3. Types and flags used to represent the media graph elements

Media entity functions

MEDIA_ENT_F_UNKNOWN and MEDIA_ENT_F_V4L2_SUBDEV_UNKNOWN	Unknown entity. That generally indicates that a driver didn’t initialize properly the entity, which is a Kernel bug
MEDIA_ENT_F_IO_V4L	Data streaming input and/or output entity.
MEDIA_ENT_F_IO_VBI	V4L VBI streaming input or output entity
MEDIA_ENT_F_IO_SWRADIO	V4L Software Digital Radio (SDR) streaming input or output entity
MEDIA_ENT_F_IO_DTV	DVB Digital TV streaming input or output entity
MEDIA_ENT_F_DTV_DEMOD	Digital TV demodulator entity.
MEDIA_ENT_F_TS_DEMUX	MPEG Transport stream demux entity. Could be implemented on hardware or in Kernelspace by the Linux DVB subsystem.
MEDIA_ENT_F_DTV_CA	Digital TV Conditional Access module (CAM) entity
MEDIA_ENT_F_DTV_NET_DECAP	Digital TV network ULE/MLE desencapsulation entity. Could be implemented on hardware or in Kernelspace
MEDIA_ENT_F_CONN_RF	Connector for a Radio Frequency (RF) signal.
MEDIA_ENT_F_CONN_SVIDEO	Connector for a S-Video signal.
MEDIA_ENT_F_CONN_COMPOSITE	Connector for a RGB composite signal.
MEDIA_ENT_F_CAM_SENSOR	Camera video sensor entity.
MEDIA_ENT_F_FLASH	Flash controller entity.
MEDIA_ENT_F_LENS	Lens controller entity.
MEDIA_ENT_F_ATV_DECODER	Analog video decoder, the basic function of the video decoder is to accept analogue video from a wide variety of sources such as broadcast, DVD players, cameras and video cassette recorders, in either NTSC, PAL, SECAM or HD format, separating the stream into its component parts, luminance and chrominance, and output it in some digital video standard, with appropriate timing signals.
MEDIA_ENT_F_TUNER	Digital TV, analog TV, radio and/or software radio tuner, with consists on a PLL tuning stage that converts radio frequency (RF) signal into an Intermediate Frequency (IF). Modern tuners have internally IF-PLL decoders for audio and video, but older models have those stages implemented on separate entities.
MEDIA_ENT_F_IF_VID_DECODER	IF-PLL video decoder. It receives the IF from a PLL and decodes the analog TV video signal. This is commonly found on some very old analog tuners, like Philips MK3 designs. They all contain a tda9887 (or some software compatible similar chip, like tda9885). Those devices use a different I2C address than the tuner PLL.
MEDIA_ENT_F_IF_AUD_DECODER	IF-PLL sound decoder. It receives the IF from a PLL and decodes the analog TV audio signal. This is commonly found on some very old analog hardware, like Micronas msp3400, Philips tda9840, tda985x, etc. Those devices use a different I2C address than the tuner PLL and should be controlled together with the IF-PLL video decoder.
MEDIA_ENT_F_AUDIO_CAPTURE	Audio Capture Function Entity.
MEDIA_ENT_F_AUDIO_PLAYBACK	Audio Playback Function Entity.
MEDIA_ENT_F_AUDIO_MIXER	Audio Mixer Function Entity.
MEDIA_ENT_F_PROC_VIDEO_COMPOSER	Video composer (blender). An entity capable of video composing must have at least two sink pads and one source pad, and composes input video frames onto output video frames. Composition can be performed using alpha blending, color keying, raster operations (ROP), stitching or any other means.
MEDIA_ENT_F_PROC_VIDEO_PIXEL_FORMATTER	Video pixel formatter. An entity capable of pixel formatting must have at least one sink pad and one source pad. Read pixel formatters read pixels from memory and perform a subset of unpacking, cropping, color keying, alpha multiplication and pixel encoding conversion. Write pixel formatters perform a subset of dithering, pixel encoding conversion and packing and write pixels to memory.
