pa_process.h

一个开源SIP协议栈

#ifndef PA_PROCESS_H
#define PA_PROCESS_H
/*
 * $Id: pa_process.h,v 1.1.2.30 2004/12/13 09:48:44 rossbencina Exp $
 * Portable Audio I/O Library callback buffer processing adapters
 *
 * Based on the Open Source API proposed by Ross Bencina
 * Copyright (c) 1999-2002 Phil Burk, Ross Bencina
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files
 * (the "Software"), to deal in the Software without restriction,
 * including without limitation the rights to use, copy, modify, merge,
 * publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * Any person wishing to distribute modifications to the Software is
 * requested to send the modifications to the original developer so that
 * they can be incorporated into the canonical version.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR
 * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
 * CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
 
/** @file
 @brief Buffer Processor prototypes. A Buffer Processor performs buffer length
 adaption, coordinates sample format conversion, and interleaves/deinterleaves
 channels.

 <h3>Overview</h3>

 The "Buffer Processor" (PaUtilBufferProcessor) manages conversion of audio
 data from host buffers to user buffers and back again. Where required, the
 buffer processor takes care of converting between host and user sample formats,
 interleaving and deinterleaving multichannel buffers, and adapting between host
 and user buffers with different lengths. The buffer processor may be used with
 full and half duplex streams, for both callback streams and blocking read/write
 streams.

 One of the important capabilities provided by the buffer processor is
 the ability to adapt between user and host buffer sizes of different lengths
 with minimum latency. Although this task is relatively easy to perform when
 the host buffer size is an integer multiple of the user buffer size, the
 problem is more complicated when this is not the case - especially for
 full-duplex callback streams. Where necessary the adaption is implemented by
 internally buffering some input and/or output data. The buffer adation
 algorithm used by the buffer processor was originally implemented by
 Stephan Letz for the ASIO version of PortAudio, and is described in his
 Callback_adaption_.pdf which is included in the distribution.

 The buffer processor performs sample conversion using the functions provided
 by pa_converters.c.

 The following sections provide an overview of how to use the buffer processor.
 Interested readers are advised to consult the host API implementations for
 examples of buffer processor usage.
 

 <h4>Initialization, resetting and termination</h4>

 When a stream is opened, the buffer processor should be initialized using
 PaUtil_InitializeBufferProcessor. This function initializes internal state
 and allocates temporary buffers as neccesary according to the supplied
 configuration parameters. Some of the parameters correspond to those requested
 by the user in their call to Pa_OpenStream(), others reflect the requirements
 of the host API implementation - they indicate host buffer sizes, formats,
 and the type of buffering which the Host API uses. The buffer processor should
 be initialized for callback streams and blocking read/write streams.

 Call PaUtil_ResetBufferProcessor to clear any sample data which is present
 in the buffer processor before starting to use it (for example when
 Pa_StartStream is called).

 When the buffer processor is no longer used call
 PaUtil_TerminateBufferProcessor.

 
 <h4>Using the buffer processor for a callback stream</h4>

 The buffer processor's role in a callback stream is to take host input buffers
 process them with the stream callback, and fill host output buffers. For a
 full duplex stream, the buffer processor handles input and output simultaneously
 due to the requirements of the minimum-latency buffer adation algorithm.

 When a host buffer becomes available, the implementation should call
 the buffer processor to process the buffer. The buffer processor calls the
 stream callback to consume and/or produce audio data as necessary. The buffer
 processor will convert sample formats, interleave/deinterleave channels,
 and slice or chunk the data to the appropriate buffer lengths according to
 the requirements of the stream callback and the host API.

 To process a host buffer (or a pair of host buffers for a full-duplex stream)
 use the following calling sequence:

 -# Call PaUtil_BeginBufferProcessing
 -# For a stream which takes input:
    - Call PaUtil_SetInputFrameCount with the number of frames in the host input
        buffer.
    - Call one of the following functions one or more times to tell the
        buffer processor about the host input buffer(s): PaUtil_SetInputChannel,
        PaUtil_SetInterleavedInputChannels, PaUtil_SetNonInterleavedInputChannel.
        Which function you call will depend on whether the host buffer(s) are
        interleaved or not.
    - If the available host data is split accross two buffers (for example a
        data range at the end of a circular buffer and another range at the
        beginning of the circular buffer), also call
        PaUtil_Set2ndInputFrameCount, PaUtil_Set2ndInputChannel,
        PaUtil_Set2ndInterleavedInputChannels,
        PaUtil_Set2ndNonInterleavedInputChannel as necessary to tell the buffer
        processor about the second buffer.
 -# For a stream which generates output:
    - Call PaUtil_SetOutputFrameCount with the number of frames in the host
        output buffer.
    - Call one of the following functions one or more times to tell the
        buffer processor about the host output buffer(s): PaUtil_SetOutputChannel,
        PaUtil_SetInterleavedOutputChannels, PaUtil_SetNonInterleavedOutputChannel.
        Which function you call will depend on whether the host buffer(s) are
        interleaved or not.
    - If the available host output buffer space is split accross two buffers
        (for example a data range at the end of a circular buffer and another
        range at the beginning of the circular buffer), call
        PaUtil_Set2ndOutputFrameCount, PaUtil_Set2ndOutputChannel,
        PaUtil_Set2ndInterleavedOutputChannels,
        PaUtil_Set2ndNonInterleavedOutputChannel as necessary to tell the buffer
        processor about the second buffer.
 -# Call PaUtil_EndBufferProcessing, this function performs the actual data
    conversion and processing.


