poke/alac/codec/ALACDecoder.cpp

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2023-02-12 10:14:46 +01:00
/*
* Copyright (c) 2011 Apple Inc. All rights reserved.
*
* @APPLE_APACHE_LICENSE_HEADER_START@
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* @APPLE_APACHE_LICENSE_HEADER_END@
*/
/*
File: ALACDecoder.cpp
*/
#include <stdlib.h>
#include <string.h>
#include "ALACDecoder.h"
#include "dplib.h"
#include "aglib.h"
#include "matrixlib.h"
#include "ALACBitUtilities.h"
#include "EndianPortable.h"
// constants/data
const uint32_t kMaxBitDepth = 32; // max allowed bit depth is 32
// prototypes
static void Zero16( int16_t * buffer, uint32_t numItems, uint32_t stride );
static void Zero24( uint8_t * buffer, uint32_t numItems, uint32_t stride );
static void Zero32( int32_t * buffer, uint32_t numItems, uint32_t stride );
/*
Constructor
*/
ALACDecoder::ALACDecoder() :
mMixBufferU( nil ),
mMixBufferV( nil ),
mPredictor( nil ),
mShiftBuffer( nil )
{
memset( &mConfig, 0, sizeof(mConfig) );
}
/*
Destructor
*/
ALACDecoder::~ALACDecoder()
{
// delete the matrix mixing buffers
if ( mMixBufferU )
{
free(mMixBufferU);
mMixBufferU = NULL;
}
if ( mMixBufferV )
{
free(mMixBufferV);
mMixBufferV = NULL;
}
// delete the dynamic predictor's "corrector" buffer
// - note: mShiftBuffer shares memory with this buffer
if ( mPredictor )
{
free(mPredictor);
mPredictor = NULL;
}
}
/*
Init()
- initialize the decoder with the given configuration
*/
int32_t ALACDecoder::Init( void * inMagicCookie, uint32_t inMagicCookieSize )
{
int32_t status = ALAC_noErr;
ALACSpecificConfig theConfig;
uint8_t * theActualCookie = (uint8_t *)inMagicCookie;
uint32_t theCookieBytesRemaining = inMagicCookieSize;
// For historical reasons the decoder needs to be resilient to magic cookies vended by older encoders.
// As specified in the ALACMagicCookieDescription.txt document, there may be additional data encapsulating
// the ALACSpecificConfig. This would consist of format ('frma') and 'alac' atoms which precede the
// ALACSpecificConfig.
// See ALACMagicCookieDescription.txt for additional documentation concerning the 'magic cookie'
// skip format ('frma') atom if present
if (theActualCookie[4] == 'f' && theActualCookie[5] == 'r' && theActualCookie[6] == 'm' && theActualCookie[7] == 'a')
{
theActualCookie += 12;
theCookieBytesRemaining -= 12;
}
// skip 'alac' atom header if present
if (theActualCookie[4] == 'a' && theActualCookie[5] == 'l' && theActualCookie[6] == 'a' && theActualCookie[7] == 'c')
{
theActualCookie += 12;
theCookieBytesRemaining -= 12;
}
// read the ALACSpecificConfig
if (theCookieBytesRemaining >= sizeof(ALACSpecificConfig))
{
theConfig.frameLength = Swap32BtoN(((ALACSpecificConfig *)theActualCookie)->frameLength);
theConfig.compatibleVersion = ((ALACSpecificConfig *)theActualCookie)->compatibleVersion;
theConfig.bitDepth = ((ALACSpecificConfig *)theActualCookie)->bitDepth;
theConfig.pb = ((ALACSpecificConfig *)theActualCookie)->pb;
theConfig.mb = ((ALACSpecificConfig *)theActualCookie)->mb;
theConfig.kb = ((ALACSpecificConfig *)theActualCookie)->kb;
theConfig.numChannels = ((ALACSpecificConfig *)theActualCookie)->numChannels;
