sox源码分析：sox_create_effect()

sox_create_effect()主要是创建一个效果器结构体sox_effect_t 并初始化，该结构体的核心处理单元是通过sox_find_effect()返回的效果器句柄。该函数源码如下

sox_effect_t * sox_create_effect(sox_effect_handler_t const * eh)
{
    
    
  sox_effect_t * effp = lsx_calloc(1, sizeof(*effp));
  effp->obuf = NULL;

  effp->global_info = sox_get_effects_globals();
  effp->handler = *eh;
  if (!effp->handler.getopts) effp->handler.getopts = default_getopts;
  if (!effp->handler.start  ) effp->handler.start   = default_function;
  if (!effp->handler.flow   ) effp->handler.flow    = lsx_flow_copy;
  if (!effp->handler.drain  ) effp->handler.drain   = default_drain;
  if (!effp->handler.stop   ) effp->handler.stop    = default_function;
  if (!effp->handler.kill   ) effp->handler.kill    = default_function;

  effp->priv = lsx_calloc(1, effp->handler.priv_size);

  return effp;
} /* sox_create_effect */

结构体sox_effect_t 贯穿整个效果器处理过程，关键核心是结构体sox_effect_handler_t 。
该结构体具体定义如下

struct sox_effect_handler_t {
    
    
  char const * name;  /**< Effect name */
  char const * usage; /**< Short explanation of parameters accepted by effect */
  unsigned int flags; /**< Combination of SOX_EFF_* flags */
  sox_effect_handler_getopts getopts; /**< Called to parse command-line arguments (called once per effect). */
  sox_effect_handler_start start;     /**< Called to initialize effect (called once per flow). */
  sox_effect_handler_flow flow;       /**< Called to process samples. */
  sox_effect_handler_drain drain;     /**< Called to finish getting output after input is complete. */
  sox_effect_handler_stop stop;       /**< Called to shut down effect (called once per flow). */
  sox_effect_handler_kill kill;       /**< Called to shut down effect (called once per effect). */
  size_t       priv_size;             /**< Size of private data SoX should pre-allocate for effect */
};

重要的参数说明
char const * name：主要用来匹配对应的效果器接口
char const * usage：帮助信息
sox_effect_handler_getopts getopts：解析命令行参数接口
sox_effect_handler_start start：初始化效果器
sox_effect_handler_flow flow：具体的处理数据操作
sox_effect_handler_drain drain：获取输出结果
sox_effect_handler_stop stop：停止处理数据
sox_effect_handler_kill kill：释放效果器
size_t priv_size：数据空间大小

每个效果器作用于一个输入流和一个输出流，处理过程大致可以划分6个处理功能，具体的调用流程图如下
在这里插入图片描述
注意：有些处理函数不是必须的，可以为NULL。

sox源码分析：sox_create_effect()

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