AC97AudioFloatLib.cpp   [plain text]


/*
 * Copyright (c) 1998-2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */

#include <IOKit/audio/IOAudioTypes.h>
#include "AC97AudioEngine.h"

#define kMaxSInt16ValueInFloat           (3.2768000000000e4)
#define kMaxFloatMinusLSBSInt32          (0.99999999953434)
#define kMaxFloatMinusLSBSInt16          (0.99996948242188)
#define kMaxFloatMinusLSBSInt8           (0.9921259843)
#define kMinusOne                        (-1.0)

#define ClipFloatValue(x)                \
do {                                     \
    if ((x) > kMaxFloatMinusLSBSInt16)   \
        (x) = kMaxFloatMinusLSBSInt16;   \
    else if ((x) < kMinusOne)            \
        (x) = kMinusOne;                 \
} while(0)

#define ConvertFloatToSInt16(x)          \
    ((SInt16)((x) * kMaxSInt16ValueInFloat))

//---------------------------------------------------------------------------
// clipOutputSamples - Copied from AppleDBDMAAudioClip.c

IOReturn
AppleIntelAC97AudioEngine::clipOutputSamples(
                           const void *                mixBuf,
                           void *                      sampleBuf,
                           UInt32                      firstSampleFrame,
                           UInt32                      numSampleFrames,
                           const IOAudioStreamFormat * streamFormat,
                           IOAudioStream *             audioStream )
{
    float *  inFloatBufferPtr;
    SInt16 * outSInt16BufferPtr;
    UInt32   numSamples;

#if 0
    IOLog("mix:%p sample:%p 1st:%d num:%d ch:%d\n",
          mixBuf, sampleBuf, firstSampleFrame, numSampleFrames,
          streamFormat->fNumChannels);
#endif

    inFloatBufferPtr   = (float *) mixBuf +
                         firstSampleFrame * streamFormat->fNumChannels;
    
    outSInt16BufferPtr = (SInt16 *) sampleBuf +
                         firstSampleFrame * streamFormat->fNumChannels;

    inFloatBufferPtr--;
    outSInt16BufferPtr--;

    numSamples = numSampleFrames * streamFormat->fNumChannels;

    for ( UInt32 i = 0; i < ( numSamples / 4 ); i++ ) 
    {
        float tempFloat1 = *(++inFloatBufferPtr);
        float tempFloat2 = *(++inFloatBufferPtr);
        float tempFloat3 = *(++inFloatBufferPtr);
        float tempFloat4 = *(++inFloatBufferPtr);

        ClipFloatValue( tempFloat1 );
        ClipFloatValue( tempFloat2 );
        ClipFloatValue( tempFloat3 );
        ClipFloatValue( tempFloat4 );

        *(++outSInt16BufferPtr) = ConvertFloatToSInt16( tempFloat1 );
        *(++outSInt16BufferPtr) = ConvertFloatToSInt16( tempFloat2 );
        *(++outSInt16BufferPtr) = ConvertFloatToSInt16( tempFloat3 );
        *(++outSInt16BufferPtr) = ConvertFloatToSInt16( tempFloat4 );
    }

    switch ( numSamples % 4 )
    {
        case 3:
        {
            float tempFloat = *(++inFloatBufferPtr);
            
            ClipFloatValue( tempFloat );

            *(++outSInt16BufferPtr) = ConvertFloatToSInt16( tempFloat );
        }
        case 2:
        {
            float tempFloat = *(++inFloatBufferPtr);
            
            ClipFloatValue( tempFloat );

            *(++outSInt16BufferPtr) = ConvertFloatToSInt16( tempFloat );
        }
        case 1:
        {
            float tempFloat = *(++inFloatBufferPtr);

            ClipFloatValue( tempFloat );

            *(++outSInt16BufferPtr) = ConvertFloatToSInt16( tempFloat );
        }
    }

    return kIOReturnSuccess;
}

//---------------------------------------------------------------------------

IOReturn
AppleIntelAC97AudioEngine::convertInputSamples(
                           const void *                sampleBuf,
                           void *                      destBuf,
                           UInt32                      firstSampleFrame,
                           UInt32                      numSampleFrames,
                           const IOAudioStreamFormat * streamFormat,
                           IOAudioStream *             audioStream )
{
    UInt32   numSamplesLeft;
    float *  floatDestBuf;
    SInt16 * inputBuf;

    floatDestBuf = (float *) destBuf;
    inputBuf = &(((SInt16 *) sampleBuf)[firstSampleFrame * streamFormat->fNumChannels]);

    numSamplesLeft = numSampleFrames * streamFormat->fNumChannels;

    while ( numSamplesLeft > 0 )
    {
        *floatDestBuf = (*inputBuf) / 32767.0;

        ++inputBuf;
        ++floatDestBuf;
        --numSamplesLeft;
    }

    return kIOReturnSuccess;
}