3 * copyright (c) 2005 Michael Niedermayer <michaelni@gmx.at>
5 * This file is part of FFmpeg.
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.
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.
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
35 #include "samplefmt.h"
38 * @defgroup avoptions AVOptions
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.
45 * @section avoptions_implement Implementing AVOptions
46 * This section describes how to add AVOptions capabilities to a struct.
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.
57 * The following example illustrates an AVOptions-enabled struct:
59 * typedef struct test_struct {
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 },
77 * static const AVClass test_class = {
78 * .class_name = "test class",
79 * .item_name = av_default_item_name,
81 * .version = LIBAVUTIL_VERSION_INT,
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
90 * When cleaning up, you may use the av_opt_free() function to automatically
91 * free all the allocated string and binary options.
93 * Continuing with the above example:
96 * test_struct *alloc_test_struct(void)
98 * test_struct *ret = av_malloc(sizeof(*ret));
99 * ret->class = &test_class;
100 * av_opt_set_defaults(ret);
103 * void free_test_struct(test_struct **foo)
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:
122 * typedef struct 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 },
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,
138 * void *child_next(void *obj, void *prev)
140 * test_struct *t = obj;
141 * if (!prev && t->child_struct)
142 * return t->child_struct;
145 * const AVClass child_class_next(const AVClass *prev)
147 * return prev ? NULL : &child_class;
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).
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.
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
171 * For example, to add some named constants for the test_flags option
172 * above, put the following into the child_opts array:
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" },
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.
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.
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.
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).
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
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().
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.
227 AV_OPT_TYPE_RATIONAL,
228 AV_OPT_TYPE_BINARY, ///< offset must point to a pointer immediately followed by an int for the length
229 AV_OPT_TYPE_CONST = 128,
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
234 FF_OPT_TYPE_FLAGS = 0,
240 FF_OPT_TYPE_RATIONAL,
241 FF_OPT_TYPE_BINARY, ///< offset must point to a pointer immediately followed by an int for the length
242 FF_OPT_TYPE_CONST=128,
249 typedef struct AVOption {
253 * short English help text
254 * @todo What about other languages?
259 * The offset relative to the context structure where the option
260 * value is stored. It should be 0 for named constants.
263 enum AVOptionType type;
266 * the default value for scalar options
272 /* TODO those are unused now */
275 double min; ///< minimum valid value for the option
276 double max; ///< maximum valid value for the option
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
289 * The logical unit to which the option belongs. Non-constant
290 * options and corresponding named constants share the same
298 * Look for an option in obj. Look only for the options which
299 * have the flags set as specified in mask and flags (that is,
300 * for which it is the case that opt->flags & mask == flags).
302 * @param[in] obj a pointer to a struct whose first element is a
303 * pointer to an AVClass
304 * @param[in] name the name of the option to look for
305 * @param[in] unit the unit of the option to look for, or any if NULL
306 * @return a pointer to the option found, or NULL if no option
309 * @deprecated use av_opt_find.
312 const AVOption *av_find_opt(void *obj, const char *name, const char *unit, int mask, int flags);
315 #if FF_API_OLD_AVOPTIONS
317 * Set the field of obj with the given name to value.
319 * @param[in] obj A struct whose first element is a pointer to an
321 * @param[in] name the name of the field to set
322 * @param[in] val The value to set. If the field is not of a string
323 * type, then the given string is parsed.
324 * SI postfixes and some named scalars are supported.
325 * If the field is of a numeric type, it has to be a numeric or named
326 * scalar. Behavior with more than one scalar and +- infix operators
328 * If the field is of a flags type, it has to be a sequence of numeric
329 * scalars or named flags separated by '+' or '-'. Prefixing a flag
330 * with '+' causes it to be set without affecting the other flags;
331 * similarly, '-' unsets a flag.
332 * @param[out] o_out if non-NULL put here a pointer to the AVOption
334 * @param alloc this parameter is currently ignored
335 * @return 0 if the value has been set, or an AVERROR code in case of
337 * AVERROR_OPTION_NOT_FOUND if no matching option exists
338 * AVERROR(ERANGE) if the value is out of range
339 * AVERROR(EINVAL) if the value is not valid
340 * @deprecated use av_opt_set()
343 int av_set_string3(void *obj, const char *name, const char *val, int alloc, const AVOption **o_out);
345 attribute_deprecated const AVOption *av_set_double(void *obj, const char *name, double n);
346 attribute_deprecated const AVOption *av_set_q(void *obj, const char *name, AVRational n);
347 attribute_deprecated const AVOption *av_set_int(void *obj, const char *name, int64_t n);
349 double av_get_double(void *obj, const char *name, const AVOption **o_out);
350 AVRational av_get_q(void *obj, const char *name, const AVOption **o_out);
351 int64_t av_get_int(void *obj, const char *name, const AVOption **o_out);
352 attribute_deprecated const char *av_get_string(void *obj, const char *name, const AVOption **o_out, char *buf, int buf_len);
353 attribute_deprecated const AVOption *av_next_option(void *obj, const AVOption *last);
357 * Show the obj options.
