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      1 /**
      2  *
      3  * File Name:  omxVCM4P2_EncodeVLCZigzag_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 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 
     24 
     25 /**
     26  * Function:  omxVCM4P2_EncodeVLCZigzag_IntraACVLC   (6.2.4.5.2)
     27  *
     28  * Description:
     29  * Performs zigzag scan and VLC encoding of AC and DC coefficients for one
     30  * intra block.  Two versions of the function (DCVLC and ACVLC) are provided
     31  * in order to support the two different methods of processing DC
     32  * coefficients, as described in [ISO14496-2], subclause 7.4.1.4,  Intra DC
     33  * Coefficient Decoding for the Case of Switched VLC Encoding.
     34  *
     35  * Input Arguments:
     36  *
     37  *   ppBitStream - double pointer to the current byte in the bitstream
     38  *   pBitOffset - pointer to the bit position in the byte pointed by
     39  *            *ppBitStream. Valid within 0 to 7.
     40  *   pQDctBlkCoef - pointer to the quantized DCT coefficient
     41  *   predDir - AC prediction direction, which is used to decide the zigzag
     42  *            scan pattern; takes one of the following values:
     43  *            -  OMX_VC_NONE - AC prediction not used.
     44  *                             Performs classical zigzag scan.
     45  *            -  OMX_VC_HORIZONTAL - Horizontal prediction.
     46  *                             Performs alternate-vertical zigzag scan.
     47  *            -  OMX_VC_VERTICAL - Vertical prediction.
     48  *                             Performs alternate-horizontal zigzag scan.
     49  *   pattern - block pattern which is used to decide whether this block is
     50  *            encoded
     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  *
     56  * Output Arguments:
     57  *
     58  *   ppBitStream - *ppBitStream is updated after the block is encoded, so
     59  *            that it points to the current byte in the bit stream buffer.
     60  *   pBitOffset - *pBitOffset is updated so that it points to the current bit
     61  *            position in the byte pointed by *ppBitStream.
     62  *
     63  * Return Value:
     64  *
     65  *    OMX_Sts_NoErr - no error
     66  *    OMX_Sts_BadArgErr - Bad arguments:
     67  *    -    At least one of the following pointers is NULL: ppBitStream,
     68  *              *ppBitStream, pBitOffset, pQDctBlkCoef.
     69  *    -   *pBitOffset < 0, or *pBitOffset >7.
     70  *    -    PredDir is not one of: OMX_VC_NONE, OMX_VC_HORIZONTAL, or
     71  *         OMX_VC_VERTICAL.
     72  *    -    VideoComp is not one component of enum OMXVCM4P2VideoComponent.
     73  *
     74  */
     75 
     76 OMXResult omxVCM4P2_EncodeVLCZigzag_IntraACVLC(
     77      OMX_U8 **ppBitStream,
     78      OMX_INT *pBitOffset,
     79      const OMX_S16 *pQDctBlkCoef,
     80      OMX_U8 predDir,
     81      OMX_U8 pattern,
     82      OMX_INT shortVideoHeader
     83 )
     84 {
     85     OMX_U8 start = 0;
     86 
     87     return armVCM4P2_EncodeVLCZigzag_Intra(
     88      ppBitStream,
     89      pBitOffset,
     90      pQDctBlkCoef,
     91      predDir,
     92      pattern,
     93      shortVideoHeader,
     94      start);
     95 }
     96 
     97 /* End of file */
     98