Ask LH: How Can I Merge Multiple Video Files?

Dear Lifehacker, I was hoping you could help me with a problem I've had for a little while now. I have a couple of movies and video files (your standard .AVI, .MP4, .MKV) that are split into two separate files. Obviously doing so makes the files easier to transport, but it plays havoc with my media library, and I'd love a quick and easy way to merge the files into one. I'm using a Mac, I've been looking for ages, but surely there's a free option to do this, right? Thanks, Splitting Up

Movie File picture from Shutterstock

Dear SU, Have you tried combining the video files in QuickTime? To do this, open Part 1 of the movie in QuickTime and move the scrubber/scroll bar to where the video ends. Then drag and drop the 'Part 2' file into the nominated position. To finish, simply close the QuickTime window and save when prompted -- your combined movie file should then be good to go.

Alternatively, there are a number of free video conversion tools for MacOS that will also do the trick. VIDEOtoolbox is a suite of three free applications for MKV, AVI and MP4 files. Download the required app and select the 'join' option under Tools. Another popular option is mpeg streamclip available for both Mac and Windows. In addition to MPEG, it also supports the following file formats: VOB, PS, M2P, MOD, VRO, DAT, MOV, DV, AVI, MP4, TS, M2T, MMV, REC, VID, AVR, M2V, M1V, MPV, AIFF, M1A, MP2, MPA and AC3.

Does anyone else have a solution that they swear by? Share your tips in the comments section below.

Cheers Lifehacker

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    Got a video problem, I'm willing to bet 99% of problems can be fixed by using ffmpeg. Of course it has a step learning curve, but even then its usually faster just to google the answer then installing random programs that just use ffmpeg as a backend solution anyway. Its available where ever good open source programs are complied e.g., linux,windows,osx

    I have used cat under terminal several times without issues. Ticks all the boxes: Mac, Free and well documented.
    Good Luck

    The mkvmerge utility that is part of mkvtoolnix has become invaluable in my video toolbox. It will produce MKV files, however, the source can be anything so don't let the name fool you.

    You can add a video file, and append several more to merge all into a single file. You can also mess with the audio/video/subtitle tracks and add chapter markings. Subtitles if you need them can be merged in from SRT or other common format files. If you have a series of VOB files, or other MKVs you can strip out the audio tracks you don't want (additional languages), or for a blu-ray rip you can drop the SD video track, and keep just the HD and all those sorts of things.

    Best feature is that it doesn't transcode, there's other tools for that anyway. Benefit is that it's fast. It'll cook through several gig of video to produce a new video file in a matter of a minute or two. Really depends on how fast the source and destination drives are.

    When I buy a BluRay, my common workflow is to rip it to disk with AnyDVD HD, then use eac3to to strip out just the video as an MKV (which preserves chapter markers), and the audio dts-ma as a separate file, then merge them using MKV merge. If I want to shrink the video you can use Handbrake on the video MKV file, still preserving chapters and knowing it's not going to mess up the audio, then merge the resulting video + dts-ma.

    The most use I get from mkvtoolnix is merging several VOBs, which preserves chapters, doesn't degrade the video and allows me to strip out the other 20 language audio tracks that I don't want.

    You can use ffmpeg. Following is an example if you're using windows:

    Make a text file with all input videos like this:

    # This is a comment
    file 'G:\adir\part1.mp4'
    file 'G:\adir\part2.mp4'

    Assuming that you named it "input.txt" execute this command:

    ffmpeg -f concat -i input.txt -codec copy output.mp4

    That's it! Your joined file is output.txt. Note that you may get a warning like "[mp4 @ 0000000002bfb480] track 1: codec frame size is not set" but everything should work fine.

    Note that you could also execute the command:

    ffmpeg -f concat -i input.txt -acodec ac3 -vcodec copy output.mp4

    And you wouldn't receive a warning, but the audio may not be selected correctly. For example when I used this command I got Dolby Digital 5.1 audio instead of the full Dolby Digital 5.1 EX audio. The first command works better because it automatically selects the correct codecs.

    I hope this works for everyone! Cheers!

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