Hi Daniel,
You can refer sample code of "sample_encode" and "sample_decode" module in latest Intel Media SDK Samples, or You can refer the "mediasdk-tutorials" also which has much more simple implementations of these decoder and encoders.
In case you have dump file of NV12 data then you can directly use 'sample_encode.exe' and 'sample_decode.exe' provided in media sdk to encode and then decode this file.
download links:
sdk: https://software.intel.com/en-us/media-sdk
samples: https://software.intel.com/en-us/media-sdk-support/code-samples
