Inspect VOB Metadata and Codecs with FFmpeg

This article provides a practical guide on using FFmpeg and its companion utility, FFprobe, to analyze unknown VOB (Video Object) files. You will learn how to quickly view stream mappings, extract detailed audio and video codec parameters, inspect container-level metadata, and format the output into human-readable or structured data for automated workflows.

Basic Stream Inspection with FFprobe

The most efficient tool included with FFmpeg for reading file attributes without processing the underlying data is ffprobe. To view a concise summary of all streams and container information in a VOB file, run:

ffprobe input.vob

This output displays the container format (mpeg), file duration, overall bitrate, and a list of all identified streams. Each stream entry provides essential high-level information:

• Video Streams: Identifies the codec (typically mpeg2video), profile, pixel format (such as yuv420p), resolution, aspect ratio, and frame rate.
• Audio Streams: Shows the audio format (such as ac3, dts, or pcm_dvd), sample rate (e.g., 48000 Hz), channel configuration (stereo, 5.1), and bitrate.
• Subtitle Streams: Identifies DVD sub-picture streams (dvd_subtitle).

Quick Inspection Using FFmpeg

If ffprobe is not available in your environment, you can invoke the core ffmpeg binary without specifying an output file:

ffmpeg -i input.vob

FFmpeg reads the headers, prints the container metadata and stream details to stderr, and exits with an error stating that at least one output file must be specified. This error can be ignored, as the stream information printed before the exit contains the desired technical specifications.

Extracting Comprehensive Stream Details

VOB files are often multiplexed MPEG-PS (Program Stream) containers that may contain complex parameter configurations. To isolate and display detailed stream-level data without container noise, use:

ffprobe -v error -show_streams input.vob

This command suppresses informational banners and outputs a comprehensive block for each stream, detailing:

• codec_name and codec_long_name
• profile and level (e.g., Main Profile at Main Level)
• width, height, coded_width, and coded_height
• sample_aspect_ratio (SAR) and display_aspect_ratio (DAR)
• pix_fmt and color space metadata
• r_frame_rate (nominal rate) and avg_frame_rate (actual average)
• Audio channel counts, channel layout, and bit-depth parameters

Filtering Specific Parameters

To retrieve only specific properties for scripting or automated processing, use the -select_streams and -show_entries flags.

To inspect only the primary video stream:

ffprobe -v error -select_streams v:0 -show_entries stream=codec_name,width,height,pix_fmt,r_frame_rate -of default=noprint_wrappers=1 input.vob

To inspect all audio streams and their language or channel configurations:

ffprobe -v error -select_streams a -show_entries stream=index,codec_name,channels,channel_layout,bit_rate -of default=noprint_wrappers=1 input.vob

Exporting Metadata to JSON

For automated parsing, you can format the output directly into structured JSON:

ffprobe -v quiet -print_format json -show_format -show_streams input.vob

This structure groups the data into streams and format objects, making it straightforward to parse in Python, Node.js, or shell scripts using tools like jq.

Handling Multiple VOB Segments

VOB files from DVDs are frequently split into 1 GB chunks (VTS_01_1.VOB, VTS_01_2.VOB, etc.). A single VOB segment from the middle of a set may not contain all header information, or it may inherit timestamps from prior segments. To inspect the full sequence seamlessly, you can concatenate them via the FFmpeg concat demuxer or pipe them:

cat VTS_01_*.VOB | ffprobe -v error -show_streams -

This guarantees that all audio tracks, subtitle channels, and resolution switches across the entire feature are correctly discovered and reported.