ref: a422180695b1c16d897210e10bccd0ac1dd43660
dir: /codec/decoder/core/src/cabac_decoder.cpp/
/*!
* \copy
* Copyright (c) 2013, Cisco Systems
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
* cabac_decoder.cpp: deals with cabac state transition and related functions
*/
#include "cabac_decoder.h"
namespace WelsDec {
static const int16_t g_kMvdBinPos2Ctx [8] = {0, 1, 2, 3, 3, 3, 3, 3};
void WelsCabacGlobalInit (PWelsDecoderContext pCtx) {
for (int32_t iModel = 0; iModel < 4; iModel++) {
for (int32_t iQp = 0; iQp <= WELS_QP_MAX; iQp++)
for (int32_t iIdx = 0; iIdx < WELS_CONTEXT_COUNT; iIdx++) {
int32_t m = g_kiCabacGlobalContextIdx[iIdx][iModel][0];
int32_t n = g_kiCabacGlobalContextIdx[iIdx][iModel][1];
int32_t iPreCtxState = WELS_CLIP3 ((((m * iQp) >> 4) + n), 1, 126);
uint8_t uiValMps = 0;
uint8_t uiStateIdx = 0;
if (iPreCtxState <= 63) {
uiStateIdx = 63 - iPreCtxState;
uiValMps = 0;
} else {
uiStateIdx = iPreCtxState - 64;
uiValMps = 1;
}
pCtx->sWelsCabacContexts[iModel][iQp][iIdx].uiState = uiStateIdx;
pCtx->sWelsCabacContexts[iModel][iQp][iIdx].uiMPS = uiValMps;
}
}
pCtx->bCabacInited = true;
}
// ------------------- 1. context initialization
void WelsCabacContextInit (PWelsDecoderContext pCtx, uint8_t eSliceType, int32_t iCabacInitIdc, int32_t iQp) {
int32_t iIdx = pCtx->eSliceType == WelsCommon::I_SLICE ? 0 : iCabacInitIdc + 1;
if (!pCtx->bCabacInited) {
WelsCabacGlobalInit (pCtx);
}
memcpy (pCtx->pCabacCtx, pCtx->sWelsCabacContexts[iIdx][iQp],
WELS_CONTEXT_COUNT * sizeof (SWelsCabacCtx));
}
// ------------------- 2. decoding Engine initialization
int32_t InitCabacDecEngineFromBS (PWelsCabacDecEngine pDecEngine, PBitStringAux pBsAux) {
int32_t iRemainingBits = - pBsAux->iLeftBits; //pBsAux->iLeftBits < 0
int32_t iRemainingBytes = (iRemainingBits >> 3) + 2; //+2: indicating the pre-read 2 bytes
uint8_t* pCurr;
pCurr = pBsAux->pCurBuf - iRemainingBytes;
if (pCurr >= (pBsAux->pEndBuf - 1)) {
return ERR_INFO_INVALID_ACCESS;
}
pDecEngine->uiOffset = ((pCurr[0] << 16) | (pCurr[1] << 8) | pCurr[2]);
pDecEngine->uiOffset <<= 16;
pDecEngine->uiOffset |= (pCurr[3] << 8) | pCurr[4];
pDecEngine->iBitsLeft = 31;
pDecEngine->pBuffCurr = pCurr + 5;
pDecEngine->uiRange = WELS_CABAC_HALF;
pDecEngine->pBuffStart = pBsAux->pStartBuf;
pDecEngine->pBuffEnd = pBsAux->pEndBuf;
pBsAux->iLeftBits = 0;
return ERR_NONE;
}
void RestoreCabacDecEngineToBS (PWelsCabacDecEngine pDecEngine, PBitStringAux pBsAux) {
//CABAC decoding finished, changing to SBitStringAux
pDecEngine->pBuffCurr -= (pDecEngine->iBitsLeft >> 3);
pDecEngine->iBitsLeft = 0; //pcm_alignment_zero_bit in CABAC
pBsAux->iLeftBits = 0;
pBsAux->pStartBuf = pDecEngine->pBuffStart;
pBsAux->pCurBuf = pDecEngine->pBuffCurr;
pBsAux->uiCurBits = 0;
pBsAux->iIndex = 0;
}
// ------------------- 3. actual decoding
int32_t Read32BitsCabac (PWelsCabacDecEngine pDecEngine, uint32_t& uiValue, int32_t& iNumBitsRead) {
intX_t iLeftBytes = pDecEngine->pBuffEnd - pDecEngine->pBuffCurr;
