/**

 * AVCodec.一个AVCodec结构体对应一个编解码器，这个结构体表示编解码器本身 */typedef struct AVCodec {     /**     * Name of the codec implementation.    编解码实现的名字     * The name is globally unique among encoders and among decoders (but an     * encoder and a decoder can share the same name).     * This is the primary way to find a codec from the user perspective.     */    const char *name;‍ //编解码器实现的名字，这个名字全局唯一（但是编解码器可以共用一个名字），从用户方面去找编解码器的主要方式‍    /**     * Descriptive name for the codec, meant to be more human readable than name.     * You should use the NULL_IF_CONFIG_SMALL() macro to define it.     */    const char *long_name;//更接近人类可阅读的编解码器的描述名字，要使用NULL_IF_CONFIG_SMALL()这个宏定义来定义它

    enum AVMediaType type‍;//媒体类型

    enum AVCodecID id;//编解码器的ID    /**     * Codec capabilities.     * see CODEC_CAP_*     */    int capabilities;    const AVRational *supported_framerates; ///< array of supported framerates, or NULL if any, array is terminated by {0,0}

supported_framerates支持的帧率的数组，NULL表示任何的都支持，数组由{0,0}结束

    const enum AVPixelFormat *pix_fmts;     ///< array of supported pixel formats, or NULL if unknown, array is terminated by -1

pix_fmts支持的像素格式的数组，NULL表示未知，数组由-1结束

    const int *supported_samplerates;       ///< array of supported audio samplerates, or NULL if unknown, array is terminated by 0

supported_samples支持的声音采样频率的数组，NULL表示未知，数组由0结束

    const enum AVSampleFormat *sample_fmts; ///< array of supported sample formats, or NULL if unknown, array is terminated by -1

sample_fmts支持的声音采样格式的数组，NULL表示未知，数组由-1结束

    const uint64_t *channel_layouts;         ///< array of support channel layouts, or NULL if unknown. array is terminated by 0

支持的声音的通道数，NULL表示未知，由0结束

#if FF_API_LOWRES    uint8_t max_lowres;                     ///< maximum value for lowres supported by the decoder, no direct access, use av_codec_get_max_lowres()#endif    const AVClass *priv_class;              ///< AVClass for the private context    const AVProfile *profiles;              ///< array of recognized profiles, or NULL if unknown, array is terminated by {FF_PROFILE_UNKNOWN}

---

    /*****************************************************************

     * No fields below this line are part of the public API. They     * may not be used outside of libavcodec and can be changed and     * removed at will.     * New public fields should be added right above.     *****************************************************************     */    int priv_data_size;    struct AVCodec *next;    /**     *  Frame-level threading support functions     * @{      */    /**     * If defined, called on thread contexts when they are created.     * If the codec allocates writable tables in init(), re-allocate them here.     * priv_data will be set to a copy of the original.     */    int (*init_thread_copy)(AVCodecContext *);    /**     * Copy necessary context variables from a previous thread context to the current one.     * If not defined, the next thread will start automatically; otherwise, the codec     * must call ff_thread_finish_setup().     *     * dst and src will (rarely) point to the same context, in which case memcpy should be skipped.     */    int (*update_thread_context)(AVCodecContext *dst, const AVCodecContext *src);    /** @} */

    /**

     * Private codec-specific defaults.     */    const AVCodecDefault *defaults;

    /**

     * Initialize codec static data, called from avcodec_register().     */    void (*init_static_data)(struct AVCodec *codec);

    int (*init)(AVCodecContext *);

    int (*encode_sub)(AVCodecContext *, uint8_t *buf, int buf_size,                      const struct AVSubtitle *sub);    /**     * Encode data to an AVPacket.     *     * @param      avctx          codec context     * @param      avpkt          output AVPacket (may contain a user-provided buffer)     * @param[in]  frame          AVFrame containing the raw data to be encoded     * @param[out] got_packet_ptr encoder sets to 0 or 1 to indicate that a     *                            non-empty packet was returned in avpkt.     * @return 0 on success, negative error code on failure     */    int (*encode2)(AVCodecContext *avctx, AVPacket *avpkt, const AVFrame *frame,                   int *got_packet_ptr);    int (*decode)(AVCodecContext *, void *outdata, int *outdata_size, AVPacket *avpkt);    int (*close)(AVCodecContext *);    /**     * Flush buffers.     * Will be called when seeking     */    void (*flush)(AVCodecContext *);} AVCodec;