Convert VOB to RMVB — Free Online Tool
Convert VOB files from DVD-Video discs to RMVB format, transcoding the MPEG-2 video stream to H.264 (libx264) and the AC-3 audio to AAC — making your DVD content compatible with media players and devices that support the RealMedia variable bitrate format. This is especially useful for compressing large DVD video files into smaller, streamable RMVB files while retaining good visual quality.
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FFmpeg Command
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Estimated output:
Conversion Complete!
DownloadHow It Works
VOB files store DVD-Video content as multiplexed MPEG-2 video and AC-3 (Dolby Digital) audio, often accompanied by subtitle streams and multiple audio tracks. Because RMVB uses H.264 for video and AAC for audio, this conversion requires a full re-encode of both streams — there is no stream copy shortcut here. FFmpeg decodes the MPEG-2 video and re-encodes it using libx264 with a Constant Rate Factor (CRF) of 23, which targets visually consistent quality at a variable bitrate. The AC-3 audio is simultaneously decoded and re-encoded into AAC at 128k. Note that RMVB does not support subtitles, chapters, or multiple audio tracks, so these DVD-specific features are dropped during conversion — only the primary video and audio streams are carried into the output file.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg binary — the open-source multimedia processing engine that handles decoding the MPEG-2 Program Stream from the VOB container, re-encoding both video and audio streams, and muxing the result into an RMVB container. |
-i input.vob
|
Specifies the input VOB file. FFmpeg automatically detects the MPEG-2 Program Stream structure, identifies the MPEG-2 video stream and AC-3 audio stream, and prepares them for decoding and re-encoding. |
-c:v libx264
|
Instructs FFmpeg to re-encode the MPEG-2 video stream using the libx264 H.264 encoder. This is a mandatory re-encode since the source VOB uses MPEG-2, which is not a valid video codec for RMVB output. H.264 provides far superior compression efficiency compared to MPEG-2. |
-c:a aac
|
Re-encodes the AC-3 (Dolby Digital) audio from the VOB file into AAC, which is the default and most compatible audio codec for RMVB containers as handled by FFmpeg. AC-3 is not supported in RMVB output, making this transcoding step mandatory. |
-crf 23
|
Sets the Constant Rate Factor for the libx264 encoder to 23, which is x264's default quality level. For DVD-resolution MPEG-2 source material, CRF 23 typically produces an output that is visually close to the source at a significantly reduced file size. Lower values increase quality and file size; higher values reduce both. |
-b:a 128k
|
Sets the AAC audio output bitrate to 128 kilobits per second. This is sufficient for stereo audio at DVD quality levels, though if the source VOB contains 5.1 surround AC-3 at 384k or higher, increasing this to 192k or 256k will better preserve audio fidelity in the downmixed stereo output. |
output.rmvb
|
Specifies the output filename with the .rmvb extension, which signals FFmpeg to use the RealMedia variable bitrate container muxer. The resulting file will contain the H.264 video and AAC audio streams in an RMVB wrapper compatible with RealPlayer and other RMVB-capable media players. |
Common Use Cases
- Archiving old DVD movie rips stored as VOB files into smaller RMVB files for long-term storage on hard drives with limited space, taking advantage of H.264's superior compression over MPEG-2.
- Making DVD-sourced video content playable on legacy media players and set-top boxes from the 2000s and 2010s that support RMVB but not raw VOB or MPEG-2.
- Sharing DVD rips over older peer-to-peer networks or forums where RMVB was the dominant distribution format for compressed video.
- Converting a VOB file from a home-recorded DVD camcorder disc into an RMVB file for easier playback on PC media players like RealPlayer or older versions of Media Player Classic.
- Reducing the file size of a multi-gigabyte DVD VOB rip for distribution or upload to platforms where bandwidth is constrained, since H.264 in RMVB achieves much higher compression than MPEG-2 in VOB.
- Consolidating split VOB chapter files from a DVD rip into a single re-encoded RMVB file that is easier to manage and play without requiring DVD navigation software.
Frequently Asked Questions
Yes, some quality loss is expected because both the MPEG-2 video and AC-3 audio must be fully re-encoded — there is no lossless path from VOB to RMVB. However, H.264 is a significantly more efficient codec than MPEG-2, meaning that at the same file size, H.264 output often looks visually comparable or even better than the MPEG-2 source. The default CRF value of 23 used in this command produces a good balance of quality and file size for most DVD-sourced content.
The AC-3 audio track from the VOB file is decoded and re-encoded as AAC at 128k, because RMVB does not support AC-3 audio natively. AAC at 128k provides decent stereo audio quality for most content. If your VOB contained surround sound (e.g., 5.1 channels), the AAC encoder will downmix it to stereo by default unless you specify additional channel mapping flags in the FFmpeg command.
RMVB does not support subtitle streams or multiple audio tracks, so all of these DVD-specific features are discarded during conversion. Only the primary video stream and the first audio track are preserved in the output RMVB file. If your VOB contains foreign-language subtitles or alternate language audio tracks that you need, you should consider converting to a format that supports these features, such as MKV or MP4.
You can control the video quality by changing the -crf value in the command. Lower CRF values (e.g., -crf 18) produce higher quality and larger file sizes, while higher values (e.g., -crf 28) produce smaller files with more compression. For audio, you can change -b:a 128k to a higher value like -b:a 192k or -b:a 256k if you want better audio fidelity, particularly useful if the source VOB has high-quality AC-3 surround audio.
Yes. On Linux or macOS, you can use a shell loop: for f in *.vob; do ffmpeg -i "$f" -c:v libx264 -c:a aac -crf 23 -b:a 128k "${f%.vob}.rmvb"; done. On Windows Command Prompt, use: for %f in (*.vob) do ffmpeg -i "%f" -c:v libx264 -c:a aac -crf 23 -b:a 128k "%~nf.rmvb". This is particularly valuable for converting full DVD rip folders where each chapter is stored as a separate VOB file.
VOB files use MPEG-2 video, an older codec that requires considerably higher bitrates to achieve comparable visual quality to modern codecs. H.264 (used in the RMVB output) typically achieves the same perceptual quality at roughly half the bitrate of MPEG-2. Additionally, DVD VOB files are often encoded at high bitrates (4–8 Mbps or more) to meet DVD specification requirements, while the CRF-based H.264 encoding targets efficient compression, resulting in output files that can be 50–75% smaller than the source VOB.
Technical Notes
VOB files are structured as MPEG-2 Program Streams with strict DVD-Video compliance requirements, and they frequently contain DVD-specific metadata, angle data, and PCI/DSI navigation packets that have no equivalent in RMVB. FFmpeg handles this by stripping all DVD navigation data and muxing only the primary video and audio elementary streams into the RMVB container. The libx264 encoder used for the output is not a native RealVideo codec — RMVB's original design used RealVideo codecs — but modern RMVB container implementations (as supported by FFmpeg) accept H.264 video with AAC audio, which is the practical standard for creating RMVB files today since RealVideo encoders are not available in FFmpeg. The -crf 23 setting is x264's default and produces good results for standard DVD resolution (720x480 NTSC or 720x576 PAL), but for high-motion content such as action films originally encoded at high DVD bitrates, you may want to lower CRF to 18–20. Interlaced video in VOB files (common in broadcast-sourced DVDs) is not automatically deinterlaced by this command; adding -vf yadif before the output filename is recommended if the source VOB is interlaced.