path: root/DOCS/xml/en/containers.xml

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<chapter id="containers">
<title>Containers</title>

<para>
It is important to clarify a common mistake. When people see a file with a
<filename>.AVI</filename> extension, they immediately conclude that it is
not an MPEG file.  That is not true. At least not entirely. Contrary to
popular belief such a file <emphasis>can</emphasis> contain MPEG-1 video.
</para>

<para>
You see, a <emphasis role="bold">codec</emphasis> is not the same as a
<emphasis role="bold">container format</emphasis>.
Examples of video <emphasis role="bold">codecs</emphasis> are: MPEG-1, MPEG-2,
MPEG-4 (DivX), Indeo5, 3ivx.
Examples of container <emphasis role="bold">formats</emphasis> are:
MPG, AVI, ASF.
</para>

<para>
In theory, you can put an OpenDivX video and MP3 audio
into an <emphasis role="bold">MPG container</emphasis>. However, most
players will not play it, since they expect MPEG-1 video and MP2 audio (unlike
<emphasis role="bold">AVI</emphasis>, <emphasis role="bold">MPG</emphasis>
does not have the necessary fields to describe its video and audio streams).
Or you might put MPEG-1 video into an AVI file.
<ulink url="http://ffmpeg.org/">FFmpeg</ulink> and
<link linkend="mencoder"><application>MEncoder</application></link>
can create these files.
</para>


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<sect1 id="video-formats">
<title>Video formats</title>

<sect2 id="mpg-vob-dat">
<title>MPEG files</title>

<para>
MPEG files come in different guises:
</para>

<itemizedlist>
<listitem><para>
  MPG: This is the most <emphasis role="bold">basic</emphasis> form of the
  MPEG file formats. It contains MPEG-1 video, and MP2 (MPEG-1 layer 2) or
  rarely MP1 audio.
</para></listitem>
<listitem><para>
  DAT: This is the very same format as MPG with a different extension. It
  is used on <emphasis role="bold">Video CDs</emphasis>. Due to the way VCDs
  are created and Linux is designed, the DAT files cannot be played nor copied
  from VCDs as regular files. You have to use <option>vcd://</option>
  to play a Video CD.
</para></listitem>
<listitem><para>
  VOB: This is the MPEG file format on <emphasis role="bold">DVDs</emphasis>.
  It is the same as MPG, plus the capability to contain subtitles or non-MPEG
  (AC-3) audio. It contains encoded MPEG-2 video and usually AC-3 audio, but DTS,
  MP2 and uncompressed LPCM are allowed, too. <emphasis role="bold">Read the
  <link linkend="dvd">DVD</link> section</emphasis>!
</para></listitem>
<listitem><para>
  TY: This is a TiVo MPEG stream. It contains MPEG PES data for audio and
  video streams, as well as extra information like closed captions. The
  container is not an MPEG program stream, but a closed format created by
  TiVo. For more information on TiVo stream format, please refer to
  <ulink url="http://dvd-create.sourceforge.net/tystudio/tystream.shtml">
  the TyStudio page</ulink>.
</para></listitem>
</itemizedlist>

<para>
Series of frames form independent groups in MPEG files. This means that you
can cut/join an MPEG file with standard file tools (like
<command>dd</command>, <command>cut</command>), and it remains completely
functional.
</para>

<para>
One important feature of MPEG files is that they have a field to describe the
aspect ratio of the video stream within. For example SVCDs have 480x480
resolution video, and in the header that field is set to 4:3, so that it is
played at 640x480. AVI files often lack this field, so they have to be
rescaled during encoding or played with the <option>-aspect</option>
option.
</para>
</sect2>

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<sect2 id="avi">
<title>AVI files</title>

<para>
Designed by Microsoft,
<emphasis role="bold">AVI (Audio Video Interleaved)</emphasis>
is a widespread multipurpose format currently used mostly for MPEG-4 (DivX and
DivX4) video. It has many known drawbacks and shortcomings (for example in
streaming).
It supports one video stream and 0 to 99 audio streams and can be as big as
2GB, but there exists an extension allowing bigger files called
<emphasis role="bold">OpenDML</emphasis>. Microsoft currently strongly
discourages its use and encourages ASF/WMV. Not that anybody cares.
</para>