iNumBitsRead = 0;
uiValue = 0;
if (iLeftBytes <= 0) {
return ERR_CABAC_NO_BS_TO_READ;
}
switch (iLeftBytes) {
case 3:
uiValue = ((pDecEngine->pBuffCurr[0]) << 16 | (pDecEngine->pBuffCurr[1]) << 8 | (pDecEngine->pBuffCurr[2]));
pDecEngine->pBuffCurr += 3;
iNumBitsRead = 24;
break;
case 2:
uiValue = ((pDecEngine->pBuffCurr[0]) << 8 | (pDecEngine->pBuffCurr[1]));
pDecEngine->pBuffCurr += 2;
iNumBitsRead = 16;
break;
case 1:
uiValue = pDecEngine->pBuffCurr[0];
pDecEngine->pBuffCurr += 1;
iNumBitsRead = 8;
break;
default:
uiValue = ((pDecEngine->pBuffCurr[0] << 24) | (pDecEngine->pBuffCurr[1]) << 16 | (pDecEngine->pBuffCurr[2]) << 8 |
(pDecEngine->pBuffCurr[3]));
pDecEngine->pBuffCurr += 4;
iNumBitsRead = 32;
break;
}
return ERR_NONE;
}
int32_t DecodeBinCabac (PWelsCabacDecEngine pDecEngine, PWelsCabacCtx pBinCtx, uint32_t& uiBinVal) {
int32_t iErrorInfo = ERR_NONE;
uint32_t uiState = pBinCtx->uiState;
uiBinVal = pBinCtx->uiMPS;
uint64_t uiOffset = pDecEngine->uiOffset;
uint64_t uiRange = pDecEngine->uiRange;
int32_t iRenorm = 1;
uint32_t uiRangeLPS = g_kuiCabacRangeLps[uiState][ (uiRange >> 6) & 0x03];
uiRange -= uiRangeLPS;
if (uiOffset >= (uiRange << pDecEngine->iBitsLeft)) { //LPS
uiOffset -= (uiRange << pDecEngine->iBitsLeft);
uiBinVal ^= 0x0001;
if (!uiState)
pBinCtx->uiMPS ^= 0x01;
pBinCtx->uiState = g_kuiStateTransTable[uiState][0];
iRenorm = g_kRenormTable256[uiRangeLPS];
uiRange = (uiRangeLPS << iRenorm);
} else { //MPS
pBinCtx->uiState = g_kuiStateTransTable[uiState][1];
if (uiRange >= WELS_CABAC_QUARTER) {
pDecEngine->uiRange = uiRange;
return ERR_NONE;
} else {
uiRange <<= 1;
}
}
//Renorm
pDecEngine->uiRange = uiRange;
pDecEngine->iBitsLeft -= iRenorm;
if (pDecEngine->iBitsLeft > 0) {
pDecEngine->uiOffset = uiOffset;
return ERR_NONE;
}
uint32_t uiVal = 0;
int32_t iNumBitsRead = 0;
iErrorInfo = Read32BitsCabac (pDecEngine, uiVal, iNumBitsRead);
pDecEngine->uiOffset = (uiOffset << iNumBitsRead) | uiVal;
pDecEngine->iBitsLeft += iNumBitsRead;
if (iErrorInfo && pDecEngine->iBitsLeft < 0) {
return iErrorInfo;
}
return ERR_NONE;
}
int32_t DecodeBypassCabac (PWelsCabacDecEngine pDecEngine, uint32_t& uiBinVal) {
int32_t iErrorInfo = ERR_NONE;
int32_t iBitsLeft = pDecEngine->iBitsLeft;
uint64_t uiOffset = pDecEngine->uiOffset;
uint64_t uiRangeValue;
if (iBitsLeft <= 0) {
uint32_t uiVal = 0;
int32_t iNumBitsRead = 0;
iErrorInfo = Read32BitsCabac (pDecEngine, uiVal, iNumBitsRead);
uiOffset = (uiOffset << iNumBitsRead) | uiVal;
iBitsLeft = iNumBitsRead;
if (iErrorInfo && iBitsLeft == 0) {
return iErrorInfo;
}
}
iBitsLeft--;
uiRangeValue = (pDecEngine->uiRange << iBitsLeft);
if (uiOffset >= uiRangeValue) {
pDecEngine->iBitsLeft = iBitsLeft;
pDecEngine->uiOffset = uiOffset - uiRangeValue;
uiBinVal = 1;
return ERR_NONE;
}
pDecEngine->iBitsLeft = iBitsLeft;
pDecEngine->uiOffset = uiOffset;
uiBinVal = 0;
return ERR_NONE;
}
int32_t DecodeTerminateCabac (PWelsCabacDecEngine pDecEngine, uint32_t& uiBinVal) {
