flags set as specified in mask and flags (that is,
334  * for which it is the case that (opt->flags & mask) == flags).
335  *
336  * @param[in] obj a pointer to a struct whose first element is a
337  * pointer to an AVClass
338  * @param[in] name the name of the option to look for
339  * @param[in] unit the unit of the option to look for, or any if NULL
340  * @return a pointer to the option found, or NULL if no option
341  * has been found
342  *
343  * @deprecated use av_opt_find.
344  */
346 const AVOption *av_find_opt(void *obj, const char *name, const char *unit, int mask, int flags);
347 #endif
348 
349 #if FF_API_OLD_AVOPTIONS
350 /**
351  * Set the field of obj with the given name to value.
352  *
353  * @param[in] obj A struct whose first element is a pointer to an
354  * AVClass.
355  * @param[in] name the name of the field to set
356  * @param[in] val The value to set. If the field is not of a string
357  * type, then the given string is parsed.
358  * SI postfixes and some named scalars are supported.
359  * If the field is of a numeric type, it has to be a numeric or named
360  * scalar. Behavior with more than one scalar and +- infix operators
361  * is undefined.
362  * If the field is of a flags type, it has to be a sequence of numeric
363  * scalars or named flags separated by '+' or '-'. Prefixing a flag
364  * with '+' causes it to be set without affecting the other flags;
365  * similarly, '-' unsets a flag.
366  * @param[out] o_out if non-NULL put here a pointer to the AVOption
367  * found
368  * @param alloc this parameter is currently ignored
369  * @return 0 if the value has been set, or an AVERROR code in case of
370  * error:
371  * AVERROR_OPTION_NOT_FOUND if no matching option exists
372  * AVERROR(ERANGE) if the value is out of range
373  * AVERROR(EINVAL) if the value is not valid
374  * @deprecated use av_opt_set()
375  */
377 int av_set_string3(void *obj, const char *name, const char *val, int alloc, const AVOption **o_out);
378 
379 attribute_deprecated const AVOption *av_set_double(void *obj, const char *name, double n);
380 attribute_deprecated const AVOption *av_set_q(void *obj, const char *name, AVRational n);
381 attribute_deprecated const AVOption *av_set_int(void *obj, const char *name, int64_t n);
382 
383 double av_get_double(void *obj, const char *name, const AVOption **o_out);
384 AVRational av_get_q(void *obj, const char *name, const AVOption **o_out);
385 int64_t av_get_int(void *obj, const char *name, const AVOption **o_out);
386 attribute_deprecated const char *av_get_string(void *obj, const char *name, const AVOption **o_out, char *buf, int buf_len);
387 attribute_deprecated const AVOption *av_next_option(void *obj, const AVOption *last);
388 #endif
389 
390 /**
391  * Show the obj options.
392  *
393  * @param req_flags requested flags for the options to show. Show only the
394  * options for which it is opt->flags & req_flags.
395  * @param rej_flags rejected flags for the options to show. Show only the
396  * options for which it is !(opt->flags & req_flags).
397  * @param av_log_obj log context to use for showing the options
398  */
399 int av_opt_show2(void *obj, void *av_log_obj, int req_flags, int rej_flags);
400 
401 /**
402  * Set the values of all AVOption fields to their default values.
403  *
404  * @param s an AVOption-enabled struct (its first member must be a pointer to AVClass)
405  */
406 void av_opt_set_defaults(void *s);
407 
408 #if FF_API_OLD_AVOPTIONS
410 void av_opt_set_defaults2(void *s, int mask, int flags);
411 #endif
412 
413 /**
414  * Parse the key/value pairs list in opts. For each key/value pair
415  * found, stores the value in the field in ctx that is named like the
416  * key. ctx must be an AVClass context, storing is done using
417  * AVOptions.
