I have two high-quality mp4 files, which are of two parts of the same show.

I want to merge them together into 1 file, and I usually use VirtualDub to merge my files... But it doesn't seem to support mp4.

What alternatives are available (especially ones that don't require re-encoding)?


8 Answers 8


I usually use VirtualDub to merge my files, but it doesn't seem to support mp4. So what alternatives are there?

Avidemux. It's just like VirtualDub, only with more formats supported and built-in codecs and filters. I always use it in preference; it joins AVC+AAC.MP4 files (without recoding) fine for me.

To join them in AviDemux:

  1. File -> Open -> Select File
  2. File -> Append -> Select File
  3. Set all to Copy
  4. File -> Save -> FileName
  5. Wait..

According to AViDemux forums, this join process is lossless (http://www.avidemux.org/smf/index.php?topic=9467.0)

  • yeah, it seems to do excellent with keeping audio in sync with video whereas the other persons answers to this question are questionable on that IMHO.
    – djangofan
    Nov 12, 2010 at 23:39
  • 1
    I tried using Avidemux to join two files together but the audio became out of sync. Jul 2, 2012 at 13:56
  • You can get sync problems when the amount of audio material available doesn't match the length of video frames, or there's any stream corruption. You may be able to fix this up with the 'stream fix' features of VideoRedo or ProjectX.
    – bobince
    Jul 2, 2012 at 21:38
  • 1
    But this method worked: superuser.com/a/255566/1780 Hooray! Jun 11, 2013 at 1:15
  • 4
    If you use AviDemux to join two Mp4 files, don't forget to select the Mp4 Demux option at the bottom left hand corner. Otherwise it may try to convert it to an avi!
    – user244816
    Aug 11, 2013 at 5:12

You can do this with ffmpeg:

mkfifo temp0 temp1
ffmpeg -i input0.mp4 -c copy -bsf:v h264_mp4toannexb -f mpegts -y temp0 2> /dev/null & \
ffmpeg -i input1.mp4 -c copy -bsf:v h264_mp4toannexb -f mpegts -y temp1 2> /dev/null & \
ffmpeg -f mpegts -i "concat:temp0|temp1" -c copy -absf aac_adtstoasc output.mp4

This doesn't re-encode anything, it places them in a new transport stream container, which makes them more easy to concatenate, and then concatenates them back into an MP4. If output.mp4 already exists, the command will fail. The version above uses named pipes, if you're on a system that doesn't support those you'd have to use intermediate files (like windows):

ffmpeg -i input0.mp4 -c copy -bsf:v h264_mp4toannexb temp0.ts
ffmpeg -i input1.mp4 -c copy -bsf:v h264_mp4toannexb temp1.ts
ffmpeg -i "concat:temp0.ts|temp1.ts" -c copy -bsf:a aac_adtstoasc output.mp4
  • can someone explain how this is done with avconv instead of ffmpeg? I was able to complete the first two steps, but the last doesn't recognize the option -absf
    – becko
    Oct 1, 2014 at 23:45
  • @becko See my edit. Now you should use a stream specifier (see here libav.org/avconv.html#Advanced-options).
    – slhck
    Oct 2, 2014 at 12:46
  • 2
    +1 just for future reference, you can substitute avconv for ffmpeg in the above commands and it will work.
    – becko
    Oct 2, 2014 at 14:00

Concat demuxer

The concat demuxer was added to ffmpeg 1.1. If your version of ffmpeg is to old, get the newest static binary from here: http://www.ffmpeg.org/download.html


Create a file mylist.txt with all the files you want to have concatenated in the following form (Lines starting with a dash are ignored):

# this is a comment
file '/path/to/file1'
file '/path/to/file2'
file '/path/to/file3'

Note that these can be either relative or absolute paths. Then you can encode your files with:

ffmpeg -f concat -i mylist.txt -c copy output

It is possible to generate this list file with a bash for loop, or using printf. Either one of the following would generate a list file containing every *.wav in the working directory:

for f in ./*.wav; do echo "file '$f'" >> mylist.txt; done
printf "file '%s'\n" ./*.wav > mylist.txt

Source: ffmpeg wiki


YAMB along with MP4BOX is a good option.
Download both and unzip them (no installation needed and together they're about 5MB), in YAMB choose Settings and set the folder path of MP4box.
To join mp4 files choose Editing > Click to Join supported...

  • 1
    Seems like the best solution, keeping the .mp4 container format which would seem the more attractive option to the author ^^ Sep 19, 2009 at 13:44
  • 1
    After difficulty, I used this config: MP4Box_path=E:\Software\Video Editing\Yamb-\MP4Box\MP4Box.exe in an attempt to merge 4 500MB MP4 files generated from AVIDemux . It didn't work. The program just sat there for 45 minutes doing nothing until I finally gave up.
    – djangofan
    Nov 27, 2009 at 23:43
  • 1
    i had trouble using this method because of audio sync problems. it was a nightmare... not trying it again.
    – djangofan
    Nov 12, 2010 at 23:37

Try using the Matroska video container.

Firstly, you need mkvtoolnix. Download and install it, then you need to fire up mkvmerge GUI (unless you like command-line tools, which is fine by me - although you might want to look at the file linking section of the mkvmerge documentation).

Add your first file by clicking "add". Then, click on "append", and open your second file. Set the output file, hit "Start muxing" at the bottom, and away you go!

enter image description here

If the container is unsuitable for your needs, you can reencode it, or try to convert it to some other format... Although MKV is a very lovely container!

  • it has to be muxed? i cant be joined without muxing?
    – djangofan
    Nov 27, 2009 at 23:45
  • Well, if you're using an MKV container, technically you are remuxing it. Try it, there is no real time penalty... Dec 7, 2009 at 2:09
  • This really works, just tried it. I had the feeling it can only work with .mkv, but that is just the name in the end, it is a very good solution.
    – conualfy
    May 13, 2020 at 22:35

SUPER © (Simplified Universal Player Encoder & Renderer) provides the following additional Output Process:

Any supported input Multimedia file can be processed:

      o Join Format-Identical Files.
      o Mux Video & Audio Streams.
      o DeMux Extract Streams. 

of course, MP4 is a supported format.

SUPER © is freeware.

  • 5
    Its user interface is the most horrible I've seen in my life. I'm not kidding, it's just horrible. I emphasize it once more: I can't name a worse interface, I'm serious about it, I've never seen anything below the "SUPER threshold". Jan 12, 2012 at 14:48

If you can play them on your system / have a codec installed, Windows Movie Maker may the quickest (and free) way to join the two files. You can then use Virtualdub to convert to a different format.

  • Audacity seems to be for audio files. This is a video file. Sep 18, 2009 at 22:40
  • So sorry, I mis-read, just saw the MP part and my brain though audacity. Sep 18, 2009 at 23:01
  • Editing answer... Sep 18, 2009 at 23:02
  • AFAIK, Movie Maker doesn't support mp4 and converting to a different format means lose of quality which the question specifies as unwanted.
    – Eran
    Sep 18, 2009 at 23:16
  • I tried MovieMaker on windows7 and the audio becomes out of sync when joining MP4 files into a WMV. This option wont work.
    – djangofan
    Nov 27, 2009 at 23:10

Another solution is Open Video Joiner. It also does transition effects.

enter image description here

  • It's a shareware though. and for 30$ it's not cheap just to merge video files
    – Eran
    Sep 19, 2009 at 12:10
  • It was said to be freeware. Sorry if I was misled.
    – harrymc
    Sep 19, 2009 at 15:51

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