The Media Kit: Constants and Defined Types

This section describes the constants and defined types that make the Media Kit tick.

Constants

Codec Type Info

Constant	Description
`B_CODEC_TYPE_INFO`	Data is in codec type info format.

The B_CODEC_TYPE_INFO constant is used to indicate that data is a codec info structure; it's used in the user_data_type field in the media_format structure, for example.

Data Endianness

Declared in: be/media/MediaDefs.h

Constant	Description
`B_MEDIA_BIG_ENDIAN`	The media data is big-endian
`B_MEDIA_LITTLE_ENDIAN`	The media data is little-endian.

These values indicate whether media data is little-endian or big-endian.

Media Message Size

Declared in: <be/media/MediaDefs.h>

   const size_t B_MEDIA_MESSAGE_SIZE = 16384;

The B_MEDIA_MESSAGE_SIZE constant specifies the maximum possible size a message a node's service thread can receive. 16k is an upper limit and won't be exceeded. Your thread can simply create a buffer this large, read_port() into it, and call HandleMessage() to process it.

media_flags

Declared in: be/media/MediaDefs.h

Constant	Description
`B_MEDIA_FLAGS_VERSION`	Returns the Media Kit version as an int32 value.

The media_flags indicate values you can pass to BMediaRoster::MediaFlags() to get information about the version of the Media Kit that your application is running under.

media_format_family

Declared in: be/media/MediaDefs.h

Constant	Meaning
`B_ANY_FORMAT_FAMILY`	Any family.
`B_BEOS_FORMAT_FAMILY`	BeOS format.
`B_QUICKTIME_FORMAT_FAMILY`	QuickTime format.
`B_AVI_FORMAT_FAMILY`	AVI format.
`B_ASF_FORMAT_FAMILY`	ASF format.
`B_MPEG_FORMAT_FAMILY`	MPEG format.
`B_WAV_FORMAT_FAMILY`	WAVE format audio.
`B_AIFF_FORMAT_FAMILY`	AIFF format audio.
`B_MISC_FORMAT_FAMILY`	Miscellaneous.

These constants indicate the media format families the BMediaFormats class can map among.

media_producer_status

Declared in: <be/media/MediaDefs.h>

Constant	Description
`B_DATA_NOT_AVAILABLE`	There aren't any buffers ready for the destination.
`B_DATA_AVAILABLE`	There are buffers ready for the destination.
`B_PRODUCER_STOPPED`	The producer isn't running.

These values can be specified when your producer node calls BBufferProducer::SendDataStatus() to tell the consumers it's feeding whether or not data is available for it to process. The B_PRODUCER_STOPPED code is sent to indicate to downstream consumers that it's no longer running.

Consumers receive these values in the BBufferConsumer::ProducerDataStatus() hook function.

media_realtime_flags

Declared in: be/media/MediaDefs.h

Constant	Description
`B_MEDIA_REALTIME_ALLOCATOR`	When set, rtm_alloc() will return locked memory.
`B_MEDIA_REALTIME_AUDIO`	Audio add-ons in the Media Server are locked in memory, and should lock their thread stacks using `media_init_realtime_thread()`.
`B_MEDIA_REALTIME_VIDEO`	Video add-ons are locked in memory, and should lock their thread stacks using `media_init_realtime_thread()`.
`B_MEDIA_REALTIME_ANYKIND`	All Media add-ons are locked in memory, and should lock their thread stacks using `media_init_realtime_thread()`.

These values are passed to realtime allocator functions to indicate what types of nodes should use locked memory.

media_type

Declared in: be/media/MediaNode.h

Constant	Description
`B_MEDIA_NO_TYPE`	Typeless media data.
`B_MEDIA_UNKNOWN_TYPE`	Unknown media type.
`B_MEDIA_RAW_AUDIO`	Uncompressed, linear audio.
`B_MEDIA_RAW_VIDEO`	Uncompressed, linear video.
`B_MEDIA_VBL`	Raw data from VBL area.
`B_MEDIA_TIMECODE`	Timecode data. Undetermined format.
`B_MEDIA_MIDI`	MIDI.
`B_MEDIA_TEXT`	Text data; typically closed-captioning information.
`B_MEDIA_HTML`	HTML data.
`B_MEDIA_MULTISTREAM`	Multi-stream media data, such as AVI or QuickTime.
`B_MEDIA_PARAMETERS`	BControllable change data.
`B_MEDIA_ENCODED_AUDIO`	Encoded audio (such as AC3 or DTS).
`B_MEDIA_ENCODED_VIDEO`	Encoded video (such as Indeo or MPEG).
`B_MEDIA_PRIVATE`	Base value for private Be media types.
`B_MEDIA_FIRST_USER_TYPE`	Base value for user-defined media types.