theConfig.maxRun = Swap16BtoN(((ALACSpecificConfig *)theActualCookie)->maxRun);
theConfig.maxFrameBytes = Swap32BtoN(((ALACSpecificConfig *)theActualCookie)->maxFrameBytes);
theConfig.avgBitRate = Swap32BtoN(((ALACSpecificConfig *)theActualCookie)->avgBitRate);
theConfig.sampleRate = Swap32BtoN(((ALACSpecificConfig *)theActualCookie)->sampleRate);
mConfig = theConfig;
RequireAction( mConfig.compatibleVersion <= kALACVersion, return kALAC_ParamError; );
// allocate mix buffers
mMixBufferU = (int32_t *) calloc( mConfig.frameLength * sizeof(int32_t), 1 );
mMixBufferV = (int32_t *) calloc( mConfig.frameLength * sizeof(int32_t), 1 );
// allocate dynamic predictor buffer
mPredictor = (int32_t *) calloc( mConfig.frameLength * sizeof(int32_t), 1 );
// "shift off" buffer shares memory with predictor buffer
mShiftBuffer = (uint16_t *) mPredictor;
RequireAction( (mMixBufferU != nil) && (mMixBufferV != nil) && (mPredictor != nil),
status = kALAC_MemFullError; goto Exit; );
}
else
{
status = kALAC_ParamError;
}
// skip to Channel Layout Info
// theActualCookie += sizeof(ALACSpecificConfig);
// Currently, the Channel Layout Info portion of the magic cookie (as defined in the
// ALACMagicCookieDescription.txt document) is unused by the decoder.
Exit:
return status;
}
/*
Decode()
- the decoded samples are interleaved into the output buffer in the order they arrive in
the bitstream
*/
int32_t ALACDecoder::Decode( BitBuffer * bits, uint8_t * sampleBuffer, uint32_t numSamples, uint32_t numChannels, uint32_t * outNumSamples )
{
BitBuffer shiftBits;
uint32_t bits1, bits2;
uint8_t tag;
uint8_t elementInstanceTag;
AGParamRec agParams;
uint32_t channelIndex;
int16_t coefsU[32]; // max possible size is 32 although NUMCOEPAIRS is the current limit
int16_t coefsV[32];
uint8_t numU, numV;
uint8_t mixBits;
int8_t mixRes;
uint16_t unusedHeader;
uint8_t escapeFlag;
uint32_t chanBits;
uint8_t bytesShifted;
uint32_t shift;
uint8_t modeU, modeV;
uint32_t denShiftU, denShiftV;
uint16_t pbFactorU, pbFactorV;
uint16_t pb;
int16_t * samples;
int16_t * out16;
uint8_t * out20;
uint8_t * out24;
int32_t * out32;
uint8_t headerByte;
uint8_t partialFrame;
uint32_t extraBits;
int32_t val;
uint32_t i, j;
int32_t status;
RequireAction( (bits != nil) && (sampleBuffer != nil) && (outNumSamples != nil), return kALAC_ParamError; );
RequireAction( numChannels > 0, return kALAC_ParamError; );
mActiveElements = 0;
channelIndex = 0;
samples = (int16_t *) sampleBuffer;
status = ALAC_noErr;
*outNumSamples = numSamples;
while ( status == ALAC_noErr )
{
// bail if we ran off the end of the buffer
RequireAction( bits->cur < bits->end, status = kALAC_ParamError; goto Exit; );
// copy global decode params for this element
pb = mConfig.pb;
// read element tag
tag = BitBufferReadSmall( bits, 3 );
switch ( tag )
{
case ID_SCE:
case ID_LFE:
{
// mono/LFE channel
elementInstanceTag = BitBufferReadSmall( bits, 4 );
mActiveElements |= (1u << elementInstanceTag);
// read the 12 unused header bits
unusedHeader = (uint16_t) BitBufferRead( bits, 12 );
RequireAction( unusedHeader == 0, status = kALAC_ParamError; goto Exit; );
// read the 1-bit "partial frame" flag, 2-bit "shift-off" flag & 1-bit "escape" flag
headerByte = (uint8_t) BitBufferRead( bits, 4 );
