ti DRC理解

你好：

Energy Filter，Attack Filters ，Decay Filters的设定分别对应DRC中的系数“ae”，“aa”,"ad"。这些系数有的是9.23格式，有的是3.23格式。分别有相应的寄存器设置这些系数。例如TAS5711中的register0x3A-0x46。这些系数最终影响的是Energy time，Attack time，Decay time。这些系数通过固定的公式可以计算得到相应的时间。无论是codec还是TAS57XX系列，TI的GUI中都有工具，用户只需要在GUI上设定时间，GUI会通过I2C修改filter的寄存器控制这三个时间。用户开发时，只需要通过GUI导出寄存器，用MCU控制即可。所以，对于用户来说，这些filter系数都是中间变量，用户需要关心的是时间如何设定，对于DRC的影响。

对于这个时间，我暂且简单的解释一下：

1.AAV estimator—This DRC element derives an estimate of the average absolute value (AAV) of the audio data stream into the DRC. A time constant, t_energy, is used to control the effective time window over which the AAV estimate is made. 

2.Compression coefficient computation—This DRC element converts the output of the AAV estimator to a logarithmic number, determines the region where the input resides, and then computes and outputs the appropriate gain coefficient to the attack/decay element. Parameters K define the slopes of the gain curve for these three regions.  T specify the boundaries of the regions, in terms of input level.  O specify offsets of the gain curve relative to a 1:1 transfer function at the thresholds.

3.Attack/decay control—This DRC element controls the transition time of changes in the coefficient computed in the compression/expansion coefficient computation element.  User-specified parameters t_a and t_d are used to set the attack and decay time constants used in the gain adjustment.   

建议先读一下文字（一定要阅读一下再看图），再配以图形，更容易理解。