A guide to mkvmerge GUI (mmg)

The only thing that mmg needs to know is the location of the mkvmerge binary. Under normal circumstances it will be found automatically. But if not then you can select the binary to use on the Settings tab.

When mmg starts up it shows the first and probably most important tab: the input tab. Here you see four different elements. The topmost input box lists all input files. Directly under this box are options that apply to the currently selected input file.

The two buttons to the right of the upper list box can be used to add files to the list box with the + button and to remove the selected entry with the - button.

Once the user selects an input file in the upper list box the second list box will contains all tracks that can be read from this file. Each track is ENabled by default and will be muxed into the resulting file. However, you can change that by simply clicking on the check box right in front of the track's name in the second list box. For each of these tracks the user can select track specific options with the input boxes and check boxes below the track listing. These options will be described in the following sections.

• Language: The user can select the language for each track regardless of its type. This language is coded in the ISO639-2 language code. The drop-down box contains all ISO639-2 codes so the user does not have to worry about selecting the wrong language code.
• Track name: The user can set a name for the current track. This name is a free-form string. Practical examples could be 'director's comments' or 'great view of Seattle'. Note that these names are not meant to contain the movie title!
• Cues: The cues are for Matroska what the index is for AVI files. They contain links to the key frames. Usually this option should be left on the value 'default'. mkvmerge will automatically chose the best method for any given track type. A full explanation of tracks can be found in mkvmerge's documentation.
• Aspect ratio: With this option the user can set the aspect ratio that should be used upon playback. It defaults to the aspect ratio that the movie was encoded with but can be changed, e.g. for anamorphic encodings. The GUI expects the format to be either a floating point number (e.g. '2.33') or a fraction (e.g. '16/9').
  This option is only available for video tracks.
• FourCC: Matroska does not normally store the Four-CC which is used in other containers to identify the codec used. Matroska has its own format, called CodecID, but it also has an AVI compatibility mode. In this mode the FourCC is also stored. With this option the FourCC can be forced to a different value. However, you cannot change the CodecID used by mkvmerge.
  This option is only available for video tracks.
• Delay (in ms): In some cases audio and video are not synchronized properly. With this option the user can offset the audio track by a given amount, either positive or negative. mkvmerge will either remove samples at the beginning or insert silence at the beginning to adjust the track.
  This option is available for audio and text subtitle tracks.
• Stretch by: In some cases audio and video slowly drift apart during playback. This can be fixed by supplying a factor of how much the time codes should be stretched by mkvmerge. If nothing is given then '1.0' is assumed which does not alter the time codes. Please note that this option has not been implemented for all audio track types yet.
  This option is available for audio and text subtitle tracks.
• Subtitle charset: Some text subtitle formats do not store the charset that they were created with. This is important because text subtitles are automatically converted to the UTF-8 charset during muxing. mkvmerge will normally assume that the system's current charset is the same that the subtitle file was written in. But in case this is not true the user can select the correct charset.
  This option is only available for text subtitle tracks.
• Make default track: Matroska knows a flag which tells the player that a specific track should be preferred upon playback if the user does not chose another one. Of course each track type has its own default track - e.g. the default audio track is the English one, and the default subtitle track is the French one. If no track is set to be the default track then mkvmerge will promote the first track of each type that it finds to be the default track. This is consistent with the behaviour of various media players.
• AAC is SBR/HE-AAC/AAC+: The new technology called 'high efficiency AAC' has some drawbacks when it is being stored in .AAC files: it is not possible to detect the HE-AAC part for these files. Therefore the user has to check this option manually if it applies. Please note that this problem does not exist for HE-AAC stored in .MP4 files.

Typical options for a video track

Typical options for an audio track

Typical options for a text subtitle track

Matroska files can also contain other files, called attachments. This works basically just like with your favourite email program. The idea is to provide additional information about the file. Some examples could be cover photos for a CD rip, additional background information in text form about the movie or even some compressed fonts for the subtitles.

Every attachment needs two things: the file name (obviously) and the MIME type that should be associated with the file. The usage is very easy and similar to adding files on the input tab.

On the second tab of the GUI, the attachment tab, you can add a file with the + button and remove the selected attachment with the - button. Once an attachment has been selected the other controls on this tab will be available. You do have to select a MIME type for each attachment, but the description is optional - although it is a good idea to always provide a description. This makes it easier for others to identify what you've attached to this Matroska file.

The last option, attachment style, is only evaluated when you also split the output into several files. (Splitting in general is explained in the following section.) If the option To all files is selected then the current file will be attached to all output files created. If the option Only to the first is selected then the file is only attached to the very first output file created.

Add and remove attachments with these buttons.

Typical options for an attachment

File/segment title

File/segment title: This title is used for the actual movie title, e.g. 'Vanilla Skies'.

Selecting a title for the movie

Automatic splitting and file linking

The Split section handles how the output file is split into several smaller files. If no splitting is selected then only one big file is generated. If splitting is activated then you can tell mkvmerge to start a new output file after either a specific amount of data has been written to the current file or after a specific amount of time has accumulated. The formats accepted are:

• For the size: A number optionally followed by the letter 'K', 'M' or 'G' indicating kilobytes (1024 bytes), megabytes (1024 * 1024 bytes) or gigabytes (1024 * 1024 * 1024 bytes). Examples: '700M' or '100000K'.
• For the time: The format is either HH:MM:SS or a number followed by the letter 's' indicating a number of seconds. Examples: '01:20:00' (split after 1 hour, 20 minutes) or '1800s' (split after 1800 seconds = 30 minutes).

Don't link: This option controls how mkvmerge will handle splitting. A little explanation about this feature:

Matroska supports file linking which simply says that a specific file is the predecessor or successor of the current file. To be precise, it's not really the files that are linked but the Matroska segments. As most files will probably only contain one Matroska segment I simply say 'file linking' although 'segment linking' would be more appropriate.

Each segment is identified by a unique 128 bit wide segment UID. This UID is automatically generated by mkvmerge. The linking is done primarily via putting the segment UIDs of the previous/next file into the segment header information. mkvinfo prints these UIDs if it finds them.

If a file is split into several smaller ones and linking is used then the time codes will not start at 0 again but will continue where the last file has left off. This way the absolute time is kept even if the previous files are not available (e.g. when streaming). If no linking is used then the time codes should start at 0 for each file. By default mkvmerge uses file linking. If you don't want that you can turn it off by enabling this Don't link check box.

Manual file/segment linking

Regardless of whether splitting is active or not the user can tell mkvmerge to link the produced files to specific UIDs. This is done by entering a valid segment UID into the two input boxes, Previous segment UID and Next segment UID. These options accept a segment UID in the format that mkvinfo outputs: 16 hexadecimal numbers between 0x00 and 0xff prefixed with '0x' each and separated with spaces, e.g. 0x41 0xda 0x73 0x66 0xd9 0xcf 0xb2 0x1e 0xae 0x78 0xeb 0xb4 0x5e 0xca 0xb3 0x93. Alternatively a shorter form can be used: 16 hexadecimal numbers between 0x00 and 0xff without the '0x' prefixes and without the spaces, e.g. 41da7366d9cfb21eae78ebb45ecab393.

If splitting is used then the first file is linked to the UID given in the Previous segment UID input box, and the last file is linked to the UID given in the Next segment UID input box. If splitting is not used then the one output file will be linked to both of the two UIDs.

Typical options for splitting. Create two files which will be approx. 700megs big.