partialFrame = headerByte >> 3;
bytesShifted = (headerByte >> 1) & 0x3u;
RequireAction( bytesShifted != 3, status = kALAC_ParamError; goto Exit; );
shift = bytesShifted * 8;
escapeFlag = headerByte & 0x1;
chanBits = mConfig.bitDepth - (bytesShifted * 8);
// check for partial frame to override requested numSamples
if ( partialFrame != 0 )
{
numSamples = BitBufferRead( bits, 16 ) << 16;
numSamples |= BitBufferRead( bits, 16 );
}
if ( escapeFlag == 0 )
{
// compressed frame, read rest of parameters
mixBits = (uint8_t) BitBufferRead( bits, 8 );
mixRes = (int8_t) BitBufferRead( bits, 8 );
//Assert( (mixBits == 0) && (mixRes == 0) ); // no mixing for mono
headerByte = (uint8_t) BitBufferRead( bits, 8 );
modeU = headerByte >> 4;
denShiftU = headerByte & 0xfu;
headerByte = (uint8_t) BitBufferRead( bits, 8 );
pbFactorU = headerByte >> 5;
numU = headerByte & 0x1fu;
for ( i = 0; i < numU; i++ )
coefsU[i] = (int16_t) BitBufferRead( bits, 16 );
// if shift active, skip the the shift buffer but remember where it starts
if ( bytesShifted != 0 )
{
shiftBits = *bits;
BitBufferAdvance( bits, (bytesShifted * 8) * numSamples );
}
// decompress
set_ag_params( &agParams, mConfig.mb, (pb * pbFactorU) / 4, mConfig.kb, numSamples, numSamples, mConfig.maxRun );
status = dyn_decomp( &agParams, bits, mPredictor, numSamples, chanBits, &bits1 );
RequireNoErr( status, goto Exit; );
if ( modeU == 0 )
{
unpc_block( mPredictor, mMixBufferU, numSamples, &coefsU[0], numU, chanBits, denShiftU );
}
else
{
// the special "numActive == 31" mode can be done in-place
unpc_block( mPredictor, mPredictor, numSamples, nil, 31, chanBits, 0 );
unpc_block( mPredictor, mMixBufferU, numSamples, &coefsU[0], numU, chanBits, denShiftU );
}
}
else
{
//Assert( bytesShifted == 0 );
// uncompressed frame, copy data into the mix buffer to use common output code
shift = 32 - chanBits;
if ( chanBits <= 16 )
{
for ( i = 0; i < numSamples; i++ )
{
val = (int32_t) BitBufferRead( bits, (uint8_t) chanBits );
val = (val << shift) >> shift;
mMixBufferU[i] = val;
}
}
else
{
// BitBufferRead() can't read more than 16 bits at a time so break up the reads
extraBits = chanBits - 16;
for ( i = 0; i < numSamples; i++ )
{
val = (int32_t) BitBufferRead( bits, 16 );
val = (val << 16) >> shift;
mMixBufferU[i] = val | BitBufferRead( bits, (uint8_t) extraBits );
}
}
mixBits = mixRes = 0;
bits1 = chanBits * numSamples;
bytesShifted = 0;
}
// now read the shifted values into the shift buffer
if ( bytesShifted != 0 )
{
shift = bytesShifted * 8;
//Assert( shift <= 16 );
for ( i = 0; i < numSamples; i++ )
mShiftBuffer[i] = (uint16_t) BitBufferRead( &shiftBits, (uint8_t) shift );
}
// convert 32-bit integers into output buffer
switch ( mConfig.bitDepth )
{
case 16:
out16 = &((int16_t *)sampleBuffer)[channelIndex];
for ( i = 0, j = 0; i < numSamples; i++, j += numChannels )
out16[j] = (int16_t) mMixBufferU[i];
break;
case 20:
out20 = (uint8_t *)sampleBuffer + (channelIndex * 3);
copyPredictorTo20( mMixBufferU, out20, numChannels, numSamples );
break;
case 24:
out24 = (uint8_t *)sampleBuffer + (channelIndex * 3);
if ( bytesShifted != 0 )
copyPredictorTo24Shift( mMixBufferU, mShiftBuffer, out24, numChannels, numSamples, bytesShifted );
