1/* 2 * AVOptions 3 * copyright (c) 2005 Michael Niedermayer <michaelni@gmx.at> 4 * 5 * This file is part of Libav. 6 * 7 * Libav 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 * Libav 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 Libav; 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 35/** 36 * @defgroup avoptions AVOptions 37 * @ingroup lavu_data 38 * @{ 39 * AVOptions provide a generic system to declare options on arbitrary structs 40 * ("objects"). An option can have a help text, a type and a range of possible 41 * values. Options may then be enumerated, read and written to. 42 * 43 * @section avoptions_implement Implementing AVOptions 44 * This section describes how to add AVOptions capabilities to a struct. 45 * 46 * All AVOptions-related information is stored in an AVClass. Therefore 47 * the first member of the struct must be a pointer to an AVClass describing it. 48 * The option field of the AVClass must be set to a NULL-terminated static array 49 * of AVOptions. Each AVOption must have a non-empty name, a type, a default 50 * value and for number-type AVOptions also a range of allowed values. It must 51 * also declare an offset in bytes from the start of the struct, where the field 52 * associated with this AVOption is located. Other fields in the AVOption struct 53 * should also be set when applicable, but are not required. 54 * 55 * The following example illustrates an AVOptions-enabled struct: 56 * @code 57 * typedef struct test_struct { 58 * AVClass *class; 59 * int int_opt; 60 * char *str_opt; 61 * uint8_t *bin_opt; 62 * int bin_len; 63 * } test_struct; 64 * 65 * static const AVOption options[] = { 66 * { "test_int", "This is a test option of int type.", offsetof(test_struct, int_opt), 67 * AV_OPT_TYPE_INT, { -1 }, INT_MIN, INT_MAX }, 68 * { "test_str", "This is a test option of string type.", offsetof(test_struct, str_opt), 69 * AV_OPT_TYPE_STRING }, 70 * { "test_bin", "This is a test option of binary type.", offsetof(test_struct, bin_opt), 71 * AV_OPT_TYPE_BINARY }, 72 * { NULL }, 73 * }; 74 * 75 * static const AVClass test_class = { 76 * .class_name = "test class", 77 * .item_name = av_default_item_name, 78 * .option = options, 79 * .version = LIBAVUTIL_VERSION_INT, 80 * }; 81 * @endcode 82 * 83 * Next, when allocating your struct, you must ensure that the AVClass pointer 84 * is set to the correct value. Then, av_opt_set_defaults() must be called to 85 * initialize defaults. After that the struct is ready to be used with the 86 * AVOptions API. 87 * 88 * When cleaning up, you may use the av_opt_free() function to automatically 89 * free all the allocated string and binary options. 90 * 91 * Continuing with the above example: 92 * 93 * @code 94 * test_struct *alloc_test_struct(void) 95 * { 96 * test_struct *ret = av_malloc(sizeof(*ret)); 97 * ret->class = &test_class; 98 * av_opt_set_defaults(ret); 99 * return ret; 100 * } 101 * void free_test_struct(test_struct **foo) 102 * { 103 * av_opt_free(*foo); 104 * av_freep(foo); 105 * } 106 * @endcode 107 * 108 * @subsection avoptions_implement_nesting Nesting 109 * It may happen that an AVOptions-enabled struct contains another 110 * AVOptions-enabled struct as a member (e.g. AVCodecContext in 111 * libavcodec exports generic options, while its priv_data field exports 112 * codec-specific options). In such a case, it is possible to set up the 113 * parent struct to export a child's options. To do that, simply 114 * implement AVClass.child_next() and AVClass.child_class_next() in the 115 * parent struct's AVClass. 