You've replied in a wrong thread, I'll ask the moderator to move both your post and my reply to Stuttering Audio - MP4 - (newbie to video edition & Avidemux)
1) I'm actually running 14.04 LTS
14.04.(5) is fine, no need to upgrade.
I tried the upgrade to the most recent LTS version, but it borked my displays on desktop and laptop, so I backed out of it until I have time to figure out why that happened
I can gladly help troubleshooting this, though distribution upgrade issues are not related to the Avidemux one this time.
2) This is the result of running avprobe
I have no clue what it means.
avprobe version 9.18-6:9.18-0ubuntu0.14.04.1, Copyright (c) 2007-2014 the Libav developers
built on Mar 16 2015 13:19:10 with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1)
[avi @ 0x1b33fe0] non-interleaved AVI
It says the 20161015_150422.mp4 is actually a badly interleaved AVI container, not a MP4 one. If the file was generated by a Samsung Galaxy S4 smartphone, I'm inclined to distrust avprobe, as AVI is unsuitable for h264. If GS4 really generates AVI masked as MP4, this is a story only short of the burning Galaxy Note 7
Input #0, avi, from '20161015_150422.mp4':
Duration: 11:07:40.67, start: 0.000000, bitrate: 8 kb/s
Wrong (too low) bitrate. Unsure if avprobe misreports or the source video is at fault.
Stream #0.0: Video: h264 (High), yuv420p, 1920x1080, 29.97 fps, 59.92 tbr, 29.94 tbn
Stream #0.1: Audio: aac, 48000 Hz, stereo, fltp, 128 kb/s
No big-endian LPCM here, so it shouldn't be a problem with 2.6.14+
Because of avprobe identifying the video as AVI: is it really the original file shot by a GS4? If it is, I'd try to remux it to a true MP4 first. With the current ffmpeg (unsure about the command syntax of the outdated libav fork) it could be accomplished by
ffmpeg -i 20161015_150422.mp4 -c copy 20161015_150422_for_real.mp4
3) I'll need to read up on how to download and compile the newest version of Avidemux
Is your system a 32bit one, unable to run the appImage, generated by the author of Avidemux? If you are OK with running unsigned third-party binaries, you could install packages built by Jan Gruuthuse
(again, only 64bit).
Otherwise you might want to look into https://github.com/mean00/avidemux2/blob/master/createDebFromSourceUbuntu.bash
for build dependencies and steps required. To get the source:
git clone https://github.com/mean00/avidemux2.git