MyMediaTools

Convert VOB to FLV — Free Online Tool

Convert VOB files from DVD discs into FLV format, transcoding MPEG-2 video to H.264 (libx264) and AC3 audio to AAC — making legacy DVD content streamable and playable in web environments that expect Flash Video containers.

FFmpeg Command

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Estimated output:

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How It Works

VOB files store DVD video as MPEG-2 streams with AC3 (Dolby Digital) audio, often alongside subtitle streams and multiple audio tracks. During this conversion, the MPEG-2 video is fully re-encoded to H.264 using libx264, which is a computationally intensive transcode — not a simple remux — because H.264 and MPEG-2 are fundamentally different codecs. The AC3 audio track is decoded and re-encoded to AAC, the standard audio codec for FLV containers. Subtitle streams are dropped entirely, as FLV has no support for subtitle data. If the VOB contains multiple audio tracks (e.g., multiple language dubs), only the default track is carried into the output. The resulting FLV file is significantly smaller than the original VOB due to H.264's superior compression efficiency over MPEG-2, even at comparable visual quality.

What Each Flag Does

Flag What it does
ffmpeg Invokes the FFmpeg transcoding engine. In this browser tool, FFmpeg runs entirely via WebAssembly (ffmpeg.wasm) inside your browser — no data is sent to a server.
-i input.vob Specifies the input VOB file. FFmpeg automatically detects the MPEG-2 Program Stream structure, identifying the MPEG-2 video track, AC3 audio track, and any embedded subtitle subpicture streams within the DVD container.
-c:v libx264 Re-encodes the MPEG-2 video stream to H.264 using the libx264 encoder. This is a full transcode — not a copy — because MPEG-2 and H.264 are incompatible codecs, and FLV requires H.264 for modern web-compatible output.
-c:a aac Transcodes the AC3 Dolby Digital audio from the VOB into AAC, which is the required audio codec for this FLV output. AC3 is not supported inside FLV, so decoding and re-encoding to AAC is mandatory.
-crf 23 Sets the Constant Rate Factor for libx264 to 23, the default quality level. This controls the H.264 encode quality on a scale of 0–51 where lower numbers mean better quality and larger files — a value of 23 is a standard web-delivery balance for DVD source material.
-b:a 128k Sets the AAC audio output bitrate to 128 kilobits per second. This is sufficient for stereo dialogue and music from DVD sources, though you can raise it to 192k or 256k if the original AC3 track was high-bitrate surround audio you want to preserve more faithfully in the downmixed stereo output.
output.flv Defines the output filename and tells FFmpeg to write a Flash Video container. The .flv extension causes FFmpeg to use the FLV muxer, which packages the H.264 video and AAC audio streams into the Flash Video format expected by legacy Flash Player-based media systems.

Common Use Cases

  • Uploading ripped DVD content to older video hosting platforms or CMS systems that were built around Flash Video infrastructure and only accept FLV uploads
  • Archiving home-recorded DVD camcorder footage into a more compressed web-friendly format for sharing on legacy intranets or Moodle-based e-learning platforms that use Flash players
  • Converting DVD bonus feature VOB files into FLV for embedding in older Flash-based interactive CD-ROM or DVD-ROM menus
  • Reducing the file size of large MPEG-2 VOB recordings from DVD camcorders before uploading to media servers where storage is limited
  • Preparing DVD lecture recordings or training videos for playback in older corporate LMS platforms that were built when FLV was the dominant web video format
  • Extracting a single VOB chapter from a DVD rip and converting it to FLV for quick web preview without re-authoring the entire disc

Frequently Asked Questions

Yes, the AC3 audio is transcoded to AAC stereo during this conversion. FLV containers do not natively support AC3 audio, so FFmpeg decodes the original Dolby Digital track and re-encodes it as AAC at 128k by default. Multichannel surround information is typically downmixed to stereo in the process. If preserving the original surround mix is critical, you should consider an output format that supports AC3 passthrough, such as MP4 or MKV.
VOB files use MPEG-2 video, an older codec that requires significantly higher bitrates to achieve the same visual quality as H.264. A typical DVD VOB might use 4–8 Mbps for video, while libx264 at CRF 23 can deliver comparable perceptual quality at 1–2 Mbps. This compression efficiency difference, combined with the removal of unused audio tracks and subtitle streams, commonly results in the FLV being 50–75% smaller than the original VOB.
This browser tool processes one file at a time. However, if you have multiple VOB files (e.g., VTS_01_1.VOB, VTS_01_2.VOB), you can concatenate them locally using FFmpeg before conversion with a command like: ffmpeg -i 'concat:VTS_01_1.VOB|VTS_01_2.VOB' -c:v libx264 -c:a aac -crf 23 -b:a 128k output.flv. This joins the MPEG-2 segments seamlessly before transcoding, which is the correct approach for split VOB files that represent a single continuous title.
The -crf flag controls H.264 quality on a scale from 0 (lossless) to 51 (worst). The default value of 23 is a good general-purpose balance. Lowering it — for example, -crf 18 — produces a higher quality, larger file that more faithfully preserves the DVD source. Raising it — for example, -crf 28 — produces a smaller file with more compression artifacts. For DVD source material that is already compressed MPEG-2, values between 18 and 23 are typically recommended to avoid introducing additional visible quality loss on top of the original encoding.
VOB files commonly carry DVD subtitle streams in a bitmap-based format (DVD subpictures). The FLV container has no support for any subtitle format, so all subtitle streams are silently discarded during this conversion. If you need to preserve subtitles, consider converting to MKV or MP4 instead, where subtitle tracks can be remuxed or burned into the video.
Converting directly from VOB to FLV is the better approach and avoids generational quality loss. Adding an intermediate step (VOB → MKV → FLV) would apply lossy re-encoding twice to the video — once to MKV and again to FLV — degrading quality unnecessarily. The FFmpeg command on this page decodes the MPEG-2 stream only once and encodes it to H.264 in a single pass, which is always preferable when the source and target codecs differ.

Technical Notes

VOB is a strict DVD-spec container built around MPEG-2 Program Stream, and its audio is almost universally AC3 (Dolby Digital) at 192–448 kbps. Neither the MPEG-2 video codec nor the AC3 audio codec is natively supported in FLV, so this conversion requires full transcoding of both streams — there is no possibility of stream copying (using -c copy) as there would be in a format-compatible remux. The libx264 encoder produces H.264 Baseline or Main Profile output inside the FLV container, which was the standard for Flash Player 9+ compatibility. FLV does not support B-frames in some strict Flash Player implementations, but libx264's defaults are generally safe. One important limitation: VOB files often span multiple physical files on a DVD (e.g., VIDEO_TS folder with split VTS files), and this tool processes a single VOB file — it will not automatically concatenate a split title. Additionally, the -f vob flag is not needed on the output side; it was a VOB input hint. The output FLV has no chapter, subtitle, or secondary audio track support, so any DVD navigation metadata, alternate language tracks, or director's commentary audio streams present in the source are permanently lost in the output.

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