116 * Assuming that the test_struct from above now also contains a 117 * child_struct field: 118 * 119 * @code 120 * typedef struct child_struct { 121 * AVClass *class; 122 * int flags_opt; 123 * } child_struct; 124 * static const AVOption child_opts[] = { 125 * { "test_flags", "This is a test option of flags type.", 126 * offsetof(child_struct, flags_opt), AV_OPT_TYPE_FLAGS, { 0 }, INT_MIN, INT_MAX }, 127 * { NULL }, 128 * }; 129 * static const AVClass child_class = { 130 * .class_name = "child class", 131 * .item_name = av_default_item_name, 132 * .option = child_opts, 133 * .version = LIBAVUTIL_VERSION_INT, 134 * }; 135 * 136 * void *child_next(void *obj, void *prev) 137 * { 138 * test_struct *t = obj; 139 * if (!prev && t->child_struct) 140 * return t->child_struct; 141 * return NULL 142 * } 143 * const AVClass child_class_next(const AVClass *prev) 144 * { 145 * return prev ? NULL : &child_class; 146 * } 147 * @endcode 148 * Putting child_next() and child_class_next() as defined above into 149 * test_class will now make child_struct's options accessible through 150 * test_struct (again, proper setup as described above needs to be done on 151 * child_struct right after it is created). 152 * 153 * From the above example it might not be clear why both child_next() 154 * and child_class_next() are needed. The distinction is that child_next() 155 * iterates over actually existing objects, while child_class_next() 156 * iterates over all possible child classes. E.g. if an AVCodecContext 157 * was initialized to use a codec which has private options, then its 158 * child_next() will return AVCodecContext.priv_data and finish 159 * iterating. OTOH child_class_next() on AVCodecContext.av_class will 160 * iterate over all available codecs with private options. 161 * 162 * @subsection avoptions_implement_named_constants Named constants 163 * It is possible to create named constants for options. Simply set the unit 164 * field of the option the constants should apply to to a string and 165 * create the constants themselves as options of type AV_OPT_TYPE_CONST 166 * with their unit field set to the same string. 167 * Their default_val field should contain the value of the named 168 * constant. 169 * For example, to add some named constants for the test_flags option 170 * above, put the following into the child_opts array: 171 * @code 172 * { "test_flags", "This is a test option of flags type.", 173 * offsetof(child_struct, flags_opt), AV_OPT_TYPE_FLAGS, { 0 }, INT_MIN, INT_MAX, "test_unit" }, 174 * { "flag1", "This is a flag with value 16", 0, AV_OPT_TYPE_CONST, { 16 }, 0, 0, "test_unit" }, 175 * @endcode 176 * 177 * @section avoptions_use Using AVOptions 178 * This section deals with accessing options in an AVOptions-enabled struct. 179 * Such structs in Libav are e.g. AVCodecContext in libavcodec or 180 * AVFormatContext in libavformat. 181 * 182 * @subsection avoptions_use_examine Examining AVOptions 183 * The basic functions for examining options are av_opt_next(), which iterates 184 * over all options defined for one object, and av_opt_find(), which searches 185 * for an option with the given name. 186 * 187 * The situation is more complicated with nesting. An AVOptions-enabled struct 188 * may have AVOptions-enabled children. Passing the AV_OPT_SEARCH_CHILDREN flag 189 * to av_opt_find() will make the function search children recursively. 190 * 191 * For enumerating there are basically two cases. The first is when you want to 192 * get all options that may potentially exist on the struct and its children 193 * (e.g. when constructing documentation). In that case you should call 194 * av_opt_child_class_next() recursively on the parent struct's AVClass. The 195 * second case is when you have an already initialized struct with all its 196 * children and you want to get all options that can be actually written or read 197 * from it. In that case you should call av_opt_child_next() recursively (and 198 * av_opt_next() on each result). 199 * 200 * @subsection avoptions_use_get_set Reading and writing AVOptions 201 * When setting options, you often have a string read directly from the 202 * user. In such a case, simply passing it to av_opt_set() is enough. For 203 * non-string type options, av_opt_set() will parse the string according to the 204 * option type. 205 * 206 * Similarly av_opt_get() will read any option type and convert it to a string 207 * which will be returned. Do not forget that the string is allocated, so you 208 * have to free it with av_free(). 