mirror of https://github.com/mpv-player/mpv
128 lines
7.0 KiB
Plaintext
128 lines
7.0 KiB
Plaintext
1. Input layer, supported devices, methods:
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- plain file, with seeking
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- STDIN, without seeking backward
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- network streaming (currently plain wget-like HTTP, no MMS support yet)
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- VCD (Video CD) track, by direct CDROM device access (not requires mounting disc)
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- DVD titles using .IFO structure, by direct DVD device access (not requires mounting disc)
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2. Demuxer/parser layer, supported file/media formats:
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- MPEG streams (ES,PES,PS. no TS support yet)
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note: mpeg demuxer silently ignore non-mpeg content, and find mpeg packets
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in arbitrary streams. it means you can play directly VCD images (for example
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CDRwin's .BIN files) without extracting mpeg files first (with tools like vcdgear)
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It accepts all PES variants, including files created by VDR.
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Note: VOB (video object) is simple mpeg stream, but it usually has 01BD
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packets which may contain subtitles and non-mpeg audio. Usually found on DVD discs.
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Headers: mpeg streams has no global header. each frame sequence (also called GOP,
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group of pictures) contains an sequence header, it describes that block.
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In normal mpeg 1/2 content there are groups of 12-15 frames (24/30 fps).
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It means you can freely seek in mpeg streams, and even can cut it to
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small parts with standard file tools (dd, cut) without destroying it.
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Codecs: video is always mpeg video (mpeg1, mpeg2 or mpeg4).
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audio is usually mpeg audio (any layer allowed, but it's layer 2 in most files)
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but 01BD packets may contain AC3, DTS or LPCM too.
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FPS: mpeg2 content allows variable framerate, in form of delayed frames.
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It's mostly used for playback 24fps content at 29.97/30 fps (NTSC) rate.
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(so called Telecine or 3:2 pulldown effect)
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It means you see 30 frames per second, but there are only 24 different
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pictures and some of them are shown longer to fill 30 frame time.
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If you encode such files with mencoder, using -ofps 24 or -ofps 23.98
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is recommended.
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- AVI streams.
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Two kind of RIFF AVI files exists:
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1. interleaved: audio and video content is interlaved. it's faster and
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requires only 1 reading thread, so it's recommended (and mostly used).
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2. non-interleaved: audio and video aren't interleaved, i mean first come
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whole video followed by whole audio. it requires 2 reading process or
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1 reading with lots of seeking. very bad for network or cdrom.
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3. badly interleaved streams: mplayer detects interleaving at startup and
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enables -ni option if it finds non-interleaved content. but sometimes
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the stream seems to be interleaved, but with bad sync so it should be
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played as non-interleaved otherwise you get a-v desync or buffer overflow.
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MPlayer supports 2 kind of timing for AVI files:
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- bps-based: it is based on bitrate/samplerate of video/audio steram.
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this method is used by most players, including avifile and wmp.
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files with broken headers, and files created with VBR audio but not
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vbr-compliant encoder will result a-v desync with this method.
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(mostly at seeking).
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- interleaving-based: note: it can't be used togethwer with -ni
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it doesn't use bitrate stuff of header, it uses the relative position
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of interleaved audio and video chunks. makes some badly encoded file
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with vbr audio playable.
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Headers: AVI files has a mandatory header at the begin of the file,
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describing video parameters (resolution, fps) and codecs. Optionally
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they have an INDEX block at the end of the file. It's optional, but
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most files has such block, because it REQUIRES for seeking.
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Btw usually it can be rebuild from file content, mplayer does it with
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the -idx switch. Mplayer can recreate broken index blocks using -forceidx.
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As AVI files needs index for random access, broken files with no index
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are usually unplayable.
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Of course, cutting/joining AVI files needs special programs.
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Codecs: any audio and video codecs allowed, but I note that VBR audio is
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not well supported by most players. The file format makes it possible to
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use VBR audio, but most players expect CBR audio and fails with VBR,
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as VBR is unusual, and Microsoft's AVI specs only describe CBR audio.
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I also note, that most AVI encoders/multiplexers create bad files if
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using VBR audio. only 2 exception (known by me): NaNDub and MEncoder.
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FPS: only constant framerate allowed, but it's possib;e to skip frames.
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- ASF streams:
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ASF (active streaming format) comes from Microsoft. they developed two
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variant of ASF, v1.0 and v2.0. v1.0 is used by their media tools (wmp and
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wme) and v2.0 is published and patented :). of course, they differ,
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no compatibility at all. (it's just a legality game)
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MPlayer supports only v1.0, as nobody ever seen v2.0 files :)
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Note, that .ASF files are nowdays come with extension .WMA or .WMV.
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Headers: Stream headers (codecs parameters) can be everywhere (in theory),
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but all files i've seen had it at the beginning of the file.
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Asf uses fixed packet size, so it is seekable without any INDEX block,
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and broken files are playable well.
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Codecs: video is mostly microsoft's mpeg4 variants: MP42, MP43 (aka DivX),
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WMV1 and WMV2. but any codecs allowed.
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audio is usually wma or voxware, sometimes mp3, but any codecs allowed.
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FPS: no fixed fps, every video frame has an exact timestamp instead.
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I've got stream with up to 3 sec frame display times.
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- QuickTime / MOV files:
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They come from Mac users, usually with .mov or .qt extension, but as
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MPEG Group choose quicktime as recommended file format for MPEG4,
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sometimes you meet quicktime files with .mpg or .mp4 extension.
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At first look, it's a mixture of ASF and AVI.
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It requires INDEX block for random access and seeking, and even for
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playback, like AVI, but uses timestamps instead of constant framerate
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and has more flexible stream options (including network stuff) like ASF.
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Headers: header can be placed at the beginning or at the end of file.
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About half of my files has it at the begining, others has it at the end.
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Broken files are only playable if they have header at the beginning!
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Codecs: any codecs allowed, both CBR and VBR.
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Note: most new mov files use Sorenson video and QDesign Music audio,
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they are patented, closed, secret, (TM)-ed etc formats, only Apple's
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quicktime player is able to playback these files (on win/mac only).
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- VIVO files:
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They are funny streams. They have a human-readable ascii header at
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the beginning, followed by interleaved audio and video chunks.
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It has no index block, has no fixed packetsize or sync bytes, and most
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files even has no keyframes, so forget seeking!
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Video is standard h.263 (in vivo/2.0 files it's modified, non-standard
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h.263), audio is either standard g.723 or Vivo Siren codec.
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Note, that microsoft licensed vivo stuff, and included in their netshow
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v2.0 program, so there are VfW/ACM codecs for vivo video and audio.
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