@chapter Output Devices @c man begin OUTPUT DEVICES Output devices are configured elements in FFmpeg that can write multimedia data to an output device attached to your system. When you configure your FFmpeg build, all the supported output devices are enabled by default. You can list all available ones using the configure option "--list-outdevs". You can disable all the output devices using the configure option "--disable-outdevs", and selectively enable an output device using the option "--enable-outdev=@var{OUTDEV}", or you can disable a particular input device using the option "--disable-outdev=@var{OUTDEV}". The option "-devices" of the ff* tools will display the list of enabled output devices. A description of the currently available output devices follows. @section alsa ALSA (Advanced Linux Sound Architecture) output device. @subsection Examples @itemize @item Play a file on default ALSA device: @example ffmpeg -i INPUT -f alsa default @end example @item Play a file on soundcard 1, audio device 7: @example ffmpeg -i INPUT -f alsa hw:1,7 @end example @end itemize @section caca CACA output device. This output device allows one to show a video stream in CACA window. Only one CACA window is allowed per application, so you can have only one instance of this output device in an application. To enable this output device you need to configure FFmpeg with @code{--enable-libcaca}. libcaca is a graphics library that outputs text instead of pixels. For more information about libcaca, check: @url{http://caca.zoy.org/wiki/libcaca} @subsection Options @table @option @item window_title Set the CACA window title, if not specified default to the filename specified for the output device. @item window_size Set the CACA window size, can be a string of the form @var{width}x@var{height} or a video size abbreviation. If not specified it defaults to the size of the input video. @item driver Set display driver. @item algorithm Set dithering algorithm. Dithering is necessary because the picture being rendered has usually far more colours than the available palette. The accepted values are listed with @code{-list_dither algorithms}. @item antialias Set antialias method. Antialiasing smoothens the rendered image and avoids the commonly seen staircase effect. The accepted values are listed with @code{-list_dither antialiases}. @item charset Set which characters are going to be used when rendering text. The accepted values are listed with @code{-list_dither charsets}. @item color Set color to be used when rendering text. The accepted values are listed with @code{-list_dither colors}. @item list_drivers If set to @option{true}, print a list of available drivers and exit. @item list_dither List available dither options related to the argument. The argument must be one of @code{algorithms}, @code{antialiases}, @code{charsets}, @code{colors}. @end table @subsection Examples @itemize @item The following command shows the @command{ffmpeg} output is an CACA window, forcing its size to 80x25: @example ffmpeg -i INPUT -vcodec rawvideo -pix_fmt rgb24 -window_size 80x25 -f caca - @end example @item Show the list of available drivers and exit: @example ffmpeg -i INPUT -pix_fmt rgb24 -f caca -list_drivers true - @end example @item Show the list of available dither colors and exit: @example ffmpeg -i INPUT -pix_fmt rgb24 -f caca -list_dither colors - @end example @end itemize @section decklink The decklink output device provides playback capabilities for Blackmagic DeckLink devices. To enable this output device, you need the Blackmagic DeckLink SDK and you need to configure with the appropriate @code{--extra-cflags} and @code{--extra-ldflags}. On Windows, you need to run the IDL files through @command{widl}. DeckLink is very picky about the formats it supports. Pixel format is always uyvy422, framerate, field order and video size must be determined for your device with @command{-list_formats 1}. Audio sample rate is always 48 kHz. @subsection Options @table @option @item list_devices If set to @option{true}, print a list of devices and exit. Defaults to @option{false}. @item list_formats If set to @option{true}, print a list of supported formats and exit. Defaults to @option{false}. @item preroll Amount of time to preroll video in seconds. Defaults to @option{0.5}. @end table @subsection Examples @itemize @item List output devices: @example ffmpeg -i test.avi -f decklink -list_devices 1 dummy @end example @item List supported formats: @example ffmpeg -i test.avi -f decklink -list_formats 1 'DeckLink Mini Monitor' @end example @item Play video clip: @example ffmpeg -i test.avi -f decklink -pix_fmt uyvy422 'DeckLink Mini Monitor' @end example @item Play video clip with non-standard framerate or video size: @example ffmpeg -i test.avi -f decklink -pix_fmt uyvy422 -s 720x486 -r 24000/1001 'DeckLink Mini Monitor' @end example @end itemize @section libndi_newtek The libndi_newtek output device provides playback capabilities for using NDI (Network Device Interface, standard created by NewTek). Output filename is a NDI name. To enable this output device, you need the NDI SDK and you need to configure with the appropriate @code{--extra-cflags} and @code{--extra-ldflags}. NDI uses uyvy422 pixel format natively, but also supports bgra, bgr0, rgba and rgb0. @subsection Options @table @option @item reference_level The audio reference level in dB. This specifies how many dB above the reference level (+4dBU) is the full range of 16 bit audio. Defaults to @option{0}. @item clock_video These specify whether video "clock" themselves. Defaults to @option{false}. @item clock_audio These specify whether audio "clock" themselves. Defaults to @option{false}. @end table @subsection Examples @itemize @item Play video clip: @example ffmpeg -i "udp://@@239.1.1.1:10480?fifo_size=1000000&overrun_nonfatal=1" -vf "scale=720:576,fps=fps=25,setdar=dar=16/9,format=pix_fmts=uyvy422" -f libndi_newtek NEW_NDI1 @end example @end itemize @section fbdev Linux framebuffer output device. The Linux framebuffer is a graphic hardware-independent abstraction layer to show graphics on a computer monitor, typically on the console. It is accessed through a file device node, usually @file{/dev/fb0}. For more detailed information read the file @file{Documentation/fb/framebuffer.txt} included in the Linux source tree. @subsection Options @table @option @item xoffset @item yoffset Set x/y coordinate of top left corner. Default is 0. @end table @subsection Examples Play a file on framebuffer device @file{/dev/fb0}. Required pixel format depends on current framebuffer settings. @example ffmpeg -re -i INPUT -vcodec rawvideo -pix_fmt bgra -f fbdev /dev/fb0 @end example See also @url{http://linux-fbdev.sourceforge.net/}, and fbset(1). @section opengl OpenGL output device. To enable this output device you need to configure FFmpeg with @code{--enable-opengl}. This output device allows one to render to OpenGL context. Context may be provided by application or default SDL window is created. When device renders to external context, application must implement handlers for following messages: @code{AV_DEV_TO_APP_CREATE_WINDOW_BUFFER} - create OpenGL context on current thread. @code{AV_DEV_TO_APP_PREPARE_WINDOW_BUFFER} - make OpenGL context current. @code{AV_DEV_TO_APP_DISPLAY_WINDOW_BUFFER} - swap buffers. @code{AV_DEV_TO_APP_DESTROY_WINDOW_BUFFER} - destroy OpenGL context. Application is also required to inform a device about current resolution by sending @code{AV_APP_TO_DEV_WINDOW_SIZE} message. @subsection Options @table @option @item background Set background color. Black is a default. @item no_window Disables default SDL window when set to non-zero value. Application must provide OpenGL context and both @code{window_size_cb} and @code{window_swap_buffers_cb} callbacks when set. @item window_title Set the SDL window title, if not specified default to the filename specified for the output device. Ignored when @option{no_window} is set. @item window_size Set preferred window size, can be a string of the form widthxheight or a video size abbreviation. If not specified it defaults to the size of the input video, downscaled according to the aspect ratio. Mostly usable when @option{no_window} is not set. @end table @subsection Examples Play a file on SDL window using OpenGL rendering: @example ffmpeg -i INPUT -f opengl "window title" @end example @section oss OSS (Open Sound System) output device. @section pulse PulseAudio output device. To enable this output device you need to configure FFmpeg with @code{--enable-libpulse}. More information about PulseAudio can be found on @url{http://www.pulseaudio.org} @subsection Options @table @option @item server Connect to a specific PulseAudio server, specified by an IP address. Default server is used when not provided. @item name Specify the application name PulseAudio will use when showing active clients, by default it is the @code{LIBAVFORMAT_IDENT} string. @item stream_name Specify the stream name PulseAudio will use when showing active streams, by default it is set to the specified output name. @item device Specify the device to use. Default device is used when not provided. List of output devices can be obtained with command @command{pactl list sinks}. @item buffer_size @item buffer_duration Control the size and duration of the PulseAudio buffer. A small buffer gives more control, but requires more frequent updates. @option{buffer_size} specifies size in bytes while @option{buffer_duration} specifies