209 * 210 * In some cases it may be more convenient to put all options into an 211 * AVDictionary and call av_opt_set_dict() on it. A specific case of this 212 * are the format/codec open functions in lavf/lavc which take a dictionary 213 * filled with option as a parameter. This allows to set some options 214 * that cannot be set otherwise, since e.g. the input file format is not known 215 * before the file is actually opened. 216 */ 217 218enum AVOptionType{ 219 AV_OPT_TYPE_FLAGS, 220 AV_OPT_TYPE_INT, 221 AV_OPT_TYPE_INT64, 222 AV_OPT_TYPE_DOUBLE, 223 AV_OPT_TYPE_FLOAT, 224 AV_OPT_TYPE_STRING, 225 AV_OPT_TYPE_RATIONAL, 226 AV_OPT_TYPE_BINARY, ///< offset must point to a pointer immediately followed by an int for the length 227 AV_OPT_TYPE_CONST = 128, 228#if FF_API_OLD_AVOPTIONS 229 FF_OPT_TYPE_FLAGS = 0, 230 FF_OPT_TYPE_INT, 231 FF_OPT_TYPE_INT64, 232 FF_OPT_TYPE_DOUBLE, 233 FF_OPT_TYPE_FLOAT, 234 FF_OPT_TYPE_STRING, 235 FF_OPT_TYPE_RATIONAL, 236 FF_OPT_TYPE_BINARY, ///< offset must point to a pointer immediately followed by an int for the length 237 FF_OPT_TYPE_CONST=128, 238#endif 239}; 240 241/** 242 * AVOption 243 */ 244typedef struct AVOption { 245 const char *name; 246 247 /** 248 * short English help text 249 * @todo What about other languages? 250 */ 251 const char *help; 252 253 /** 254 * The offset relative to the context structure where the option 255 * value is stored. It should be 0 for named constants. 256 */ 257 int offset; 258 enum AVOptionType type; 259 260 /** 261 * the default value for scalar options 262 */ 263 union { 264 double dbl; 265 const char *str; 266 /* TODO those are unused now */ 267 int64_t i64; 268 AVRational q; 269 } default_val; 270 double min; ///< minimum valid value for the option 271 double max; ///< maximum valid value for the option 272 273 int flags; 274#define AV_OPT_FLAG_ENCODING_PARAM 1 ///< a generic parameter which can be set by the user for muxing or encoding 275#define AV_OPT_FLAG_DECODING_PARAM 2 ///< a generic parameter which can be set by the user for demuxing or decoding 276#define AV_OPT_FLAG_METADATA 4 ///< some data extracted or inserted into the file like title, comment, ... 277#define AV_OPT_FLAG_AUDIO_PARAM 8 278#define AV_OPT_FLAG_VIDEO_PARAM 16 279#define AV_OPT_FLAG_SUBTITLE_PARAM 32 280//FIXME think about enc-audio, ... style flags 281 282 /** 283 * The logical unit to which the option belongs. Non-constant 284 * options and corresponding named constants share the same 285 * unit. May be NULL. 286 */ 287 const char *unit; 288} AVOption; 289 290#if FF_API_FIND_OPT 291/** 292 * Look for an option in obj. Look only for the options which 293 * have the flags set as specified in mask and flags (that is, 294 * for which it is the case that opt->flags & mask == flags). 295 * 296 * @param[in] obj a pointer to a struct whose first element is a 297 * pointer to an AVClass 298 * @param[in] name the name of the option to look for 299 * @param[in] unit the unit of the option to look for, or any if NULL 300 * @return a pointer to the option found, or NULL if no option 301 * has been found 302 * 303 * @deprecated use av_opt_find. 304 */ 305attribute_deprecated 306const AVOption *av_find_opt(void *obj, const char *name, const char *unit, int mask, int flags); 307#endif 308 309#if FF_API_OLD_AVOPTIONS 310/** 311 * Set the field of obj with the given name to value. 312 * 313 * @param[in] obj A struct whose first element is a pointer to an 314 * AVClass. 315 * @param[in] name the name of the field to set 316 * @param[in] val The value to set. If the field is not of a string 317 * type, then the given string is parsed. 318 * SI postfixes and some named scalars are supported. 319 * If the field is of a numeric type, it has to be a numeric or named 320 * scalar. Behavior with more than one scalar and +- infix operators 321 * is undefined. 