MPEG-4

MPEG-4 is a form of MPEG encoding. It is a flexible audio and video compression format. The format describes audio and video compression, with a container format for streaming across networks and saving to disk. It also contains optional extra features, including DRM and subtitles. These extra features are only included in software if needed. MPEG-4 can provide better quality than MPEG-2 at low bitrates.

Here is an example of how to transcode an AVI into an MPEG-4 video from the command prompt

% vlc file.avi --sout='#transcode{vcodec=mp4v,acodec=mpga}:std{access=file,mux=mp4,dst=file.m4v}' 

Codecs

• Video codec: mp4v (m4v)
• Audio codec: mp4a (m4a) - this is AAC.

File extension

MP4 (.mp4) is the global file extension for the official container format defined in the MPEG-4 standard (ISO 14496-14).

• .mp4: the only official extension; used for both audio and video files (and advanced content)
• .m4a: introduced by Apple for aac/alac audio-only files.

NOTE: .m4a files can safely be renamed to .mp4 -- but the distinction between audio (m4a) and video (mp4) may be useful if you are going to share files, or if you tend to forget what files you have.

For complete details on MP4, see the following link:

• http://forum.doom9.org/showthread.php?s=&threadid=62723

Container

mp4	VLC can encode and decode this container. The module name to use at the command line is mp4, but you can also use mov, or 3gp.

Accepted video codecs

• mp4v
• mpgv
• MJPG
• mjpb
• SVQ1
• SVQ3
• H263
• h264
• samr
• sawb

Accepted audio codecs

• mp4a
• mpga

Accepted subtitle codec

• subt

Source code

• modules/mux/mp4.c (output muxer)