"The encoder 'aac' is experimental but experimental codecs are not enabled"

Question

While converting flv to mp4 conversion using FFMPEG it's showing following error

[aac @ 0x2b4b640] The encoder 'aac' is experimental but experimental codecs are not enabled, add '-strict -2' if you want to use it.

Answer 1

Actually it is not enough to add -strict -2 to the command line. It is very important where the -strict -2 is added and unfortunately this is not explained in the error message. It should be just before the last argument, that is, as follows:

ffmpeg -i infile -strict -2 outfile

Answer 2

Like the message says, the native ffmpeg AAC audio encoder is experimental and you need to add -strict -2 or -strict experimental to your command use it. However, this encoder is no longer marked as experimental, so recent ffmpeg builds do not need to use this option.

For the best results use libfdk_aac instead. You need to compile ffmpeg with this lib, see the compilation guide.

To set the audio encoder use -c:a libfdk_aac.