Types of media data.

node_kind

Declared in: be/media/MediaNode.h

Constant	Description
`B_BUFFER_PRODUCER`	The flavor implements BBufferProducer.
`B_BUFFER_CONSUMER`	The flavor implements BBufferConsumer.
`B_TIME_SOURCE`	The flavor implements BTimeSource.
`B_CONTROLLABLE`	The flavor implements BControllable.
`B_FILE_INTERFACE`	The flavor implements BFileInterface.
`B_ENTITY_INTERFACE`	The flavor implements BEntityInterface (not available for R4).
`B_PHYSICAL_INPUT`	The flavor represents a physical input point (such as an input jack).
`B_PHYSICAL_OUTPUT`	The flavor represents a physical output point (such as line output).
`B_SYSTEM_MIXER`	The flavor represents the system mixer.

Defines the type or types of node that a particular flavor supports. Note that a flavor can implement more than one type of node, so you can combine these values using a bitwise or.

video_orientation

Declared in: be/media/MediaNode.h

Constant	Description
`B_VIDEO_TOP_LEFT_RIGHT`	Typical progressive scan: top to bottom, left to right.
`B_VIDEO_BOTTOM_LEFT_RIGHT`	Bottom to top, left to right (BMP and TGA graphics are oriented this way).

Indicates the orientation of video data (whether the data is oriented top to bottom or bottom to top).

Defined Types

live_node_info

Declared in: be/media/MediaDefs.h

struct live_node_info {
      live_node_info();
      ~live_node_info();
      media_node node;
      BPoint hint_point;
      char name[B_MEDIA_NAME_LENGTH];
      private:
      reserved[160];
      };

The live_node_info structure describes an active node, and is returned by BMediaRoster::GetLiveNodes().

node specifies which node the live_node_info structure describes.
hint_point is reserved for future use. Pass a BPoint with x and y both set to 0.

media_addon_id

Declared in: be/media/MediaDefs.h

typdef int32 media_addon_id;

A media add-on ID number.

media_audio_header

Declared in: be/media/MediaDefs.h

struct media_audio_header {
int32 _reserved_[16];
};

Defines the header of an audio buffer. There are no Be-defined fields in this structure as of the release of BeOS R4; however, you may append fields to the end of this structure if you wish.

media_buffer_id

Declared in: be/media/MediaDefs.h

typdef int32 media_buffer_id;

A media buffer ID number.

media_destination

Declared in: be/media/MediaDefs.h

struct media_destination {
      media_destination(port_id, int32);
      media_destination(const media_destination &clone);
      media_destination & operator= (const media_destination &clone);
      media_destination();
      ~media_destination();
      port_id port;
      int32 id;
      static media_destination null;
      private:
         uint32 _reserved_media_destination_[2];
      };

Describes the destination end of a media connection between two nodes. The port indicates the port ID on which the destination communicates. This can be different from the media_node.port value.

media_encoded_audio_format

Declared in: be/media/MediaDefs.h

struct media_encoded_audio_format {
      enum audio_encoding {
         B_ANY,
      };
      media_raw_audio_format output;
      audio_encoding encoding;
      float bit_rate;
      size_t frame_size;
      static media_encoded_audio_format wildcard;
      };

Describes the format of encoded audio data.

output indicates the raw audio format that results from decoding the encoded audio.
encoding specifies the encoding format. This should just be B_ANY; this field, and the audio_encoding enum, are depreciated. Instead, the BMediaFormats database should be used to identify the encoding format.
bit_rate specifies the bit rate (not byte rate) of the data stream.
frame_size indicates the size of each frame of audio, in bytes.

media_encoded_audio_header

Declared in: be/media/MediaDefs.h

struct media_encoded_audio_header {
      int32 _reserved_0[14];
      uint32 buffer_flags;
      uchar unused_mask;
      uchar _reserved_2[3];
      };

Defines the header of a an encoded audio buffer.

buffer_flags contains flags that provide additional information about the buffer. The only value currently defined (other than 0) is B_MEDIA_KEY_FRAME, which indicates that the buffer is a key frame.
unused_mask indicates which bits of the last byte in the buffer are unused (since encoded audio may result in a number of bits that doesn't fill up the last byte in the buffer).