418  *
419  * @param opts options string to parse, may be NULL
420  * @param key_val_sep a 0-terminated list of characters used to
421  * separate key from value
422  * @param pairs_sep a 0-terminated list of characters used to separate
423  * two pairs from each other
424  * @return the number of successfully set key/value pairs, or a negative
425  * value corresponding to an AVERROR code in case of error:
426  * AVERROR(EINVAL) if opts cannot be parsed,
427  * the error code issued by av_set_string3() if a key/value pair
428  * cannot be set
429  */
430 int av_set_options_string(void *ctx, const char *opts,
431  const char *key_val_sep, const char *pairs_sep);
432 
433 /**
434  * Parse the key-value pairs list in opts. For each key=value pair found,
435  * set the value of the corresponding option in ctx.
436  *
437  * @param ctx the AVClass object to set options on
438  * @param opts the options string, key-value pairs separated by a
439  * delimiter
440  * @param shorthand a NULL-terminated array of options names for shorthand
441  * notation: if the first field in opts has no key part,
442  * the key is taken from the first element of shorthand;
443  * then again for the second, etc., until either opts is
444  * finished, shorthand is finished or a named option is
445  * found; after that, all options must be named
446  * @param key_val_sep a 0-terminated list of characters used to separate
447  * key from value, for example '='
448  * @param pairs_sep a 0-terminated list of characters used to separate
449  * two pairs from each other, for example ':' or ','
450  * @return the number of successfully set key=value pairs, or a negative
451  * value corresponding to an AVERROR code in case of error:
452  * AVERROR(EINVAL) if opts cannot be parsed,
453  * the error code issued by av_set_string3() if a key/value pair
454  * cannot be set
455  *
456  * Options names must use only the following characters: a-z A-Z 0-9 - . / _
457  * Separators must use characters distinct from option names and from each
458  * other.
459  */
460 int av_opt_set_from_string(void *ctx, const char *opts,
461  const char *const *shorthand,
462  const char *key_val_sep, const char *pairs_sep);
463 /**
464  * Free all string and binary options in obj.
465  */
466 void av_opt_free(void *obj);
467 
468 /**
469  * Check whether a particular flag is set in a flags field.
470  *
471  * @param field_name the name of the flag field option
472  * @param flag_name the name of the flag to check
473  * @return non-zero if the flag is set, zero if the flag isn't set,
474  * isn't of the right type, or the flags field doesn't exist.
475  */
476 int av_opt_flag_is_set(void *obj, const char *field_name, const char *flag_name);
477 
478 /**
479  * Set all the options from a given dictionary on an object.
480  *
481  * @param obj a struct whose first element is a pointer to AVClass
482  * @param options options to process. This dictionary will be freed and replaced
483  * by a new one containing all options not found in obj.
484  * Of course this new dictionary needs to be freed by caller
485  * with av_dict_free().
486  *
487  * @return 0 on success, a negative AVERROR if some option was found in obj,
488  * but could not be set.
489  *
490  * @see av_dict_copy()
491  */
492 int av_opt_set_dict(void *obj, struct AVDictionary **options);
493 
494 /**
495  * Extract a key-value pair from the beginning of a string.
496  *
497  * @param ropts pointer to the options string, will be updated to
498  * point to the rest of the string (one of the pairs_sep
499  * or the final NUL)
500  * @param key_val_sep a 0-terminated list of characters used to separate
501  * key from value, for example '='
502  * @param pairs_sep a 0-terminated list of characters used to separate
503  * two pairs from each other, for example ':' or ','
504  * @param flags flags; see the AV_OPT_FLAG_* values below
505  * @param rkey parsed key; must be freed using av_free()
506  * @param rval parsed value; must be freed using av_free()
507  *
508  * @return >=0 for success, or a negative value corresponding to an
509  * AVERROR code in case of error; in particular:
510  * AVERROR(EINVAL) if no key is present
511  *
512  */
513 int av_opt_get_key_value(const char **ropts,
514  const char *key_val_sep, const char *pairs_sep,
515  unsigned flags,
516  char **rkey, char **rval);
517 
518 enum {
519 
520  /**
521  * Accept to parse a value without a key; the key will then be returned
522  * as NULL.
