How to use the AAC to MP3 converter
- Choose the .aac files, or drop the folder your recorder saved them to.
- Pick an MP3 bitrate a step above the AAC’s own.
- Convert to MP3 and save.
Raw AAC compared with M4A
A .aac file is an unwrapped AAC stream with a small ADTS header in front of each frame; an .m4a puts the same audio inside an MP4 container with an index. Without that index, players struggle with duration and seeking. MP3 has no such trouble in practically any player.
HE-AAC from internet radio, which sounds good at 48–64 kbps thanks to spectral band replication, is fully decoded before LAME encodes the MP3.
Matching the quality
AAC is the more efficient codec, so 128 kbps AAC sounds about like 160 kbps MP3. Choose 160 or 192 kbps to hold on to what you have. Matching the AAC rate exactly tends to lose a little clarity, because MP3 needs those extra bits to reach the same sound.
A radio show captured as 48 kbps HE-AAC needs no more than 96 or 128 kbps as MP3.
Separate audio from recorders
Some screen recorders and radio capture tools write the soundtrack as its own .aac file next to the video. Converting that file gives you something any audio editor will import.
A file whose extension is wrong still converts, since ffmpeg identifies the format by looking inside it.
Questions
Could I get M4A instead?
Yes. Choose M4A in the audio converter and the AAC is copied into the container without re-encoding.
Is anything uploaded?
No. The conversion runs in your browser.
Why does my AAC file show no length?
Raw ADTS streams carry no index, so players cannot read the duration easily. Once converted to MP3, the running time appears in practically any player.
Which bitrate suits an internet radio capture?
For a low-bitrate HE-AAC capture, 96 or 128 kbps MP3 is enough. Going higher only makes the file bigger.