Extract Audio from 3GP to M4B — Free Online Tool
Extract audio from 3GP mobile video files and convert it to M4B, the MPEG-4 audiobook format with chapter and bookmarking support. Since both 3GP and M4B natively use AAC audio, the conversion is fast and efficient — the audio is re-encoded at a higher bitrate for improved quality in the audiobook-ready output.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your 3GP file here
or click to browse
Free — no uploads, no signups. Your files never leave your browser.
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
3GP files store AAC audio at low bitrates (typically 64k or below) optimized for 3G mobile networks. This tool strips the video stream entirely using the -vn flag, then re-encodes the AAC audio at 128k bitrate and wraps it in the M4B container — an MPEG-4 variant (.mp4 under the hood) specifically structured for audiobooks and podcasts. The -movflags +faststart flag reorganizes the file's metadata index to the beginning of the file, which enables progressive playback in podcast apps and audiobook players. While the source 3GP audio is already AAC, a full re-encode is performed to apply the higher target bitrate and ensure full M4B container compatibility.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool. In this browser-based tool, FFmpeg runs locally via WebAssembly (FFmpeg.wasm) — no file data leaves your device. |
-i input.3gp
|
Specifies the input 3GP file. FFmpeg reads the 3GPP container and identifies both the video stream (typically H.264) and the low-bitrate AAC audio stream for processing. |
-vn
|
Disables video output entirely, discarding the H.264 video track from the 3GP file. Since M4B is a pure audio format for audiobooks, no video data is carried into the output. |
-c:a aac
|
Encodes the output audio using AAC (Advanced Audio Coding), the native and only recommended codec for M4B. The source 3GP audio is already AAC but is re-encoded here to apply the new bitrate and ensure full M4B container compliance. |
-b:a 128k
|
Sets the output AAC audio bitrate to 128 kilobits per second. This is a significant upgrade over the typical 32k–64k AAC bitrate found in 3GP mobile files, improving clarity and dynamic range in the M4B audiobook output. |
-movflags +faststart
|
Relocates the MP4/M4B metadata atom ('moov') to the beginning of the output file. This is essential for M4B audiobook and podcast use cases, as it allows players like Apple Books and Overcast to begin playback or seek through the file before it is fully downloaded. |
output.m4b
|
The output filename with the .m4b extension. This extension signals to Apple Books, Overcast, and other audiobook-aware players that the file supports bookmarking and should be treated as an audiobook rather than a standard music track. |
Common Use Cases
- Converting a recorded voice memo or spoken-word clip from a 3G-era mobile phone into an M4B audiobook file compatible with Apple Books or podcast apps
- Archiving field recordings or audio captured on older Nokia or Samsung 3GP-format phones into a playback-friendly audiobook format with bookmarking so you can resume where you left off
- Repurposing a mobile-recorded lecture or sermon stored as a 3GP video into an M4B audio file for distribution as a podcast episode
- Extracting the audio commentary from a 3GP mobile video to create an M4B chapter file that can be loaded into Overcast, Pocket Casts, or Apple Podcasts
- Stripping video from 3GP clips recorded on older dashcams or security cameras to produce compact M4B audio logs that support chapter markers for time-stamped review
- Preparing audio from a 3GP-format interview recording for submission to an audiobook production pipeline that requires M4B with AAC encoding
Frequently Asked Questions
Because both formats use AAC audio, this conversion is a transcode from one AAC stream to another — not a lossless remux. Some generation loss is theoretically introduced. However, since 3GP audio is typically encoded at very low bitrates (32k–64k) for mobile bandwidth constraints, and this tool outputs at 128k AAC, the resulting M4B file will generally sound noticeably cleaner and fuller than the source, even though a re-encode occurred.
The M4B container format supports chapters, but this conversion does not automatically generate chapter markers — it simply places the audio into a chapter-capable container. To add actual chapter data, you would need to use a dedicated audiobook authoring tool like Hindenburg, Chapter and Verse, or mp4chaps after the conversion. The M4B file produced here is a valid, single-chapter audiobook track ready to be enhanced with chapter metadata.
3GP files are engineered for minimum file size on constrained mobile networks, so the audio bitrate is often as low as 32k–64k. This tool encodes the M4B audio at 128k AAC, which roughly doubles the audio data size for improved fidelity. The video stream, which took up significant space in the 3GP file, is discarded entirely — so the final M4B is audio-only, but the higher audio bitrate means it may still be comparable in size or slightly larger than the original 3GP.
Yes. Apple's audiobook ecosystem — including Apple Books on iOS and macOS — recognizes .m4b files natively and treats them as audiobooks, preserving your playback position automatically. For best results, add ID3/iTunes metadata tags (title, author, cover art) using a tag editor like Mp3tag or iTunes after conversion, since the 3GP source is unlikely to carry compatible audiobook metadata.
Replace the value after -b:a in the command. For example, to encode at 64k for a smaller file use '-b:a 64k', or use '-b:a 192k' for higher fidelity. M4B with AAC supports bitrates up to 320k, though anything above 128k offers diminishing returns for speech audio. Keep in mind that the source 3GP audio was recorded at a low bitrate, so encoding above 128k will not recover detail that was lost during the original 3GP encoding.
Yes, on the command line you can use a shell loop to batch process files. On Linux or macOS, run: for f in *.3gp; do ffmpeg -i "$f" -vn -c:a aac -b:a 128k -movflags +faststart "${f%.3gp}.m4b"; done. On Windows Command Prompt, use: for %f in (*.3gp) do ffmpeg -i "%f" -vn -c:a aac -b:a 128k -movflags +faststart "%~nf.m4b". The browser-based tool processes one file at a time, but the displayed FFmpeg command makes desktop batch processing straightforward.
Technical Notes
3GP uses a restricted subset of the MPEG-4 container, originally defined by 3GPP for devices with limited CPU, memory, and network bandwidth. Its AAC audio is typically encoded in the AAC-LC profile at bitrates of 32k–64k with a sample rate of 8–22 kHz — adequate for voice but noticeably compressed compared to standard audio. M4B is structurally identical to MP4/M4A but uses the .m4b extension to signal audiobook intent to compatible players. The -movflags +faststart flag is essential for M4B distribution: it moves the 'moov' atom to the front of the file so podcast apps and audiobook players can begin streaming or scanning the file before it is fully loaded. The source 3GP format does not support subtitles, embedded chapters, or multiple audio tracks, so none of those can be carried into the M4B output — chapter data must be added in post using a dedicated tool. Metadata from 3GP (such as title or artist tags, if present) may not transfer cleanly due to the tag format differences between 3GPP metadata boxes and iTunes-style MP4 atoms; manual retagging after conversion is recommended.