Add rotation step after decoder and before outputs video filtergrapth

[AlexKordic]

[cyberj0g]

Interesting! Would we need to use transpose ffmpeg filter? Need to measure performance impact, and there seem to be no CUDA version, as is the case with scale.

[AlexKordic]

for software surface we should use transpose and for nvidia transpose_npp. I am modifying install_ffmpeg.sh to include support for this.

Still need to nail down for 180 degree rotation do we need to apply transpose_npp twice or we get mirrored image..

[cyberj0g]

Got it. From the docs, mirroring is controlled by _flip suffix of dir parameter.