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 test_options[] = { 66 * { "test_int", "This is a test option of int type.", offsetof(test_struct, int_opt), 67 * AV_OPT_TYPE_INT, { .i64 = -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 = test_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, { .i64 = 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, { .i64 = 0 }, INT_MIN, INT_MAX, "test_unit" }, 174 * { "flag1", "This is a flag with value 16", 0, AV_OPT_TYPE_CONST, { .i64 = 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 */ 217 218 enum 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 }; 229 230 /** 231 * AVOption 232 */ 233 typedef struct AVOption { 234 const char *name; 235 236 /** 237 * short English help text 238 * @todo What about other languages? 239 */ 240 const char *help; 241 242 /** 243 * The offset relative to the context structure where the option 244 * value is stored. It should be 0 for named constants. 245 */ 246 int offset; 247 enum AVOptionType type; 248 249 /** 250 * the default value for scalar options 251 */ 252 union { 253 int64_t i64; 254 double dbl; 255 const char *str; 256 /* TODO those are unused now */ 257 AVRational q; 258 } default_val; 259 double min; ///< minimum valid value for the option 260 double max; ///< maximum valid value for the option 261 262 int flags; 263 #define AV_OPT_FLAG_ENCODING_PARAM 1 ///< a generic parameter which can be set by the user for muxing or encoding 264 #define AV_OPT_FLAG_DECODING_PARAM 2 ///< a generic parameter which can be set by the user for demuxing or decoding 265 #define AV_OPT_FLAG_METADATA 4 ///< some data extracted or inserted into the file like title, comment, ... 266 #define AV_OPT_FLAG_AUDIO_PARAM 8 267 #define AV_OPT_FLAG_VIDEO_PARAM 16 268 #define AV_OPT_FLAG_SUBTITLE_PARAM 32 269 //FIXME think about enc-audio, ... style flags 270 271 /** 272 * The logical unit to which the option belongs. Non-constant 273 * options and corresponding named constants share the same 274 * unit. May be NULL. 275 */ 276 const char *unit; 277 } AVOption; 278 279 /** 280 * Show the obj options. 281 * 282 * @param req_flags requested flags for the options to show. Show only the 283 * options for which it is opt->flags & req_flags. 284 * @param rej_flags rejected flags for the options to show. Show only the 285 * options for which it is !(opt->flags & req_flags). 286 * @param av_log_obj log context to use for showing the options 287 */ 288 int av_opt_show2(void *obj, void *av_log_obj, int req_flags, int rej_flags); 289 290 /** 291 * Set the values of all AVOption fields to their default values. 292 * 293 * @param s an AVOption-enabled struct (its first member must be a pointer to AVClass) 294 */ 295 void av_opt_set_defaults(void *s); 296 297 /** 298 * Parse the key/value pairs list in opts. For each key/value pair 299 * found, stores the value in the field in ctx that is named like the 300 * key. ctx must be an AVClass context, storing is done using 301 * AVOptions. 302 * 303 * @param key_val_sep a 0-terminated list of characters used to 304 * separate key from value 305 * @param pairs_sep a 0-terminated list of characters used to separate 306 * two pairs from each other 307 * @return the number of successfully set key/value pairs, or a negative 308 * value corresponding to an AVERROR code in case of error: 309 * AVERROR(EINVAL) if opts cannot be parsed, 310 * the error code issued by av_set_string3() if a key/value pair 311 * cannot be set 312 */ 313 int av_set_options_string(void *ctx, const char *opts, 314 const char *key_val_sep, const char *pairs_sep); 315 316 /** 317 * Free all string and binary options in obj. 318 */ 319 void av_opt_free(void *obj); 320 321 /** 322 * Check whether a particular flag is set in a flags field. 323 * 324 * @param field_name the name of the flag field option 325 * @param flag_name the name of the flag to check 326 * @return non-zero if the flag is set, zero if the flag isn't set, 327 * isn't of the right type, or the flags field doesn't exist. 328 */ 329 int av_opt_flag_is_set(void *obj, const char *field_name, const char *flag_name); 330 331 /* 332 * Set all the options from a given dictionary on an object. 