Many AVI files already contain MP3
AVI files shared in the 2000s were usually made with Xvid or DivX video and MP3 sound. That means the audio you want may already be an MP3 inside the video. With the Original audio option, the track is copied out exactly as it is: no re-encoding, no quality loss, and it takes only a moment even for a long film. The input list shows the audio codec of each file, so you can see whether a copy is possible.
Other AVI files use different audio. Camera clips usually have uncompressed PCM, DVD rips often have AC-3 (Dolby Digital), and some old recorders use ADPCM. In those cases the sound is converted to MP3 with the settings you choose.
Picking a bitrate
- 128 kbps is fine for speech, lectures and interviews.
- 192 kbps is a good general choice for music and film sound.
- 256 to 320 kbps is for music you care about, when the source is good.
- VBR spends more bits on complex parts and fewer on quiet ones, so it usually gives a smaller file at the same quality.
A higher bitrate cannot improve a weak source. If the AVI already had 128 kbps MP3 sound, saving it at 320 kbps only makes the file bigger. Copying the original track is the better choice in that case. Also note that MP3 holds at most two channels, so 5.1 surround sound from a DVD rip becomes stereo.
Keep only the part you need
When you convert AVI to MP3, you often want one song from a concert video or one scene from a film. Open Trim & tags, play the video and press Use current time to set the start and the end. In the same panel you can add a title, artist and album, and choose a video frame or your own picture as the cover. Music players and phones show these tags.
No sound in the result?
Some AVI files from screen recorders or security cameras have no audio track at all. The tool tells you this instead of creating an empty file. If the video plays with sound in VLC but the tool reports no audio, the file may be damaged. Converting it first with AVI to MP4 can help. For lossless sound for editing, use AVI to WAV, and for other targets see the AVI converter.