If you wish, you can add more fields to the end of the header.

media_encoded_video_format

Declared in: be/media/MediaDefs.h

struct media_encoded_video_format {
      enum video_encoding {
         B_ANY
      };
      media_raw_video_format output;
      float avg_bit_rate;
      float max_bit_rate;
      video_encoding encoding;
      size_t frame_size;
      int16 forward_history;
      int16 backward_history;
      static media_encoded_video_format wildcard;
      };

Describes the format of encoded video data.

output specifies the raw video format that results from decoding the video. Set this to media_raw_video_format::wildcard.
avg_bit_rate indicates the average bit rate of the video, and max_bit_rate specifies the maximum bit rate that occurs at any point in the video.
encoding has been depreciated, and should always be B_ANY; use the BMediaFormats lookup database to identify the encoding format.
frame_size indicates the size in bytes of a frame of data.
forward_history indicates the maximum number of future frames the encoding algorithm requires in order to decode the current frame.
backward_history indicates the maximum number of past frames the encoding algorithm requires in order to decode the current frame.

media_encoded_video_header

Declared in: be/media/MediaDefs.h

struct first_active_line {
      uint32 first_active_line[9];
      uint32 first_active_line;
      int16 first_active_line;
      int16 first_active_line;
      uchar first_active_line;
      uchar first_active_line[3];
      float first_active_line;
      uint32 first_active_line;
      uint16 first_active_line;
      uint16 first_active_line;
      uint16 first_active_line;
      uint32 first_active_line;
      uint32 line_count;
      };

Defines the header of a video buffer. The fields in this buffer are the same as those in the media_video_header structure, except for the reserved fields, the forward_history and backward_history fields, the unused_mask, which indicates which bits are unused in the last byte of the video buffer, and field_flags, which can be either 0 or B_MEDIA_KEY_FRAME (which indicates that the field is a key frame).

The forward_history field indicates how many buffers ahead of the current one are required in order to decode the current buffer. The backward_history field indicates the number of previous buffers are required to decode the current buffer.

You may add fields to the end of this buffer if your video format requires them.

media_file_format

Declared in: be/media/MediaDefs.h

struct media_file_format {
      enum {
         B_READABLE = 0x1,
         B_WRITABLE = 0x2,
         B_PERFECTLY_SEEKABLE = 0x4,
         B_IMPERFECTLY_SEEKABLE = 0x8,
         B_KNOWS_RAW_VIDEO = 0x10,
         B_KNOWS_RAW_AUDIO = 0x20,
         B_KNOWS_MIDI = 0x40,
         B_KNOWS_ENCODED_VIDEO = 0x80,
         B_KNOWS_ENCODED_AUDIO = 0x100,
         B_KNOWS_OTHER = 0x1000000,
         B_KNOWS_ANYTHING = 0x2000000
      };
      uint32 capabilities;
      media_file_format_id id;
      media_format_family family;
      int32 version;

      uint32 _reserved_[25];
      char mime_type[64];
      char pretty_name[64];
      char short_name[32];
      char file_extension[8];
      char reserved[88];
      };

Describes a media file format.

capabilities is a bitfield providing informational flags describing the file format's capabilities.
B_READABLE indicates that the file format is readable.
id is an opaque ID used by the Media Kit to construct a BMediaFile object.
family is one of the media_format_family constants.
version should be 100.
mime_type specifies the MIME type string that identifies the file format.
pretty_name is a nice user-viewable name, such as "QuickTime File Format".
short_name is a short-form name, like "QuickTime".
file_extension specifies the file extension used on files containing this format, such as ".mov".

media_file_format_id

Declared in: be/media/MediaDefs.h

struct media_file_format_id {
      ino_t node;
      dev_t device;
      uint32 internal_id;
      };

A simple means for identifying file formats; used by the media_file_format structure.

