pcm混音

I am not sure weather I have fully understood your question or not, I persume that you are asking 
"How can we mix two or more audio stream", If this is the question then I am explaning below the 
mixing of the two audio stream (You Can Mix More Audio Stream),

Step 1,

Get the Raw data of the two files, (Example, of the sample 8bit and 8Kh, means one sample is of
8bit)

Step 2

Let the two audio signal be A and B respectively, the range is between 0 and 255.  Where A and B are the
Sample Values (Each raw data) And store the resultant into the Y

If Both the samples Values are possitve

Y = A  +  B - A * B / 255

Where Y is the resultant signal which contains both signal A and B, merging two audio streams into single 
stream by this method solves the  problem of overflow and information loss to an extent.

   If the range of 8-bit sampling is between -127 to 128

   If both A and B are negative       Y = A +B - (A * B / (-127)) 
   Else                                       Y = A + B - A * B / 128

Similarly for the nbit (ex 16bit data)

   For  n-bit sampling audio signal

   If both A and B are negative       Y = A + B - (A * B  /  (-(2 pow(n-1) -1))) 
   Else                                       Y = A + B - (A * B /  (2 pow(n-1))

Step 3.

Add the Header to the Resultant (mixed) data and play back.

If some thing is unclear and ambigious let me know.

Regards
Ranjeet Gupta.

 

需要注意样本长度和采样率通道数及符号。

求和是最简单的混音方式，需要注意溢出。