
It offers MPEG editing and requantization. In the recent version, Avidemux boasts such features as support for OGM and MP4 files natively, direct read input for various types of MPEGs, and many other video formats and containers. While it cannot do everything that VirtualDub can, Avidemux can do many things that its Windows counterpart cannot.

(these are free and have similar use as Pinnacle).Some people think of Avidemux as VirtualDub (or VirtualDubMod) for Linux, and it is generally reputed by many Linux and Windows users alike to be the closest thing available.

If you prefer more user friendly approach, then use some more advanced editor - maybe Pinnacle Studio (have to pay for it, and it needs to recompress your video before saving) or on linux something like Kdenlive, Open Movie Editor etc. Save that new audio still in audacity, then tell avidemux to use that external audio instead of the original one. whatever seconds in but say it was 10 seconds in length, you now have an audio in there that is 10 minutes 10 seconds. So if the original was 10 minutes, and the inserted clip you put in e.g. you want to insert audio at 12 seconds so cut after 12 seconds of the imported audio, add your audio clip in then paste what you cut to be after that. Looks like you're saying, to extract the audio from the video with avidemux, import the audio into Audacity, and in Audacity, use features like cut/paste/join, to add your audio clip into the desired position within the audio you imported, e.g. So if you need to combine your MP3 with the video sound, then save your audio track from Avidemux, use Audacity to cut and combine it with your MP3 files and finally import it back to video using Avidemux again.

This solution has one limitation (as I know) - the new audio replaces your original audio track and always starts with the video.

Just open your video, select Copy for Video in the left settings tab and then go to main menu Audio/Main track and you will get dialog Main audio track and choose for Audio: External MP3 instead of default setting Video. Avidemux is able to use external audio track from MP3, AC3 or WAV.
