dmic(4)								       dmic(4)

NAME    [Toc]    [Back]

     DMimageconverter -	Digital	Media image conversion and compression

SYNOPSIS    [Toc]    [Back]

     #include <dmedia/dm_imageconvert.h>

     -ldmedia

     DMimageconverter ic;

DESCRIPTION    [Toc]    [Back]

     The DMimageconverter data type and	its operations implement the Digital
     Media image converter subsystem.  This is a framework which supports a
     variety of	compression and	decompression devices and algorithms video
     rate JPEG and MPEG.  NOTE:	Some realtime compression devices are
     available only as extra optional products.

     The DMimageconverter data type represents an image	converter context
     which performs a specific image conversion.  The image conversion is
     principally a specific compression	or decompression possibly including
     color space conversion, cropping, zooming,	or other such image
     reformatting.  The	image converter	context	takes input from enqueued
     DMbuffers and produces an output queue of new DMbuffers representing
     converted data.

INITIALIZATION OVERVIEW    [Toc]    [Back]

     An	image converter	is first selected on the basis of the type of
     conversion	desired.  The image converter context is then created.
     Appropriate buffering is created to hold the input	and output data.
     Other producers and consumers of image data are initialized at this time
     as	well (such as OpenGL graphics rendering	and live video I/O).

OPERATIONAL OVERVIEW    [Toc]    [Back]

     The image converter either	encodes	or decodes a given specific data
     format.

     The image converter takes input packetized	in DMbuffer's.

     The image converter produces output also packetized in DMbuffer's.

     The image converter operates asynchronously to the	process.  A process
     may determine when	newly converted	data is	available using	select on a
     file descriptor associated	with the image converter context.

IMAGE CONVERTER	SELECTION
     dmICGetNum, dmICGetDescription, and dmICChooseConverter are used to
     discover the image	converters installed in	the system.

CONTEXT	CREATION
     dmICCreate	creates	a DMimageconverter context for one of the image
     converters	discovered above.  A process may create	one or more
     DMimageconverter contexts of the same or different	image converter.



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     Multiple DMimageconverter contexts	are fully independent and share	and
     exchange data only	as directed by the DMbuffer operations used in the
     process.

     dmICDestroy destroys the specified	DMimageconverter. No further
     operations	on the context are valid.

BUFFERING    [Toc]    [Back]

     A mechanism for opaquely passing memory buffering requirements from the
     image converter to	the DMbuffer system is available using the following
     operations.

     dmICGetSrcPoolParams adds the image converter's src (input) memory
     buffering requirements to the passed DMparams.

     dmICGetDstPoolParams adds the image converter's dst (output) memory
     buffering requirements to the passed DMparams.

     dmICSetDstPool indicates to the image converter the DMbufferpool from
     which it will allocate each DMbuffer placed in the	output queue.

DATA TRANSFER    [Toc]    [Back]

     An	image converter	has one	input queue and	one output queue.

     dmICSend places the DMbuffer on the image converter's input queue.	 The
     meaning of	the additional DMbuffer	arguments is dependent on the image
     converter.	 For example, the MPEG image converter uses this mechanism to
     find the reference	data needed for	interframe decode.

     dmICReceive returns a DMbuffer from the image converter's output queue.

IMAGE FORMAT CONTROL    [Toc]    [Back]

     The process describes the image format of the input data and the format
     of	the desired output.

     The DMparams passed to dmICSetSrcParams describes the image format	of
     input to the image	converter.

     The DMparams passed to dmICSetDstParams describes the image format	of
     output from the image converter.

     mvAddTrackDataParams and dmSetImageDefaults set parameters	useful in
     these calls including:

     DM_IMAGE_WIDTH    [Toc]    [Back]

     DM_IMAGE_HEIGHT    [Toc]    [Back]

     DM_IMAGE_PACKING    [Toc]    [Back]






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CONVERSION CONTROL    [Toc]    [Back]

     dmICSetConvParams is used to pass parameters to the image converter to
     control the conversion process.  All converters accept the	following
     controls:

     DM_IMAGE_QUALITY_SPATIAL    [Toc]    [Back]

     DM_IMAGE_QUALITY_TEMPORAL    [Toc]    [Back]

     DM_IMAGE_BITRATE    [Toc]    [Back]

VIDEO I/O - VL
     Image data	is transported between video I/O devices and image converters
     using the DMbuffer	subsystem.  Refer to vlEventRecv(3dm),
     vlEventToDMBuffer(3dm), and vlDMBufferSend(3dm).

GRAPHICS RENDERING AND TEXTURING - OpenGL    [Toc]    [Back]

     Image data	is transported between graphics	rendering and texturing	using
     the DMbuffer subsystem and	operations in the OpenGL DMbuffer extension.

SEE ALSO    [Toc]    [Back]

     dmICGetNum(3dm), dmICGetDescription(3dm), dmICChooseConverter(3dm),
     dmICCreate(3dm), dmICDestroy(3dm),	dmICGetSrcParams(3dm),
     dmICSetSrcParams(3dm), dmICGetDefaultSrcParams(3dm),
     dmICGetDstParams(3dm), dmICSetDstParams(3dm),
     dmICGetDefaultDstParams(3dm), dmICGetConvParams(3dm),
     dmICSetConvParams(3dm), dmICGetDefaultConvParams(3dm),
     dmICGetSrcPoolParams(3dm),	dmICGetDstPoolParams(3dm),
     dmICSetDstPool(3dm), dmICGetDstQueueFD(3dm), dmICGetDstQueueFilled(3dm),
     dmICSend(3dm), dmICReceive(3dm).

     dm_jpeg(3dm).

     dmBufferSetPoolDefaults(3dm), dmBufferCreatePool(3dm),
     dmBufferDestroyPool(3dm), dmBufferGetAllocSize(3dm),
     dmBufferGetPoolFD(3dm), dmBufferSetPoolSelectSize(3dm),
     dmBufferAllocate(3dm), dmBufferFree(3dm), dmBufferMapData(3dm),
     dmBufferGetUSTMSCpair(3dm), dmBufferSetUSTMSCpair(3dm),
     dmBufferGetSize(3dm), dmBufferSetSize(3dm), dmBufferGetImageType(3dm),
     dmBufferSetImageType(3dm),	dmBufferGetGLPoolParams(3dm).


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