libmpeg2 - a free MPEG-2 video stream decoder

News

July 18, 2008: bugfix release - This minor bugfix release corrects various installation issues introduced in 0.5.0.

July 12, 2008: new release - This release brings libmpeg2 up to date with recent contributions, compilers and systems.

New optimizations have been provided for SSE2 and ARM instruction sets, while a lot of warnings triggered by recent compiler changes have been fixed.

A new function has been added to guess the aspect ratio of streams where it is not properly coded. Also it is now possible to retrieve the value of the MPEG-2 repeat_first_field flag, and to be notified when the sequence header of a stream changes (eg. aspect ratio on-the-fly changes).

September 19, 2006: bugfix release - The build system now supports newer versions of the autotools and can find them in weird places on FreeBSD and OS X systems. We also support x86 accelerations on the AMD64 CPU, including on FreeBSD. The AltiVec features are now better detected.

Peter Gubanov found a bug in the 4:4:4 chroma handling, Nicolas Joly found a memory leak in the Xshm code on remote displays and Roberto Huelga found alignment issues in the sample3 and sample5 examples. Gildas Bazin contributed a patch for more tolerance for invalid sequence display extensions.

There are also two new maintainers to help Michel in his task: Sam Hocevar and Christophe Massiot, from the VideoLAN project.

January 21, 2004: minor bugfix release - MMX color conversions were accidentally disabled in 0.4.0 (Ooooops!)

December 23, 2003: new mpeg2dec release! It now supports 4:2:2-profile decoding, robustness has been enhanced to the point that we dont know how to crash it anymore despite trying hard, it supports concatenated streams with different sizes, the color conversion routines are now in a reuseable helper library, we have sparc VIS optimizations for the MC, and some start of a basic documentation directory too.

October 8, 2003: The next release is coming up nicely:

• Conformance: Support for the decoding of 4:2:2 streams is checked in in a sub-branch, and is being polished before being promoted to the top of trunk. We might not hold the release for it though.
• Speed: On the sparc architecture, VIS-optimized implementations of the color space conversion and motion compensation code is checked in. This allows us to get rid of the mlib dependency. Similar optimization of the IDCT code is being worked on.
• Robustness: Using a new robustness test suite (not checked in yet), we greatly improved the library's ability to handle corrupted streams. In particular, the library can now groke truncated and/or concatenated streams.
• Documentation: Code samples for all types of buffer management are checked in.
• Re-usability: We are planning to move the color space conversion code from the video output library to its own library, and to help people associate a full 33-bit PTS to their pictures.

About libmpeg2

libmpeg2 is a free library for decoding mpeg-2 and mpeg-1 video streams. It is released under the terms of the GPL license.

The main goals in libmpeg2 development are:

• Conformance - libmpeg2 is able to decode all mpeg streams that conform to certain restrictions: "constrained parameters" for mpeg-1, and "main profile" for mpeg-2. In practice, this is what most people are using. For streams that follow these restrictions, we believe libmpeg2 is 100% conformant to the mpeg standards - and we have a pretty extensive test suite to check this.
• Speed - there has been huge efforts there, and we believe libmpeg2 is the fastest library around for what it does. Please tell us if you find a faster one! With typical video streams as found on DVD's, and doing only decoding with no display, you should be able to get about 110 fps on a PIII/666, or 150 fps on an Athlon/950. This is less than 20 cycles per output pixel. In a real player program, the display routines will probably take as much time as the actual decoding!
• Portability - most of the code is written in C, and when we use platform-specific optimizations (typically assembly routines, currently used for the motion compensation and the inverse cosine transform stages) we always have a generic C routine to fall back on. This should be portable to all architectures - at least we have heard reports from people running this code on x86, ppc, sparc, arm and sh4. Assembly-optimized implementations are available on x86 (MMX) and ppc (AltiVec) architectures. Ultrasparc (VIS) is probably the next on the list - we'll see.
• Reuseability - we do not want libmpeg2 to include any project-specific code, but it should still include enough features to be used by very diverse projects. We are only starting to get there - the best way to help here is to give us some feedback!

The project homepage is at http://libmpeg2.sourceforge.net/

mpeg2dec

mpeg2dec is a test program for libmpeg2. It decodes mpeg-1 and mpeg-2 video streams, and also includes a demultiplexer for mpeg-1 and mpeg-2 program streams. It is purposely kept simple : it does not include features like reading files from a DVD, CSS, fullscreen output, navigation, etc... The main purpose of mpeg2dec is to have a simple test bed for libmpeg2.

The libmpeg2 source code is always distributed in the mpeg2dec package, to make it easier for people to test it.

Other projects using libmpeg2

libmpeg2 is being used by various other projects, including:

• xine - started as a simple mpeg-2 audio and video decoder, but it since became a full-featured DVD and video media player.
• VideoLAN - video streaming over an ethernet network, can also be used as a standalone player.
• MPlayer - another good player, it is also very robust against damaged streams.
• movietime - still quite young, but it looks very promising!
• mpeg2decX - a graphical interface for mpeg2dec for macintosh osX.
• TCVP - video and music player for unix.
• drip - a DVD to DIVX transcoder.
• PoMP - a research player optimized to minimize disk power consumption.
• OMS
• XMPS
• GStreamer - a framework for streaming media; it has an mpeg2 decoding plugin based on libmpeg2.
• mpeglib - a video decoding library that usess libmpeg2 when decoding mpeg streams.
• daphne - a laserdisc arcade game simulator.
• GOPchop - a GOP-accurate editor for MPEG2 streams.
• XBMC - multimedia player jukebox for Microsoft Xbox.
• VeMP - VIA enhanced MPlayer.
• VeXP - VIA enhanced Xine Player.
• MPC - Media Player Classic for Windows.
• DScaler - video deinterlacer and scaler.
• HandBrake - a DVD to MPEG-4 ripper / converter.
• WinCE port - libmpeg2 ported to Windows CE.

If you use libmpeg2 in another project, let us know!

Tasks

There are several places where we could easily use some help:

• Web design: This site sucks! at the very least, we'd like to come up with a nicer background picture and a logo.
• Documentation: libmpeg2 still has no documentation. Every project using it has had to figure things out by looking at the header files, at the mpeg2dec sample application, and by asking questions. Writing down a nice documentation would make the code more easily reuseable.
• Testing: If you find any stream that does not decode right with libmpeg2, let us know! The best thing would be to mail to the libmpeg2-devel mailing list. Also, it would be nice to build a stress test so we can make sure libmpeg2 never crashes on bad streams.
• Coding: There is a small TODO list in the mpeg2dec package, you can have a look there! Most items are pretty terse though.
• Porting: If you're porting to a new architecture, you might want to experiment with the compile flags defined in configure.in . When you figure out whats fastest on your platform, send us a patch!
• Assembly optimizations: We only have x86 and AltiVec optimizations yet, it would be worthwhile writing routines for other architectures, especially those that have SIMD instruction set extensions! Also the yuv2rgb x86 routines could probably be optimized a lot.