I tried avidemux but it seems to be missing codecs? There are no audio codecs and only two video codecs. Oddly enough avidemux can open and play video files just fine - with no audio. However there seem to be no audio/video compression codecs.
The command line version says
[ADM_ad_plugin] Scanning directory /usr/lib/ADM_plugins/audioDecoder/
[ADM_ad_plugin] Cannot parse plugin
[ADM_vf_plugin] Scanning directory /usr/lib/ADM_plugins/videoFilter/
[ADM_vf_plugin] Cannot parse plugin
[ADM_av_plugin] Scanning directory /usr/lib/ADM_plugins/audioDevices/
[ADM_av_plugin] Cannot parse plugin
[ADM_ae_plugin] Scanning directory /usr/lib/ADM_plugins/audioEncoders/
[ADM_ae_plugin] Cannot parse plugin
[ADM_ad_plugin] Scanning directory /home/tux/.avidemux/plugins/audioDecoder/
[ADM_ad_plugin] Cannot parse plugin
[ADM_vf_plugin] Scanning directory /home/tux/.avidemux/plugins/videoFilter/
[ADM_vf_plugin] Cannot parse plugin
[ADM_vidEnc_plugin] Scanning directory /usr/lib/ADM_plugins/videoEncoder/
[ADM_vidEnc_plugin] Cannot parse plugin
[ADM_vidEnc_plugin] Scanning done, found 0 codec
and indeed all those files/dirs are missing and don't seem to be part of the SliTaz package?