Representation of coordinates in signature. OpenSSL

Representation of coordinates in signature. OpenSSL

I want to calculate the v-value from the signature obtained using the OpenSSL ECDSA_do_sign function. I found that this value is calculated using the parity of y-coordinate of r. Here I also found that the parity of y is equal to the parity of r. I want to understand whether it depends on the implementation. Can anyone tell exactly how the coordinates x and y are stored inside r in OpenSSL. I can't find it in the code.

edited: I understand how v is calculated. My question is how to get the y-coordinate of r in the specific implementation of ECDSA in the OpenSSL library.

http://bit.ly/2SrR0Ug