cl Demultiplexing(3dm) cl Demultiplexing(3dm)NAME
clOpenDemux, clDemux, clCloseDemux - Demultiplex into video and audio
streams
SYNOPSIS
#include <dmedia/cl.h>
int clOpenDemux(int scheme, CLhandle *handlePtr)
int clDemux(CLhandle handle, int count)
int clCloseDemux(CLhandle handle)
ARGUMENTS
scheme The demultiplexing scheme to use.
handlePtr A pointer to the returned handle of the demultiplexer.
Used by subsequent calls to identify the demultiplexer.
handle A handle to the demultiplexer.
count The number of iterations to execute. The amount of
processing done during each iteration is scheme and data
dependent. count may also be specified as
CL_CONTINUOUS_BLOCK or CL_CONTINUOUS_NONBLOCK.
DESCRIPTION
clOpenDemux opens a demultiplexer for a given scheme. It is called
before clDemux or any call that requires a demultiplexer handle.
clCloseDemux closes the demultiplexer after which handle is no longer
valid.
clDemux takes no buffer arguments so it always invokes the Implicit
Buffering model (see CLintro(3dm)). An input buffer of type CL_BUF_MUX,
and output buffers of types CL_BUF_VIDEO and CL_BUF_AUDIO, must have been
created previously with clCreateBuf. The input buffer is filled with
calls to clQueryFree, clUpdateHead, and clDoneUpdatingHead. The output
buffers are emptied with calls to clQueryValid and clUpdateTail.
Buffers should be appropriately sized for proper execution of clDemux.
The input buffer should have a minimum capacity of CL_MUX_BUFFER_SIZE.
The output buffers should have minimum capacities of CL_VIDEO_BUFFER_SIZE
and CL_AUDIO_BUFFER_SIZE. These parameters may be determined by calling
clGetParams, after first calling clReadHeader to configure the
demultiplexer.
If count is non-negative, clDemux attempts to perform count iterations of
the demultiplexing operation. The actual amount of data processed in
each iteration is scheme and data dependent. The call to clDemux may
consume up to CL_MUX_BUFFER_SIZE * count bytes of multiplexed data. This
may produce up to CL_VIDEO_BUFFER_SIZE * count bytes of video data, and
up to CL_AUDIO_BUFFER_SIZE * count bytes of audio data. The call does
not return until processing is completed.
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cl Demultiplexing(3dm) cl Demultiplexing(3dm)
If count is specified as CL_CONTINUOUS_BLOCK or CL_CONTINUOUS_NONBLOCK
then clDemux continues until the input buffer is marked done, or a call
to clCloseDemux is made. CL_CONTINUOUS_NONBLOCK differs from
CL_CONTINUOUS_BLOCK in that the call to clDemux returns immediately while
the demultiplexing occurs in a separate thread.
Several demultiplexers can be open simultaneously. handle identifies
which one is being referenced.
RETURN VALUES
Each routine returns a negative error code if the call fails. Upon
success, clOpenDemux and clCloseDemux return SUCCESS, and clDemux returns
either the count actually processed or, in the case of
CL_CONTINUOUS_NONBLOCK, returns SUCCESS immediately.
EXAMPLE
#include <dmedia/cl.h>
int paramValueBuffer[][2] = {
CL_MUX_BUFFER_SIZE, 0,
CL_VIDEO_BUFFER_SIZE, 0,
CL_AUDIO_BUFFER_SIZE, 0,
};
/* Open the demultiplexer */
clOpenDemux(CL_MPEG1_SYSTEMS_SOFTWARE, &handle);
/* Configure the demultiplexer by reading the header */
headerSize = clQueryMaxHeaderSize(CL_MPEG1_SYSTEMS_SOFTWARE);
/* Get the header data from somewhere */
...
clReadHeader(handle, headerSize, header);
/* Allocate buffers of the required size */
clGetParams(handle, (int *)paramValueBuffer, 6);
clCreateBuf(handle, CL_BUF_MUX, paramValueBuffer[0][1], 1, NULL);
clCreateBuf(handle, CL_BUF_VIDEO, paramValueBuffer[1][1], 1, NULL);
clCreateBuf(handle, CL_BUF_AUDIO, paramValueBuffer[2][1], 1, NULL);
/* Demultiplex a few iterations */
for(i = 0; i < N; i++)
{
/* Keep the input buffer full */
...
clDemux(handle, 1);
/* Write the video and audio data to somewhere */
...
}
/* Close the demultiplexer */
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cl Demultiplexing(3dm) cl Demultiplexing(3dm)clCloseDemux(handle);
SEE ALSOCLintro(3dm), clReadHeader(3dm), clGetParams(3dm), clCreateBuf(3dm),
clQueryFree(3dm), clUpdateHead(3dm), clQueryValid(3dm),
clUpdateTail(3dm), clDoneUpdatingHead(3dm)
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