333 * 334 * @param obj a struct whose first element is a pointer to AVClass 335 * @param options options to process. This dictionary will be freed and replaced 336 * by a new one containing all options not found in obj. 337 * Of course this new dictionary needs to be freed by caller 338 * with av_dict_free(). 339 * 340 * @return 0 on success, a negative AVERROR if some option was found in obj, 341 * but could not be set. 342 * 343 * @see av_dict_copy() 344 */ 345 int av_opt_set_dict(void *obj, struct AVDictionary **options); 346 347 /** 348 * @defgroup opt_eval_funcs Evaluating option strings 349 * @{ 350 * This group of functions can be used to evaluate option strings 351 * and get numbers out of them. They do the same thing as av_opt_set(), 352 * except the result is written into the caller-supplied pointer. 353 * 354 * @param obj a struct whose first element is a pointer to AVClass. 355 * @param o an option for which the string is to be evaluated. 356 * @param val string to be evaluated. 357 * @param *_out value of the string will be written here. 358 * 359 * @return 0 on success, a negative number on failure. 360 */ 361 int av_opt_eval_flags (void *obj, const AVOption *o, const char *val, int *flags_out); 362 int av_opt_eval_int (void *obj, const AVOption *o, const char *val, int *int_out); 363 int av_opt_eval_int64 (void *obj, const AVOption *o, const char *val, int64_t *int64_out); 364 int av_opt_eval_float (void *obj, const AVOption *o, const char *val, float *float_out); 365 int av_opt_eval_double(void *obj, const AVOption *o, const char *val, double *double_out); 366 int av_opt_eval_q (void *obj, const AVOption *o, const char *val, AVRational *q_out); 367 /** 368 * @} 369 */ 370 371 #define AV_OPT_SEARCH_CHILDREN 0x0001 /**< Search in possible children of the 372 given object first. */ 373 /** 374 * The obj passed to av_opt_find() is fake -- only a double pointer to AVClass 375 * instead of a required pointer to a struct containing AVClass. This is 376 * useful for searching for options without needing to allocate the corresponding 377 * object. 378 */ 379 #define AV_OPT_SEARCH_FAKE_OBJ 0x0002 380 381 /** 382 * Look for an option in an object. Consider only options which 383 * have all the specified flags set. 384 * 385 * @param[in] obj A pointer to a struct whose first element is a 386 * pointer to an AVClass. 387 * Alternatively a double pointer to an AVClass, if 388 * AV_OPT_SEARCH_FAKE_OBJ search flag is set. 389 * @param[in] name The name of the option to look for. 390 * @param[in] unit When searching for named constants, name of the unit 391 * it belongs to. 392 * @param opt_flags Find only options with all the specified flags set (AV_OPT_FLAG). 393 * @param search_flags A combination of AV_OPT_SEARCH_*. 394 * 395 * @return A pointer to the option found, or NULL if no option 396 * was found. 397 * 398 * @note Options found with AV_OPT_SEARCH_CHILDREN flag may not be settable 399 * directly with av_set_string3(). Use special calls which take an options 400 * AVDictionary (e.g. avformat_open_input()) to set options found with this 401 * flag. 402 */ 403 const AVOption *av_opt_find(void *obj, const char *name, const char *unit, 404 int opt_flags, int search_flags); 405 406 /** 407 * Look for an option in an object. Consider only options which 408 * have all the specified flags set. 409 * 410 * @param[in] obj A pointer to a struct whose first element is a 411 * pointer to an AVClass. 412 * Alternatively a double pointer to an AVClass, if 413 * AV_OPT_SEARCH_FAKE_OBJ search flag is set. 414 * @param[in] name The name of the option to look for. 415 * @param[in] unit When searching for named constants, name of the unit 416 * it belongs to. 417 * @param opt_flags Find only options with all the specified flags set (AV_OPT_FLAG). 418 * @param search_flags A combination of AV_OPT_SEARCH_*. 419 * @param[out] target_obj if non-NULL, an object to which the option belongs will be 420 * written here. It may be different from obj if AV_OPT_SEARCH_CHILDREN is present 421 * in search_flags. This parameter is ignored if search_flags contain 422 * AV_OPT_SEARCH_FAKE_OBJ. 423 * 424 * @return A pointer to the option found, or NULL if no option 425 * was found. 