else
copyPredictorTo24( mMixBufferU, out24, numChannels, numSamples );
break;
case 32:
out32 = &((int32_t *)sampleBuffer)[channelIndex];
if ( bytesShifted != 0 )
copyPredictorTo32Shift( mMixBufferU, mShiftBuffer, out32, numChannels, numSamples, bytesShifted );
else
copyPredictorTo32( mMixBufferU, out32, numChannels, numSamples);
break;
}
channelIndex += 1;
*outNumSamples = numSamples;
break;
}
case ID_CPE:
{
// if decoding this pair would take us over the max channels limit, bail
if ( (channelIndex + 2) > numChannels )
goto NoMoreChannels;
// stereo channel pair
elementInstanceTag = BitBufferReadSmall( bits, 4 );
mActiveElements |= (1u << elementInstanceTag);
// read the 12 unused header bits
unusedHeader = (uint16_t) BitBufferRead( bits, 12 );
RequireAction( unusedHeader == 0, status = kALAC_ParamError; goto Exit; );
// read the 1-bit "partial frame" flag, 2-bit "shift-off" flag & 1-bit "escape" flag
headerByte = (uint8_t) BitBufferRead( bits, 4 );
partialFrame = headerByte >> 3;
bytesShifted = (headerByte >> 1) & 0x3u;
RequireAction( bytesShifted != 3, status = kALAC_ParamError; goto Exit; );
shift = bytesShifted * 8;
escapeFlag = headerByte & 0x1;
chanBits = mConfig.bitDepth - (bytesShifted * 8) + 1;
// check for partial frame length to override requested numSamples
if ( partialFrame != 0 )
{
numSamples = BitBufferRead( bits, 16 ) << 16;
numSamples |= BitBufferRead( bits, 16 );
}
if ( escapeFlag == 0 )
{
// compressed frame, read rest of parameters
mixBits = (uint8_t) BitBufferRead( bits, 8 );
mixRes = (int8_t) BitBufferRead( bits, 8 );
headerByte = (uint8_t) BitBufferRead( bits, 8 );
modeU = headerByte >> 4;
denShiftU = headerByte & 0xfu;
headerByte = (uint8_t) BitBufferRead( bits, 8 );
pbFactorU = headerByte >> 5;
numU = headerByte & 0x1fu;
for ( i = 0; i < numU; i++ )
coefsU[i] = (int16_t) BitBufferRead( bits, 16 );
headerByte = (uint8_t) BitBufferRead( bits, 8 );
modeV = headerByte >> 4;
denShiftV = headerByte & 0xfu;
headerByte = (uint8_t) BitBufferRead( bits, 8 );
pbFactorV = headerByte >> 5;
numV = headerByte & 0x1fu;
for ( i = 0; i < numV; i++ )
coefsV[i] = (int16_t) BitBufferRead( bits, 16 );
// if shift active, skip the interleaved shifted values but remember where they start
if ( bytesShifted != 0 )
{
shiftBits = *bits;
BitBufferAdvance( bits, (bytesShifted * 8) * 2 * numSamples );
}
// decompress and run predictor for "left" channel
set_ag_params( &agParams, mConfig.mb, (pb * pbFactorU) / 4, mConfig.kb, numSamples, numSamples, mConfig.maxRun );
status = dyn_decomp( &agParams, bits, mPredictor, numSamples, chanBits, &bits1 );
RequireNoErr( status, goto Exit; );
if ( modeU == 0 )
{
unpc_block( mPredictor, mMixBufferU, numSamples, &coefsU[0], numU, chanBits, denShiftU );
}
else
{
// the special "numActive == 31" mode can be done in-place
unpc_block( mPredictor, mPredictor, numSamples, nil, 31, chanBits, 0 );
unpc_block( mPredictor, mMixBufferU, numSamples, &coefsU[0], numU, chanBits, denShiftU );
}
// decompress and run predictor for "right" channel
set_ag_params( &agParams, mConfig.mb, (pb * pbFactorV) / 4, mConfig.kb, numSamples, numSamples, mConfig.maxRun );
