AVI to MP3 Converter

Extract useful sound from an old AVI video

An old camera recording, a family interview or a screen capture may contain audio you want to keep even when the picture is no longer useful. This AVI to MP3 converter selects the first audio track, encodes it as MP3 and lets you download it. You can keep a whole recording or choose a start and end time. The video and resulting audio stay on your device.

Before you start: choose one AVI up to 500 MB and keep this tab open while it converts. A supported filename does not guarantee that a damaged file or every uncommon audio codec will work. Keep the original until you have checked the downloaded sound.

Choose a bitrate by content and duration

The default is 192 kbps. A higher setting leaves more space for the new MP3 encode, but cannot restore missing frequencies, remove tape hiss or repair a clipped microphone recording. For an interview, try a short section at 128 and 192 kbps and compare the voices before converting the whole file.

MP3 bitrate	Approx. 1 minute	Approx. 10 minutes	A practical starting point
128 kbps	0.96 MB	9.60 MB	Speech, interviews and small downloads
192 kbps	1.44 MB	14.40 MB	Mixed voice and music; the default
320 kbps	2.40 MB	24.00 MB	Music when a larger file is acceptable

These are calculated audio payload estimates, not measured downloads: size in MB ≈ bitrate in kbps × duration in seconds ÷ 8,000. MB here means 1,000,000 bytes; headers, tags and MP3 frame padding can change the final size. The estimate uses the selected audio duration, not the AVI's file size or video resolution. For example, a five-minute selection at 192 kbps is about 7.2 MB even if its video occupies hundreds of megabytes.

Trimming reduces output size and often processing time. It does not bypass the 500 MB input limit: the converter must still open the source AVI.

AVI playback and AVI conversion are different checks

AVI is a container, not a single audio or video codec. Its picture and sound are separate streams, and the extension alone does not tell you which decoders they need. The Library of Congress AVI format description documents this container structure and examples of audio it can carry.

A browser's inability to preview an old AVI does not, by itself, prove that this converter cannot read its sound. This tool uses FFmpeg compiled to WebAssembly and processes the selected audio stream without needing to display the video. Conversely, changing an extension to .mp3 never converts the audio, and a valid AVI extension does not repair missing or damaged audio data.

MP3 mode always decodes and re-encodes the first audio stream. That includes an AVI that already contains MP3 audio. If your priority is avoiding another lossy encode, choose Original mode: it copies that first encoded track to MKA, rather than making an MP3. Original-mode trimming follows existing packet boundaries, so its start and end can differ slightly from the requested times.

Diagnose an old recording before trying again

The AVI has no audio track

Some time-lapse exports and capture files are silent. A conversion cannot create a missing microphone recording. Check whether a desktop player reports an audio track; distinguish a track that is absent from one that is present but silent.

The browser cannot read the duration

AVI metadata may not be readable by the browser even when FFmpeg can read the file. You can try conversion if the file passes validation; inspect the result rather than relying on the preview alone. If seeking or trimming is inconsistent, use native desktop FFmpeg to inspect the source and make a local working copy. Keep the original.

The result contains the wrong voice or language

This converter uses the first audio track and has no track selector. An AVI with more than one track can therefore produce commentary or a different language. Use a desktop tool with explicit audio-track selection when another track is required.

Conversion fails or the tab runs out of memory

A file under 500 MB can still exceed the memory available to a phone. Keep the page in the foreground, close heavy tabs and try a desktop browser. Repeated failures may indicate an unsupported audio codec or damaged data; native desktop FFmpeg is a better next step for inspection and large files. The ffmpeg.wasm FAQ explains why browser processing has different performance and memory constraints from native FFmpeg.

The converted speech is noisy or distorted

This tool converts formats and trims time ranges; it does not denoise, separate voices or repair clipping. A larger MP3 bitrate does not solve those problems. For further editing, select WAV: this site's preset is 16-bit, 48 kHz stereo PCM, about 11.52 MB per minute before headers. It avoids another lossy encoding stage, but cannot recover details already lost in the original recording.

Check the downloaded MP3 before discarding the AVI

Listen to the beginning, middle and end. Check the intended speaker, the selected range and whether any channel is unexpectedly silent. MP3 framing and encoder delay can affect the exact duration shown by different players. Keep an archival AVI separately: an MP3 preserves sound for listening, not the picture or the complete original file.

A reproducible conversion check

On October 31, 2026, we checked a generated four-second AVI with MPEG-4 video and a 48 kHz mono PCM test tone in desktop Chrome. Converting the range from 1 to 2 seconds at 192 kbps produced a 25,423-byte MP3 with both the single-thread and multi-thread cores. The calculated one-second payload is 24,000 bytes; the complete MP3 also contains headers and encoded frames.

We also converted an AVI containing an MP3 track and confirmed that an AVI with no audio stream produces a missing-audio error. These are small functional checks, not a speed benchmark or evidence that every camera codec, browser or phone is compatible.

How this guidance is maintained

Written and maintained by Video to Audio, the developer of this converter. Last updated October 31, 2026. Recommendations above reflect the current presets and processing behavior; they are not a promise that every historical AVI codec is supported. Report a problem through Contact with your browser, file size and known audio codec, without sending private media.

The size examples are our calculations from the available MP3 bitrates. Container facts are checked against the Library of Congress reference above; stream selection, re-encoding and stream-copy behavior follow the FFmpeg documentation. These references explain the underlying formats and processing, not an endorsement of this website.