523  */
525 };
526 
527 /**
528  * @defgroup opt_eval_funcs Evaluating option strings
529  * @{
530  * This group of functions can be used to evaluate option strings
531  * and get numbers out of them. They do the same thing as av_opt_set(),
532  * except the result is written into the caller-supplied pointer.
533  *
534  * @param obj a struct whose first element is a pointer to AVClass.
535  * @param o an option for which the string is to be evaluated.
536  * @param val string to be evaluated.
537  * @param *_out value of the string will be written here.
538  *
539  * @return 0 on success, a negative number on failure.
540  */
541 int av_opt_eval_flags (void *obj, const AVOption *o, const char *val, int *flags_out);
542 int av_opt_eval_int (void *obj, const AVOption *o, const char *val, int *int_out);
543 int av_opt_eval_int64 (void *obj, const AVOption *o, const char *val, int64_t *int64_out);
544 int av_opt_eval_float (void *obj, const AVOption *o, const char *val, float *float_out);
545 int av_opt_eval_double(void *obj, const AVOption *o, const char *val, double *double_out);
546 int av_opt_eval_q (void *obj, const AVOption *o, const char *val, AVRational *q_out);
547 /**
548  * @}
549  */
550 
551 #define AV_OPT_SEARCH_CHILDREN 0x0001 /**< Search in possible children of the
552  given object first. */
553 /**
554  * The obj passed to av_opt_find() is fake -- only a double pointer to AVClass
555  * instead of a required pointer to a struct containing AVClass. This is
556  * useful for searching for options without needing to allocate the corresponding
557  * object.
558  */
559 #define AV_OPT_SEARCH_FAKE_OBJ 0x0002
560 
561 /**
562  * Look for an option in an object. Consider only options which
563  * have all the specified flags set.
564  *
565  * @param[in] obj A pointer to a struct whose first element is a
566  * pointer to an AVClass.
567  * Alternatively a double pointer to an AVClass, if
568  * AV_OPT_SEARCH_FAKE_OBJ search flag is set.
569  * @param[in] name The name of the option to look for.
570  * @param[in] unit When searching for named constants, name of the unit
571  * it belongs to.
572  * @param opt_flags Find only options with all the specified flags set (AV_OPT_FLAG).
573  * @param search_flags A combination of AV_OPT_SEARCH_*.
574  *
575  * @return A pointer to the option found, or NULL if no option
576  * was found.
577  *
578  * @note Options found with AV_OPT_SEARCH_CHILDREN flag may not be settable
579  * directly with av_set_string3(). Use special calls which take an options
580  * AVDictionary (e.g. avformat_open_input()) to set options found with this
581  * flag.
582  */
583 const AVOption *av_opt_find(void *obj, const char *name, const char *unit,
584  int opt_flags, int search_flags);
585 
586 /**
587  * Look for an option in an object. Consider only options which
588  * have all the specified flags set.
589  *
590  * @param[in] obj A pointer to a struct whose first element is a
591  * pointer to an AVClass.
592  * Alternatively a double pointer to an AVClass, if
593  * AV_OPT_SEARCH_FAKE_OBJ search flag is set.
594  * @param[in] name The name of the option to look for.
595  * @param[in] unit When searching for named constants, name of the unit
596  * it belongs to.
597  * @param opt_flags Find only options with all the specified flags set (AV_OPT_FLAG).
598  * @param search_flags A combination of AV_OPT_SEARCH_*.
599  * @param[out] target_obj if non-NULL, an object to which the option belongs will be
600  * written here. It may be different from obj if AV_OPT_SEARCH_CHILDREN is present
601  * in search_flags. This parameter is ignored if search_flags contain
602  * AV_OPT_SEARCH_FAKE_OBJ.