status = dyn_decomp( &agParams, bits, mPredictor, numSamples, chanBits, &bits2 );
RequireNoErr( status, goto Exit; );
if ( modeV == 0 )
{
unpc_block( mPredictor, mMixBufferV, numSamples, &coefsV[0], numV, chanBits, denShiftV );
}
else
{
// the special "numActive == 31" mode can be done in-place
unpc_block( mPredictor, mPredictor, numSamples, nil, 31, chanBits, 0 );
unpc_block( mPredictor, mMixBufferV, numSamples, &coefsV[0], numV, chanBits, denShiftV );
}
}
else
{
//Assert( bytesShifted == 0 );
// uncompressed frame, copy data into the mix buffers to use common output code
chanBits = mConfig.bitDepth;
shift = 32 - chanBits;
if ( chanBits <= 16 )
{
for ( i = 0; i < numSamples; i++ )
{
val = (int32_t) BitBufferRead( bits, (uint8_t) chanBits );
val = (val << shift) >> shift;
mMixBufferU[i] = val;
val = (int32_t) BitBufferRead( bits, (uint8_t) chanBits );
val = (val << shift) >> shift;
mMixBufferV[i] = val;
}
}
else
{
// BitBufferRead() can't read more than 16 bits at a time so break up the reads
extraBits = chanBits - 16;
for ( i = 0; i < numSamples; i++ )
{
val = (int32_t) BitBufferRead( bits, 16 );
val = (val << 16) >> shift;
mMixBufferU[i] = val | BitBufferRead( bits, (uint8_t)extraBits );
val = (int32_t) BitBufferRead( bits, 16 );
val = (val << 16) >> shift;
mMixBufferV[i] = val | BitBufferRead( bits, (uint8_t)extraBits );
}
}
bits1 = chanBits * numSamples;
bits2 = chanBits * numSamples;
mixBits = mixRes = 0;
bytesShifted = 0;
}
// now read the shifted values into the shift buffer
if ( bytesShifted != 0 )
{
shift = bytesShifted * 8;
//Assert( shift <= 16 );
for ( i = 0; i < (numSamples * 2); i += 2 )
{
mShiftBuffer[i + 0] = (uint16_t) BitBufferRead( &shiftBits, (uint8_t) shift );
mShiftBuffer[i + 1] = (uint16_t) BitBufferRead( &shiftBits, (uint8_t) shift );
}
}
// un-mix the data and convert to output format
// - note that mixRes = 0 means just interleave so we use that path for uncompressed frames
switch ( mConfig.bitDepth )
{
case 16:
out16 = &((int16_t *)sampleBuffer)[channelIndex];
unmix16( mMixBufferU, mMixBufferV, out16, numChannels, numSamples, mixBits, mixRes );
break;
case 20:
out20 = (uint8_t *)sampleBuffer + (channelIndex * 3);
unmix20( mMixBufferU, mMixBufferV, out20, numChannels, numSamples, mixBits, mixRes );
break;
case 24:
out24 = (uint8_t *)sampleBuffer + (channelIndex * 3);
unmix24( mMixBufferU, mMixBufferV, out24, numChannels, numSamples,
mixBits, mixRes, mShiftBuffer, bytesShifted );
break;
case 32:
out32 = &((int32_t *)sampleBuffer)[channelIndex];
unmix32( mMixBufferU, mMixBufferV, out32, numChannels, numSamples,
mixBits, mixRes, mShiftBuffer, bytesShifted );
break;
}
channelIndex += 2;
*outNumSamples = numSamples;
break;
}
case ID_CCE:
case ID_PCE:
{
// unsupported element, bail
//AssertNoErr( tag );
status = kALAC_ParamError;
break;
}
case ID_DSE:
{
// data stream element -- parse but ignore
status = this->DataStreamElement( bits );
break;
}
case ID_FIL:
{
// fill element -- parse but ignore
status = this->FillElement( bits );
break;
}
case ID_END:
{
// frame end, all done so byte align the frame and check for overruns
BitBufferByteAlign( bits, false );
//Assert( bits->cur == bits->end );
goto Exit;
}
}
#if ! DEBUG
