NV12 pix_fmt for encoding

[jahwanoh]

Hi
is there any way to use encoder with NV12 pixel format? such as a manual patching.
currently it is only support YUV420p in this repository.

codec name : h264_nvmpi
[h264_nvmpi @ 0x7ea40041b0] Specified pixel format nv12 is invalid or not supported
cannot open encoder

[gjrtimmer]

NV12 pixel format is supported for both encoding input and decoding output in this fork (gjrtimmer/jetson-ffmpeg). Also added YUVJ420P acceptance, P010 10-bit decode, and XRGB32 converter. Tracked in gjrtimmer#12, regression-tested in hardware test suite.