media_format

Declared in: be/media/MediaDefs.h

   struct media_format {
      media_type type;
      type_code user_data_type;
      uchar user_data[64];
   
      private:
   
      void *meta_data;
      int32 meta_data_size;
      area_id meta_data_area;
      area_id use_area;
      team_id team;
      void *thisPtr;
   
      public:
   
      union {
         media_raw_audio_format raw_audio;
         media_raw_video_format raw_video;
         media_multistream_format multistream;
         media_encoded_audio_format encoded_audio;
         media_encoded_video_format encoded_video;
         char _reserved_[96];
      } u;
   
      bool IsVideo();
      uint32 &Width();
      uint32 &Height();
      color_space &ColorSpace();
   
      bool IsAudio();
      uint32 &AudioFormat();
   
      bool Matches(media_format *otherFormat);
      void SpecializeTo(media_format *otherFormat);
   
      void SetMetaData(void *data, int32 size);
      void *MetaData() const;
      int32 MetaDataSize() const;
   
      media_format();
      media_format(const media_format &other);
      ~media_format();
      media_format & operator=(const media_format &clone);
   };

The media_format structure can describe any media data format the BeOS can support.

type indicates the type of media the format describes.
user_data_type and user_data allow the application to store custom data in the media_format structure; user_data_type specifies the type of data stored in user_data (B_INT32_TYPE, B_STRING_TYPE, etc).
meta_data, meta_data_size, meta_data_area, use_area, team, and thisPtr are currently only used by decoders when communicating with the file reader; they're not currently for public use.
The union, u, permits the selection of a specific media format, such as raw audio or multistream data, and contains the descriptive information specific to that media format.

If any field is 0, it's treated as a wildcard.

There are several convenience functions for fetching information from the format that take care of dealing with different types automatically:

IsVideo() returns true if the format represents video (either raw or encoded), otherwise it returns false.
Width() returns the width of the video data; its value is undetermined if the format doesn't represent video.
Height() returns the height of the video data; its value is undetermined if the format doesn't represent video.
ColorSpace() returns the video's color space. Its value is undetermined if the format doesn't represent video.
IsAudio() returns true if the format represents audio (either raw or encoded), otherwise it returns false.
AudioFormat() returns the audio's sample format.
Matches() returns true if the format matches the specified otherFormat, otherwise it returns false.
SpecializeTo() adjusts the specified otherFormat as needed to match the format.

media_header

Declared in: be/media/MediaDefs.h

struct media_header {
      media_type type;
      media_buffer_id buffer;
      int32 destination;
      media_node_id time_source;
      uint32 _depreciated_       uint32 size_used;
      bigtime_t start_time;
      area_id owner;
      enum {
         B_SEEK_TAG = 'TRST'
      };
      type_code user_data_type;
      uchar user_data[64];
      uint32 _reserved_[2];
      off_t file_pos;
      size_t orig_size;
      uint32 data_offset;
      union {
         media_audio_header raw_audio;
         media_video_header raw_video;
         media_multistream_header multistream;
         media_encoded_audio_header encoded_audio;
         media_encoded_video_header encoded_video;
         char _reserved_[64];
      } u;
      };

Defines the header of a media data buffer.

type indicates the type of media the format describes.
buffer indicates what buffer the header goes with. This field is filled out by the BBufferProducer::SendBuffer() function.
destination specifies the ID number of the media_destination to which the buffer is being sent. This field is filled out by the BBufferProducer::SendBuffer() function.
time_source indicates the ID number of the node that encoded the start_time.
size_used specifies how many bytes of the buffer actually contain data.
start_time indicates the performance time at which the buffer should be performed.
owner specifies the area ID of the buffer's owner.
user_data_type and user_data allow the application to store custom data in the media_format structure; user_data_type specifies the type of data stored in user_data (B_INT32_TYPE, B_STRING_TYPE, etc). The B_SEEK_TAG constant indicates that the user_data contains a seek tag.
file_pos indicates where in the corresponding file the data came from, and orig_size indicates how big it was; if the data didn't come from a file, these should be zero.
data_offset indicates the offset within the buffer to the data. This is reflected by the BBuffer::Data() function.
The union, u, permits the selection of a specific media format, such as raw audio or multistream data, and contains the descriptive information specific to that media format.

media_input

Declared in: be/media/MediaDefs.h

struct media_input {
      media_input();
      ~media_input();
      media_node node;
      media_source source;
      media_destination destination;
      media_format format;
      char name[B_MEDIA_NAME_LENGTH];
      private:
      _reserved_media_input_[4];
      };

The media_input structure describes a complete connection between a media_source and media_destination, from the point-of-view of the consumer (the destination).

node is the media_node that owns the input.
source is the source socket from which the data is being sent.
destination is the destination socket at which the data is arriving.
format is the format of the data.
name is the input's name.

