Inspect MKV Container Structure Using FFprobe

This guide explains how to analyze the internal architecture of a Matroska (MKV) multimedia container using ffprobe, the powerful media analysis tool included with FFmpeg. You will learn the essential command-line flags required to reveal container-level metadata, stream configurations, individual frame and packet allocations, chapters, and track-specific properties in human-readable and machine-parsable formats.

Basic Container and Stream Information

To get a complete overview of the streams (video, audio, subtitles) and general container metadata inside an MKV file, run:

ffprobe -v error -show_format -show_streams input.mkv
  • -v error: Suppresses redundant FFmpeg build information and logs, displaying only parsing errors and the requested output.
  • -show_format: Displays container-level attributes, including duration, file size, bit rate, and global tags.
  • -show_streams: Lists technical parameters for each track, such as codecs, frame rates, pixel formats, channel layouts, and stream indices.

Filtering by Stream Type

MKV files often contain multiple tracks, such as alternate audio tracks or multilingual subtitles. Use -select_streams to inspect a specific stream type:

  • Video only:

    ffprobe -v error -select_streams v -show_streams input.mkv

  • Audio only:

    ffprobe -v error -select_streams a -show_streams input.mkv

  • Subtitles only:

    ffprobe -v error -select_streams s -show_streams input.mkv

Inspecting Packets and Frames

To examine the low-level data structure of an MKV container, inspect the packets (demuxed data chunks) and frames (decoded presentation units).

Packet Inspection

Viewing packet data reveals how video and audio samples are interleaved throughout the container:

ffprobe -v error -show_packets -select_streams v:0 -read_intervals "%10" input.mkv
  • -show_packets: Outputs PTS (Presentation Time Stamp), DTS (Decoding Time Stamp), packet size, duration, and stream mapping.
  • -read_intervals "%10": Restricts analysis to the first 10 seconds to prevent huge terminal logs.

Frame-by-Frame Analysis

To analyze keyframe placement and frame types (I, P, B frames) in the video track:

ffprobe -v error -select_streams v:0 -show_frames -show_entries frame=pict_type,pts_time,key_frame,pkt_size -read_intervals "%5" input.mkv
  • -show_entries: Narrows the output to essential attributes, minimizing clutter.

Extracting Chapters and Attachments

MKV containers natively support embedded chapters and attachments (such as font files for subtitles).

Viewing Chapters

ffprobe -v error -show_chapters input.mkv

This lists chapter IDs, start and end timestamps, and embedded chapter title tags.

Checking for Attachments

MKV attachments are recognized by ffprobe as distinct streams with a codec type of attachment:

ffprobe -v error -select_streams t -show_streams input.mkv

Formatting the Output

By default, ffprobe prints data in an [INI]-style key-value format. You can change this structure into common interchange formats for scripting or automated processing.

  • JSON format:

    ffprobe -v error -show_format -show_streams -of json input.mkv

  • XML format:

    ffprobe -v error -show_format -show_streams -of xml input.mkv

  • Flat format (ideal for grep and shell parsing):

    ffprobe -v error -show_format -show_streams -of flat input.mkv