nvcodec: Fix framerate related issues
nvdec: Use upstream framerate if possible
Encoded bitstream might not have valid framerate. If upstream
provided non-variable-framerate (i.e., fps_n > 0 and fps_d > 0)
use upstream framerate instead of parsed one
nvenc: Fix crash with unspecified framerate
Nvidia driver seems to calculating floating point framerate
without validation. This causes crash both on linux and Windows.
Fixes: #1012 (closed)
Edited by Seungha Yang