Ubuntu – How to convert an ogv file to mp4

Perhaps the easiest tool for that is ffmpeg, or avconv from the libav-tools package. Libav is a fork of FFmpeg, which Ubuntu switched to for a few years until Ubuntu 15.04. It is one of the backends for many of the GUI tools mentioned in other answers.

Changing container without re-enconding content could not be simpler:

ffmpeg -i input.mkv -codec copy output.mp4

• It auto-detects a Matroska to MP4 container conversion based on input/output filenames.

• -codec copy stream copies, or "re-muxes", the streams from the input to the output without re-encoding. Think of it like a copy and paste.

• Default stream selection behavior is to select only one stream per stream type. For example, if your input has two video streams and one audio stream then only the video stream with the largest frame size will be selected. Add -map 0 if you want to select all streams from the input.

• Some containers may not support some formats. So check if your chosen container format, be it mkv, mp4 or even avi has support for all the content in your files (video, audio, subtitles, data, etc). For example, mp4 does not support SubRip subtitles (.srt files).

If you are happy to use FFmpeg, and yes this is command line not gui, one suggested command line to produce a wmv files that should play on a lot of devices and platforms is:

ffmpeg -i input.ogv \
       -c:v wmv2 -q:v 4  \
       -c:a wmav2 -b:a 128k \
       output.wmv

You can experiment a little with the quality settings for the wmv2 video, decreasing to 2 will get better quality and increasing above this will get progressively lower quality. With the bitrate settings for the wmav2 sound increasing the bitrate may get you better quality sound. All of this depends a lot on the quality of the input audio and video streams.

To run this command on multiple streams you would need to construct a for loop and this would be easy enough to demonstrate if you are happy with the suggested encoding syntax.