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Matroska Metadata

Matroska tagging documentation is available at matroska.org.

Adding tags with FFmpeg

Just add use the -metadata in FFmpeg to add any metadata tag, replace the KEY with the name of the metadata value that you'd like to use and the VALUE with that metadata value.

-metadata KEY="VALUE"

Example:

ffmpeg -f lavfi -i testsrc -t 1 -metadata ARCHIVAL=yes -metadata PRESERVE_THIS=okay -metadata DESCRIPTION="Just color bars" some_metadata.mkv

Look at the tags for these files with mkvinfo, mediainfo, and ffprobe.

mkvinfo some_metadata.mkv
mediainfo some_metadata.mkv
ffprobe some_metadata.mkv

You can also add metadata specifically to certain tracks. This says that the first video track (counting starts at zero) has a language code of 'eng'.

ffmpeg -f lavfi -i testsrc -t 1 -metadata:s:v:0 language=eng more_metadata.mkv

Look at the tags for these files with mkvinfo, mediainfo, and ffprobe.

mkvinfo more_metadata.mkv
mediainfo more_metadata.mkv
ffprobe more_metadata.mkv

Extracting tags from an existing file with mkvextract

mkvextract can be used to extract the metadata tags from a file into an XML document. The following command reads the file called hamburger.mkv and extracts the metadata tags to a file called hamburger.xml. (different syntax to do the same thing)

mkvextract hamburger.mkv tags hamburger.xml

or

mkvextract tags hamburger.mkv > hamburger.xml

Open hamburger.xml in your text editor. You should see a number of tags in the file, each nested with a <tag> element, looking something like this:

<Tag>
    <Simple>
        <Name>PRODUCER</Name>
        <String>Rudy C. Granados</String>
    </Simple>
    <Targets />
</Tag>

For this exercise we're going to do two things:

(1): Update the description

(2): Add nested data to the Producer

Update description

Change the <String> tag to a new description. Be as creative as you like!

Add nested data

Update the PRODUCER tag to look like this. In this example, we're adding the tag TWITTER HANDLE and associating it with the PRODUCER tag.

<Tag>
    <Simple>
        <Name>PRODUCER</Name>
        <String>Rudy C. Granados</String>
        <Simple>
            <Name>TWITTER HANDLE</Name>
            <String>@therealrudy</String>
        </Simple>
    </Simple>
    <Targets />
</Tag>

Adding tags to an existing file with mkvpropedit

To write the metadata from hamburger.xml into hamburger.mkv then use mkvpropedit like this:

mkvpropedit hamburger.mkv --tags global:hamburger.xml

Run ffprobe on the file to see the results.

ffprobe hamburger.mkv

If you look at the metadata portion of the output you should see the following information

    PRODUCER                : Rudy C. Granados
    PRODUCER/TWITTER HANDLE : @therealrudy

Changing technical metadata with mkvpropedit

mkvpropedit can be used to change the properties of an MKV file without having to rewrite the file entirely. The standard template for an mkvpropedit command looks something like this

mkvpropedit [input_file.mkv] --edit track:[target_track] --set [target_element]=[new_value]

To use this template, you'll need to replace everything in square brakets with your own values:

[input_file.mkv] = the path to the files you wish edit [target_track] = the track you wish to edit. This could be a video track, audio track, subtitle track, etc. [target_element] = the element you wish to edit [new_value] = the new value for the element that you're updating.

The syntax for [target_track] is "v1" for "first video track". "a1" for "first audio track, "a2" for second audio track, etc...

The syntax for [target_element], and [new_value] can be seen by typing mkvpropedit -l

Change Aspect Ratio

The following command will change the aspect ratio of a the chapters_test.mkv to 16:9

mkvpropedit chapters_test.mkv --edit track:v1 --set display-width=16 --set display-height=9 --set display-unit=3

After running the command, open chapters_test.mkv. You should be able to immediately see the video display as 16:9 now.

You can also run mediainfo on the file, and see that it reports as 16:9

mediainfo chapters_test.mkv

To set the aspect ratio back to 4:3 use the following command

mkvpropedit chapters_test.mkv --edit track:v1 --set display-width=4 --set display-height=3 --set display-unit=3

See Matroska's tagging example pages for ideas.