media_multistream_format

Declared in: be/media/MediaDefs.h

struct media_multistream_format {
      enum {         B_ANY = 0,
         B_VID = 1,
         B_AVI,
         B_MPEG1,
         B_MPEG2,
         B_QUICKTIME,
         B_PRIVATE = 90000,
         B_FIRST_USER_TYPE = 100000
      };
      float avg_bit_rate;
      float max_bit_rate;
      uint32 avg_chunk_size;
      uint32 max_chunk_size;
      enum {
         B_HEADER_HAS_FLAGS = 0x1,
         B_CLEAN_BUFFERS = 0x2,
         B_HOMOGENOUS_BUFFERS = 0x4
      };
      uint32 flags;
      int32 format;
      uint32 _reserved_[2];
      struct vid_info {
         float frame_rate;
         uint16 width;
         uint16 height;
         color_space space;
         float sampling_rate;
         uint32 sample_format;
         uint16 byte_order;
         uint16 channel_count;
      };
      struct avi_info {
         uint32 us_per_frame;
         uint16 width;
         uint16 height;
         uint16 _reserved_;
         uint16 type_count;
         media_type types[5];
      };
      union {
         vid_info vid;
         avi_info avi;
      } u;
      static media_multistream_format wildcard;
      };

Describes the format of multistream media data, such as a QuickTime, AVI, or MPEG movie.

avg_bit_rate and max_bit_rate indicate the average and maximum bit rates of the media data.
avg_chunk_size and max_chunk_size indicate the average and maximum buffer sizes; if all buffers are the same size, these two values should be equal.
flags provides informational flags for the buffers. B_HEADER_HAS_FLAGS indicates that the buffers' headers have valid flags; B_CLEAN_BUFFERS indicates that each buffer represents an integral number of frames, and B_HOMOGENOUS_BUFFERS indicates that each buffer has only one format in it.
format indicates the multistream data format (B_AVI, B_QUICKTIME, etc).
The union u contains either a vid_info or an avi_info structure that describes the video stream:

vid_info

frame_rate specifies the video frame rate (in frames per second).

avi_info

us_per_frame specifies the number of microseconds each frame should be displayed.

media_multistream_header

Declared in: be/media/MediaDefs.h

struct media_multistream_header {
      uint32 _reserved_[14];
      uchar unused_mask;
      uchar _reserved_2[3];
      enum {
         B_MASTER_HEADER = 0x1,
         B_SUBSTREAM_HEADER = 0x2,
         B_COMPLETE_BUFFER = 0x4
      };
      uint32 flags;
      };

Defines the header of a multistream media buffer.

unused_mask indicates which bits of the last byte in the buffer are unused.
flags provides informational flags about the buffer. If B_MASTER_HEADER is specified, master stream header data is in the buffer; B_SUBSTREAM_HEADER indicates that the buffer contains substream header information. B_COMPLETE_BUFFER indicates that the buffer's data represents an integral number of frames.

You may add fields to the end of this structure if your multistream media format requires them.

media_node

Declared in: <be/media/MediaDefs.h>

class media_node {
      public:
      media_node();
      ~media_node();
      media_node_id node;
      port_id port;
      uint32 kind;
      static media_node null;
      private:
      uint32 _reserved_[3];
      };

The media_node structure is the class that defines a node to client applications; interactions with the BMediaRoster regarding nodes is done using media_node objects.

node indicates the node's ID number.
port specifies the port ID number of the node's control port.
kind specifies the node's media kind. See node_kind for a list of node kinds.
null represents a null node

Applications will usually treat this as a black box.

media_node_attribute

Declared in: be/media/MediaNode.h

struct media_node_attribute {
         enum {
            B_R40_COMPILED = 1,
            B_USER_ATTRIBUTE_NAME = 0x1000000,
            B_FIRST_USER_ATTRIBUTE          };
         uint32 what;
         uint32 flags;
         uint64 data;
      };

The media_node_attribute structure provides additional information about nodes. Nodes can have as many of these as they want, and will return them from their BMediaNode::GetNodeAttributes() function. Applications query the node using the BMediaRoster::GetNodeAttributesFor() function.

The what field indicates the attribute type. B_R40_COMPILED indicates that the node was compiled using BeOS Release 4.0; BMediaNode returns this attribute automatically for nodes that were compiled using the Release 4.0 headers. Nodes may create their own attribute types, beginning at B_FIRST_USER_ATTRIBUTE.