int32_t iErrorInfo = ERR_NONE;
uint64_t uiRange = pDecEngine->uiRange - 2;
uint64_t uiOffset = pDecEngine->uiOffset;
if (uiOffset >= (uiRange << pDecEngine->iBitsLeft)) {
uiBinVal = 1;
} else {
uiBinVal = 0;
// Renorm
if (uiRange < WELS_CABAC_QUARTER) {
int32_t iRenorm = g_kRenormTable256[uiRange];
pDecEngine->uiRange = (uiRange << iRenorm);
pDecEngine->iBitsLeft -= iRenorm;
if (pDecEngine->iBitsLeft < 0) {
uint32_t uiVal = 0;
int32_t iNumBitsRead = 0;
iErrorInfo = Read32BitsCabac (pDecEngine, uiVal, iNumBitsRead);
pDecEngine->uiOffset = (pDecEngine->uiOffset << iNumBitsRead) | uiVal;
pDecEngine->iBitsLeft += iNumBitsRead;
}
if (iErrorInfo && pDecEngine->iBitsLeft < 0) {
return iErrorInfo;
}
return ERR_NONE;
} else {
pDecEngine->uiRange = uiRange;
return ERR_NONE;
}
}
return ERR_NONE;
}
int32_t DecodeUnaryBinCabac (PWelsCabacDecEngine pDecEngine, PWelsCabacCtx pBinCtx, int32_t iCtxOffset,
uint32_t& uiSymVal) {
uiSymVal = 0;
WELS_READ_VERIFY (DecodeBinCabac (pDecEngine, pBinCtx, uiSymVal));
if (uiSymVal == 0) {
return ERR_NONE;
} else {
uint32_t uiCode;
pBinCtx += iCtxOffset;
uiSymVal = 0;
do {
WELS_READ_VERIFY (DecodeBinCabac (pDecEngine, pBinCtx, uiCode));
++uiSymVal;
} while (uiCode != 0);
return ERR_NONE;
}
}
int32_t DecodeExpBypassCabac (PWelsCabacDecEngine pDecEngine, int32_t iCount, uint32_t& uiSymVal) {
uint32_t uiCode;
int32_t iSymTmp = 0;
int32_t iSymTmp2 = 0;
uiSymVal = 0;
do {
WELS_READ_VERIFY (DecodeBypassCabac (pDecEngine, uiCode));
if (uiCode == 1) {
iSymTmp += (1 << iCount);
++iCount;
}
} while (uiCode != 0 && iCount != 16);
if (iCount == 16) {
return ERR_CABAC_UNEXPECTED_VALUE;
}
while (iCount--) {
WELS_READ_VERIFY (DecodeBypassCabac (pDecEngine, uiCode));
if (uiCode == 1) {
iSymTmp2 |= (1 << iCount);
}
}
uiSymVal = (uint32_t) (iSymTmp + iSymTmp2);
return ERR_NONE;
}
uint32_t DecodeUEGLevelCabac (PWelsCabacDecEngine pDecEngine, PWelsCabacCtx pBinCtx, uint32_t& uiCode) {
uiCode = 0;
WELS_READ_VERIFY (DecodeBinCabac (pDecEngine, pBinCtx, uiCode));
if (uiCode == 0)
return ERR_NONE;
else {
uint32_t uiTmp, uiCount = 1;
uiCode = 0;
do {
WELS_READ_VERIFY (DecodeBinCabac (pDecEngine, pBinCtx, uiTmp));
++uiCode;
++uiCount;
} while (uiTmp != 0 && uiCount != 13);
if (uiTmp != 0) {
WELS_READ_VERIFY (DecodeExpBypassCabac (pDecEngine, 0, uiTmp));
uiCode += uiTmp + 1;
}
return ERR_NONE;
}
return ERR_NONE;
}
int32_t DecodeUEGMvCabac (PWelsCabacDecEngine pDecEngine, PWelsCabacCtx pBinCtx, uint32_t iMaxBin, uint32_t& uiCode) {
WELS_READ_VERIFY (DecodeBinCabac (pDecEngine, pBinCtx + g_kMvdBinPos2Ctx[0], uiCode));
if (uiCode == 0)
return ERR_NONE;
else {
uint32_t uiTmp, uiCount = 1;
uiCode = 0;
do {
WELS_READ_VERIFY (DecodeBinCabac (pDecEngine, pBinCtx + g_kMvdBinPos2Ctx[uiCount++], uiTmp));
uiCode++;
} while (uiTmp != 0 && uiCount != 8);
if (uiTmp != 0) {
WELS_READ_VERIFY (DecodeExpBypassCabac (pDecEngine, 3, uiTmp));
uiCode += (uiTmp + 1);
}
return ERR_NONE;
}
}
}