FFmpeg command to convert mp3 to aac

Question

I can issue this command:

ffmpeg -i input.mp3 -acodec alac -ab 128k -ar 48000 -ac 2 -y output.m4a 

to create a m4a file.

But when I issue this command

ffmpeg -i input.mp3 -acodec alac -ab 128k -ar 48000 -ac 2 -y output.aac

ffmpeg is throwing an error saying

Could not write header for output file #0 (incorrect codec parameters ?).

Also, the size of the m4a file is really almost 5.8 times larger than the original file, which is absolutely not what I wanted and why I wanted to convert to AAC.

Answer 1

There are several problems with your approach:

• alac is not AAC. ALAC is the Apple Lossless Audio Codec, whereas AAC is Advanced Audio Coding.

• That's why your output is larger than the input, because in contrast to MP3, ALAC is still compressed, but it needs to be lossless – that's why it needs to store more data.

• .aac is not an output container for ALAC audio. If you use AAC, that should work. I would use MP4 or M4A though.

Therefore, something along the following would work:

ffmpeg -i input.mp3 -acodec libfaac … output.m4a

-acodec libvo_aacenc can also be used instead of libfaac if your FFmpeg is configured to support it.

A third option, -acodec aac -strict experimental, is the "native" FFmpeg AAC encoder, but it is considered experimental.