I will share an info that might be useful to someone. You can decode the source to wav and after use the NeroAacEnc CLI. For a 2-pass AAC encode you need a physical wav file. You're right that it's easier to use opus, but a lot of devices can't play that.Is not possible.

As always, experiment to see what works for your ears. If you are only going to play it on your computer, or you are sure that your hardware player supports HE-AAC, you can aim for a bit rate of 160kb/s for version 1, or 128kb/s for version 2. Unfortunately, many devices that can play AAC-LC (the default profile for libfdk_aac) simply cannot play either version of HE-AAC, so this is not recommended for surround sound audio, which normally needs to be compatible with such hardware players.

If you have mono, or want to down-mix to mono, use HE-AAC version 1. Note: HE-AAC version 2 only handles stereo. HE-AAC version 1 is suited for bit rates below 64kb/s (for stereo audio) down to about 48 kb/s, while HE-AAC version 2 is suited for bit rates as low as 32 kb/s (again, for stereo). This is a pair of AAC profiles tailored for low bit rates (version 1 and version 2). Video:0kB audio:2759kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 2.183906% Handler_name : ISO Media file produced by Google Inc. Just don't redistribute it.Īnd then it can be done: 🙂 ffmpeg -i in.m4a -c:a libfdk_aac -profile:a aac_he_v2 -b:a 32k out.m4aįfmpeg version N-106448-gc2d1597a8a-Nico-20220328 Copyright (c) 2000-2022 the FFmpeg developersīuilt with gcc 9 (Ubuntu 9.4.0-1ubuntu1~20.04.1)Ĭonfiguration: -prefix=/home/nico/ffmpeg_build -pkg-config-flags=-static -extra-cflags=-I/home/nico/ffmpeg_build/include -extra-ldflags=-L/home/nico/ffmpeg_build/lib -extra-libs='-lpthread -lm' -bindir=/home/nico/bin -extra-version=Nico-20220328 -enable-gpl -enable-libdav1d -enable-libass -enable-libfdk-aac -enable-libfreetype -enable-libmp3lame -enable-libopus -enable-libvorbis -enable-libvpx -enable-libx264 -enable-libx265 -enable-openssl -enable-demuxer=dash -enable-libxml2 -enable-nonfree But it's perfectly legal to compile ffmpeg yourself with libfdk-aac support, like I do.

Download he aac v2 sample file