extended ascii version of formats.html

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+1. Input layer, supported devices, methods:
+  - plain file, with seeking
+  - STDIN, without seeking backward
+  - network streaming (currently plain wget-like HTTP, no MMS support yet)
+  - VCD (Video CD) track, by direct CDROM device access (not requires mounting disc)
+  - DVD titles using .IFO structure, by direct DVD device access (not requires mounting disc)
+
+2. Demuxer/parser layer, supported file/media formats:
+
+  - MPEG streams (ES,PES,PS. no TS support yet)
+    note: mpeg demuxer silently ignore non-mpeg content, and find mpeg packets
+    in arbitrary streams. it means you can play directly VCD images (for example
+    CDRwin's .BIN files) without extracting mpeg files first (with tools like vcdgear)
+    It accepts all PES variants, including files created by VDR.
+    Note: VOB (video object) is simple mpeg stream, but it usually has 01BD
+    streams which may contain subtitles and non-mpeg audio. Usually found on DVD discs.
+    
+    Headers: mpeg streams has no global header. each frame sequecne (also called GOP,
+    group of pictures) contains an sequence header, it describes that block.
+    In normal mpeg 1/2 content there are GOPs of 12-15 frames (24/30 fps).
+    It means you can freely seek in mpeg streams, and even can cut it to
+    small parts with standard file tools (dd, cut) without destroying it.
+    
+    Codecs: video is always mpeg video (mpeg1, mpeg2 or mpeg4).
+    audio is usually mpeg audio (any layer allowed, but it's layer 2 in most files)
+    but 01BD streams may contain AC3 or LPCM too.
+    
+    FPS: mpeg2 content allow variable framerate, in form of delayed frames.
+    It's mostly used for playback 24fps contant at 29.97/30 fps (NTSC) rate.
+    (so called Telecine or 3:2 pulldown effect)
+    It means you see 30 frames per second, but there are only 24 different
+    pictures and some of them are shown longer to fill 30 frame time.
+    If you encode such files with mencoder, using -ofps 24 or -ofps 23.98
+    is recommended.
+
+  - AVI streams.
+    Two kind of RIFF AVI files exists:
+    1. interleaved: audio and video contant is interlaved. it's faster and
+       requires only 1 reading thread, so it's recommended (and mostly used).
+    2. non-interleaved: audio and video aren't interleaved, i mean first come
+       whole video followed by whole audio. it requires 2 reading process or
+       1 reading with lots of seeking. very bad for network or cdrom.
+    3. badly interleaved streams: mplayer detects interleaving at startup and
+       enables -ni option if it finds non-interleaved content. but sometimes
+       the stream seems to be interleaved, but with bad sync so it should be
+       played as non-interleaved otherwise you get a-v desync or buffer overflow.
+    MPlayer supports 2 kind of timing for AVI files:
+    - bps-based: it is baed on bitrate/samplerate of video/audio steram.
+      this method is used by most players, including avifile and wmp.
+      files with broken headers, and files created with VBR audio but not
+      vbr-compliant encoder will result a-v desync with this method.
+      (mostly at seeking).
+    - interleaving-based: note: it can't be used togethwer with -ni
+      it doesn't use bitrate stuff of header, it uses the relative position
+      of interleaved audio and video chunks. makes some badly encoded file
+      with vbr audio playable.
+
+    Headers: AVI files has a mandatory header at the begin of the file,
+    describing video parameters (resolution, fps) and codecs. Optionally
+    they have an INDEX block at the end of the file. It's optional, but
+    most files has such block, because it REQUIRES for seeking.
+    Btw usually it can be rebuild from file content, mplayer does it with
+    the -idx switch. Mplayer can fix broken index blocks using -forceidx.
+    As AVI files needs index for random access, broken files with no index
+    are usually unplayable.
+    Of course, cutting/joining AVI files needs special programs.
+
+    Codecs: any audio and video codecs allowed, but I 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 and fails with VBR,
+    as VBR is unusual, and Microsoft's AVI specs only describe CBR audio.
+    I also note, that most AVI encoders/multiplexers create bad files if
+    using VBR audio. only 2 exception (known by me): NaNDub and MEncoder.
+    
+    FPS: must be constant, but skipping frames are allowed.
+
+  - ASF streams:
+    ASF (active streaming format) comes from Microsoft. they developed two
+    variant of ASF, v1.0 and v2.0. v1.0 is used by their media tools (wmp and
+    wme) and v2.0 is published and patented :). of course, they differ,
+    no compatibility at all. (it's just a legality game)
+    MPlayer supports only v1.0, as nobody ever seen v2.0 files :)
+    Note, that .ASF files are nowdays come with extension .WMA or .WMV.
+
+    Headers: Stream headers (codecs parameters) can be everywhere (in theory),
+    but all files i've seen had it at the beginning of the file.
+    Asf uses fixed packet size, so it is seekable without any INDEX block,
+    and broken files are playable well.
+    
+    Codecs: video is mostly microsoft's mpeg4 variants, MP42, MP43 (aka DivX),
+            WMV1 and WMV2. but any codecs allowed.
+            audio is usually wma or voxware, but any codecs allowed.
+
+    FPS: no fixed fps, every video frame has an exact timestamp instead.
+    I've got stream with up to 3 sec frame display times.
+
+  - QuickTime / MOV files:
+    They come from Mac users, usually with .mov or .qt extension, but as
+    MPEG Group choose quicktime as recommended file format for MPEG4,
+    sometimes you meet quicktime files with .mpg extension.
+  
+    At first look, it's a mixture of ASF and AVI.
+    It requires INDEX block for random access and seeking, and even for
+    playback, like AVI, but uses timestamps instead of constant framerate
+    and has more flexible stream options (including network stuff) like ASF.
+    
+    Headers: header can be placed at the beginning or at the end of file.
+    About half of my files has it at the begining, others has it at the end.
+    Broken files are only playable if they have header at the beginning!
+    
+    Codecs: any codecs allowed, both CBR and VBR.
+    Note: most new mov files use Sorenson video and audio, they are
+    patented, closed, secret, (TM)-ed etc formats, only Apple's quicktime
+    player is able to playback these files (on win/mac only).
+
+  - VIVO files:
+    They are funny streams. They have a human-readable ascii header at
+    the beginning, followed by interleaved audio and video chunks.
+    It has no index block, has no fixed packetsize or sync bytes, and most
+    files even has no keyframes, so forget seeking!
+    Video is standard h.263 (in vivo/2.0 files it's modified, non-standard
+    h.263), audio is either standard g.723 or Vivo Siren codec.
+    
+    Note, that microsoft licensed vivo stuff, and included in their netshow
+    v2.0 program, so there are VfW/ACM codecs for vivo video and audio.
+