omxacaac_decodechanpairelt.c

The OpenMAX DL (Development Layer) APIs contain a comprehensive set of audio, video, signal processi

/**
 * 
 * File Name:  omxACAAC_DecodeChanPairElt.c
 * OpenMAX DL: v1.0.2
 * Revision:   10586
 * Date:       Wednesday, March 5, 2008
 * 
 * (c) Copyright 2007-2008 ARM Limited. All Rights Reserved.
 * 
 * 
 *
 * Description:
 * This file contains module for Parsing channel pair element information from AAC bitstream
 *
 */

#include "omxtypes.h"
#include "armOMX.h"
#include "omxAC.h"

#include "armAC.h"
#include "armACAAC.h"
#include "armCOMM.h"
#include "armCOMM_Bitstream.h"

/**
 * Function:  omxACAAC_DecodeChanPairElt   (3.2.3.1.4)
 *
 * Description:
 * Decodes the contents of a channel pair element (CPE) from the input 
 * bitstream and copies the information into the output CPE data structure 
 * *pChanPairElt, output individual channel stream side information structure 
 * (ICS) *pIcsInfo, and output array of LTP information structures 
 * *(pLtpInfo[0]), *(pLtpInfo[1]). Updates are conditional and depend on the 
 * contents of the bitstream.  The ICS information structure *pIcsInfo is 
 * updated only if the flag parameter pChanPairElt->CommonWin== 1.  The array 
 * of LTP information structures *pLtpInfo is updated only if 
 * (pChanPairElt >CommonWin == 1) && (audioObjectType==4). If 
 * pChanPairElt->CommonWin == 0, then DecodeChanPairElt updates only the 
 * structure member pChanPairElt->commonWin, and all other *pIcsInfo, 
 * *pChanPairElt, and *pLtpInfo structure members/array elements remain 
 * unchanged. 
 *
 * Reference: [ISO14496-3], Table 4.5 
 *
 * Input Arguments:
 *   
 *   ppBitStream - double pointer to the current byte in the input bitstream 
 *   pOffset - pointer to the next available bit of the input bitstream byte 
 *            referenced by *ppBitStream. Valid in the range 0 to 7, where 0 
 *            signifies the most significant bit and 7 signifies the least 
 *            significant bit 
 *   audioObjectType - index of the audio object type:  2=LC, 4=LTP 
 *
 * Output Arguments:
 *   
 *   ppBitStream - double pointer to the current byte in the input bitstream, 
 *            updated after decoding the channel pair element. 
 *   pOffset - pointer to the next available bit of the input bitstream byte 
 *            referenced by *ppBitStream. Valid in the range 0 to 7, where 0 
 *            signifies the most significant bit and 7 signifies the least 
 *            significant bit. 
 *   pIcsInfo - if pChanPairElt->CommonWin == 1, then pIcsInfo points to the 
 *            updated OMXAACIcsInfo structure.  In this case, all structure 
 *            elements are updated unconditionally except as shown in Table 
 *            3-9.  Also in this case, only the first pIcsInfo->numWinGrp 
 *            elements in pIcsInfo-> pWinGrpLen are updated. Otherwise, if 
 *            pChanPairElt->CommonWin == 0 then none of the structure members 
 *            are modified; in this case the array pIcsInfo will be updated by 
 *            the function omxACAAC_NoiselessDecode. 
 *   pChanPairElt - pointer to the updated OMXAACChanPairElt structure.  The 
 *            function modifies the commonWin structure member 
 *            unconditionally, but modifies the other members (msMaskPres and 
 *            ppMsMask array) only if (pChanPairElt->CommonWin == 1, as shown 
 *            in Table 3-10. 
 *   pLtpInfo - array containing two LTP information structure pointers.  If 
 *            (pChanPairElt >CommonWin == 1) && (audioObjectType==4), then the 
 *            structures referenced by the pointers in this array are updated 
 *            to contain the LTP information associated with the individual 
 *            channels in the current CPE on which LTP has been enabled.  Four 
 *            update scenarios are possible:  i) no LTP information - if the 
 *            bit field predictor_data_present==0 within the ics_info syntax 
 *            element of the current CPE, then the array pLtpInfo is not 
 *            modified ii) LTP on the first CPE channel - if the elementary 
 *            stream bit field predictor_data_present==1 && the first 
 *            occurrence of the bit field ltp_data_present==1 then the 
 *            contents of *(pLtpInfo[0]) are updated; iii) LTP on the second 
 *            CPE channel - if predictor_data_present==1 && the second 
 *            occurrence of the bit field ltp_data_present==1 then the 
 *            contents of *(pLtpInfo[1]) are updated; iv) LTP on both CPE 
 *            channels - both cases ii) and iii) may occur simultaneously, in 
 *            which case both array elements are updated.  Otherwise, if 
 *            (pChanPairElt->CommonWin == 0) || (audioObjectType!=4) then the 
 *            function omxACAAC_DecodeChanPairElt does not update the contents 
 *            of the structures referenced by the pointers in the array.  
 *            Under this condition, the array will be updated later in the 
 *            stream decoding process by the function 
 *            omxACAAC_NoiselessDecode. Reference:  [ISO14496-3], sub-clause 
 *            4.4.2.1 and Tables 4.5-4.6. Table 3-9: pIcsInfo Members Modified 
 *            Conditionally by DecodeChanPairElt Members  Required Condition 
 *            SfGrouping pChanPairElt->CommonWin == 1 && pIcsInfo >winSequence 
 *            == 2 Members  Required Condition predResetGroupNum  Never 
 *            modified predReset  Never modified pPredUsed[.]  Never modified 
 *            Table 3-10: pChanPairElt Members Modified Conditionally by 
 *            DecodeChanPairElt Members Required Condition msMaskPres 
 *             pChanPairElt->CommonWin == 1 pMsMask[sfb] 
 *            pChanPairElg->CommonWin==1 && pChanPairElt >msMaskPres == 1 
 *
 * Return Value:
 *    
 *    OMX_Sts_NoErr - no error 
 *    OMX_Sts_BadArgErr - bad arguments 
 *    -    at least one of the following pointers is NULL: ppBitStream, 
 *              pOffset, *ppBitStream, pIcsInfo or pChanPairElt. 
 *    -   *pOffset exceeds [0, 7] 
 *    -    audioObjectType!=2 && audioObjectType!=4 
 *    OMX_Sts_InvalidBitstreamValErr - invalid bitstream parameter value 
 *              detected 
 *    -    commonWin==1 and the decoded value of pIcsInfo->maxSfb is out of 
 *              range, i.e., exceeds [0,51] 
 *
 */
 
