Unable to compile FFmpeg on Ubuntu 20.04

Question

I am following this compilation guide for FFmpeg. After compiling all the required dependencies, I get the following error in the last section.

ERROR: gnutls not found using pkg-config

This error occurs when I run the configure command as below :

PATH="$HOME/bin:$PATH" PKG_CONFIG_PATH="$HOME/ffmpeg_build/lib/pkgconfig" ./configure \
  --prefix="$HOME/ffmpeg_build" \
  --pkg-config-flags="--static" \
  --extra-cflags="-I$HOME/ffmpeg_build/include" \
  --extra-ldflags="-L$HOME/ffmpeg_build/lib" \
  --extra-libs="-lpthread -lm" \
  --bindir="$HOME/bin" \
  --enable-gpl \
  --enable-gnutls \
  --enable-libaom \
  --enable-libass \
  --enable-libfdk-aac \
  --enable-libfreetype \
  --enable-libmp3lame \
  --enable-libopus \
  --enable-libvorbis \
  --enable-libvpx \
  --enable-libx264 \
  --enable-libx265 \
  --enable-nonfree

I am compiling FFmpeg on a fresh install of Ubuntu 20.04.

Solution 1

In the ffbuild directory (path : ffmpeg_sources/ffmpeg/ffbuild/), inspecting the config.log gives more info on the error message :

/usr/bin/ld: cannot find -lunistring
collect2: error: ld returned 1 exit status
ERROR: gnutls not found using pkg-config

With help from ffmpeg's IRC channel, installing the libunistring-dev package fixed the problem.

sudo apt-get install libunistring-dev

Solution 2

The other solutions didn't work for me, although I'm on Debian not Ubuntu. For me the solution was:

apt install libgnutls28-dev

Comments

[doug]

Hardly makes sense as one normally doesn't need libunistring-dev. The option --pkg-config-flags="--static" is what causes this.., not clear on value of that option, see none here.

[Tony]

I've just had this same error (on Debian 10.4) and installing libunistring-dev solved the problem for me too.

[ezwrighter]

@doug - This is on the default compile command line from ffmpeg compile instructions: trac.ffmpeg.org/wiki/CompilationGuide/Ubuntu

[doug]

I understand it's in the guide. The configure option was added 5 yrs ago with no comment (trac.ffmpeg.org/wiki/CompilationGuide/…) . Now it needs a dep installed that isn't part of the guide. As far as option, it serves no purpose in this particular build/install of 3 binaries. No practical need for..

[LFMekz]

Thanks. This was the problem. Once i installed libunistring dev headers it compiled.

[llogan]

@doug Old Q/A I haven't seen before. I don't remember why --pkg-config-flags="--static" was added or why no comment was left (laziness?). IIRC, something to do with x265? Maybe I'll look into it. Haven't touched the guide much in a long time but made a few minor changes and cleanups today.