322 * If the field is of a flags type, it has to be a sequence of numeric 323 * scalars or named flags separated by '+' or '-'. Prefixing a flag 324 * with '+' causes it to be set without affecting the other flags; 325 * similarly, '-' unsets a flag. 326 * @param[out] o_out if non-NULL put here a pointer to the AVOption 327 * found 328 * @param alloc this parameter is currently ignored 329 * @return 0 if the value has been set, or an AVERROR code in case of 330 * error: 331 * AVERROR_OPTION_NOT_FOUND if no matching option exists 332 * AVERROR(ERANGE) if the value is out of range 333 * AVERROR(EINVAL) if the value is not valid 334 * @deprecated use av_opt_set() 335 */ 336attribute_deprecated 337int av_set_string3(void *obj, const char *name, const char *val, int alloc, const AVOption **o_out); 338 339attribute_deprecated const AVOption *av_set_double(void *obj, const char *name, double n); 340attribute_deprecated const AVOption *av_set_q(void *obj, const char *name, AVRational n); 341attribute_deprecated const AVOption *av_set_int(void *obj, const char *name, int64_t n); 342 343attribute_deprecated double av_get_double(void *obj, const char *name, const AVOption **o_out); 344attribute_deprecated AVRational av_get_q(void *obj, const char *name, const AVOption **o_out); 345attribute_deprecated int64_t av_get_int(void *obj, const char *name, const AVOption **o_out); 346attribute_deprecated const char *av_get_string(void *obj, const char *name, const AVOption **o_out, char *buf, int buf_len); 347attribute_deprecated const AVOption *av_next_option(void *obj, const AVOption *last); 348#endif 349 350/** 351 * Show the obj options. 352 * 353 * @param req_flags requested flags for the options to show. Show only the 354 * options for which it is opt->flags & req_flags. 355 * @param rej_flags rejected flags for the options to show. Show only the 356 * options for which it is !(opt->flags & req_flags). 357 * @param av_log_obj log context to use for showing the options 358 */ 359int av_opt_show2(void *obj, void *av_log_obj, int req_flags, int rej_flags); 360 361/** 362 * Set the values of all AVOption fields to their default values. 363 * 364 * @param s an AVOption-enabled struct (its first member must be a pointer to AVClass) 365 */ 366void av_opt_set_defaults(void *s); 367 368#if FF_API_OLD_AVOPTIONS 369attribute_deprecated 370void av_opt_set_defaults2(void *s, int mask, int flags); 371#endif 372 373/** 374 * Parse the key/value pairs list in opts. For each key/value pair 375 * found, stores the value in the field in ctx that is named like the 376 * key. ctx must be an AVClass context, storing is done using 377 * AVOptions. 378 * 379 * @param key_val_sep a 0-terminated list of characters used to 380 * separate key from value 381 * @param pairs_sep a 0-terminated list of characters used to separate 382 * two pairs from each other 383 * @return the number of successfully set key/value pairs, or a negative 384 * value corresponding to an AVERROR code in case of error: 385 * AVERROR(EINVAL) if opts cannot be parsed, 386 * the error code issued by av_set_string3() if a key/value pair 387 * cannot be set 388 */ 389int av_set_options_string(void *ctx, const char *opts, 390 const char *key_val_sep, const char *pairs_sep); 391 392/** 393 * Free all string and binary options in obj. 394 */ 395void av_opt_free(void *obj); 396 397/** 398 * Check whether a particular flag is set in a flags field. 399 * 400 * @param field_name the name of the flag field option 401 * @param flag_name the name of the flag to check 402 * @return non-zero if the flag is set, zero if the flag isn't set, 403 * isn't of the right type, or the flags field doesn't exist. 404 */ 405int av_opt_flag_is_set(void *obj, const char *field_name, const char *flag_name); 406 407/* 408 * Set all the options from a given dictionary on an object. 