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By Reuben Zaback - Last Updated: Contact Author

How to Simply Convert Multi-Track MKV to MP4 with FFmpeg Losslessly?

Struggling with using an MKV file with two or more audio tracks? Wondering how to convert MKV to MP4 without re-encoding or lossless? Well, don't worry. We have got your back!

Although smartphones have become the smartest thing ever, they can't read every formats out there - MKV, for example, is rejected by Android devices. This is why we need to convert MKV to MP4, as MP4 is the most widely supported format by various types of electronic devices. Also, it is a saving grace for video editors who want to convert their files for a faster editing experience. If something like this can help you, you are in the right place.

If you googled, you must have come across a lot of answers on how to use FFmpeg to change the video format from MKV to MP4. It is difficult and grilling to follow those discussions in order to find the right way to get your job done as not everyone knows about FFmpeg and video-related terminologies well. But take it easy, this article will guide you on what FFmpeg exactly is and how to convert MKV to MP4 using FFmpeg step by step. Let's dive in to check out the best converters available.

What Is FFmpeg?

FFmpeg is an open-source tool to deal with multimedia based data. It supports to convert MKV to MP4 and other formats without quality loss. Besides, it enables you to record, stream media files, and decode, encode, transcode, play, filter, mux, demux almost anything created by machine or human. As a cross-platform converter, FFmpeg goes compatible with Linux, Mac OS X, Microsoft Windows, and other platforms like Android and iOS in mobile platforms.

FFmpeg is impressively powerful to many extents, but the drawback for many users is it doesn't provide you a common and straightforward interface like +Video or Select Output Format. Let's take you through a beginner-friendly tutorial on how to convert MKV to MP4 using FFmpeg.

FFmpeg MKV to MP4 FAQ Page

Q: After FFmpeg converting MKV to MP4, why my audio file is lost?

A: There are two possible reasons and fixes:
1. Your FFmpeg may be out of date. You can upgrade your FFmpeg to its latest versions and install an upgraded audio decoder.
2. The MKV file imported has a DTS audio format, which may not be compatible with your player. You can choose the supported audio encoder/decoder from AAC, AC4, MP3, WAV1, WAV2, Vorbis, MP2, Opus.

Q: How to solve the subtitle track loss after FFmpeg converting MKV to MP4?

A: There are two ways to solve the issue:
1. Add the subtitle track as the independent optional track, add the commands in FFmpeg: ffmpeg -i infile.mp4 -i infile.srt -c > copy -c:s mov_text outfile.mp4.
2. Add the subtitle track as the hardcode subtitle:
> a. In the Libass Library, covert the subtitle file format from .srt to .ass. Insert the command: ffmpeg -i subtitles.srt subtitles.ass;
> b. Use the filter to add the subtitle. Insert the command: ffmpeg -i mymovie.mp4 -vf ass = subtitles.ass mysubtitledmovie.mp4.

Q: Which one is the best? MP4 or MKV?

A: It depends on your personal needs.
The compatibility: The MKV format is rejected to be played on some devices while almost every media players support playing the MP4 file.
The file size: normally speaking, MP4 has a smaller file size than MKV does.
The audio track and subtitle support: MKV supports ASS and SSA optional subtitle and audio track, while MP4 doesn't. When you need to burn a DVD or Blu-ray disc, the MKV container format will be your best choice.

Q: How can I convert MKV to MP4 in the fastest way?

A: We recommend you the most versatile media converter - VideoProc. With its built-in Level-3 Hardware Acceleration technology, you may have got the converted MKV to MP4 file within several eyes blinking.

Need a One-Click Way to Convert MKV to MP4? Free Download the Best MKV to MP4 Converter - VideoProc

Part 1: How to FFmpeg Convert MKV to MP4 on PC/Mac?

Step1: Download and Install FFmpeg on Mac/PC

Go to www.ffmpeg.org and press Download to begin. You can choose which operating system you want to install in.

