the pmap of encoder problem

[TCZWJ]

why the pmap from the encoder is different from the original data?
i follow the steps below:

1. i use decoder api to parse the original binary data, i got the json file;
2. using the encoder api to encode json file,then binary data was obtained,but i found the pmap in this binary data is different from the original data.
   can someone tell me why? thanks very much!!