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libvo --- the library to handle video output by A'rpi, 2002.04
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============================================
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Note: before start on this, read colorspaces.txt !
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The constants for different pixelformats are defined in img_format.h,
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their usage is mandatory.
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Each vo driver _has_ to implement these:
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init the video system (to support querying for supported formats)
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Uninit the whole system, this is on the same "level" as preinit.
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VOCTRL_QUERY_FORMAT - queries if a given pixelformat is supported.
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It also returns various flags decsirbing the capabilities
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of the driver with teh given mode. for the flags, see
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the most important flags, every driver must properly report
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0x1 - supported (with or without conversion)
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0x2 - supported without conversion (define 0x1 too!)
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0x100 - driver/hardware handles timing (blocking)
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also SET sw/hw scaling and osd support flags, and flip,
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and accept_stride if you implement VOCTRL_DRAW_IMAGE (see bellow)
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NOTE: VOCTRL_QUERY_FORMAT may be called _before_ first config()
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but is always called between preinit() and uninit()
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libmpcodecs Direct Rendering interface
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You need to update mpi (mp_image.h) structure, for example,
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look at vo_x11, vo_sdl, vo_xv or mga_common.
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replacement for the current draw_slice/draw_frame way of
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passing video frames. by implementing SET_IMAGE, you'll get
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image in mp_image struct instead of by calling draw_*.
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unless you return VO_TRUE for VOCTRL_DRAW_IMAGE call, the
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old-style draw_* functils will be called!
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Note: draw_slice is still mandatory, for per-slice rendering!
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VOCTRL_RESET - reset the video device
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This is sent on seeking and similar and is useful if you are
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using a device which prebuffers frames that need to flush them
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before refilling audio/video buffers.
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return true only if driver supports co-operation with
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MPlayer's GUI (not yet used by GUI)
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set the video equalizer to the given values
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two arguments are provided: item and value
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item is a string, the possible values are (currently):
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brightness, contrast, saturation, hue
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get the current video equalizer values
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two arguments are provided: item and value
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item is a string, the possible values are (currently):
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brightness, contrast, saturation, hue
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Makes the player window stay-on-top. Only supported (currently)
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by drivers which use X11, except SDL, as well as directx and
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Makes the player window borderless. Only supported by directx.
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Set up the video system. You get the dimensions and flags.
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width, height: size of the source image
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d_width, d_height: wanted scaled/display size (it's a hint)
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0x01 - force fullscreen (-fs)
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0x02 - allow mode switching (-vm)
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0x04 - allow software scaling (-zoom)
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0x08 - flipping (-flip)
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They're defined as VOFLAG_* (see libvo/video_out.h)
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IMPORTAMT NOTE: config() may be called 0 (zero), 1 or more (2,3...)
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times between preinit() and uninit() calls. You MUST handle it, and
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you shouldn't crash at second config() call or at uninit() without
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any config() call! To make your life easier, vo_config_count is
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set to the number of previous config() call, counted from preinit().
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It's set by the caller (vf_vo.c), you don't have to increase it!
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So, you can check for vo_config_count>0 in uninit() when freeing
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resources allocated in config() to avoid crash!
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You should call geometry() in config() to enable user defined
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window size and position. The code should look as following:
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set x,y,w,h to the values supplied by the caller or to those you deam
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call geometry(&x, &y, &w, &h, screenw, screenh)
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see libvo/geometry.c for further information
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draw_slice(): this displays YV12 pictures (3 planes, one full sized that
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contains brightness (Y), and 2 quarter-sized which the colour-info
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(U,V). MPEG codecs (libmpeg2, opendivx) use this. This doesn't have
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to display the whole frame, only update small parts of it.
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draw_frame(): this is the older interface, this displays only complete
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frames, and can do only packed format (YUY2, RGB/BGR).
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Win32 codecs use this (DivX, Indeo, etc).
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If you implement VOCTRL_DRAW_IMAGE, you can left draw_frame.
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draw_osd(): this displays subtitles and OSD.
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It's a bit tricky to use it, since it's a callback-style stuff.
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It should call vo_draw_text() with screen dimension and your
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draw_alpha implementation for the pixelformat (function pointer).
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The vo_draw_text() checks the characters to draw, and calls
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draw_alpha() for each. As a help, osd.c contains draw_alpha for
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each pixelformats, use this if possible!
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NOTE: this one will be obsolete soon! But it's still usefull when
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you want to do tricks, like rendering osd _after_ hardware scaling
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(tdfxfb) or render subtitles under of the image (vo_mpegpes, sdl)
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flip_page(): this is called after each frame, this diplays the buffer for
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real. This is 'swapbuffers' when doublebuffering.
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DOCS/tech/libvo.txt
