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      1 /**
      2  *
      3  * File Name:  omxVCM4P2_EncodeVLCZigzag_IntraDCVLC.c
      4  * OpenMAX DL: v1.0.2
      5  * Revision:   9641
      6  * Date:       Thursday, February 7, 2008
      7  *
      8  * (c) Copyright 2007-2008 ARM Limited. All Rights Reserved.
      9  *
     10  *
     11  *
     12  * Description:
     13  * Contains modules for zigzag scanning and VLC encoding
     14  * for intra block.
     15  *
     16  */
     17 
     18 #include "omxtypes.h"
     19 #include "armOMX.h"
     20 #include "omxVC.h"
     21 
     22 #include "armVC.h"
     23 #include "armCOMM_Bitstream.h"
     24 #include "armCOMM.h"
     25 #include "armVCM4P2_Huff_Tables_VLC.h"
     26 #include "armVCM4P2_ZigZag_Tables.h"
     27 
     28 
     29 
     30 /**
     31  * Function:  omxVCM4P2_EncodeVLCZigzag_IntraDCVLC   (6.2.4.5.2)
     32  *
     33  * Description:
     34  * Performs zigzag scan and VLC encoding of AC and DC coefficients for one
     35  * intra block.  Two versions of the function (DCVLC and ACVLC) are provided
     36  * in order to support the two different methods of processing DC
     37  * coefficients, as described in [ISO14496-2], subclause 7.4.1.4, "Intra DC
     38  * Coefficient Decoding for the Case of Switched VLC Encoding".
     39  *
     40  * Input Arguments:
     41  *
     42  *   ppBitStream - double pointer to the current byte in the bitstream
     43  *   pBitOffset - pointer to the bit position in the byte pointed by
     44  *            *ppBitStream. Valid within 0 to 7.
     45  *   pQDctBlkCoef - pointer to the quantized DCT coefficient
     46  *   predDir - AC prediction direction, which is used to decide the zigzag
     47  *            scan pattern; takes one of the following values:
     48  *            -  OMX_VC_NONE - AC prediction not used.
     49  *                             Performs classical zigzag scan.
     50  *            -  OMX_VC_HORIZONTAL - Horizontal prediction.
     51  *                             Performs alternate-vertical zigzag scan.
     52  *            -  OMX_VC_VERTICAL - Vertical prediction.
     53  *                             Performs alternate-horizontal zigzag scan.
     54  *   pattern - block pattern which is used to decide whether this block is
     55  *            encoded
     56  *   shortVideoHeader - binary flag indicating presence of
     57  *            short_video_header; escape modes 0-3 are used if
     58  *            shortVideoHeader==0, and escape mode 4 is used when
     59  *            shortVideoHeader==1.
     60  *   videoComp - video component type (luminance, chrominance) of the current
     61  *            block
     62  *
     63  * Output Arguments:
     64  *
     65  *   ppBitStream - *ppBitStream is updated after the block is encoded, so
     66  *            that it points to the current byte in the bit stream buffer.
     67  *   pBitOffset - *pBitOffset is updated so that it points to the current bit
     68  *            position in the byte pointed by *ppBitStream.
     69  *
     70  * Return Value:
     71  *
     72  *    OMX_Sts_NoErr - no error
     73  *    OMX_Sts_BadArgErr - Bad arguments:
     74  *    -    At least one of the following pointers is NULL: ppBitStream,
     75  *              *ppBitStream, pBitOffset, pQDctBlkCoef.
     76  *    -   *pBitOffset < 0, or *pBitOffset >7.
     77  *    -    PredDir is not one of: OMX_VC_NONE, OMX_VC_HORIZONTAL, or
     78  *         OMX_VC_VERTICAL.
     79  *    -    VideoComp is not one component of enum OMXVCM4P2VideoComponent.
     80  *
     81  */
     82 
     83 OMXResult omxVCM4P2_EncodeVLCZigzag_IntraDCVLC(
     84      OMX_U8 **ppBitStream,
     85      OMX_INT *pBitOffset,
     86      const OMX_S16 *pQDctBlkCoef,
     87      OMX_U8 predDir,
     88      OMX_U8 pattern,
     89      OMX_INT shortVideoHeader,
     90      OMXVCM4P2VideoComponent videoComp
     91 )
     92 {
     93     OMX_S16 dcValue, powOfSize;
     94     OMX_U8  DCValueSize, start = 1;
     95     OMX_U16 absDCValue;
     96 
     97     /* Argument error checks */
     98     armRetArgErrIf(ppBitStream == NULL, OMX_Sts_BadArgErr);
     99     armRetArgErrIf(*ppBitStream == NULL, OMX_Sts_BadArgErr);
    100     armRetArgErrIf(pBitOffset == NULL, OMX_Sts_BadArgErr);
    101     armRetArgErrIf(pQDctBlkCoef == NULL, OMX_Sts_BadArgErr);
    102     armRetArgErrIf((*pBitOffset < 0) || (*pBitOffset >7), OMX_Sts_BadArgErr);
    103 	armRetArgErrIf((videoComp != OMX_VC_LUMINANCE) && (videoComp != OMX_VC_CHROMINANCE), OMX_Sts_BadArgErr);
    104 	armRetArgErrIf((predDir != OMX_VC_NONE) && (predDir != OMX_VC_HORIZONTAL) && (predDir != OMX_VC_VERTICAL) , OMX_Sts_BadArgErr);
    105 
    106     if (pattern)
    107     {
    108         dcValue = pQDctBlkCoef[0];
    109         absDCValue = armAbs(dcValue);
    110 
    111         /* Find the size */
    112         DCValueSize = armLogSize (absDCValue);
    113         absDCValue = armAbs(dcValue);
    114 
    115         /* Insert the code into the bitstream */
    116         if (videoComp == OMX_VC_LUMINANCE)
    117         {
    118 
    119             armPackVLC32 (ppBitStream, pBitOffset,
    120                           armVCM4P2_aIntraDCLumaIndex[DCValueSize]);
    121         }
    122         else if (videoComp == OMX_VC_CHROMINANCE)
    123         {
    124 
    125             armPackVLC32 (ppBitStream, pBitOffset,
    126                           armVCM4P2_aIntraDCChromaIndex[DCValueSize]);
    127         }
    128 
    129         /* Additional code generation in case of negative
    130            dc value the additional */
    131         if (DCValueSize > 0)
    132         {
    133             if (dcValue < 0)
    134             {
    135                 /* calulate 2 pow */
    136                 powOfSize = (1 << DCValueSize);
    137 
    138                 absDCValue =  absDCValue ^ (powOfSize - 1);
    139             }
    140             armPackBits(ppBitStream, pBitOffset, (OMX_U32)absDCValue, \
    141                         DCValueSize);
    142 
    143             if (DCValueSize > 8)
    144             {
    145                 armPackBits(ppBitStream, pBitOffset, 1, 1);
    146             }
    147         }
    148     }
    149 
    150     return armVCM4P2_EncodeVLCZigzag_Intra(
    151                 ppBitStream,
    152                 pBitOffset,
    153                 pQDctBlkCoef,
    154                 predDir,
    155                 pattern,
    156                 shortVideoHeader,
    157                 start);
    158 }
    159 
    160 /* End of file */
    161