The B_USER_ATTRIBUTE_NAME attribute specifies the name of a protocol for the user attributes implemented by the node. For example, if you devise a third-party standard for attribute values whose attribute IDs are greater than B_FIRST_USER_ATTRIBUTE, the value of B_USER_ATTRIBUTE_NAME would be the name of the standard.

The flags and data fields are used for different things depending on the what value; the B_R40_COMPILED attribute doesn't use them.

media_node_id

Declared in: be/media/MediaDefs.h

typdef int32 media_node_id;

A node ID number.

media_output

Declared in: be/media/MediaDefs.h

struct media_output {
      media_output();
      ~media_output();
      media_node node;
      media_source source;
      media_destination destination;
      media_format format;
      char name[B_MEDIA_NAME_LENGTH];

      private:
      _reserved_media_output_[4];
      };

The media_output structure describes a complete connection between a media_source and media_destination, from the point-of-view of the consumer (the destination).

node is the media_node that owns the output.
source is the source socket from which the data is being sent.
destination is the destination socket to which the data is being sent.
format is the format of the data.
name is the output's name.

media_raw_audio_format

Declared in: be/media/MediaDefs.h

struct media_raw_audio_format {
      enum {
         B_AUDIO_UCHAR = 0x11,
         B_AUDIO_SHORT = 0x2,
         B_AUDIO_FLOAT = 0x24,
         B_AUDIO_INT = 0x4
      }
      float frame_rate;
      uint32 channel_count;
      uint32 format;
      uint32 byte_order;
      size_t buffer_size;

      static media_raw_audio_format wildcard;
      };

Describes the format of raw audio data.

The frame_rate indicates the frame rate, in Hertz. One frame is one sample per channel (stereo buffers contain two samples per channel). For audio, each buffer contains multiple audio samples, whereas video contains one frame, or one field (half-frame) per buffer.

The channel_count indicates the number of channels of audio (typically this is either 1 for mono or 2 for stereo).

The format specifies the sample format (for compressed formats, see media_encoded_audio_format):

B_AUDIO_UCHAR. Each sample is one byte; 128 is the midpoint, 1 is the bottom, 255 is the top.
B_AUDIO_SHORT. Each sample is two bytes; 0 is the middle, -32767 is the bottom, 32767 is the top.
B_AUDIO_FLOAT. Each sample is four bytes; 0 is the middle, -1.0 is the bottom, 1.0 is the top.
B_AUDIO_INT. Each sample is four bytes; 0 is the middle, 0x80000001 is the bottom, 0x7FFFFFFF is the top.

The byte_order indicates the endianness of the data (either B_MEDIA_BIG_ENDIAN or B_MEDIA_LITTLE_ENDIAN).

buffer_size indicates the size of each buffer.

media_raw_video_format

Declared in: be/media/MediaDefs.h

struct media_raw_video_format {
      float field_rate;
      uint32 interlace;
      uint32 first_active;
      uint32 last_active;
      uint32 orientation;
      uint16 pixel_width_aspect;
      uint16 pixel_height_aspect;
      media_video_display_info display
      static media_raw_video_format wildcard;
      };

Describes the format of raw video data.

field_rate indicates the field rate. This is 59.94 for NTSC and 50.0 for PAL. If you use BT848 in non-interlaced mode (thereby picking out only every other field), you'd specify 29.97.
interlace specifies how many fields there are per frame. A value of 1 indicates that the video is progressive (non-interlaced). NTSC video is interlaced such that there are two fields per frame, so for standard NTSC video, this value is 2.
first_active and last_active indicate where the VBL lines at the top of the frame end, and where they resume at the bottom of the frame; video data is confined between these two scan lines.
orientation indicates the orientation of the video; this is typically B_VIDEO_TOP_LEFT_RIGHT.
pixel_width_aspect and pixel_height_aspect specify the numerator and denominator of the video's aspect ratio. If the aspect ratio is 4:3, these values will be 4 and 3, respectively.

media_request_info

Declared in: be/media/MediaNode.h

struct media_request_info {
      enum what_code {
         B_SET_VIDEO_CLIPPING_FOR = 1,
         B_REQUEST_FORMAT_CHANGE,
         B_SET_OUTPUT_ENABLED,
         B_SET_OUTPUT_BUFFERS_FOR,
         B_FORMAT_CHANGED = 4097
      };
      what_code what;
      int32 change_tag;
      status_t status;
      int32 cookie;
      void * user_data;
      media_source source;
      media_destination destination;
      media_format format;
      uint32 _reserved_[32];
      };

This structure contains information that describes a request that has been completed (or has failed). It gets passed into the BMediaNode::RequestCompleted() function.