 <h4>Using the buffer processor for a blocking read/write stream</h4>

 Blocking read/write streams use the buffer processor to convert and copy user
 output data to a host buffer, and to convert and copy host input data to
 the user's buffer. The buffer processor does not perform any buffer adaption.
 When using the buffer processor in a blocking read/write stream the input and
 output conversion are performed separately by the PaUtil_CopyInput and
 PaUtil_CopyOutput functions.

 To copy data from a host input buffer to the buffer(s) which the user supplies
 to Pa_ReadStream, use the following calling sequence.

 - Repeat the following three steps until the user buffer(s) have been filled
    with samples from the host input buffers:
     -# Call PaUtil_SetInputFrameCount with the number of frames in the host
        input buffer.
     -# Call one of the following functions one or more times to tell the
        buffer processor about the host input buffer(s): PaUtil_SetInputChannel,
        PaUtil_SetInterleavedInputChannels, PaUtil_SetNonInterleavedInputChannel.
        Which function you call will depend on whether the host buffer(s) are
        interleaved or not.
     -# Call PaUtil_CopyInput with the user buffer pointer (or a copy of the
        array of buffer pointers for a non-interleaved stream) passed to
        Pa_ReadStream, along with the number of frames in the user buffer(s).
        Be careful to pass a <i>copy</i> of the user buffer pointers to
        PaUtil_CopyInput because PaUtil_CopyInput advances the pointers to
        the start of the next region to copy.
 - PaUtil_CopyInput will not copy more data than is available in the
    host buffer(s), so the above steps need to be repeated until the user
    buffer(s) are full.

 
 To copy data to the host output buffer from the user buffers(s) supplied
 to Pa_WriteStream use the following calling sequence.

 - Repeat the following three steps until all frames from the user buffer(s)
    have been copied to the host API:
     -# Call PaUtil_SetOutputFrameCount with the number of frames in the host
        output buffer.
     -# Call one of the following functions one or more times to tell the
        buffer processor about the host output buffer(s): PaUtil_SetOutputChannel,
        PaUtil_SetInterleavedOutputChannels, PaUtil_SetNonInterleavedOutputChannel.
        Which function you call will depend on whether the host buffer(s) are
        interleaved or not.
     -# Call PaUtil_CopyOutput with the user buffer pointer (or a copy of the
        array of buffer pointers for a non-interleaved stream) passed to
        Pa_WriteStream, along with the number of frames in the user buffer(s).
        Be careful to pass a <i>copy</i> of the user buffer pointers to 
        PaUtil_CopyOutput because PaUtil_CopyOutput advances the pointers to
        the start of the next region to copy.
 - PaUtil_CopyOutput will not copy more data than fits in the host buffer(s),
    so the above steps need to be repeated until all user data is copied.
*/


#include "portaudio.h"
#include "pa_converters.h"
#include "pa_dither.h"

#ifdef __cplusplus
extern "C"
{
#endif /* __cplusplus */


/** @brief Mode flag passed to PaUtil_InitializeBufferProcessor indicating the type
 of buffering that the host API uses.

 The mode used depends on whether the host API or the implementation manages
 the buffers, and how these buffers are used (scatter gather, circular buffer).
*/
typedef enum {
/** The host buffer size is a fixed known size. */
    paUtilFixedHostBufferSize,

/** The host buffer size may vary, but has a known maximum size. */
    paUtilBoundedHostBufferSize,

/** Nothing is known about the host buffer size. */
    paUtilUnknownHostBufferSize,

/** The host buffer size varies, and the client does not require the buffer
 processor to consume all of the input and fill all of the output buffer. This
 is useful when the implementation has access to the host API's circular buffer
 and only needs to consume/fill some of it, not necessarily all of it, with each
 call to the buffer processor. This is the only mode where
 PaUtil_EndBufferProcessing() may not consume the whole buffer.
*/
    paUtilVariableHostBufferSizePartialUsageAllowed
}PaUtilHostBufferSizeMode;


/** @brief An auxilliary data structure used internally by the buffer processor
 to represent host input and output buffers. */
typedef struct PaUtilChannelDescriptor{
    void *data;
    unsigned int stride;  /**< stride in samples, not bytes */
}PaUtilChannelDescriptor;


/** @brief The main buffer processor data structure.

 Allocate one of these, initialize it with PaUtil_InitializeBufferProcessor
 and terminate it with PaUtil_TerminateBufferProcessor.
*/
typedef struct {
    unsigned long framesPerUserBuffer;
    unsigned long framesPerHostBuffer;

    PaUtilHostBufferSizeMode hostBufferSizeMode;