FFmpeg configure complains about not finding ffnvcodec

[eero-t]

Summary of the bug:

FFmpeg configure complains about missing ffnvcodec, although it's present.

How to reproduce:

$ git clone https://git.videolan.org/git/ffmpeg/nv-codec-headers.git
$ cd nv-codec-headers
$ make
$ sudo make install
$ pkg-config --modversion ffnvcodec
9.0.18.2
$ git clone  --depth 1 https://github.com/FFmpeg/FFmpeg
$ cd FFmpeg
$ ./configure --enable-cuvid

Gives:

ERROR: cuvid requested, but not all dependencies are satisfied: ffnvcodec

If you think configure made a mistake, make sure you are using the latest
version from Git.  If the latest version fails, report the problem to the
ffmpeg-user@ffmpeg.org mailing list or IRC #ffmpeg on irc.freenode.net.
Include the log file "ffbuild/config.log" produced by configure as this will help
solve the problem.

There's no error about ffnvcodec in config.log except the above bogus one. FFmpeg test including ffnvcodec headers compiles without any issues (both according to config.log, and when compiling the same code manually).

This is on Nvidia Jetson Nano with Nvidia's Ubuntu 18.04 based ARM SDK image.

[eero-t]

FFmpeg build config.log

[Hendrik]

nvcodec is not supported on ARM in ffmpeg.

[eero-t]

How one is then supposed to do HW encoding with FFmpeg on Tegras?

VDPAU seems to support only decoding.

At least FFmpeg documentation, or FFmpeg configure error message should be updated to mention that the problem is about CPU architecture, not about finding ffnvcodec.