The what field describes what type of request has been completed:

B_SET_VIDEO_CLIPPING_FOR indicates that a BBufferConsumer::SetVideoClippingFor() request has been completed. The source and destination fields contain these values from the request, and format.u.raw_video.display describes the new video display settings.
B_REQUEST_FORMAT_CHANGE indicates that a BBufferConsumer::RequestFormatChange() request has been completed. The source and destination fields contain these values from the request, and format contains the negotiated format (it may have been altered by the producer if there were wildcard fields).
B_SET_OUTPUT_ENABLED indicates that a BBufferConsumer::SetOutputEnabled() request has been completed. The source and destination fields contain these values from the request, and status is always B_OK.
B_SET_OUTPUT_BUFFERS_FOR indicates that a BBufferConsumer::SetOutputBuffersFor() request has been completed. The source and destination fields contain these values from the request, and cookie is a pointer to the BBufferGroup that was set. Note that the change was only applied if status is B_OK.
B_FORMAT_CHANGED indicates that a BBufferConsumer::FormatChanged() request has been completed. The source and destination fields contain these values from the request, and format indicates the new format. The values seen here are from the initator's point of view.

The user_data field contains the userData pointer passed to the function that initiated the request; this can be anything the node making the request wants.

status indicates the status of the function called, and is B_OK if no error occurred.

media_seek_tag

Declared in: be/media/MediaDefs.h

struct media_seek_tag {
char data[16];
};

The media_seek_tag type is used to contain the seek tag data placed in buffer headers by producers. This can contain whatever information the producer deems necessary.

media_source

Declared in: be/media/MediaDefs.h

struct media_source {
      media_source(port_id, int32);
      media_source(const media_source &clone);
      media_source & operator= (const media_source &clone);
      media_source();
      ~media_source();
      port_id port;
      int32 id;
      static media_source null;
      private:
      uint32 _reserved_media_source_[2];
      };

Describes the source end of a media connection between two nodes. The port field indicates the port ID on which the source communicates. This must be the same as the media_node.port value.

media_video_display_info

Declared in: be/media/MediaDefs.h

struct media_video_display_info {
      color_space format;
      uint32 line_width;
      uint32 line_count;
      uint32 bytes_per_row;
      uint32 pixel_offset;
      uint32 line_offset;
      uint32 _reserved_[4];
      static media_video_display_info wildcard;
      };

Describes a video buffer in terms of how its contents should be interpreted in order to display it on the screen.

format specifies the buffer's color space.
line_width and line_count indicate the total width of the buffer in pixels, and the total height of the buffer in lines.
bytes_per_row specifies the number of bytes wide the buffer's image is, including any slop space.
pixel_offset indicates the number of bytes between the start of the buffer and the start of the video field.
line_offset specifies the offset between the start of the buffer and the start of the field, in lines.

media_video_header

Declared in: be/media/MediaDefs.h

struct media_video_header {
      uint32 _reserved_[11];
      float field_gamma;
      uint32 field_sequence;
      uint16 field_number;
      uint16 pulldown_number;
      uint32 first_active_line;
      uint32 line_count;
      };

Defines the header of a video buffer.

field_gamma specifies the gamma at which the video was captured.
field_sequence is an identifying number assigned to the field when it was captured. They progress in sequence; you can tell if a field was dropped by looking for skips in the sequence. Note that this value doesn't necessarily start at 0, and it can wrap back around to 0.
field_number indicates which field of a video frame the buffer represents. It's 0 for field 1, 1 for field 2, and so forth.
pulldown_number indicates that the field represented by the buffer is a duplicate of a field pulldown_number fields back. If this value is 0, it's not a duplicate field. This is used in cases when the video has been converted from one field rate to another, resulting in duplication of fields; these duplicated fields can be marked using pulldown numbers so video hardware and software can optimize their performance by knowing that duplicate fields exist.
first_active_line indicates the topmost line that actually contains video data (instead of VBL data). line_count indicates the number of active video lines in the field.

You may add fields to the end of this buffer if your video format requires them.

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The Media Kit: Constants and Defined Types