Extract Audio from VOB to AMR — Free Online Tool
Extract audio from VOB DVD files and convert it to AMR format, transcoding the AC3 (Dolby Digital) or other DVD audio streams into the Adaptive Multi-Rate narrowband codec optimized for speech. Ideal for pulling voice content, dialogue, or commentary tracks from DVD recordings into a compact, mobile-friendly format.
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FFmpeg Command
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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
VOB files store multiplexed MPEG-2 video alongside audio streams typically encoded in AC3 (Dolby Digital), sometimes at bitrates up to 448k. During this conversion, FFmpeg demuxes the VOB container, discards the MPEG-2 video stream entirely (-vn), and transcodes the audio — regardless of whether it is AC3, AAC, or MP3 — into AMR-NB (Adaptive Multi-Rate Narrowband) using the libopencore_amrnb encoder. AMR-NB is a speech-optimized codec designed for telephony, so it operates at very low bitrates (peaking at 12.2 kbps) and is engineered specifically around the frequency range of human speech. The audio is also resampled to 8000 Hz mono, since AMR-NB only supports that sample rate and channel count — this means music, surround sound effects, and high-frequency content from the DVD will be significantly reduced in fidelity, while spoken dialogue is preserved reasonably well.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool, which handles the demuxing of the VOB container, decoding of its audio stream, and re-encoding into AMR format. |
-i input.vob
|
Specifies the input VOB file. FFmpeg reads the multiplexed MPEG-2 video, AC3 audio, and any subtitle or chapter data stored in the DVD Video Object container. |
-vn
|
Disables video output entirely, telling FFmpeg to ignore the MPEG-2 video stream from the VOB and produce an audio-only output — essential since AMR is a pure audio format. |
-c:a libopencore_amrnb
|
Selects the libopencore_amrnb encoder to transcode the DVD's audio (typically AC3 Dolby Digital) into AMR-NB (Adaptive Multi-Rate Narrowband), the speech-optimized codec used in mobile telephony. |
-b:a 12200
|
Sets the AMR-NB bitrate to 12200 bps (12.2 kbps), which is the highest quality mode available in the AMR-NB specification and corresponds to Mode 7 in the 3GPP codec definition. |
output.amr
|
Defines the output filename with the .amr extension, which tells FFmpeg to write the encoded audio into an AMR file container compatible with mobile devices and telephony applications. |
Common Use Cases
- Extracting spoken commentary tracks or director's audio commentary from DVD VOB files to use in voice-note apps or mobile playback
- Converting interview or documentary dialogue from a DVD recording into AMR for storage on older mobile phones or feature phones that natively support the format
- Pulling speech from a DVD language-learning disc to create compact, low-bandwidth audio lessons compatible with AMR-capable players
- Archiving voice-only content from DVD menus or narration tracks in a highly compressed format to minimize storage footprint
- Preparing DVD dialogue audio for upload to telephony or IVR (Interactive Voice Response) systems that accept AMR-NB files
- Extracting a specific audio track from a multi-language VOB file to produce a single-language AMR voice file for distribution
Frequently Asked Questions
Only for speech. AMR-NB is engineered specifically for the human voice frequency range and operates at a maximum of 12.2 kbps with an 8000 Hz sample rate in mono. Music, surround sound effects, and the wide dynamic range typical of AC3 DVD audio will sound heavily degraded — tinny, muffled, and mono. If your VOB contains primarily dialogue or narration, the result will be intelligible; if it contains a film soundtrack, expect significant quality loss.
No. AMR-NB (libopencore_amrnb) is strictly mono and limited to an 8000 Hz sample rate. When FFmpeg converts the AC3 5.1 or stereo audio from the VOB, it automatically downmixes all channels to mono and resamples to 8 kHz. Any spatial or surround information from the DVD audio will be lost in the process.
Yes. VOB files often contain multiple audio streams for different languages or commentary. You can target a specific stream by adding -map 0:a:1 (for the second audio track, zero-indexed) to the FFmpeg command before the output filename. For example: ffmpeg -i input.vob -vn -map 0:a:1 -c:a libopencore_amrnb -b:a 12200 output.amr. Without specifying -map, FFmpeg selects the default (first) audio stream.
Replace the value after -b:a with one of the valid AMR-NB bitrates: 4750, 5150, 5900, 6700, 7400, 7950, 10200, or 12200 (in bits per second, not kilobits). For example, use -b:a 7950 for a slightly smaller file, or keep -b:a 12200 for the highest AMR-NB quality. Note that even at 12200 bps, quality is optimized for speech and will not approach the fidelity of the original AC3 stream.
VOB files are large for multiple reasons: they contain a full MPEG-2 video stream, AC3 audio at bitrates typically between 192k and 448k, subtitle streams, and sometimes multiple audio tracks — all inside a container sized for DVD storage. This conversion strips the video entirely and encodes only the audio at a maximum of 12.2 kbps mono. A 4 GB VOB file may produce an AMR file of just a few megabytes, representing the audio duration at that extremely low bitrate.
Yes, on the command line you can use a shell loop to process multiple files. On Linux or macOS: for f in *.vob; do ffmpeg -i "$f" -vn -c:a libopencore_amrnb -b:a 12200 "${f%.vob}.amr"; done. On Windows Command Prompt: for %f in (*.vob) do ffmpeg -i "%f" -vn -c:a libopencore_amrnb -b:a 12200 "%~nf.amr". The browser-based tool processes one file at a time, so the FFmpeg command is especially useful for batch jobs or files over 1GB.
Technical Notes
AMR-NB via libopencore_amrnb imposes strict constraints that make this conversion a lossy, speech-focused transformation. The codec mandates exactly 8000 Hz sample rate and mono channel output — FFmpeg will automatically insert a resampler and downmixer if the source VOB audio (commonly 48000 Hz stereo or 5.1 AC3) does not match. The eight fixed bitrate modes (4750 to 12200 bps) correspond to AMR codec modes defined in 3GPP specifications; FFmpeg maps the -b:a value to the nearest valid mode. Metadata from the VOB file (track titles, language tags) is generally not preserved in AMR output, as the AMR container has minimal metadata support. Subtitles embedded in the VOB are discarded since AMR does not support subtitle streams. If you need higher-quality audio from a DVD VOB, consider extracting to AAC or MP3 instead; AMR should only be chosen when compatibility with telephony systems or legacy mobile devices is a specific requirement.