I abandoned my quest not too long after I posted my rant. I figured the incremental gain of compiling FFmpeg with that library was not worth the effort. Compiling is definitely a viable barrier to entry for noobs like me who don't really know how computer software really works haha.

So just happily converting my videos using the basic build. I suppose this detour in video editing/formatting was just a distraction from my earlier project of cataloging the collection.

• divided in chunks

• distributed in the cluster

• transcoded

• joined together again

• and lastly (finally  :cheers:) showed to you

Given the wide & great community support

• VLC is using it

• Handbrake is essentially a GUI for it

• Chrome/Chromium use it to support HTML5 streaming

• and so so on

it can read quite every video formats/codecs users like to throw into a transcoder.

Do not bother you trying to compile libfdk_aac, you don't need it anymore :
since the third version the native AAC encoder has no longer been considered experimental.

Fraunhofer FDK AAC (Full title Fraunhofer FDK AAC Codec Library for Android) is an open-source[4] software library for encoding and decoding Advanced Audio Coding (AAC) format audio, developed by Fraunhofer IIS, and included as part of Android. It supports several Audio Object Types including MPEG-2 and MPEG-4 AAC LC, HE-AAC (AAC LC + SBR), HE-AACv2 (LC + SBR + PS) as well AAC-LD (low delay) and AAC-ELD (enhanced low delay) for real-time communication. The encoding library supports sample rates up to 96 kHz and up to eight channels (7.1 surround).[5]

The fdk library used by ffmpeg is the portable version maintained by mstorsjo [ [url=https://github.com/mstorsjo/fdk-aac]https://github.com/mstorsjo/fdk-aac ]
It was useful in a common transcoding practise when the native aac encoder was considered experimental.
The guide states that libfdk_aac produces higher quality audio then the aac encoder, well in reality it depends on the profile used and the tracks you are working on :

• aac_lc (optimal for variable bitrates > 192kbps )
• aac_he ( optimal for 50-80 constant kbps )
• aac_he_v2 ( optimal for bitrate under 50 kbps )
  Be aware that to gain optimal results you should set an optimal cutoff !  ::)

In the real world libfdkaac has some issues (one of the biggest is that the aac_he_v2 profile is not able to encode audio with 6+ channels).
So, in the real world, based on the output of ffprobe <file path=""> you should choose the right profile …
The advantage is that when you are able to use the high efficient profile, you will have a smaller output file.
A benchmark for the processor is not really useful here: your mileage may vary depending on your track.

For me, it's usage is not worth it, the native encoder is safe, robust and case-free (just use the -c:a aac flag and that's it).

To download prebuilt binaries :
Windows zeranoe builds: [https://ffmpeg.zeranoe.com/builds/]
macOS: [http://evermeet.cx/ffmpeg/]
Debian: (just use the backports repo if in stable) [https://backports.debian.org]
Ubuntu: [http://wiki.ubuntu-it.org/Repository/Backports]
You just have to be sure to install the 3.0 version (or an earlier one).

If you just wanna transcode your (peaceful) porno to mp4 h264/aac.
`ffmpeg -i -map 00 -map 00 -c:v libx264 -c:a aac -movflags +faststart

<output file="">`</output></file>