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Joining Videos without Conversion using MKVToolNix

This article is a follow-up to the one on free tools that can join videos without conversion. The explanation on how this works as well as the conditions necessary for it to work are in that post, so make a point to read it should you encounter any problems joining your videos, as detailed below.

In this guide, we’ll be using MKVToolNix, a free multiplatform software for creating and manipulating Matroska (*.MKV) files. The tool supports many functions such as identifying codecs, editing metadata and adding compatible audio and subtitles tracks to videos.

MKVToolNix also supports joining videos losslessly. The codecs and other parameters (e.g. resolution) of the source videos however need to match for this to work. It also goes without saying that the output is limited to the MKV container.

To output to a different format such as MP4 you can use some of the other tools or use a traditional video converter.

Join Videos Losslessly with MKVToolNix

  1. Download MKVToolNix and install it. It’s available for almost all platforms out there including Windows, macOS, Linux and BSD. There’s also a portable version should you not want to use the installable one.
  2. Run MKVToolNix GUI then add your first video by dragging and dropping it into the Source file box.
  3. Drag and drop the rest of the remaining videos in the order you wish to join them and when you get prompted, select the Append to existing file option.
    A screenshot of MKVToolNix main window with video files added.
  4. You can also add the videos using the Add source files button at the bottom of the window. After adding the first video, the remaining videos will have to be appended to it. To do that, select the loaded video then click on the the small arrow on the “Add source files” button then select append files.
    A screenshot of MKVToolNix's add source files button menu.
  5. In the tracks, chapters and tags box, confirm that only two codecs are there — one for the video (e.g. MPEG-4/AVC/h.264) and the second for the audio (AC-3, MP3, DTS etc.). If the video(s) has embedded subtitles, it will also be listed here.
  6. If you have an extra video or audio codecs listed, the process will not work. All the videos need to have the same codecs for them to be joined. Ideally, this should be the case if the files are all from the same source.
    A screenshot showing a video and audio codecs of a video file loaded in MKVToolNix.
  7. Before joining, you may want to edit the video’s metadata, though it’s not necessary. These includes properties such as the default languages, frame rate, aspect ratio, adjustment of time codes (delays or stretch) etc. To do that, just select the video or audio item in the tracks, chapters and tags box, then in the properties box adjust the properties as you wish.
    A screenshot of MKVToolNix's properties section.
  8. Next, select the output folder and adjust the file name in the destination file, otherwise leave it as it is to output the MKV in the same folder as the source files.
  9. To finish, just hit the Start multiplexing button and wait for the muxing to complete. Alternatively, you can add the job to the queue using the Add to job queue button. This way you can add other jobs and run all of them in batch.

Note when joining DVD VOB files:

  • For DVD VOB files that haven’t been renamed (i.e. VTS_XX_X.VOB), MKVToolnix automatically adds and appends the remaining videos in the folder when you drag the first part. This makes it easy to join DVD VOB files into one MKV with no quality loss.
  • For DVDs that have title, root and/or chapter menus, make sure to not add their VOB parts. Only load the parts that have the actual video.

Verify Output

Depending on the size of the video, the joining process will take from a few seconds to a few minutes to finish the job. The process may end with some warning and/or errors, which you can look in the job output page.

While you can ignore most of the warnings, the errors usually mean that the job did not complete successfully. Regardless, make sure to open the output video to verify it joined well.

Most importantly, confirm that the length of the output video matches to that of the original videos and that the audio and video sync.

Some minor audio syncs issues can be fixed quickly using the Delay option in the Timestamps and default duration section in the Properties.

With that said, it’s advisable to make sure beforehand that all source videos’ parameters match to avoid running into any issues.


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Kelvin Kathia

Kelvin Kathia is a writer that's passionate about sharing solutions to everyday tech problems. He's the founder and editor of Journey Bytes, a tech blog and web design agency. Feel free to leave him comments or questions regarding this post, or by leaving him a message on the contact page. If you found his content helpful, a donation is much appreciated.