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cl Decompression(3dm)					 cl Decompression(3dm)

NAME    [Toc]    [Back]

     clOpenDecompressor, clDecompress, clCloseDecompressor - Decompress	a
     video or audio stream

SYNOPSIS    [Toc]    [Back]

     #include <dmedia/cl.h>

     int clOpenDecompressor(int	scheme,	CLhandle *handlePtr)
     int clDecompress(CLhandle handle, int numberOfFrames,
	 int compressedBufferSize, void	*compressedBuffer, void	*frameBuffer)
     int clCloseDecompressor(CLhandle handle)

ARGUMENTS    [Toc]    [Back]

     scheme	    The	decompression scheme to	use.

     handlePtr	    A pointer to the returned handle of	the decompressor. Used
		    by subsequent calls	to identify the	decompressor.

     handle	    A handle to	the decompressor.

     numberOfFrames The	number of frames to decompress,	which should be	a
		    multiple of	CL_FRAMES_PER_CHUNK (usually 1 for video).
		    numberOfFrames may also be specified as

		    The	size of	the data to be decompressed in bytes.  Used
		    with non-NULL compressedBuffer to describe buffer length.

		    A pointer to the data to be	decompressed.  A value of NULL
		    selects the	use of a previously created buffer to supply
		    the	compressed data	(Implicit Buffering).

     frameBuffer    A pointer to where decompressed frames are to be placed.
		    A value of CL_EXTERNAL_DEVICE may be used with some
		    decompressors to indicate a	direct connection to an
		    external video or audio destination.  A value of NULL
		    selects the	use of a previously created buffer to hold the
		    decompressed frames	(Implicit Buffering).

DESCRIPTION    [Toc]    [Back]

     clOpenDecompressor	opens a	decompressor for a given scheme. It is called
     before clDecompress or any	call that requires a decompressor handle.
     clCloseDecompressor closes	the decompressor after which handle is no
     longer valid.

     clDecompress invokes different buffering models depending on the values
     of	the buffer arguments (see CLintro(3dm)).

     1.	Direct Buffering

									Page 1

cl Decompression(3dm)					 cl Decompression(3dm)

	  If compressedBuffer and frameBuffer are non-NULL,
	  clDecompress decompresses numberOfFrames from
	  compressedBuffer and stores the result in frameBuffer.
	  frameBuffer may also be set to CL_EXTERNAL_DEVICE to indicate
	  a hardware output destination	(currently supported by	CL_JPEG_COSMO).

     2.	Implicit Buffering

	  If compressedBuffer and frameBuffer are NULL,
	  clDecompress operates	on buffers that	have been created
	  previously with clCreateBuf.	The input buffer should	be
	  filled with calls to clQueryFree, clUpdateHead, and
	  clDoneUpdatingHead.  The output buffer should	be emptied
	  with calls to	clQueryValid and clUpdateTail.

     Direct and	Implicit Buffering models may be mixed in one call by setting
     one of the	buffer arguments to be non-NULL, and the other to be NULL.

     With either model,	buffers	should be appropriately	sized for proper
     execution of clDecompress.	 The input compressed buffer should have a
     minimum capacity of CL_COMPRESSED_BUFFER_SIZE bytes.  The output frame
     buffer should have	a minimum capacity of CL_FRAMES_PER_CHUNK frames.
     These parameters may be determined	by calling clGetParams,	after first
     calling clReadHeader to configure the decompressor.

     If	numberOfFrames is non-negative,	clDecompress may consume up to
     input data	and attempts to	produce	numberOfFrames frames of output	data.
     The call does not return until processing is completed.

     If	numberOfFrames is specified as CL_CONTINUOUS_BLOCK or
     CL_CONTINUOUS_NONBLOCK then clDecompress continues	until either the input
     buffer is marked done, or a call to clCloseDecompressor is	made.
     CL_CONTINUOUS_NONBLOCK differs from CL_CONTINUOUS_BLOCK in	that the call
     to	clDecompress returns immediately while the decompression occurs	in a
     separate thread.  These special values should only	be used	with Implicit

     Multiple decompressors can	be open	simultaneously.	handle identifies
     which one is being	referenced.

RETURN VALUES    [Toc]    [Back]

     Upon success, clOpenDecompressor and clCloseDecompressor return SUCCESS,
     and clDecompress returns the numberOfFrames actually produced or, in the
     case of CL_CONTINUOUS_NONBLOCK, returns SUCCESS immediately.

     Upon failure, each	routine	returns	a negative error code.	With some
     schemes, clOpenDecompressor returns CL_SCHEME_BUSY	if there is a system
     resource (e.g. a piece of hardware) which is in use by another process.
     A return code of CL_SCHEME_NOT_AVAILABLE indicates	that the hardware or
     software required by the scheme is	not installed on the system.

									Page 2

cl Decompression(3dm)					 cl Decompression(3dm)

EXAMPLE    [Toc]    [Back]

	  #include <dmedia/cl.h>
	  /* Open the decompressor */
	  clOpenDecompressor(CL_MVC1_SOFTWARE, &handle);

	  /* Configure the decompressor	by reading the header */
	  headerSize = clQueryMaxHeaderSize(CL_MVC1_SOFTWARE);
	  /* Get the header data from somewhere	*/
	  clReadHeader(handle, headerSize, header);

	  /* Allocate implicit input buffer of the required size */
	  compressedBufferSize = clGetParam(handle, CL_COMPRESSED_BUFFER_SIZE);
	  clCreateBuf(handle, CL_BUF_COMPRESSED, compressedBufferSize, 1, NULL);

	  /* Decompress	a series of frames */
	  for(i	= 0; i < N; i++)
	      /* Keep input buffer full	with compressed	data */
	      clDecompress(handle, 1, 0, NULL, frameBuffer);
	      /* Write the frame to somewhere (such as the screen) */

	  /* Close the decompressor */

SEE ALSO    [Toc]    [Back]

     CLintro(3dm), clReadHeader(3dm), clGetParams(3dm),	clCreateBuf(3dm),
     clQueryFree(3dm), clUpdateHead(3dm), clQueryValid(3dm),
     clUpdateTail(3dm),	clDoneUpdatingHead(3dm)

									PPPPaaaaggggeeee 3333
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