Using LibMPEG3 to make your own MPEG applications

Author: Heroine Virtual (Motion picture solutions for Linux) broadcast@earthling.net
Homepage: heroinewarrior.com

XMovie is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version.

XMovie is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

In addition to the GPL's warranty stipulation, XMovie is distributed WITHOUT GUARANTEED SUPPORT; without even the guarantee of ADDITIONAL LABOR. Support that is not guaranteed includes technical support, compiler troubleshooting, debugging, version matching, updating, among other additional labor which may or may not be required to meet a user's requirements.

XMovie User's Guide

XMovie was originally written as a simple, fast method to play uncompressed movies with stereo sound. Today its primary use is high resolution, high quality movies. Much of the underlying code was used in making Shrek. XMovie not only supports stereo sound, it can decode 6 discrete channels of audio for users with theater sound systems. Additional codecs were added over the years.

MPEG-1 program streams
MPEG-2 program streams
MPEG-2 transport streams
MP3 audio
MP2 audio
AC3 audio
WAV audio
AIFF audio
MPEG-1 video
MPEG-2 video
DVD
VCD rips
Quicktime video:
OpenDivx
Motion JPEG A
Uncompressed RGB
Component video
Progressive JPEG
PNG
YUV 4:2:0 uncompressed
YUV 4:2:2 uncompressed
DV
Quicktime audio:
Twos complement
IMA4
ulaw
Vorbis

Menus

OPTIONS
PLAY EVERY FRAME
Forces every frame to be played regardless of synchronization.
FULL SCREEN
Toggles between fullscreen and windowed output. Remember to use the f key to toggle back.
ORIGINAL SIZE
Size the frame so that horizontal resolution is 1:1.
SYNCHRONIZE USING SOFTWARE
Try to guess the synchronization instead of locking on the soundcard.
SETTINGS
Display aspect ratio - Determines the aspect ratio of the intended screen size by stretching pixels. Usually either 4:3 or 16:9. Can optionally be disabled so that pixels are always square.

Letterbox aspect ratio - For a letterboxed movie this determines what the movie's aspect ratio would be if the letterbox was cropped, usually 2.2:1. Then by enabling Crop letterbox you can save CPU time and desktop area by displaying only the part of the screen containing the movie.

Enable MMX - MMX uses a lossy algorithm developed by Intel to speed up playback.

Audio Priority - Some people think the audio interferes with smooth video. You can set the nice value for the audio here. A nice of 0 puts audio on the same priority as video. A nice of 20 puts audio in the lowest priority.

Preload size - CD-ROM drives can't handle seeking in Quicktime movies so preload size determines a maximum number of bytes ahead of the current file pointer the drive should read sequentially before resorting to a SEEK_SET. This speeds up Quicktime playback from CD-ROM drives.

Downmixing strategy - When playing DVD's and 6 channel audio sources you can either mix 6 channels down to stereo, send 6 discrete channels to the soundcard, or upmix a stereo signal to 6 channels. When you plug a 6 channel soundcard into a home theater amplifier, the channel assignments are as follows: 


Channel:        1         2           3           4           5            6
Speaker:    Main Left | Center | Main Right | Surr Left | Surr Right | Subwoofer

Video device - An alternative device other than X Windows can be used for video output. If you have a DVS SDStation card you can send video to a TV set with this option. Video must be 720 pixels wide to work with this card. This is a genlocked uncompressed video output.

AUDIO
Selects among the audio streams.
VIDEO
Selects among the video streams. After switching video streams you should restart the program since not all video streams have the same dimensions.

Quicktime Info

Although not developed by Microsoft, and not the standard UNIX format, Quicktime is really a wrapper for the various compression standards out there with 64 bit filesystem support. What you know as Quicktime 4 is really the same as any other version of Quicktime. Quicktime 4 wraps two additional compression standards which aren't present in the previous versions but the method it uses for wrapping is identical to Quicktime 2.

The Quicktime support in XMovie wasn't designed to play movies from the internet. Internet movies are encoded using the two compression standards: Sorenson Vision and QDesign Music. Apple licensed these compression standards for their own use after Microsoft introduced Windows Media Player in 1998 to avert competition, hence it is impossible for anyone but Apple to use Sorenson Vision or QDesign Music.

Your primary use of XMovie is uncompressed Quicktime movies that you create yourself, as in using your computer as a VCR.

Low bitrate MPEG Info

Be sure to disable MMX in settings->preferences. This improves quality. A lot of users notice what they call "color drifting". This is because MMX is enabled.

DVD Info

XMovie can be used as a rudimentary DVD player by playing the IFO files one by one. 50% of the DVD support in Linux is integrated in the kernel. The following kernel is known to play DVD's

Kernel 2.4.7

The files you want to play off of DVDs are .IFO files. Each of these is a movie. After loading an IFO file you'll notice the time indicator jumping around. This shows the timecode in the MPEG stream at every point, which on DVD's is discontinuous.

Most DVD's are encoded with 6 channel audio. If you have a 6 channel sound card you can play all 6 channels as described above. Otherwise downmix to stereo.

MPEG transport stream info

XMovie can play transport streams downloaded from the WinTV-D card and the scrawny women streams from UC Berkeley. When switching between the HDTV and the SDTV video you need to restart the program since the frame size changes.

IDE bug

The IDE drivers set the maximum CD-ROM size to 700MB. Attempting to load a DVD results in "attempt to seek beyond end of device" errors and crashes the program. The solution is to reboot and make sure the DVD is the first disk mounted on the CD-ROM drive. The kernel will accept DVD sizes until you insert the first 700MB CD in the drive.

Another thing that worked around the IDE bug in some kernel revisions was SCSI emulation. SCSI emulation drifts in and out of functionality depending on the kernel revision.