409 * 410 * @param obj a struct whose first element is a pointer to AVClass 411 * @param options options to process. This dictionary will be freed and replaced 412 * by a new one containing all options not found in obj. 413 * Of course this new dictionary needs to be freed by caller 414 * with av_dict_free(). 415 * 416 * @return 0 on success, a negative AVERROR if some option was found in obj, 417 * but could not be set. 418 * 419 * @see av_dict_copy() 420 */ 421int av_opt_set_dict(void *obj, struct AVDictionary **options); 422 423/** 424 * @defgroup opt_eval_funcs Evaluating option strings 425 * @{ 426 * This group of functions can be used to evaluate option strings 427 * and get numbers out of them. They do the same thing as av_opt_set(), 428 * except the result is written into the caller-supplied pointer. 429 * 430 * @param obj a struct whose first element is a pointer to AVClass. 431 * @param o an option for which the string is to be evaluated. 432 * @param val string to be evaluated. 433 * @param *_out value of the string will be written here. 434 * 435 * @return 0 on success, a negative number on failure. 436 */ 437int av_opt_eval_flags (void *obj, const AVOption *o, const char *val, int *flags_out); 438int av_opt_eval_int (void *obj, const AVOption *o, const char *val, int *int_out); 439int av_opt_eval_int64 (void *obj, const AVOption *o, const char *val, int64_t *int64_out); 440int av_opt_eval_float (void *obj, const AVOption *o, const char *val, float *float_out); 441int av_opt_eval_double(void *obj, const AVOption *o, const char *val, double *double_out); 442int av_opt_eval_q (void *obj, const AVOption *o, const char *val, AVRational *q_out); 443/** 444 * @} 445 */ 446 447#define AV_OPT_SEARCH_CHILDREN 0x0001 /**< Search in possible children of the 448 given object first. */ 449/** 450 * The obj passed to av_opt_find() is fake -- only a double pointer to AVClass 451 * instead of a required pointer to a struct containing AVClass. This is 452 * useful for searching for options without needing to allocate the corresponding 453 * object. 454 */ 455#define AV_OPT_SEARCH_FAKE_OBJ 0x0002 456 457/** 458 * Look for an option in an object. Consider only options which 459 * have all the specified flags set. 460 * 461 * @param[in] obj A pointer to a struct whose first element is a 462 * pointer to an AVClass. 463 * Alternatively a double pointer to an AVClass, if 464 * AV_OPT_SEARCH_FAKE_OBJ search flag is set. 465 * @param[in] name The name of the option to look for. 466 * @param[in] unit When searching for named constants, name of the unit 467 * it belongs to. 468 * @param opt_flags Find only options with all the specified flags set (AV_OPT_FLAG). 469 * @param search_flags A combination of AV_OPT_SEARCH_*. 470 * 471 * @return A pointer to the option found, or NULL if no option 472 * was found. 473 * 474 * @note Options found with AV_OPT_SEARCH_CHILDREN flag may not be settable 475 * directly with av_set_string3(). Use special calls which take an options 476 * AVDictionary (e.g. avformat_open_input()) to set options found with this 477 * flag. 478 */ 479const AVOption *av_opt_find(void *obj, const char *name, const char *unit, 480 int opt_flags, int search_flags); 481 482/** 483 * Look for an option in an object. Consider only options which 484 * have all the specified flags set. 485 * 486 * @param[in] obj A pointer to a struct whose first element is a 487 * pointer to an AVClass. 488 * Alternatively a double pointer to an AVClass, if 489 * AV_OPT_SEARCH_FAKE_OBJ search flag is set. 490 * @param[in] name The name of the option to look for. 491 * @param[in] unit When searching for named constants, name of the unit 492 * it belongs to. 493 * @param opt_flags Find only options with all the specified flags set (AV_OPT_FLAG). 494 * @param search_flags A combination of AV_OPT_SEARCH_*. 495 * @param[out] target_obj if non-NULL, an object to which the option belongs will be 496 * written here. It may be different from obj if AV_OPT_SEARCH_CHILDREN is present 497 * in search_flags. This parameter is ignored if search_flags contain 498 * AV_OPT_SEARCH_FAKE_OBJ. 499 * 500 * @return A pointer to the option found, or NULL if no option 501 * was found. 