Extract Audio from AVI to AAC — Free Online Tool
Extract the audio track from an AVI file and save it as an AAC file — stripping the video entirely and encoding the audio using the AAC codec at 128k bitrate. Ideal for salvaging audio from legacy AVI recordings without carrying the overhead of the video container.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
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Settings
Note: Browser-based encoding uses approximate quality targets. For precise CRF compression, copy the FFmpeg command above and run it on your desktop.
Estimated output:
Conversion Complete!
DownloadHow It Works
AVI files commonly store audio encoded with MP3 (libmp3lame) or occasionally AAC or Vorbis. When extracting to AAC, FFmpeg discards the video stream entirely using the -vn flag and then re-encodes the audio stream using the native AAC encoder. Because AVI's default audio codec is MP3 (libmp3lame) and the output target is AAC, a full re-encode is necessary — the audio is decoded from its original format and then compressed again using AAC at the specified bitrate. This generation of re-encoding introduces a small amount of additional quality loss, which is worth considering if your source AVI already used lossy audio compression. The output is a raw AAC bitstream (.aac file), not wrapped in a container like MP4 or M4A.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg program. In this browser-based tool, FFmpeg runs locally in your browser via WebAssembly (FFmpeg.wasm) — no data is sent to a server. The same command can be run in a terminal on any desktop with FFmpeg installed. |
-i input.avi
|
Specifies the input AVI file. FFmpeg reads the interleaved audio and video chunks from the AVI container, identifying all available streams — in this case, at minimum a video stream and an audio stream encoded with a codec such as MP3 or AAC. |
-vn
|
Disables video output entirely, telling FFmpeg to ignore all video streams from the AVI file. This is what makes this an audio extraction rather than a full conversion — the video data is read and then discarded, keeping only the audio stream for processing. |
-c:a aac
|
Sets the audio codec to AAC using FFmpeg's built-in AAC encoder. Since AVI files most commonly carry MP3 audio, this triggers a full re-encode from MP3 to AAC rather than a simple stream copy, producing a modern lossy audio output that is compatible with Apple devices, mobile browsers, and streaming platforms. |
-b:a 128k
|
Sets the AAC audio bitrate to 128 kilobits per second. This is a widely used default that balances file size and audio quality well for most content including speech and music. For the AAC codec, 128k typically yields noticeably cleaner results than MP3 at the same bitrate due to AAC's more efficient compression algorithm. |
output.aac
|
Specifies the output filename with the .aac extension, which tells FFmpeg to write a raw AAC bitstream file. Unlike M4A or MP4, a raw .aac file has no container wrapping — it is a plain stream of AAC-encoded audio data, which is lightweight but may lack metadata support depending on the playback application. |
Common Use Cases
- Pulling the audio commentary track from an old AVI screen recording or tutorial video to repurpose as a standalone audio file
- Extracting audio from legacy AVI home videos or camcorder footage to create AAC files compatible with iPhone, iPad, or iTunes
- Stripping the audio from an AVI movie clip to use as background music or a sound effect in a video editing project
- Converting AVI audio to AAC for streaming or web playback, since AAC is natively supported by HTML5 audio players and most mobile browsers
- Reducing file size by discarding unwanted video from large AVI archive files when only the audio content is needed for archival or transcription
- Preparing audio extracted from AVI game recordings or livestream captures for upload to podcast platforms that accept AAC files
Frequently Asked Questions
Yes, some quality loss is unavoidable. AVI files most commonly store audio as MP3, which is already a lossy format. Converting that MP3 audio to AAC means decoding the lossy MP3 and re-encoding it into lossy AAC — a process sometimes called 'lossy-to-lossy transcoding.' Each generation of lossy compression introduces additional artifacts. For most casual listening purposes the difference at 128k is subtle, but if audio fidelity is critical, you should increase the output bitrate to 192k or 256k to minimize the degradation.
The FFmpeg command produces a raw AAC bitstream with the .aac extension, which is the AAC audio without any container wrapping. An M4A file is simply AAC audio wrapped inside an MP4 container, which adds metadata support and slightly better compatibility with some players and devices. If you need an M4A instead, you can change the output filename to output.m4a in the FFmpeg command — FFmpeg will automatically wrap the AAC stream in an MP4 container. For Apple devices and iTunes, M4A is generally the better choice.
At equivalent bitrates, AAC generally offers better audio quality than MP3 due to its more advanced compression algorithm — this is by design, as AAC was developed as MP3's successor. However, since the AVI's original MP3 audio must be decoded and re-encoded, the final AAC output won't surpass the quality ceiling set by the original MP3 source. You may notice improvements in how the encoder handles certain frequencies, but you won't recover information that was discarded during the original MP3 encoding.
Change the value after the -b:a flag to your desired bitrate. For example, replace 128k with 192k for higher quality: ffmpeg -i input.avi -vn -c:a aac -b:a 192k output.aac. The AAC format supports bitrates from 64k up to 320k. For voice recordings or podcasts, 96k or 128k is typically sufficient. For music with a wide dynamic range, 192k or 256k will preserve more detail. Keep in mind that increasing the bitrate cannot recover quality lost in the original AVI's lossy audio encoding.
Generally, no. AVI has limited and non-standardized metadata support, and a raw .aac bitstream file has essentially no metadata container to store tags like artist, title, or album. Even metadata that exists in the AVI source is unlikely to transfer meaningfully. If you need metadata support, output to M4A instead by changing the output filename, as the MP4 container supports ID3-style tags and FFmpeg will attempt to map available metadata from the source.
The command as shown processes a single file, but you can batch process on your desktop using a shell loop. On Linux or macOS, run: for f in *.avi; do ffmpeg -i "$f" -vn -c:a aac -b:a 128k "${f%.avi}.aac"; done. On Windows Command Prompt, use: for %f in (*.avi) do ffmpeg -i "%f" -vn -c:a aac -b:a 128k "%~nf.aac". This is especially useful for large collections of AVI files since the browser-based tool handles one file at a time and supports files up to 1GB.
Technical Notes
AVI is a legacy container that uses index-based interleaving of audio and video chunks, and it does not support modern container features like chapter markers, embedded subtitles, or multiple audio tracks exposed cleanly via standard stream mapping. When FFmpeg reads an AVI with multiple audio streams, it defaults to extracting the first audio stream — if you need a secondary track, you must add -map 0:a:1 to the command manually. The output format here is a raw AAC bitstream, not an ADTS-framed file or an MP4-wrapped M4A; some media players may not handle raw .aac files correctly, in which case renaming the output to .m4a and allowing FFmpeg to apply the MP4 container is a practical workaround. FFmpeg's built-in aac encoder is good quality but the optional libfdk_aac encoder (if compiled into your local FFmpeg build) is generally considered superior, particularly at lower bitrates — you can substitute -c:a libfdk_aac in the command if available. Finally, note that AVI's OpenDML extension allows files larger than 2GB, so very large AVI source files may exist; the browser tool supports up to 1GB, and the provided FFmpeg command can be run locally for larger files with no size restrictions.