MKV for a home video library
MKV (Matroska) is an open container that can hold almost any video and audio codec. Media server software such as Plex, Jellyfin and Emby, players like Kodi and VLC, and most smart TVs and media boxes from the last decade play MKV files. If you are building a home library of family videos, converting 3GP to MKV puts your old phone clips into the same format as the rest of the collection, so they show up and play like any other video.
Why not keep the 3GP files?
Media servers often fail on 3GP: they cannot read the AMR sound, show the wrong length or need to transcode the file every time it is played. TVs and media boxes are even less forgiving. A converted file with common codecs plays directly, without extra work for the server.
What happens to your clips
- 3GP with H.264 and AAC: the streams can be copied into MKV without re-encoding. It is fast and keeps every detail.
- 3GP with H.263, MPEG-4 Part 2 or AMR: the built-in converter engine decodes the old codecs and encodes them again in modern ones that TVs and players handle.
Everything runs on your computer. Even a large batch of clips never leaves your device, which is important for private family recordings.
Practical advice
Name your files before you convert them, for example by date and event, because old phones gave them names like VID00012.3gp. Keep the original resolution: a 320×240 clip will be stretched to full screen by the TV anyway, and scaling it up in advance only increases the size. If you see sound drift on a TV, convert again with a fixed frame rate.
MKV is not ideal for Apple devices, since QuickTime and iPhones do not play it. If you also want the clips in Apple Photos, use 3GP to MP4 instead. To edit an MKV afterwards, open the MKV Editor. To go back to 3GP, see MKV to 3GP.