502 */ 503const AVOption *av_opt_find2(void *obj, const char *name, const char *unit, 504 int opt_flags, int search_flags, void **target_obj); 505 506/** 507 * Iterate over all AVOptions belonging to obj. 508 * 509 * @param obj an AVOptions-enabled struct or a double pointer to an 510 * AVClass describing it. 511 * @param prev result of the previous call to av_opt_next() on this object 512 * or NULL 513 * @return next AVOption or NULL 514 */ 515const AVOption *av_opt_next(void *obj, const AVOption *prev); 516 517/** 518 * Iterate over AVOptions-enabled children of obj. 519 * 520 * @param prev result of a previous call to this function or NULL 521 * @return next AVOptions-enabled child or NULL 522 */ 523void *av_opt_child_next(void *obj, void *prev); 524 525/** 526 * Iterate over potential AVOptions-enabled children of parent. 527 * 528 * @param prev result of a previous call to this function or NULL 529 * @return AVClass corresponding to next potential child or NULL 530 */ 531const AVClass *av_opt_child_class_next(const AVClass *parent, const AVClass *prev); 532 533/** 534 * @defgroup opt_set_funcs Option setting functions 535 * @{ 536 * Those functions set the field of obj with the given name to value. 537 * 538 * @param[in] obj A struct whose first element is a pointer to an AVClass. 539 * @param[in] name the name of the field to set 540 * @param[in] val The value to set. In case of av_opt_set() if the field is not 541 * of a string type, then the given string is parsed. 542 * SI postfixes and some named scalars are supported. 543 * If the field is of a numeric type, it has to be a numeric or named 544 * scalar. Behavior with more than one scalar and +- infix operators 545 * is undefined. 546 * If the field is of a flags type, it has to be a sequence of numeric 547 * scalars or named flags separated by '+' or '-'. Prefixing a flag 548 * with '+' causes it to be set without affecting the other flags; 549 * similarly, '-' unsets a flag. 550 * @param search_flags flags passed to av_opt_find2. I.e. if AV_OPT_SEARCH_CHILDREN 551 * is passed here, then the option may be set on a child of obj. 552 * 553 * @return 0 if the value has been set, or an AVERROR code in case of 554 * error: 555 * AVERROR_OPTION_NOT_FOUND if no matching option exists 556 * AVERROR(ERANGE) if the value is out of range 557 * AVERROR(EINVAL) if the value is not valid 558 */ 559int av_opt_set (void *obj, const char *name, const char *val, int search_flags); 560int av_opt_set_int (void *obj, const char *name, int64_t val, int search_flags); 561int av_opt_set_double(void *obj, const char *name, double val, int search_flags); 562int av_opt_set_q (void *obj, const char *name, AVRational val, int search_flags); 563/** 564 * @} 565 */ 566 567/** 568 * @defgroup opt_get_funcs Option getting functions 569 * @{ 570 * Those functions get a value of the option with the given name from an object. 571 * 572 * @param[in] obj a struct whose first element is a pointer to an AVClass. 573 * @param[in] name name of the option to get. 574 * @param[in] search_flags flags passed to av_opt_find2. I.e. if AV_OPT_SEARCH_CHILDREN 575 * is passed here, then the option may be found in a child of obj. 576 * @param[out] out_val value of the option will be written here 577 * @return 0 on success, a negative error code otherwise 578 */ 579/** 580 * @note the returned string will av_malloc()ed and must be av_free()ed by the caller 581 */ 582int av_opt_get (void *obj, const char *name, int search_flags, uint8_t **out_val); 583int av_opt_get_int (void *obj, const char *name, int search_flags, int64_t *out_val); 584int av_opt_get_double(void *obj, const char *name, int search_flags, double *out_val); 585int av_opt_get_q (void *obj, const char *name, int search_flags, AVRational *out_val); 586/** 587 * @} 588 * @} 589 */ 590 591#endif /* AVUTIL_OPT_H */ 592