<para>
There is a hack that allows AVI files to contain an Ogg Vorbis audio
stream, but makes them incompatible with standard AVI.
<application>MPlayer</application> supports playing these files. Seeking is
also implemented but severely hampered by badly encoded files with
confusing headers. Unfortunately the only encoder currently capable of
creating these files, <application>NanDub</application>, has this problem.
</para>

<note><para>
DV cameras create raw DV streams that DV grabbing utilities convert to two
different types of AVI files. The AVI will then contain either separate
audio and video streams that <application>MPlayer</application> can play or
the raw DV stream for which support is under development.
</para></note>

<para>
There are two kinds of AVI files:
<itemizedlist>
<listitem><para>
  <emphasis role="bold">Interleaved:</emphasis> Audio and video content is
  interleaved. This is the standard usage. Recommended and mostly used. Some
  tools create interleaved AVIs with bad sync.
  <application>MPlayer</application> detects these as interleaved, and this
  climaxes in loss of A/V sync, probably at seeking.
  These files should be played as non-interleaved
  (with the <option>-ni</option> option).
</para></listitem>
<listitem><para>
  <emphasis role="bold">Non-interleaved:</emphasis> First comes the whole
  video stream, then the whole audio stream. It thus needs a lot of seeking,
  making playing from network or CD-ROM difficult.
</para></listitem>
</itemizedlist>
</para>

<para>
<application>MPlayer</application> supports two kinds of timings for AVI
files:
<itemizedlist>
<listitem><para>
  <emphasis role="bold">bps-based:</emphasis> It is based on the
  bitrate/samplerate of the video/audio stream. This method is used by
  most players, including <ulink url="http://avifile.sf.net">avifile</ulink>
  and <application>Windows Media Player</application>. Files with broken
  headers, and files created with VBR audio but not VBR-compliant encoder
  will result in A/V desync with this method (mostly at seeking).
</para></listitem>
<listitem><para>
  <emphasis role="bold">interleaving-based:</emphasis> It does not use the
  bitrate value of the header, instead it uses the relative position of
  interleaved audio and video chunks,
  making badly encoded files with VBR audio playable.
</para></listitem>
</itemizedlist>
</para>

<para>
Any audio and video codec is allowed, but note that VBR audio is not well
supported by most players. The file format makes it possible to use VBR
audio, but most players expect CBR audio, thus they fail with VBR. VBR is
uncommon and Microsoft's AVI specs only describe CBR audio. I also noticed
that most AVI encoders/multiplexers create bad files when using VBR audio.
There are only two known exceptions: <application>NanDub</application> and
<link linkend="mencoder"><application>MEncoder</application></link>.
</para>
</sect2>

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<sect2 id="asf-wmv">
<title>ASF/WMV files</title>

<para>
ASF (Active Streaming Format) comes from Microsoft. They developed two
variants of ASF, v1.0 and v2.0. v1.0 is used by their media tools
(<application>Windows Media Player</application> and
<application>Windows Media Encoder</application>)
and is very secret. v2.0 is published and patented :). Of course they differ,
there is no compatibility at all (it is just another legal game).
<application>MPlayer</application> supports only v1.0, as nobody has ever seen
v2.0 files :). Note that ASF files nowadays come with the extension
<filename>.WMA</filename> or <filename>.WMV</filename>.
</para>
</sect2>

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<sect2 id="mov">
<title>QuickTime/MOV files</title>

<para>
These formats were designed by Apple and can contain any codec, CBR or VBR.
They usually have a <filename>.QT</filename> or <filename>.MOV</filename>
extension. Note that since the MPEG-4 group chose QuickTime as the recommended
file format for MPEG-4, their MOV files come with a <filename>.MPG</filename> or
<filename>.MP4</filename> extension (Interestingly the video and audio
streams in these files are real MPG and AAC files. You can even extract them
with the <option>-dumpvideo</option> and <option>-dumpaudio</option> options.).
</para>
</sect2>

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<sect2 id="vivo">
<title>VIVO files</title>

<para>
<application>MPlayer</application> happily demuxes VIVO file formats. The
biggest disadvantage of the format is that it has no index block, nor a
fixed packet size or sync bytes and most files lack even keyframes, so
forget seeking!
</para>

