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      1 /**
      2  *
      3  * File Name:  omxVCM4P2_DecodeVLCZigzag_IntraACVLC.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 decoding
     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.h"
     24 
     25 
     26 
     27 /**
     28  * Function:  omxVCM4P2_DecodeVLCZigzag_IntraACVLC   (6.2.5.2.2)
     29  *
     30  * Description:
     31  * Performs VLC decoding and inverse zigzag scan of AC and DC coefficients
     32  * for one intra block.  Two versions of the function (DCVLC and ACVLC) are
     33  * provided in order to support the two different methods of processing DC
     34  * coefficients, as described in [ISO14496-2], subclause 7.4.1.4,  Intra DC
     35  * Coefficient Decoding for the Case of Switched VLC Encoding.
     36  *
     37  * Input Arguments:
     38  *
     39  *   ppBitStream - pointer to the pointer to the current byte in the
     40  *            bitstream buffer
     41  *   pBitOffset - pointer to the bit position in the current byte referenced
     42  *            by *ppBitStream.  The parameter *pBitOffset is valid in the
     43  *            range [0-7]. Bit Position in one byte:  |Most Least| *pBitOffset
     44  *            |0 1 2 3 4 5 6 7|
     45  *   predDir - AC prediction direction; used to select the zigzag scan
     46  *            pattern; takes one of the following values: OMX_VC_NONE - AC
     47  *            prediction not used; performs classical zigzag scan.
     48  *            OMX_VC_HORIZONTAL - Horizontal prediction; performs
     49  *            alternate-vertical zigzag scan; OMX_VC_VERTICAL - Vertical
     50  *            prediction; performs alternate-horizontal zigzag scan.
     51  *   shortVideoHeader - binary flag indicating presence of
     52  *            short_video_header; escape modes 0-3 are used if
     53  *            shortVideoHeader==0, and escape mode 4 is used when
     54  *            shortVideoHeader==1.
     55  *   videoComp - video component type (luminance or chrominance) of the
     56  *            current block
     57  *
     58  * Output Arguments:
     59  *
     60  *   ppBitStream - *ppBitStream is updated after the block is decoded such
     61  *            that it points to the current byte in the bit stream buffer
     62  *   pBitOffset - *pBitOffset is updated such that it points to the current
     63  *            bit position in the byte pointed by *ppBitStream
     64  *   pDst - pointer to the coefficient buffer of current block; must be
     65  *            4-byte aligned.
     66  *
     67  * Return Value:
     68  *
     69  *    OMX_Sts_NoErr - no error
     70  *    OMX_Sts_BadArgErr - bad arguments At least one of the following
     71  *              pointers is NULL: ppBitStream, *ppBitStream, pBitOffset, pDst,
     72  *              or At least one of the following conditions is true:
     73  *              *pBitOffset exceeds [0,7], preDir exceeds [0,2], or pDst is
     74  *              not 4-byte aligned
     75  *    OMX_Sts_Err In DecodeVLCZigzag_IntraDCVLC, dc_size > 12 At least one of
     76  *              mark bits equals zero Illegal stream encountered; code cannot
     77  *              be located in VLC table Forbidden code encountered in the VLC
     78  *              FLC table The number of coefficients is greater than 64
     79  *
     80  */
     81 
     82 
     83 OMXResult omxVCM4P2_DecodeVLCZigzag_IntraACVLC(
     84      const OMX_U8 ** ppBitStream,
     85      OMX_INT * pBitOffset,
     86      OMX_S16 * pDst,
     87      OMX_U8 predDir,
     88      OMX_INT shortVideoHeader
     89 )
     90 {
     91     OMX_U8 start = 0;
     92 
     93     return armVCM4P2_DecodeVLCZigzag_Intra(
     94      ppBitStream,
     95      pBitOffset,
     96      pDst,
     97      predDir,
     98      shortVideoHeader,
     99      start);
    100 }
    101 
    102 /* End of file */
    103 
    104