359 * @param req_flags requested flags for the options to show. Show only the
360 * options for which it is opt->flags & req_flags.
361 * @param rej_flags rejected flags for the options to show. Show only the
362 * options for which it is !(opt->flags & req_flags).
363 * @param av_log_obj log context to use for showing the options
365 int av_opt_show2(void *obj, void *av_log_obj, int req_flags, int rej_flags);
368 * Set the values of all AVOption fields to their default values.
370 * @param s an AVOption-enabled struct (its first member must be a pointer to AVClass)
372 void av_opt_set_defaults(void *s);
374 #if FF_API_OLD_AVOPTIONS
376 void av_opt_set_defaults2(void *s, int mask, int flags);
380 * Parse the key/value pairs list in opts. For each key/value pair
381 * found, stores the value in the field in ctx that is named like the
382 * key. ctx must be an AVClass context, storing is done using
385 * @param opts options string to parse, may be NULL
386 * @param key_val_sep a 0-terminated list of characters used to
387 * separate key from value
388 * @param pairs_sep a 0-terminated list of characters used to separate
389 * two pairs from each other
390 * @return the number of successfully set key/value pairs, or a negative
391 * value corresponding to an AVERROR code in case of error:
392 * AVERROR(EINVAL) if opts cannot be parsed,
393 * the error code issued by av_set_string3() if a key/value pair
396 int av_set_options_string(void *ctx, const char *opts,
397 const char *key_val_sep, const char *pairs_sep);
400 * Parse the key-value pairs list in opts. For each key=value pair found,
401 * set the value of the corresponding option in ctx.
403 * @param ctx the AVClass object to set options on
404 * @param opts the options string, key-value pairs separated by a
406 * @param shorthand a NULL-terminated array of options names for shorthand
407 * notation: if the first field in opts has no key part,
408 * the key is taken from the first element of shorthand;
409 * then again for the second, etc., until either opts is
410 * finished, shorthand is finished or a named option is
411 * found; after that, all options must be named
412 * @param key_val_sep a 0-terminated list of characters used to separate
413 * key from value, for example '='
414 * @param pairs_sep a 0-terminated list of characters used to separate
415 * two pairs from each other, for example ':' or ','
416 * @return the number of successfully set key=value pairs, or a negative
417 * value corresponding to an AVERROR code in case of error:
418 * AVERROR(EINVAL) if opts cannot be parsed,
419 * the error code issued by av_set_string3() if a key/value pair
422 * Options names must use only the following characters: a-z A-Z 0-9 - . / _
423 * Separators must use characters distinct from option names and from each
426 int av_opt_set_from_string(void *ctx, const char *opts,
427 const char *const *shorthand,
428 const char *key_val_sep, const char *pairs_sep);
430 * Free all string and binary options in obj.
432 void av_opt_free(void *obj);
435 * Check whether a particular flag is set in a flags field.
437 * @param field_name the name of the flag field option
438 * @param flag_name the name of the flag to check
439 * @return non-zero if the flag is set, zero if the flag isn't set,
440 * isn't of the right type, or the flags field doesn't exist.
442 int av_opt_flag_is_set(void *obj, const char *field_name, const char *flag_name);
445 * Set all the options from a given dictionary on an object.
447 * @param obj a struct whose first element is a pointer to AVClass
448 * @param options options to process. This dictionary will be freed and replaced
449 * by a new one containing all options not found in obj.
450 * Of course this new dictionary needs to be freed by caller
451 * with av_dict_free().
453 * @return 0 on success, a negative AVERROR if some option was found in obj,
454 * but could not be set.
456 * @see av_dict_copy()
458 int av_opt_set_dict(void *obj, struct AVDictionary **options);
461 * Extract a key-value pair from the beginning of a string.
