system clock即为SCLK， sampling clock即为LRCK=fs。 那么BCLK和LRCK的关系datasheet中有给出解释：
标准的右对齐方式：BCLK=32，48，64*LRCK。
16bit的右对齐方式：BCLK=32*LRCK
左对齐方式： BCLK=48，64*LRCK
The BCK pin can be operated at 32, 48, or 64 times the sampling frequency for standard (right justified) format, and 32 times the sampling frequency of the BCK pin is limited to 16-bit right-justified format only. The BCK pin can be operated at 48 or 64 times the sampling frequency for the I2S and left-justified formats. 48 times the sampling frequency of BCK is limited to 192/384/768 fS SCKI.
那么系统时钟SCK的话，参考：
