VOB Format Guide: DVD Video Files Explained

VOB Format Guide: Everything You Need to Know About DVD Video Files

VOB (Video Object) files are the core video containers found on every commercial and home-burned DVD disc. If you have ever ripped a DVD, found a .vob file on an old hard drive, or tried to play a VIDEO_TS folder, this guide explains exactly what VOB files are, how they work internally, and the best methods to convert them to modern formats like MP4 or MKV.

What Is a VOB File?

A VOB file is a container format defined by the DVD Forum as part of the DVD-Video specification (published 1995, first discs 1996). The name stands for Video Object, and each file packages multiplexed MPEG-2 program streams that carry video, audio, subtitles, and navigation data together in a single binary file.

VOB files are not a stand-alone format in the way MP4 or MKV are. They only make full sense within the context of the DVD file system and the IFO control files that accompany them. Without the IFO files the player cannot know chapter positions, stream language mappings, or menu navigation.

The DVD Directory Structure

When you insert a DVD or open a DVD rip folder you will always find this layout:

DVD_ROOT/
├── VIDEO_TS/
│   ├── VIDEO_TS.IFO    ← Root menu information
│   ├── VIDEO_TS.BUP    ← Backup copy of VIDEO_TS.IFO
│   ├── VIDEO_TS.VOB    ← Root menu video (usually small)
│   ├── VTS_01_0.IFO    ← Title Set 1 information
│   ├── VTS_01_0.BUP    ← Backup of VTS_01_0.IFO
│   ├── VTS_01_0.VOB    ← Title Set 1 menu video
│   ├── VTS_01_1.VOB    ← Title Set 1, segment 1 (up to 1 GB)
│   ├── VTS_01_2.VOB    ← Title Set 1, segment 2
│   └── VTS_01_3.VOB    ← Title Set 1, segment 3
└── AUDIO_TS/           ← Usually empty (reserved for DVD-Audio)

File Types Explained

Why are VOB files limited to ~1 GB each? The DVD-Video spec mandates a maximum VOB size of 1,073,709,056 bytes (just under 1 GiB). This was a FAT16 filesystem compatibility requirement. A feature film is split across VTS_01_1.VOB, VTS_01_2.VOB, etc., which must be concatenated in order to decode the full stream.

Codecs Inside a VOB File

A VOB is an MPEG-2 Program Stream (PS) container. The multiplexed streams it can carry are:

Video

• MPEG-2 Part 2 — by far the most common, mandatory for DVD-Video compliance. Typical bitrate: 3–9 Mbps. Maximum: 9.8 Mbps.
• MPEG-1 — used on some low-budget discs and VCD-era content.

Audio (up to 8 tracks)

Subtitles

VOB subtitles are bitmap-based (not text). They are stored as RLE-compressed images in DVD subpicture streams (0x20–0x3F). This means you cannot directly search or copy the text — you need OCR (e.g., VobSub + SubRip) to convert them to SRT.

Technical Specifications

Anamorphic widescreen is important: a 16:9 DVD stores video at 720×480 (NTSC) but flags it for display as 720×534 (or 853×480 depending on the player). FFmpeg handles this automatically using the DAR (Display Aspect Ratio) metadata from the IFO.

Why Do VOB Files Exist in DVD Rips?

When you rip a DVD with software like MakeMKV, DVD Decrypter, or AnyDVD, the tool copies the raw file system from the disc to your hard drive. The result is the VIDEO_TS folder with all its .IFO, .BUP, and .VOB files intact.

Some rippers go further and produce a single .iso disc image, which contains the same structure inside a virtual disc container.

Commercial DVDs add CSS (Content Scramble System) encryption. CSS scrambles the VOB data with a 40-bit key derived from disc and player keys. You cannot read the video bytes directly from a CSS-encrypted disc without first decrypting — this is why ripping tools must either decrypt on-the-fly or use libdvdcss.

How to Convert VOB to MP4 with FFmpeg

Scenario 1 — Converting a Single VOB File

If you already have a decrypted VOB (from a rip folder), you can convert it directly:

ffmpeg -i VTS_01_1.VOB -c:v libx264 -crf 18 -preset slow -c:a aac -b:a 192k output.mp4

Options explained:

• -c:v libx264 — re-encode video to H.264 (wide compatibility)
• -crf 18 — constant rate factor; lower = better quality (18–23 is a good range)
• -preset slow — better compression at the cost of encoding time
• -c:a aac -b:a 192k — re-encode audio to AAC at 192 kbps

To copy the video stream without re-encoding (faster, lossless quality, but less compatible):

ffmpeg -i VTS_01_1.VOB -c:v copy -c:a aac -b:a 192k output.mp4

Scenario 2 — Concatenating Multiple VOB Segments into One MP4

A feature film is spread across VTS_01_1.VOB, VTS_01_2.VOB, VTS_01_3.VOB, etc. Concatenate them before converting using the concat protocol:

ffmpeg -i "concat:VTS_01_1.VOB|VTS_01_2.VOB|VTS_01_3.VOB" \
  -c:v libx264 -crf 18 -preset slow \
  -c:a aac -b:a 192k \
  -map 0:v:0 -map 0:a:0 \
  output.mp4