OMXResult omxACAAC_DecodeChanPairElt(
     const OMX_U8 **ppBitStream,
     OMX_INT *pOffset,
     OMXAACIcsInfo *pIcsInfo,
     OMXAACChanPairElt *pChanPairElt,
     OMX_INT audioObjectType,
     OMXAACLtpInfoPtr *pLtpInfo
 )
{
    OMX_INT i,j;
    OMXResult errorCode;

    /* Argument Check */        
    armRetArgErrIf( ppBitStream    == NULL, OMX_Sts_BadArgErr);
    armRetArgErrIf( *ppBitStream   == NULL, OMX_Sts_BadArgErr);
    armRetArgErrIf( pOffset        == NULL, OMX_Sts_BadArgErr);

    armRetArgErrIf( pIcsInfo       == NULL, OMX_Sts_BadArgErr);
    armRetArgErrIf( pLtpInfo       == NULL, OMX_Sts_BadArgErr);
    armRetArgErrIf( pChanPairElt   == NULL, OMX_Sts_BadArgErr);

    armRetArgErrIf( (*pOffset > 7) || (*pOffset < 0)   , OMX_Sts_BadArgErr);
    
    armRetArgErrIf( (audioObjectType != 2) &&
                    (audioObjectType != 4), OMX_Sts_BadArgErr);

    /* Processing */    
    armSkipBits(ppBitStream,pOffset,4); /*element_instance_tag*/
    
    pChanPairElt->commonWin = (OMX_INT)armGetBits(ppBitStream,pOffset,1); 
     

    if(pChanPairElt->commonWin == 1)
    {
        
        errorCode = armACAAC_DecodeIcsInfoData(ppBitStream,pOffset,
                            pChanPairElt->commonWin,audioObjectType,
                            0,NULL,pIcsInfo,pLtpInfo);
    
        armRetDataErrIf(errorCode != OMX_Sts_NoErr , errorCode);
       
        pChanPairElt->msMaskPres = (OMX_INT)armGetBits(ppBitStream,pOffset,2);

        
        if(pChanPairElt->msMaskPres == 1)
        {
            for(i = 0;i < pIcsInfo->numWinGrp;i++)
            {
                for(j = 0 ; j < pIcsInfo->maxSfb ; j++ )
                {
                    pChanPairElt->ppMsMask[i][j] = (OMX_INT)armGetBits(ppBitStream,pOffset,1);
                }
            }
        }
        
    }/*End if() */
    
        
    return OMX_Sts_NoErr;

}
 /* End of File */