Install FFmpeg on Windows:

  • 1. Download FFmpeg Windows's package and choose the latest 32bit or 64bit Static version.
  • 2. Right-click it and extract the ffmpeg.exe from the 7z file with 7zip.
  • 3. Create a new folder under system directory (usually the OS/C: folder), and name it as FFmpeg.
  • 4. Paste all the unpacked files to the file folder FFmpeg.
  • 5. Go to My computer > Properties > Advanced system settings > Environmental Variables > New, then set the variable name as Path, and the Variable value as C:\FFmpeg\bin. > Click OK.
  • Install FFmpeg
    Install FFmpeg
  • 6. Press Windows Key and R, and then tap in CMD to open Command Prompt in administrator mode.
  • 7. Tap in ffmpeg –version, and press Enter. If there are many content displays, you have got the installation work done.
  • Install FFmpeg on Mac OS X:
  • 1. Install Homebrew: Enter Homebrew. Copy the line of code, and paste it on your Terminal.
  • Homebrew
  • 2. Tap in brew install ffmpeg, and then press Enter to install FFmpeg
  • Step 2: Change Video Format from MKV to MP4

  • How to Create MP4 from MKV with FFmpeg on Windows?
  • 1. Copy the path of the source MKV video.
  • 2. Enter a space, tap in cd, press space, then paste the path of the source video there. Press Enter.
  • Enter Command
    Enter Command
  • 3. Enter ffmpeg -i my_movie.mkv -vcodec copy -acodec copy my_movie.mp4, then press Enter.
  • 4. Warm note: my_movie means the name of the source video. Do not miss any space.
  • How to Use FFmpeg to Convert MKV to MP4 on Mac?

  • 1. Press Space and tap in clear to clear the Terminal.
  • 2. Press Space and tap in cd, press Space again, and then paste the path of the source video. Press enter.
  • 3. Press Space to enter: ffmpeg -i my_movie.mkv -vcodec copy -acodec copy my_movie.mp4.
  • Part 2: What is the Best FFmpeg Alternative to Convert MKV to MP4?

    There is no doubt about the fact that FFmpeg is an extremely powerful tool. But, at the same time, it can't be denied that it is also an extremely complex tool. Even for a person with a technical background, it is not a simple process to convert MKV to MP4, especially when the MKV file comes with multiple tracks.

    If you are looking for something much more efficient, faster, and not to mention, easier to use, then look no further. You can use VideoProc to convert anything to MP4. VideoProc is a one - stop video editing software that makes it easy to edit, transcode, resize, and adjust files to produce exactly what you want.

    How to Convert MKV to MP4 in One Click Using the Best FFmpeg Alternative?

    Lossless quality, impressive speed, and ease of use are 3 killer features of VideoProc. All these features are benefited from the distinct conversion tech, known as Remux. It enables the simply lossless extraction through format without re-encoding. So, the whole process barely cost you any time. Let's take you through the quickest and easiest 3-step process of Remuxing using VideoProc.

    Step 1: Download and Install VideoProc on Your PC or Mac.

    Step 2: Input the Source Video to VideoProc

    Open the software and choose the Video option.Click +Video to add your MKV file to remux to MP4.

    Step 3: Start to Convert the Video

    If you have multiple files to remux, just choose the +Video Folder tab to import all of them. Select the target format with MP4. After that, simply hit the RUN button to see the job getting done.

    Note: Don't forget to check the Auto Copy feature on its right side, which allows the software to remux without re-encoding.

    Convert MKV to MP4
    Convert MKV to MP4

    Final Thoughts

    Both the ways do their job reasonably well, but FFmpeg is clearly hard to understand and not user-friendly for ordinary people. Also, finding out and trying plenty of confusing coding for the conversion purpose can be a time consuming and extremely tedious job. With an easy-to-use interface, VideoProc gives you an alternative to batch process & convert MKV to MP4 with fast speed, high quality, and an amazingly hassle-free conversion. Just give it a try now!

    Video Tutorial: How to Convert MKV to MP4 with VideoProc

    How to Convert MKV to MP4 with VideoProc
    Free Download VideoProc to Convert MKV to MP4 Fast with Ease


    Reuben Zaback

    Hi, I'm Reuben Zaback and I've been an award-winning editor of Digiarty for four years. Writer by day and reader by night, I share programs reviews & tutorials, multimedia solutions, latest tech trends, devices tips, etc. I geek out over Apple products, sports cameras, drones, gadgets and always look to learn something new. My spare time is dominated by sports rehab and part-time study.

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