duration in milliseconds. When both options are provided then the highest value is used (duration is recalculated to bytes using stream parameters). If they are set to 0 (which is default), the device will use the default PulseAudio duration value. By default PulseAudio set buffer duration to around 2 seconds. @item prebuf Specify pre-buffering size in bytes. The server does not start with playback before at least @option{prebuf} bytes are available in the buffer. By default this option is initialized to the same value as @option{buffer_size} or @option{buffer_duration} (whichever is bigger). @item minreq Specify minimum request size in bytes. The server does not request less than @option{minreq} bytes from the client, instead waits until the buffer is free enough to request more bytes at once. It is recommended to not set this option, which will initialize this to a value that is deemed sensible by the server. @end table @subsection Examples Play a file on default device on default server: @example ffmpeg -i INPUT -f pulse "stream name" @end example @section sdl SDL (Simple DirectMedia Layer) output device. This output device allows one to show a video stream in an SDL window. Only one SDL window is allowed per application, so you can have only one instance of this output device in an application. To enable this output device you need libsdl installed on your system when configuring your build. For more information about SDL, check: @url{http://www.libsdl.org/} @subsection Options @table @option @item window_title Set the SDL window title, if not specified default to the filename specified for the output device. @item icon_title Set the name of the iconified SDL window, if not specified it is set to the same value of @var{window_title}. @item window_size Set the SDL window size, can be a string of the form @var{width}x@var{height} or a video size abbreviation. If not specified it defaults to the size of the input video, downscaled according to the aspect ratio. @item window_fullscreen Set fullscreen mode when non-zero value is provided. Default value is zero. @end table @subsection Interactive commands The window created by the device can be controlled through the following interactive commands. @table @key @item q, ESC Quit the device immediately. @end table @subsection Examples The following command shows the @command{ffmpeg} output is an SDL window, forcing its size to the qcif format: @example ffmpeg -i INPUT -vcodec rawvideo -pix_fmt yuv420p -window_size qcif -f sdl "SDL output" @end example @section sndio sndio audio output device. @section xv XV (XVideo) output device. This output device allows one to show a video stream in a X Window System window. @subsection Options @table @option @item display_name Specify the hardware display name, which determines the display and communications domain to be used. The display name or DISPLAY environment variable can be a string in the format @var{hostname}[:@var{number}[.@var{screen_number}]]. @var{hostname} specifies the name of the host machine on which the display is physically attached. @var{number} specifies the number of the display server on that host machine. @var{screen_number} specifies the screen to be used on that server. If unspecified, it defaults to the value of the DISPLAY environment variable. For example, @code{dual-headed:0.1} would specify screen 1 of display 0 on the machine named ``dual-headed''. Check the X11 specification for more detailed information about the display name format. @item window_id When set to non-zero value then device doesn't create new window, but uses existing one with provided @var{window_id}. By default this options is set to zero and device creates its own window. @item window_size Set the created window size, can be a string of the form @var{width}x@var{height} or a video size abbreviation. If not specified it defaults to the size of the input video. Ignored when @var{window_id} is set. @item window_x @item window_y Set the X and Y window offsets for the created window. They are both set to 0 by default. The values may be ignored by the window manager. Ignored when @var{window_id} is set. @item window_title Set the window title, if not specified default to the filename specified for the output device. Ignored when @var{window_id} is set. @end table For more information about XVideo see @url{http://www.x.org/}. @subsection Examples @itemize @item Decode, display and encode video input with @command{ffmpeg} at the same time: @example ffmpeg -i INPUT OUTPUT -f xv display @end example @item Decode and display the input video to multiple X11 windows: @example ffmpeg -i INPUT -f xv normal -vf negate -f xv negated @end example @end itemize @c man end OUTPUT DEVICES