The -map flags are important. VOB files can contain multiple audio streams (different languages, commentary tracks). Without explicit mapping FFmpeg may pick a stream at random. Use ffprobe to inspect the streams first:

ffprobe -v quiet -print_format json -show_streams VTS_01_1.VOB

To select the second audio stream instead (e.g., surround sound vs. stereo):

ffmpeg -i "concat:VTS_01_1.VOB|VTS_01_2.VOB" \
  -map 0:v:0 -map 0:a:1 \
  -c:v libx264 -crf 18 -c:a aac -b:a 192k \
  output.mp4

Scenario 3 — Preserving Dolby Digital (AC-3) Audio

If the source has AC-3 5.1 and you want to keep it losslessly in an MP4:

ffmpeg -i "concat:VTS_01_1.VOB|VTS_01_2.VOB|VTS_01_3.VOB" \
  -c:v libx264 -crf 18 -preset slow \
  -c:a copy \
  -map 0:v:0 -map 0:a:0 \
  output.mp4

Note: AC-3 copy inside MP4 works but some players prefer MKV for multi-channel audio.

Scenario 4 — Convert VOB to MKV (Preserving All Streams)

MKV is better for archiving because it supports all DVD audio/subtitle streams natively:

ffmpeg -i "concat:VTS_01_1.VOB|VTS_01_2.VOB|VTS_01_3.VOB" \
  -c:v libx264 -crf 18 -preset slow \
  -c:a copy \
  -c:s copy \
  output.mkv

Ripping a Full DVD with HandBrake

For full DVD ripping (including menu navigation, chapter markers, and subtitle handling), HandBrake is the gold standard:

1. Open HandBrake and select the VIDEO_TS folder (or ISO) as the source.
2. HandBrake reads the IFO files and displays all title sets with their durations.
3. Select the main title (usually the longest one).
4. Choose a preset: H.264 MKV 1080p or H.265 MKV 1080p for archiving.
5. Under Audio, select the AC-3 track or AAC passthrough.
6. Under Subtitles, add the subtitle track you want and optionally burn it in.
7. Click Start Encode.

HandBrake uses libdvdnav and can handle some copy protection schemes but requires libdvdcss for CSS-encrypted commercial discs.

Common VOB Problems and Solutions

Problem: IFO files are missing

Symptom: FFmpeg or your player cannot find chapter markers or audio tracks. Cause: The rip only copied the VOB files without the IFO/BUP files. Solution: Re-rip the disc copying the full VIDEO_TS folder. If you only have the VOBs, FFmpeg can still decode them — you just lose chapter info.

Problem: CSS encryption (disc won't rip)

Symptom: The ripping tool reports permission errors or produces corrupted VOBs. Solution: Install libdvdcss (used by VLC, HandBrake, and MakeMKV internally). On Linux: sudo apt install libdvd-pkg && sudo dpkg-reconfigure libdvd-pkg. On Windows, MakeMKV handles this automatically.

Problem: Video plays with wrong aspect ratio

Symptom: The converted MP4 looks squished or stretched. Cause: Anamorphic widescreen flag not handled. Solution: Use FFmpeg with the -vf filter to set the correct display size:

ffmpeg -i VTS_01_1.VOB -vf "scale=854:480" -c:v libx264 -crf 18 -c:a aac output.mp4

Or let HandBrake auto-detect the DAR from the IFO.

Problem: Audio out of sync after conversion

Symptom: The audio drifts over the course of the converted file. Cause: Some MPEG-2 streams have DTS discontinuities at VOB boundaries. Solution: Add -async 1 or use the concat demuxer with a file list instead of the concat protocol:

# Create concat.txt
echo "file 'VTS_01_1.VOB'" > concat.txt
echo "file 'VTS_01_2.VOB'" >> concat.txt
echo "file 'VTS_01_3.VOB'" >> concat.txt

ffmpeg -f concat -safe 0 -i concat.txt -c:v libx264 -crf 18 -c:a aac output.mp4

VOB vs MKV vs MP4 for Archiving DVDs

Recommendation: For archival, use MKV with H.264 (CRF 18) and copy the AC-3 audio. For devices and sharing, use MP4 with H.264 (CRF 20) and AAC audio.

Summary

VOB files are the video backbone of DVD discs — MPEG-2 program streams segmented into ~1 GB chunks and governed by IFO control files. Understanding the DVD directory structure (VIDEO_TS, IFO, BUP, VOB) is the key to converting them correctly. FFmpeg handles the heavy lifting for single files and multi-segment concatenation, while HandBrake excels at full disc ripping with chapter and subtitle support. For long-term storage, MKV is the superior container; for universal device compatibility, MP4 is the practical choice.

Related conversions

Common video conversions that pair well with this guide:

• MOV to MP4
• AVI to MP4
• MKV to MP4
• MP4 to WEBM
• MP4 to GIF
• MP4 to MP3