463 * @param ropts pointer to the options string, will be updated to
464 * point to the rest of the string (one of the pairs_sep
466 * @param key_val_sep a 0-terminated list of characters used to separate
467 * key from value, for example '='
468 * @param pairs_sep a 0-terminated list of characters used to separate
469 * two pairs from each other, for example ':' or ','
470 * @param flags flags; see the AV_OPT_FLAG_* values below
471 * @param rkey parsed key; must be freed using av_free()
472 * @param rval parsed value; must be freed using av_free()
474 * @return >=0 for success, or a negative value corresponding to an
475 * AVERROR code in case of error; in particular:
476 * AVERROR(EINVAL) if no key is present
479 int av_opt_get_key_value(const char **ropts,
480 const char *key_val_sep, const char *pairs_sep,
482 char **rkey, char **rval);
487 * Accept to parse a value without a key; the key will then be returned
490 AV_OPT_FLAG_IMPLICIT_KEY = 1,
494 * @defgroup opt_eval_funcs Evaluating option strings
496 * This group of functions can be used to evaluate option strings
497 * and get numbers out of them. They do the same thing as av_opt_set(),
498 * except the result is written into the caller-supplied pointer.
500 * @param obj a struct whose first element is a pointer to AVClass.
501 * @param o an option for which the string is to be evaluated.
502 * @param val string to be evaluated.
503 * @param *_out value of the string will be written here.
505 * @return 0 on success, a negative number on failure.
507 int av_opt_eval_flags (void *obj, const AVOption *o, const char *val, int *flags_out);
508 int av_opt_eval_int (void *obj, const AVOption *o, const char *val, int *int_out);
509 int av_opt_eval_int64 (void *obj, const AVOption *o, const char *val, int64_t *int64_out);
510 int av_opt_eval_float (void *obj, const AVOption *o, const char *val, float *float_out);
511 int av_opt_eval_double(void *obj, const AVOption *o, const char *val, double *double_out);
512 int av_opt_eval_q (void *obj, const AVOption *o, const char *val, AVRational *q_out);
517 #define AV_OPT_SEARCH_CHILDREN 0x0001 /**< Search in possible children of the
518 given object first. */
520 * The obj passed to av_opt_find() is fake -- only a double pointer to AVClass
521 * instead of a required pointer to a struct containing AVClass. This is
522 * useful for searching for options without needing to allocate the corresponding
525 #define AV_OPT_SEARCH_FAKE_OBJ 0x0002
528 * Look for an option in an object. Consider only options which
529 * have all the specified flags set.
531 * @param[in] obj A pointer to a struct whose first element is a
532 * pointer to an AVClass.
533 * Alternatively a double pointer to an AVClass, if
534 * AV_OPT_SEARCH_FAKE_OBJ search flag is set.
535 * @param[in] name The name of the option to look for.
536 * @param[in] unit When searching for named constants, name of the unit
538 * @param opt_flags Find only options with all the specified flags set (AV_OPT_FLAG).
539 * @param search_flags A combination of AV_OPT_SEARCH_*.
541 * @return A pointer to the option found, or NULL if no option
544 * @note Options found with AV_OPT_SEARCH_CHILDREN flag may not be settable
545 * directly with av_set_string3(). Use special calls which take an options
546 * AVDictionary (e.g. avformat_open_input()) to set options found with this
549 const AVOption *av_opt_find(void *obj, const char *name, const char *unit,
550 int opt_flags, int search_flags);
553 * Look for an option in an object. Consider only options which
554 * have all the specified flags set.
556 * @param[in] obj A pointer to a struct whose first element is a
557 * pointer to an AVClass.
558 * Alternatively a double pointer to an AVClass, if
559 * AV_OPT_SEARCH_FAKE_OBJ search flag is set.
560 * @param[in] name The name of the option to look for.
561 * @param[in] unit When searching for named constants, name of the unit
563 * @param opt_flags Find only options with all the specified flags set (AV_OPT_FLAG).
564 * @param search_flags A combination of AV_OPT_SEARCH_*.
565 * @param[out] target_obj if non-NULL, an object to which the option belongs will be
566 * written here. It may be different from obj if AV_OPT_SEARCH_CHILDREN is present
567 * in search_flags. This parameter is ignored if search_flags contain
568 * AV_OPT_SEARCH_FAKE_OBJ.
570 * @return A pointer to the option found, or NULL if no option
573 const AVOption *av_opt_find2(void *obj, const char *name, const char *unit,
574 int opt_flags, int search_flags, void **target_obj);
577 * Iterate over all AVOptions belonging to obj.