<para>
The video codec of VIVO/1.0 files is standard
<emphasis role="bold">h.263</emphasis>.
The video codec of VIVO/2.0 files is a modified, nonstandard
<emphasis role="bold">h.263v2</emphasis>. The audio is the same, it may be
<emphasis role="bold">g.723 (standard)</emphasis>, or
<emphasis role="bold">Vivo Siren</emphasis>.
</para>
</sect2>

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<sect2 id="fli">
<title>FLI files</title>

<para>
<emphasis role="bold">FLI</emphasis> is a very old file format used by
Autodesk Animator, but it is a common file format for short animations on the
net.
<application>MPlayer</application> demuxes and decodes FLI movies and is
even able to seek within them (useful when looping with the
<option>-loop</option> option). FLI files do not have keyframes, so the
picture will be messy for a short time after seeking.
</para>
</sect2>

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<sect2 id="realmedia">
<title>RealMedia (RM) files</title>

<para>
Yes, <application>MPlayer</application> can read (demux) RealMedia
(<filename>.rm</filename>) files.
</para>
</sect2>

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<sect2 id="nuppelvideo">
<title>NuppelVideo files</title>

<para>
NuppelVideo
is a TV grabber tool (AFAIK:). <application>MPlayer</application> can read
its <filename>.NUV</filename> files (only NuppelVideo 5.0). Those files can
contain uncompressed YV12, YV12+RTJpeg compressed, YV12 RTJpeg+lzo
compressed, and YV12+lzo compressed frames.
<application>MPlayer</application> decodes (and also
<emphasis role="bold">encodes</emphasis>
them with <application>MEncoder</application> to MPEG-4 (DivX)/etc!) them all.
Seeking works.
</para>
</sect2>

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<sect2 id="yuv4mpeg">
<title>yuv4mpeg files</title>

<para>
<ulink url="http://mjpeg.sf.net">yuv4mpeg / yuv4mpeg2</ulink>
is a file format used by the
<ulink url="http://mjpeg.sf.net">mjpegtools programs</ulink>.
You can grab, produce, filter or encode video in this format using these tools.
The file format is really a sequence of uncompressed YUV 4:2:0 images.
</para>
</sect2>

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<sect2 id="film">
<title>FILM files</title>

<para>
This format is used on old Sega Saturn CD-ROM games.
</para>
</sect2>

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<sect2 id="roq">
<title>RoQ files</title>

<para>
RoQ files are multimedia files used in some ID games such as Quake III and
Return to Castle Wolfenstein.
</para>
</sect2>

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<sect2 id="ogg">
<title>OGG/OGM files</title>

<para>
This is a new file format from the
<ulink url="http://www.xiph.org">Xiph.Org Foundation</ulink>.
It can contain any video or audio codec, CBR or VBR. You'll need
<systemitem class="library">libogg</systemitem> and
<systemitem class="library">libvorbis</systemitem> installed before
compiling <application>MPlayer</application> to be able to play it.
</para>
</sect2>

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<sect2 id="sdp">
<title>SDP files</title>

<para>
<ulink url="ftp://ftp.rfc-editor.org/in-notes/rfc2327.txt">SDP</ulink> is an
IETF standard format for describing video and/or audio RTP streams.
(The "<ulink url="http://www.live555.com/mplayer/">LIVE555 Streaming Media</ulink>"
are required.)
</para>
</sect2>

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<sect2 id="pva">
<title>PVA files</title>

<para>
PVA is an MPEG-like format used by DVB TV boards' software (e.g.:
<application>MultiDec</application>,
<application>WinTV</application> under Windows).
</para>
</sect2>

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<sect2 id="nsv">
<title>NSV files</title>

<para>
NSV (NullSoft Video) is the file format used by the
<application>Winamp</application> player to stream audio and video.
Video is VP3, VP5 or VP6, audio is MP3, AAC or VLB.
The audio only version of NSV has the <filename>.nsa</filename> extension.
<application>MPlayer</application> can play both NSV streams and files.
Please note that most files from the
<ulink url="http://www.winamp.com">Winamp site</ulink> use VLB audio, that
can't be decoded yet. Moreover streams from that site need an extra
depacketization layer that still has to be implemented (those files are
unplayable anyway because they use VLB audio).
</para>
</sect2>