// if we've decoded all of our channels, bail (but not in debug b/c we want to know if we're seeing bad bits)
// - this also protects us if the config does not match the bitstream or crap data bits follow the audio bits
if ( channelIndex >= numChannels )
break;
#endif
}
NoMoreChannels:
// if we get here and haven't decoded all of the requested channels, fill the remaining channels with zeros
for ( ; channelIndex < numChannels; channelIndex++ )
{
switch ( mConfig.bitDepth )
{
case 16:
{
int16_t * fill16 = &((int16_t *)sampleBuffer)[channelIndex];
Zero16( fill16, numSamples, numChannels );
break;
}
case 24:
{
uint8_t * fill24 = (uint8_t *)sampleBuffer + (channelIndex * 3);
Zero24( fill24, numSamples, numChannels );
break;
}
case 32:
{
int32_t * fill32 = &((int32_t *)sampleBuffer)[channelIndex];
Zero32( fill32, numSamples, numChannels );
break;
}
}
}
Exit:
return status;
}
#if PRAGMA_MARK
#pragma mark -
#endif
/*
FillElement()
- they're just filler so we don't need 'em
*/
int32_t ALACDecoder::FillElement( BitBuffer * bits )
{
int16_t count;
// 4-bit count or (4-bit + 8-bit count) if 4-bit count == 15
// - plus this weird -1 thing I still don't fully understand
count = BitBufferReadSmall( bits, 4 );
if ( count == 15 )
count += (int16_t) BitBufferReadSmall( bits, 8 ) - 1;
BitBufferAdvance( bits, count * 8 );
RequireAction( bits->cur <= bits->end, return kALAC_ParamError; );
return ALAC_noErr;
}
/*
DataStreamElement()
- we don't care about data stream elements so just skip them
*/
int32_t ALACDecoder::DataStreamElement( BitBuffer * bits )
{
uint8_t element_instance_tag;
int32_t data_byte_align_flag;
uint16_t count;
// the tag associates this data stream element with a given audio element
element_instance_tag = BitBufferReadSmall( bits, 4 );
data_byte_align_flag = BitBufferReadOne( bits );
// 8-bit count or (8-bit + 8-bit count) if 8-bit count == 255
count = BitBufferReadSmall( bits, 8 );
if ( count == 255 )
count += BitBufferReadSmall( bits, 8 );
// the align flag means the bitstream should be byte-aligned before reading the following data bytes
if ( data_byte_align_flag )
BitBufferByteAlign( bits, false );
// skip the data bytes
BitBufferAdvance( bits, count * 8 );
RequireAction( bits->cur <= bits->end, return kALAC_ParamError; );
return ALAC_noErr;
}
/*
ZeroN()
- helper routines to clear out output channel buffers when decoding fewer channels than requested
*/
static void Zero16( int16_t * buffer, uint32_t numItems, uint32_t stride )
{
if ( stride == 1 )
{
memset( buffer, 0, numItems * sizeof(int16_t) );
}
else
{
for ( uint32_t index = 0; index < (numItems * stride); index += stride )
buffer[index] = 0;
}
}
static void Zero24( uint8_t * buffer, uint32_t numItems, uint32_t stride )
{
if ( stride == 1 )
{
memset( buffer, 0, numItems * 3 );
}
else
{
for ( uint32_t index = 0; index < (numItems * stride * 3); index += (stride * 3) )
{
buffer[index + 0] = 0;
buffer[index + 1] = 0;
buffer[index + 2] = 0;
}
}
}
static void Zero32( int32_t * buffer, uint32_t numItems, uint32_t stride )
{
if ( stride == 1 )
{
memset( buffer, 0, numItems * sizeof(int32_t) );
}
else
{
for ( uint32_t index = 0; index < (numItems * stride); index += stride )
buffer[index] = 0;
}
}