Hello world,

This patch adds a pixel format guess based on probed bit depth.
With current FFMpeg ToT, when the cuvid codec is opened, input sw_pix_fmt
is AV_PIX_FMT_NV12 until the first frame is decoded. Even if input has 10
or 12 bit depth, the format will be NV12 for some time.

What's the need for this patch ?
Applications that rely on libavcodec will have a chance to calculate the
proper amount of vRAM required to store a reconstructed video frame before
decoding begins.