MEDIA_ENT_F_PROC_VIDEO_PIXEL_ENC_CONV	Video pixel encoding converter. An entity capable of pixel encoding conversion must have at least one sink pad and one source pad, and convert the encoding of pixels received on its sink pad(s) to a different encoding output on its source pad(s). Pixel encoding conversion includes but isn’t limited to RGB to/from HSV, RGB to/from YUV and CFA (Bayer) to RGB conversions.
MEDIA_ENT_F_PROC_VIDEO_LUT	Video look-up table. An entity capable of video lookup table processing must have one sink pad and one source pad. It uses the values of the pixels received on its sink pad to look up entries in internal tables and output them on its source pad. The lookup processing can be performed on all components separately or combine them for multi-dimensional table lookups.
MEDIA_ENT_F_PROC_VIDEO_SCALER	Video scaler. An entity capable of video scaling must have at least one sink pad and one source pad, and scale the video frame(s) received on its sink pad(s) to a different resolution output on its source pad(s). The range of supported scaling ratios is entity-specific and can differ between the horizontal and vertical directions (in particular scaling can be supported in one direction only). Binning and sub-sampling (occasionally also referred to as skipping) are considered as scaling.
MEDIA_ENT_F_PROC_VIDEO_STATISTICS	Video statistics computation (histogram, 3A, etc.). An entity capable of statistics computation must have one sink pad and one source pad. It computes statistics over the frames received on its sink pad and outputs the statistics data on its source pad.
MEDIA_ENT_F_PROC_VIDEO_ENCODER	Video (MPEG, HEVC, VPx, etc.) encoder. An entity capable of compressing video frames. Must have one sink pad and at least one source pad.
MEDIA_ENT_F_PROC_VIDEO_DECODER	Video (MPEG, HEVC, VPx, etc.) decoder. An entity capable of decompressing a compressed video stream into uncompressed video frames. Must have one sink pad and at least one source pad.
MEDIA_ENT_F_PROC_VIDEO_ISP	An Image Signal Processor (ISP) device. ISPs generally are one of a kind devices that have their specific control interfaces using a combination of custom V4L2 controls and IOCTLs, and parameters supplied in a metadata buffer.
MEDIA_ENT_F_VID_MUX	Video multiplexer. An entity capable of multiplexing must have at least two sink pads and one source pad, and must pass the video frame(s) received from the active sink pad to the source pad.
MEDIA_ENT_F_VID_IF_BRIDGE	Video interface bridge. A video interface bridge entity must have at least one sink pad and at least one source pad. It receives video frames on its sink pad from an input video bus of one type (HDMI, eDP, MIPI CSI-2, etc.), and outputs them on its source pad to an output video bus of another type (eDP, MIPI CSI-2, parallel, etc.).
MEDIA_ENT_F_DV_DECODER	Digital video decoder. The basic function of the video decoder is to accept digital video from a wide variety of sources and output it in some digital video standard, with appropriate timing signals.
MEDIA_ENT_F_DV_ENCODER	Digital video encoder. The basic function of the video encoder is to accept digital video from some digital video standard with appropriate timing signals (usually a parallel video bus with sync signals) and output this to a digital video output connector such as HDMI or DisplayPort.

