“The encoder ‘aac’ is experimental but experimental codecs are not enabled”

ffmpeg

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.

Best Answer

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

Related Solutions

Rotating videos with FFmpeg

Rotate 90 clockwise:

ffmpeg -i in.mov -vf "transpose=1" out.mov

For the transpose parameter you can pass:

0 = 90CounterCLockwise and Vertical Flip (default)
1 = 90Clockwise
2 = 90CounterClockwise
3 = 90Clockwise and Vertical Flip

Use -vf "transpose=2,transpose=2" for 180 degrees.

Make sure you use a recent ffmpeg version from here (a static build will work fine).

Note that this will re-encode the audio and video parts. You can usually copy the audio without touching it, by using -c:a copy. To change the video quality, set the bitrate (for example with -b:v 1M) or have a look at the H.264 encoding guide if you want VBR options.

A solution is also to use this convenience script.

How to concatenate two MP4 files using FFmpeg

FFmpeg has three concatenation methods:

1. concat video filter

Use this method if your inputs do not have the same parameters (width, height, etc), or are not the same formats/codecs, or if you want to perform any filtering.

Note that this method performs a re-encode of all inputs. If you want to avoid the re-encode, you could re-encode just the inputs that don't match so they share the same codec and other parameters, then use the concat demuxer to avoid re-encoding everything.

ffmpeg -i opening.mkv -i episode.mkv -i ending.mkv \
-filter_complex "[0:v] [0:a] [1:v] [1:a] [2:v] [2:a] \
concat=n=3:v=1:a=1 [v] [a]" \
-map "[v]" -map "[a]" output.mkv

2. concat demuxer

Use this method when you want to avoid a re-encode and your format does not support file-level concatenation (most files used by general users do not support file-level concatenation).

$ cat mylist.txt
file '/path/to/file1'
file '/path/to/file2'
file '/path/to/file3'
    
$ ffmpeg -f concat -safe 0 -i mylist.txt -c copy output.mp4

For Windows:

(echo file 'first file.mp4' & echo file 'second file.mp4' )>list.txt
ffmpeg -safe 0 -f concat -i list.txt -c copy output.mp4

3. concat protocol

Use this method with formats that support file-level concatenation (MPEG-1, MPEG-2 PS, DV). Do not use with MP4.

ffmpeg -i "concat:input1|input2" -codec copy output.mkv

This method does not work for many formats, including MP4, due to the nature of these formats and the simplistic concatenation performed by this method.

If in doubt about which method to use, try the concat demuxer.