603  *
604  * @return A pointer to the option found, or NULL if no option
605  * was found.
606  */
607 const AVOption *av_opt_find2(void *obj, const char *name, const char *unit,
608  int opt_flags, int search_flags, void **target_obj);
609 
610 /**
611  * Iterate over all AVOptions belonging to obj.
612  *
613  * @param obj an AVOptions-enabled struct or a double pointer to an
614  * AVClass describing it.
615  * @param prev result of the previous call to av_opt_next() on this object
616  * or NULL
617  * @return next AVOption or NULL
618  */
619 const AVOption *av_opt_next(void *obj, const AVOption *prev);
620 
621 /**
622  * Iterate over AVOptions-enabled children of obj.
623  *
624  * @param prev result of a previous call to this function or NULL
625  * @return next AVOptions-enabled child or NULL
626  */
627 void *av_opt_child_next(void *obj, void *prev);
628 
629 /**
630  * Iterate over potential AVOptions-enabled children of parent.
631  *
632  * @param prev result of a previous call to this function or NULL
633  * @return AVClass corresponding to next potential child or NULL
634  */
635 const AVClass *av_opt_child_class_next(const AVClass *parent, const AVClass *prev);
636 
637 /**
638  * @defgroup opt_set_funcs Option setting functions
639  * @{
640  * Those functions set the field of obj with the given name to value.
641  *
642  * @param[in] obj A struct whose first element is a pointer to an AVClass.
643  * @param[in] name the name of the field to set
644  * @param[in] val The value to set. In case of av_opt_set() if the field is not
645  * of a string type, then the given string is parsed.
646  * SI postfixes and some named scalars are supported.
647  * If the field is of a numeric type, it has to be a numeric or named
648  * scalar. Behavior with more than one scalar and +- infix operators
649  * is undefined.
650  * If the field is of a flags type, it has to be a sequence of numeric
651  * scalars or named flags separated by '+' or '-'. Prefixing a flag
652  * with '+' causes it to be set without affecting the other flags;
653  * similarly, '-' unsets a flag.
654  * @param search_flags flags passed to av_opt_find2. I.e. if AV_OPT_SEARCH_CHILDREN
655  * is passed here, then the option may be set on a child of obj.
656  *
657  * @return 0 if the value has been set, or an AVERROR code in case of
658  * error:
659  * AVERROR_OPTION_NOT_FOUND if no matching option exists
660  * AVERROR(ERANGE) if the value is out of range
661  * AVERROR(EINVAL) if the value is not valid
662  */
663 int av_opt_set (void *obj, const char *name, const char *val, int search_flags);
664 int av_opt_set_int (void *obj, const char *name, int64_t val, int search_flags);
665 int av_opt_set_double(void *obj, const char *name, double val, int search_flags);
666 int av_opt_set_q (void *obj, const char *name, AVRational val, int search_flags);
667 int av_opt_set_bin (void *obj, const char *name, const uint8_t *val, int size, int search_flags);
668 int av_opt_set_image_size(void *obj, const char *name, int w, int h, int search_flags);
669 int av_opt_set_pixel_fmt (void *obj, const char *name, enum AVPixelFormat fmt, int search_flags);
670 int av_opt_set_sample_fmt(void *obj, const char *name, enum AVSampleFormat fmt, int search_flags);
671 int av_opt_set_video_rate(void *obj, const char *name, AVRational val, int search_flags);
672 int av_opt_set_channel_layout(void *obj, const char *name, int64_t ch_layout, int search_flags);
673 
674 /**
675  * Set a binary option to an integer list.
