MP4 joiner

Ian UK · Mar 11, 2021

Has anyone successfully joined together the MP4 files the drone creates?
I tried MP4 Joiner program and it fails after 5 seconds.
May be it can't handle 4k video.
The files I was attempting to join were 3.6gig and 0.8gig.
I also tried 2 smaller 4k MP4s and it still failed!

Any ideas for an MP4 joining program that works on 4k videos?

Thomas B · Mar 11, 2021

I just drag and drop in iMovie.

Ian UK · Mar 11, 2021

That sounds like a Mac app.
I have windows. I used a windows 10 app called PHOTOS, which edits video, and I joined my MP4 with that, but it re-encodes to lower quality 1080P, so I wasn't very happy with that.
I obviously want to keep the original 4k quality.

I read on this forum some people used MP4 joiner a few (2-3) years ago and there were no complaints - but I guess the resolution and files were a lot smaller in those days.

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tibzee · Mar 11, 2021

I haven't tried that with DJI's files (I did with GoPro's) but if you are not affraid of command line then you might look at ffmpeg (there are dozens of GUIs for it) and concat demuxer: How to concatenate two MP4 files using FFmpeg?
Files are joined without re-encoding.

Tufargon · Mar 11, 2021

I just drag and drop into Filmora. I cut and delete parts in Filmora also. Losslesscut (it's free) should be able to cut or join them with no problems also.

Kilrah · Mar 11, 2021

Avidemux works fine.

nick0 · Mar 11, 2021

Kilrah said:
Avidemux works fine.

I second this! And its free.

Dave Maine · Mar 12, 2021

Any non-linear editor will join the two seamlessly on the timeline by butting them together at the joint. You can then export the joined clip as a single composite clip. If you are going to do further editing, you can skip that export step and use as is.

Ian UK · Mar 12, 2021

I just installed AVIDEMUX.
I looked at the instructions

build:doctop [Avidemux]

www.avidemux.org

And it all looks incredibly complicated!
I thought joining 2 MP4 files together would be straight forward, so I loaded the first MP4 in to the app.
I looked at the optopn to see how to insert another MP4 and there was no clear option, so I loaded the other MP4 and the first one disappeared. So I gave up, and thought I'd ask on here for some step by step help!
Surely it can't be that complicated! Please help me!

UPDATE: I found the APPEND option and put in the second video.
Then I did SAVE.
But it is RE ENCODING the video!
I don't want it re-encoded, I just want them joined.
Am I missing something?

Kilrah · Mar 12, 2021

- Drop first clip in window
- Drop next clip in window, repeat as needed

Make sure both video and audio are set to copy, select output format as mp4 and save. It won't reencode.

Pretty much as simple as it gets.

Ian UK · Mar 12, 2021

Hi Kilrah, Thank you - it worked!
The output format I used was "MP4 muxer".
When I saved the file, I got the dialog box saying Encoding, and it took about 6 minutes to complete.
The resulting files size is about 0.5Meg less than the sum of the 2 individual files.
Unfortunately the sub titles do not exist on the new file.
Subtitles are cool because they show the telemetry data, and the Drone Viewer PC app uses the subtitles to show all the flight information.
Do you know why the subtitles are missing?

Pappy · Mar 12, 2021

If you do not want to use an editor to join multiple files for one long video, you can use "ffmpeg" to concatenate the files together to produce one single file.

(echo file '20201023-DJI_0028.MP4' & echo file '20201023-DJI_0029.MP4' )>list.txt
"C:\Program Files\ffmpeg\bin\ffmpeg" -safe 0 -f concat -i list.txt -c copy DJI_output.mp4

The above command takes the two split files, 20201023-DJI_0028.MP4 and 20201023-DJI_0029.MP4, to produce one continuous video "DJI_output.mp4".

Kilrah · Mar 13, 2021

Ian UK said:
Subtitles are cool because they show the telemetry data, and the Drone Viewer PC app uses the subtitles to show all the flight information.
Do you know why the subtitles are missing?

Subtitles are in a separate file that needs to have the same name as the matching clip, and if you're gonna merge the video files you should merge the srt files as well but I don't know of a tool for that.

tibzee · Mar 15, 2021

Kilrah said:
Subtitles are in a separate file that needs to have the same name as the matching clip, and if you're gonna merge the video files you should merge the srt files as well but I don't know of a tool for that.

Subtitles in DJI's files are embedded inside .mp4 files as .srt files (with time codes relative to the beginning of the video). Unfortunately when 2 or more DJI's videos are joined .srt files are not correctly stitched together, and that requires further work (eg. script that extracts subs and joins them with correct time shifts)

Ian UK · Mar 19, 2021

Thank you for description of the subtitles. I'd like to do that extraction and joining of the .SRT files, but I need to get the hang of manipulating the MP4s first.

I am quite happy to do the command line approach to doing things with FFMPEG (especially when somebody kindly spells it out for me!). But - that FFMPEG software looks huge and on youtube there is a complicated tutorial just about installing it! So that put me off it!
I like the idea that the command just "bolts" them together. Thank you for spelling that out.

I'll stick with using the AVIDEMUX program for now.