AVDictionary

AVDictionary is a lightweight, string-based key-value store used in FFmpeg’s libavutil to hold metadata and option pairs. It is designed for simple transfer of attributes between components such as demuxers, muxers, and codecs.

Internally it is implemented as a hash table of AVDictionaryEntry entries, each with a char* key and a char* value. The API governs memory management; keys and values can be duplicated or borrowed depending on flags used when inserting.

Common operations include av_dict_set() to insert or replace a pair, av_dict_get() to fetch a value by key, av_dict_count() to report the number of entries, and av_dict_free() to release memory. Parsing helpers such as av_dict_parse_string() convert between text and dictionary form.

Flags control behavior, including case sensitivity and whether to duplicate strings or append to existing values (AV_DICT_APPEND). There are utilities to copy or merge dictionaries.

In practice, a dictionary is initialized as NULL, populated as needed, and passed through FFmpeg components to convey metadata (for example, title or artist) or to convey codec/container options. AVDictionary thus provides a flexible, portable mechanism for carrying key-value pairs across the FFmpeg ecosystem.