Media entity flags

MEDIA_ENT_FL_DEFAULT	Default entity for its type. Used to discover the default audio, VBI and video devices, the default camera sensor, etc.
MEDIA_ENT_FL_CONNECTOR	The entity represents a connector.

Media interface types

MEDIA_INTF_T_DVB_FE	Device node interface for the Digital TV frontend	typically, /dev/dvb/adapter?/frontend?
MEDIA_INTF_T_DVB_DEMUX	Device node interface for the Digital TV demux	typically, /dev/dvb/adapter?/demux?
MEDIA_INTF_T_DVB_DVR	Device node interface for the Digital TV DVR	typically, /dev/dvb/adapter?/dvr?
MEDIA_INTF_T_DVB_CA	Device node interface for the Digital TV Conditional Access	typically, /dev/dvb/adapter?/ca?
MEDIA_INTF_T_DVB_NET	Device node interface for the Digital TV network control	typically, /dev/dvb/adapter?/net?
MEDIA_INTF_T_V4L_VIDEO	Device node interface for video (V4L)	typically, /dev/video?
MEDIA_INTF_T_V4L_VBI	Device node interface for VBI (V4L)	typically, /dev/vbi?
MEDIA_INTF_T_V4L_RADIO	Device node interface for radio (V4L)	typically, /dev/radio?
MEDIA_INTF_T_V4L_SUBDEV	Device node interface for a V4L subdevice	typically, /dev/v4l-subdev?
MEDIA_INTF_T_V4L_SWRADIO	Device node interface for Software Defined Radio (V4L)	typically, /dev/swradio?
MEDIA_INTF_T_V4L_TOUCH	Device node interface for Touch device (V4L)	typically, /dev/v4l-touch?
MEDIA_INTF_T_ALSA_PCM_CAPTURE	Device node interface for ALSA PCM Capture	typically, /dev/snd/pcmC?D?c
MEDIA_INTF_T_ALSA_PCM_PLAYBACK	Device node interface for ALSA PCM Playback	typically, /dev/snd/pcmC?D?p
MEDIA_INTF_T_ALSA_CONTROL	Device node interface for ALSA Control	typically, /dev/snd/controlC?
MEDIA_INTF_T_ALSA_COMPRESS	Device node interface for ALSA Compress	typically, /dev/snd/compr?
MEDIA_INTF_T_ALSA_RAWMIDI	Device node interface for ALSA Raw MIDI	typically, /dev/snd/midi?
MEDIA_INTF_T_ALSA_HWDEP	Device node interface for ALSA Hardware Dependent	typically, /dev/snd/hwC?D?
MEDIA_INTF_T_ALSA_SEQUENCER	Device node interface for ALSA Sequencer	typically, /dev/snd/seq
MEDIA_INTF_T_ALSA_TIMER	Device node interface for ALSA Timer	typically, /dev/snd/timer

Media pad flags

MEDIA_PAD_FL_SINK	Input pad, relative to the entity. Input pads sink data and are targets of links.
MEDIA_PAD_FL_SOURCE	Output pad, relative to the entity. Output pads source data and are origins of links.
MEDIA_PAD_FL_MUST_CONNECT	If this flag is set, then for this pad to be able to stream, it must be connected by at least one enabled link. There could be temporary reasons (e.g. device configuration dependent) for the pad to need enabled links even when this flag isn’t set; the absence of the flag doesn’t imply there is none.

One and only one of MEDIA_PAD_FL_SINK and MEDIA_PAD_FL_SOURCE must be set for every pad.

Media link flags

MEDIA_LNK_FL_ENABLED	The link is enabled and can be used to transfer media data. When two or more links target a sink pad, only one of them can be enabled at a time.
MEDIA_LNK_FL_IMMUTABLE	The link enabled state can’t be modified at runtime. An immutable link is always enabled.
MEDIA_LNK_FL_DYNAMIC	The link enabled state can be modified during streaming. This flag is set by drivers and is read-only for applications.
MEDIA_LNK_FL_LINK_TYPE	This is a bitmask that defines the type of the link. The following link types are currently supported: MEDIA_LNK_FL_DATA_LINK for links that represent a data connection between two pads. MEDIA_LNK_FL_INTERFACE_LINK for links that associate an entity to its interface. MEDIA_LNK_FL_ANCILLARY_LINK for links that represent a physical relationship between two entities. The link may or may not be immutable, so applications must not assume either case.