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<sect2 id="matroska">
<title>Matroska files</title>

<para>
Matroska is an open container format.
Read more on the <ulink url="http://www.matroska.org/">official site</ulink>.
</para>
</sect2>

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<sect2 id="nut">
<title>NUT files</title>

<para>
NUT is the container format developed by <application>MPlayer</application> and
<application>FFmpeg</application> folks. Both projects support it.
Read more on the <ulink url="http://www.nut.hu/">official site</ulink>.
</para>
</sect2>

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<sect2 id="gif">
<title>GIF files</title>

<para>
The <emphasis role="bold">GIF</emphasis> format is a common format for web
graphics. There are two versions of the GIF spec, GIF87a and GIF89a.
The main difference is that GIF89a allows for animation.
<application>MPlayer</application> supports both formats through use of
<systemitem class="library">libungif</systemitem> or
another libgif-compatible library. Non-animated GIFs will be displayed as
single frame videos. (Use the <option>-loop</option> and
<option>-fixed-vo</option> options to display these longer.)
</para>

<para>
<application>MPlayer</application> currently does not support seeking in GIF
files. GIF files do not necessarily have a fixed frame size, nor a fixed
framerate. Rather, each frame is of independent size and is supposed to be
positioned in a certain place on a field of fixed-size. The framerate is
controlled by an optional block before each frame that specifies the next
frame's delay in centiseconds.
</para>

<para>
Standard GIF files contain 24-bit RGB frames with at most an 8-bit indexed
palette. These frames are usually LZW-compressed, although some GIF encoders
produce uncompressed frames to avoid patent issues with LZW compression.
</para>

<para>
If your distribution does not come with
<systemitem class="library">libungif</systemitem>, download a copy from the
<ulink url="http://sourceforge.net/projects/libungif">libungif
homepage</ulink>. For detailed technical information, have a look at the
<ulink url="http://www.w3.org/Graphics/GIF/spec-gif89a.txt">GIF89a specification</ulink>.
</para>
</sect2>
</sect1>


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<sect1 id="audio-formats">
<title>Audio formats</title>

<para>
<application>MPlayer</application> is a <emphasis role="bold">movie</emphasis>
and not a <emphasis role="bold">media</emphasis> player, although it can play
some audio file formats (they are listed in the sections below).  This is not
a recommended usage of <application>MPlayer</application>, you better use <ulink
url="http://www.xmms.org">XMMS</ulink>.
</para>

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<sect2 id="mp3">
<title>MP3 files</title>

<para>
You may have problems playing certain MP3 files that
<application>MPlayer</application> will misdetect as MPEGs and play
incorrectly or not at all. This cannot be fixed without dropping support
for certain broken MPEG files and thus will remain like this for the
foreseeable future. The <option>-demuxer</option> flag described in the
man page may help you in these cases.
</para>
</sect2>

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<sect2 id="ogg-vorbis">
<title>OGG/OGM files (Vorbis)</title>

<para>
Requires properly installed
<systemitem class="library">libogg</systemitem> and
<systemitem class="library">libvorbis</systemitem>.
</para>
</sect2>

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<sect2 id="cdda">
<title>CD audio</title>

<para>
<application>MPlayer</application> can use <application>cdparanoia</application>
to play CDDA (Audio CD). The scope of this section does not contain enumerating
<application>cdparanoia</application>'s features.
</para>

<para>
See the man page's <option>-cdda</option> option which can be used to pass
options to <application>cdparanoia</application>.
</para>
</sect2>

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<sect2 id="xmms">
<title>XMMS</title>

<para>
<application>MPlayer</application> can use <application>XMMS</application> input
plugins to play many file formats. There are plugins for SNES game tunes, SID
tunes (from Commodore 64), many Amiga formats, .xm, .it, VQF, Musepack, Bonk,
shorten and many others. You can find them at the
<ulink url="http://www.xmms.org/plugins.php?category=input">XMMS input plugin page</ulink>.
</para>

<para>
For this feature you need to have <application>XMMS</application> and compile
<application>MPlayer</application> with
<filename>./configure --enable-xmms</filename>.
</para>
</sect2>
</sect1>

</chapter>