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I have two MP4 files that I generated with Camtasia Studio. I need to join them together post rendering with Camtasia (it can't be done during the Camtasia rendering process). Looking for a utility or technique that will work to join these, preferably that doesn't require re-rendering all the video again.

Update: Either Windows (preferred) or Mac. Doesn't need a GUI if it is a good command-line app.

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It would help to know what platform/OS you are using. – filzilla Apr 2 '12 at 23:21
@filzilla: Either Windows (preferred) or Mac. – Jim McKeeth Apr 3 '12 at 17:44
See – 200_success Apr 12 '12 at 10:50

I think the simplest way to this is to use MP4Box.

./MP4Box -add file1.mp4 -cat file2.mp4 -cat file3.mp4 output.mp4
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I was encountering audio sync issues when trying to do this with Avidemux, but I came upon a two-step process that keeps the audio in sync:

  1. Concatenate files using MKVToolNix (I used version 7.4.0 for Mac). This results in a Matroska video (.mkv) file.
  2. Remux the .mkv file to MP4 format using Avidemux (I used verison 2.6 for Mac). I chose the MP4v2muxer option in the Output Format section. This results in an MP4 file with audio and video in sync.
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Avidemux should do the work.

  1. Load File
  2. Go to File -> Append and select File
  3. To the left of the video window,
    • set video mode to Copy;
    • same for audio mode;
    • set format to MP4.
  4. Go to File -> Save -> Video.
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This does what I am looking for, but it is causing the audio to go out of sync at the join point. I am going to try and join and mix the audio from a separate channel. – Jim McKeeth Apr 3 '12 at 17:43

I would suggest using ffmpeg, and the -vcopy switch. Usually this will work, but it depends on codec support.

Various builds of it have various codecs. If one version of it doesn't work, try downloading a copy from a different site.

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i think MPEG Streamclip can do this. It's free on mac and pc.

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