Extract Audio from VOB to CAF — Free Online Tool
Extract audio from VOB DVD files and save it as a CAF (Core Audio Format) file — converting the AC3 Dolby Digital soundtrack to uncompressed PCM audio ideal for use in Apple's ecosystem. This tool runs entirely in your browser using FFmpeg.wasm; no files leave your device.
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FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your VOB file here
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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
VOB files store multiplexed MPEG-2 video alongside AC3 (Dolby Digital) audio tracks — the standard audio encoding found on DVD-Video discs. This conversion strips the video stream entirely using the -vn flag, then transcodes the AC3 audio into PCM (16-bit signed little-endian) audio wrapped in Apple's Core Audio Format container. Because AC3 is a lossy compressed format and PCM is uncompressed, this process decodes the compressed Dolby Digital bitstream and re-encodes it as raw audio samples — resulting in a larger file that is fully uncompressed and compatible with macOS and iOS audio toolchains. CAF was designed by Apple to overcome the 4GB file-size limit of AIFF, making it well-suited for long DVD audio extractions.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg media processing tool. In the browser, this runs via FFmpeg.wasm, a WebAssembly port that executes the same conversion logic locally on your device without any server upload. |
-i input.vob
|
Specifies the input VOB file from your DVD. FFmpeg reads the MPEG program stream inside the VOB, which typically contains multiplexed MPEG-2 video and AC3 Dolby Digital audio tracks. |
-vn
|
Disables video output entirely, telling FFmpeg to ignore the MPEG-2 video stream in the VOB. Since the goal is audio-only extraction to CAF, there is no reason to decode or carry the DVD video data. |
-c:a pcm_s16le
|
Decodes the AC3 Dolby Digital audio from the VOB and re-encodes it as 16-bit signed little-endian PCM — the uncompressed audio codec used as the default in CAF files and the standard expected by Apple audio frameworks on macOS and iOS. |
-b:a 128k
|
Specifies a target audio bitrate, though this flag has no effect when the codec is PCM (pcm_s16le), since uncompressed audio has a fixed data rate determined by sample rate and bit depth rather than a configurable bitrate. It is included as a harmless default and would become meaningful if you switch to a compressed codec like AAC. |
output.caf
|
Sets the output filename and format. The .caf extension tells FFmpeg to wrap the extracted PCM audio in Apple's Core Audio Format container, which supports large file sizes beyond the 4GB AIFF limit and integrates natively with macOS and iOS audio APIs. |
Common Use Cases
- Extracting the Dolby Digital AC3 audio track from a DVD's VOB files to archive or re-edit the audio in Logic Pro or GarageBand on macOS
- Pulling the uncompressed audio from a DVD concert or live performance VOB to use as a high-fidelity source for mastering or remixing
- Converting DVD commentary tracks stored in VOB format to CAF for import into Apple's audio or video editing tools like Final Cut Pro
- Extracting dialogue or narration from a DVD training video VOB file to use as audio-only content in macOS-based e-learning production workflows
- Archiving the full uncompressed audio from a home-recorded or authored DVD before the disc media degrades, in a format suitable for Apple ecosystem storage
- Obtaining an FFmpeg command to batch-extract audio from large collections of VOB files on a desktop machine when individual files exceed the 1GB browser limit
Frequently Asked Questions
The conversion involves one generation of quality loss: the AC3 Dolby Digital audio in the VOB is a lossy compressed format, and decoding it to PCM does not recover information that AC3 discarded during its original encoding. However, the resulting PCM in the CAF file is itself uncompressed, so no further lossy compression is added. The CAF output faithfully represents everything in the AC3 track, but it cannot exceed the quality ceiling set by the original DVD encode.
VOB files store audio as AC3, which is a heavily compressed format — typically at 192–448 kbps for DVD audio. PCM audio in a CAF file is uncompressed, storing raw audio samples at 16-bit depth and the source sample rate. A typical 90-minute DVD audio track compressed at 192 kbps AC3 might be around 130 MB, while the same content as 16-bit PCM at 48 kHz in CAF could reach 900 MB or more. This size increase is expected and reflects the move from compressed to uncompressed storage.
Yes. DVD VOB files commonly carry multiple audio streams for different languages or commentary tracks. In the FFmpeg command, you can target a specific stream by adding -map 0:a:1 (for the second audio track, using zero-based indexing) before the output filename. Without a -map flag, FFmpeg defaults to the first detected audio stream, which is typically the primary language track. You can inspect available streams by running ffmpeg -i input.vob in a terminal before deciding which track to extract.
CAF is primarily an Apple format and is natively supported by macOS and iOS audio frameworks, Logic Pro, GarageBand, and Final Cut Pro. It is not natively supported by Windows or most Linux audio applications, and many non-Apple media players will not open it without additional codecs. If you need the extracted audio on a non-Apple platform, consider using WAV or FLAC as the output format instead, which provide similarly high-quality uncompressed or lossless storage with broader compatibility.
Since the output codec is PCM (pcm_s16le), the -b:a 128k flag in this command has no practical effect — PCM is uncompressed and its data rate is determined entirely by sample rate and bit depth, not a bitrate setting. To change quality, you can switch to a higher bit depth by replacing pcm_s16le with pcm_s24le or pcm_s32le. Alternatively, to use a compressed codec like AAC inside CAF, replace -c:a pcm_s16le with -c:a aac and set -b:a 256k to control the lossy compression level.
DVDs typically split their content across multiple VOB files (VTS_01_1.VOB, VTS_01_2.VOB, etc.). FFmpeg can concatenate them during extraction using the concat demuxer: create a text file listing each VOB path, then run ffmpeg -f concat -safe 0 -i filelist.txt -vn -c:a pcm_s16le output.caf. This is especially useful for processing full DVD titles that span several VOB segments, and is best done on a desktop installation of FFmpeg for files exceeding the 1GB browser limit.
Technical Notes
VOB files use MPEG program stream format with a mandatory -f vob flag in FFmpeg to ensure correct demuxing, as the VOB container can sometimes be misidentified. The default audio codec on DVD-Video is AC3 (Dolby Digital), though some DVDs also carry DTS, PCM, or MPEG audio tracks — FFmpeg will select the first audio stream by default. The output PCM codec pcm_s16le produces 16-bit signed little-endian samples, which is standard CD-quality depth; 48 kHz is the native sample rate of DVD audio, so no sample rate conversion occurs unless specified. CAF supports a wide range of audio codecs including AAC, FLAC, and Opus, so the PCM output can later be re-encoded using macOS's built-in afconvert tool or Logic Pro without any additional cross-platform friction. Metadata embedded in VOB files (title, language tags on audio streams) is generally not transferred to CAF during extraction, as VOB metadata structures are DVD-specific and do not map cleanly to CAF's metadata model. Chapter markers from the DVD's IFO navigation files are also not preserved in CAF, as the format does not support chapter data.