579 * @param obj an AVOptions-enabled struct or a double pointer to an
580 * AVClass describing it.
581 * @param prev result of the previous call to av_opt_next() on this object
583 * @return next AVOption or NULL
585 const AVOption *av_opt_next(void *obj, const AVOption *prev);
588 * Iterate over AVOptions-enabled children of obj.
590 * @param prev result of a previous call to this function or NULL
591 * @return next AVOptions-enabled child or NULL
593 void *av_opt_child_next(void *obj, void *prev);
596 * Iterate over potential AVOptions-enabled children of parent.
598 * @param prev result of a previous call to this function or NULL
599 * @return AVClass corresponding to next potential child or NULL
601 const AVClass *av_opt_child_class_next(const AVClass *parent, const AVClass *prev);
604 * @defgroup opt_set_funcs Option setting functions
606 * Those functions set the field of obj with the given name to value.
608 * @param[in] obj A struct whose first element is a pointer to an AVClass.
609 * @param[in] name the name of the field to set
610 * @param[in] val The value to set. In case of av_opt_set() if the field is not
611 * of a string type, then the given string is parsed.
612 * SI postfixes and some named scalars are supported.
613 * If the field is of a numeric type, it has to be a numeric or named
614 * scalar. Behavior with more than one scalar and +- infix operators
616 * If the field is of a flags type, it has to be a sequence of numeric
617 * scalars or named flags separated by '+' or '-'. Prefixing a flag
618 * with '+' causes it to be set without affecting the other flags;
619 * similarly, '-' unsets a flag.
620 * @param search_flags flags passed to av_opt_find2. I.e. if AV_OPT_SEARCH_CHILDREN
621 * is passed here, then the option may be set on a child of obj.
623 * @return 0 if the value has been set, or an AVERROR code in case of
625 * AVERROR_OPTION_NOT_FOUND if no matching option exists
626 * AVERROR(ERANGE) if the value is out of range
627 * AVERROR(EINVAL) if the value is not valid
629 int av_opt_set (void *obj, const char *name, const char *val, int search_flags);
630 int av_opt_set_int (void *obj, const char *name, int64_t val, int search_flags);
631 int av_opt_set_double(void *obj, const char *name, double val, int search_flags);
632 int av_opt_set_q (void *obj, const char *name, AVRational val, int search_flags);
633 int av_opt_set_bin (void *obj, const char *name, const uint8_t *val, int size, int search_flags);
634 int av_opt_set_image_size(void *obj, const char *name, int w, int h, int search_flags);
635 int av_opt_set_pixel_fmt (void *obj, const char *name, enum AVPixelFormat fmt, int search_flags);
636 int av_opt_set_sample_fmt(void *obj, const char *name, enum AVSampleFormat fmt, int search_flags);
642 * @defgroup opt_get_funcs Option getting functions
644 * Those functions get a value of the option with the given name from an object.
646 * @param[in] obj a struct whose first element is a pointer to an AVClass.
647 * @param[in] name name of the option to get.
648 * @param[in] search_flags flags passed to av_opt_find2. I.e. if AV_OPT_SEARCH_CHILDREN
649 * is passed here, then the option may be found in a child of obj.
650 * @param[out] out_val value of the option will be written here
651 * @return 0 on success, a negative error code otherwise
654 * @note the returned string will av_malloc()ed and must be av_free()ed by the caller
656 int av_opt_get (void *obj, const char *name, int search_flags, uint8_t **out_val);
657 int av_opt_get_int (void *obj, const char *name, int search_flags, int64_t *out_val);
658 int av_opt_get_double(void *obj, const char *name, int search_flags, double *out_val);
659 int av_opt_get_q (void *obj, const char *name, int search_flags, AVRational *out_val);
660 int av_opt_get_image_size(void *obj, const char *name, int search_flags, int *w_out, int *h_out);
661 int av_opt_get_pixel_fmt (void *obj, const char *name, int search_flags, enum AVPixelFormat *out_fmt);
662 int av_opt_get_sample_fmt(void *obj, const char *name, int search_flags, enum AVSampleFormat *out_fmt);
667 * Gets a pointer to the requested field in a struct.
668 * This function allows accessing a struct even when its fields are moved or
669 * renamed since the application making the access has been compiled,
671 * @returns a pointer to the field, it can be cast to the correct type and read
674 void *av_opt_ptr(const AVClass *avclass, void *obj, const char *name);
679 #endif /* AVUTIL_OPT_H */