FFmpeg結構體完全分析——AVCodec

/**
 * AVCodec.一個AVCodec結構體對應一個編解碼器，這個結構體表示編解碼器自己
 */
typedef struct AVCodec {
    /**
     * Name of the codec implementation.    編解碼實現的名字
     * 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;‍ //編解碼器實現的名字，這個名字全局惟一（可是編解碼器能夠共用一個名字），從用戶方面去找編解碼器的主要方式‍
    /**
     * 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;//更接近人類可閱讀的編解碼器的描述名字，要使用NULL_IF_CONFIG_SMALL()這個宏定義來定義它

    enum AVMediaType type‍;//媒體類型
    enum AVCodecID id;//編解碼器的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支持的幀率的數組，NULL表示任何的都支持，數組由{0,0}結束
    const enum AVPixelFormat *pix_fmts;     ///< array of supported pixel formats, or NULL if unknown, array is terminated by -1

pix_fmts支持的像素格式的數組，NULL表示未知，數組由-1結束
    const int *supported_samplerates;       ///< array of supported audio samplerates, or NULL if unknown, array is terminated by 0

supported_samples支持的聲音採樣頻率的數組，NULL表示未知，數組由0結束

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

sample_fmts支持的聲音採樣格式的數組，NULL表示未知，數組由-1結束
    const uint64_t *channel_layouts;         ///< array of support channel layouts, or NULL if unknown. array is terminated by 0

支持的聲音的通道數，NULL表示未知，由0結束
#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;
    /**
     * @name  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;