426 */ 427 const AVOption *av_opt_find2(void *obj, const char *name, const char *unit, 428 int opt_flags, int search_flags, void **target_obj); 429 430 /** 431 * Iterate over all AVOptions belonging to obj. 432 * 433 * @param obj an AVOptions-enabled struct or a double pointer to an 434 * AVClass describing it. 435 * @param prev result of the previous call to av_opt_next() on this object 436 * or NULL 437 * @return next AVOption or NULL 438 */ 439 const AVOption *av_opt_next(void *obj, const AVOption *prev); 440 441 /** 442 * Iterate over AVOptions-enabled children of obj. 443 * 444 * @param prev result of a previous call to this function or NULL 445 * @return next AVOptions-enabled child or NULL 446 */ 447 void *av_opt_child_next(void *obj, void *prev); 448 449 /** 450 * Iterate over potential AVOptions-enabled children of parent. 451 * 452 * @param prev result of a previous call to this function or NULL 453 * @return AVClass corresponding to next potential child or NULL 454 */ 455 const AVClass *av_opt_child_class_next(const AVClass *parent, const AVClass *prev); 456 457 /** 458 * @defgroup opt_set_funcs Option setting functions 459 * @{ 460 * Those functions set the field of obj with the given name to value. 461 * 462 * @param[in] obj A struct whose first element is a pointer to an AVClass. 463 * @param[in] name the name of the field to set 464 * @param[in] val The value to set. In case of av_opt_set() if the field is not 465 * of a string type, then the given string is parsed. 466 * SI postfixes and some named scalars are supported. 467 * If the field is of a numeric type, it has to be a numeric or named 468 * scalar. Behavior with more than one scalar and +- infix operators 469 * is undefined. 470 * If the field is of a flags type, it has to be a sequence of numeric 471 * scalars or named flags separated by '+' or '-'. Prefixing a flag 472 * with '+' causes it to be set without affecting the other flags; 473 * similarly, '-' unsets a flag. 474 * @param search_flags flags passed to av_opt_find2. I.e. if AV_OPT_SEARCH_CHILDREN 475 * is passed here, then the option may be set on a child of obj. 476 * 477 * @return 0 if the value has been set, or an AVERROR code in case of 478 * error: 479 * AVERROR_OPTION_NOT_FOUND if no matching option exists 480 * AVERROR(ERANGE) if the value is out of range 481 * AVERROR(EINVAL) if the value is not valid 482 */ 483 int av_opt_set (void *obj, const char *name, const char *val, int search_flags); 484 int av_opt_set_int (void *obj, const char *name, int64_t val, int search_flags); 485 int av_opt_set_double(void *obj, const char *name, double val, int search_flags); 486 int av_opt_set_q (void *obj, const char *name, AVRational val, int search_flags); 487 int av_opt_set_bin (void *obj, const char *name, const uint8_t *val, int size, int search_flags); 488 /** 489 * @} 490 */ 491 492 /** 493 * @defgroup opt_get_funcs Option getting functions 494 * @{ 495 * Those functions get a value of the option with the given name from an object. 496 * 497 * @param[in] obj a struct whose first element is a pointer to an AVClass. 498 * @param[in] name name of the option to get. 499 * @param[in] search_flags flags passed to av_opt_find2. I.e. if AV_OPT_SEARCH_CHILDREN 500 * is passed here, then the option may be found in a child of obj. 501 * @param[out] out_val value of the option will be written here 502 * @return 0 on success, a negative error code otherwise 503 */ 504 /** 505 * @note the returned string will av_malloc()ed and must be av_free()ed by the caller 506 */ 507 int av_opt_get (void *obj, const char *name, int search_flags, uint8_t **out_val); 508 int av_opt_get_int (void *obj, const char *name, int search_flags, int64_t *out_val); 509 int av_opt_get_double(void *obj, const char *name, int search_flags, double *out_val); 510 int av_opt_get_q (void *obj, const char *name, int search_flags, AVRational *out_val); 511 /** 512 * @} 513 * @} 514 */ 515 516 #endif /* AVUTIL_OPT_H */ 517