clipping (in time) an mp4 video using ffmpeg produces an mp4 file with bad or no video

[Tomislav]

Observed:
Ran:
$ ffmpeg -i my_kazam_recording.mp4 -ss 00:08:02 -t 00:00:05 -c copy out.mp4

Got an mp4 file that mplayer cannot reproduce (plays audio only):
[...]
AO: [pulse] 44100Hz 2ch s16le (2 bytes per sample)
Video: no video
Starting playback...
[...]

Expected:
An mp4 file that's 5 seconds long, containing both the video and audio tracks.

Repeatability: 2/2

Workarounds:
* if it's longer than 5s, the video can be played back, but can't be processed by e.g. kdenlive

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ffmpeg 7:3.4.11-0ubuntu0.1
ProcVersionSignature: Ubuntu 5.4.0-139.156~18.04.1-generic 5.4.224
Uname: Linux 5.4.0-139-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.28
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Thu Feb 23 19:04:34 2023
DistributionChannelDescriptor:
 # This is a distribution channel descriptor
 # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
 canonical-oem-somerville-xenial-amd64-20160624-2
InstallationDate: Installed on 2018-05-10 (1750 days ago)
InstallationMedia: Ubuntu 16.04 "Xenial" - Build amd64 LIVE Binary 20160624-10:47
SourcePackage: ffmpeg
UpgradeStatus: Upgraded to bionic on 2020-03-04 (1086 days ago)

[Luís Infante da Câmara (luis220413)]

Can you provide my_kazam_recording.mp4?

Furthermore, Ubuntu 18.04 is out of standard support and ESM does not provide bug fixes other than security fixes. Please upgrade to an Ubuntu release under standard support and check if your problem persists.

[Launchpad Janitor (janitor)]

[Expired for ffmpeg (Ubuntu) because there has been no activity for 60 days.]