676  *
677  * @param obj AVClass object to set options on
678  * @param name name of the binary option
679  * @param val pointer to an integer list (must have the correct type with
680  * regard to the contents of the list)
681  * @param term list terminator (usually 0 or -1)
682  * @param flags search flags
683  */
684 #define av_opt_set_int_list(obj, name, val, term, flags) \
685  (av_int_list_length(val, term) > INT_MAX / sizeof(*(val)) ? \
686  AVERROR(EINVAL) : \
687  av_opt_set_bin(obj, name, (const uint8_t *)(val), \
688  av_int_list_length(val, term) * sizeof(*(val)), flags))
689 /**
690  * @}
691  */
692 
693 /**
694  * @defgroup opt_get_funcs Option getting functions
695  * @{
696  * Those functions get a value of the option with the given name from an object.
697  *
698  * @param[in] obj a struct whose first element is a pointer to an AVClass.
699  * @param[in] name name of the option to get.
700  * @param[in] search_flags flags passed to av_opt_find2. I.e. if AV_OPT_SEARCH_CHILDREN
701  * is passed here, then the option may be found in a child of obj.
702  * @param[out] out_val value of the option will be written here
703  * @return >=0 on success, a negative error code otherwise
704  */
705 /**
706  * @note the returned string will be av_malloc()ed and must be av_free()ed by the caller
707  */
708 int av_opt_get (void *obj, const char *name, int search_flags, uint8_t **out_val);
709 int av_opt_get_int (void *obj, const char *name, int search_flags, int64_t *out_val);
710 int av_opt_get_double(void *obj, const char *name, int search_flags, double *out_val);
711 int av_opt_get_q (void *obj, const char *name, int search_flags, AVRational *out_val);
712 int av_opt_get_image_size(void *obj, const char *name, int search_flags, int *w_out, int *h_out);
713 int av_opt_get_pixel_fmt (void *obj, const char *name, int search_flags, enum AVPixelFormat *out_fmt);
714 int av_opt_get_sample_fmt(void *obj, const char *name, int search_flags, enum AVSampleFormat *out_fmt);
715 int av_opt_get_video_rate(void *obj, const char *name, int search_flags, AVRational *out_val);
716 int av_opt_get_channel_layout(void *obj, const char *name, int search_flags, int64_t *ch_layout);
717 /**
718  * @}
719  */
720 /**
721  * Gets a pointer to the requested field in a struct.
722  * This function allows accessing a struct even when its fields are moved or
723  * renamed since the application making the access has been compiled,
724  *
725  * @returns a pointer to the field, it can be cast to the correct type and read
726  * or written to.
727  */
728 void *av_opt_ptr(const AVClass *avclass, void *obj, const char *name);
729 
730 /**
731  * Free an AVOptionRanges struct and set it to NULL.
732  */
733 void av_opt_freep_ranges(AVOptionRanges **ranges);
734 
735 /**
736  * Get a list of allowed ranges for the given option.
737  *
738  * The returned list may depend on other fields in obj like for example profile.
739  *
740  * @param flags is a bitmask of flags, undefined flags should not be set and should be ignored
741  * AV_OPT_SEARCH_FAKE_OBJ indicates that the obj is a double pointer to a AVClass instead of a full instance
742  *
743  * The result must be freed with av_opt_freep_ranges.
744  *
745  * @return >= 0 on success, a negative errro code otherwise
746  */
747 int av_opt_query_ranges(AVOptionRanges **, void *obj, const char *key, int flags);
748 
749 /**
750  * Get a default list of allowed ranges for the given option.
751  *
752  * This list is constructed without using the AVClass.query_ranges() callback
753  * and can be used as fallback from within the callback.
754  *
755  * @param flags is a bitmask of flags, undefined flags should not be set and should be ignored
756  * AV_OPT_SEARCH_FAKE_OBJ indicates that the obj is a double pointer to a AVClass instead of a full instance
757  *
758  * The result must be freed with av_opt_free_ranges.
759  *
760  * @return >= 0 on success, a negative errro code otherwise
761  */
762 int av_opt_query_ranges_default(AVOptionRanges **, void *obj, const char *key, int flags);
763 
764 /**
765  * @}
766  */
767 
768 #endif /* AVUTIL_OPT_H */