xref: /frameworks/av/media/libstagefright/codecs/on2/h264dec/omxdl/reference/vc/m4p10/src/omxVCM4P10_DecodeCoeffsToPairCAVLC.c

/* ----------------------------------------------------------------
 *
 *
 * File Name:  omxVCM4P10_DecodeCoeffsToPairCAVLC.c
 * OpenMAX DL: v1.0.2
 * Revision:   9641
 * Date:       Thursday, February 7, 2008
 *
 * (c) Copyright 2007-2008 ARM Limited. All Rights Reserved.
 *
 *
 *
 * H.264 decode coefficients module
 *
 */

#include "omxtypes.h"
#include "armOMX.h"
#include "omxVC.h"
#include "armCOMM.h"
#include "armVC.h"

/**
 * Function:  omxVCM4P10_DecodeCoeffsToPairCAVLC   (6.3.4.1.2)
 *
 * Description:
 * Performs CAVLC decoding and inverse zigzag scan for 4x4 block of
 * Intra16x16DCLevel, Intra16x16ACLevel, LumaLevel, and ChromaACLevel. Inverse
 * field scan is not supported. The decoded coefficients in the packed
 * position-coefficient buffer are stored in reverse zig-zag order, i.e., the
 * first buffer element contains the last non-zero postion-coefficient pair of
 * the block. Within each position-coefficient pair, the position entry
 * indicates the raster-scan position of the coefficient, while the
 * coefficient entry contains the coefficient value.
 *
 * Input Arguments:
 *
 *   ppBitStream -Double pointer to current byte in bit stream buffer
 *   pOffset - Pointer to current bit position in the byte pointed to by
 *            *ppBitStream; valid in the range [0,7].
 *   sMaxNumCoeff - Maximum the number of non-zero coefficients in current
 *            block
 *   sVLCSelect - VLC table selector, obtained from the number of non-zero
 *            coefficients contained in the above and left 4x4 blocks.  It is
 *            equivalent to the variable nC described in H.264 standard table
 *            9 5, except its value can t be less than zero.
 *
 * Output Arguments:
 *
 *   ppBitStream - *ppBitStream is updated after each block is decoded.
 *            Buffer position (*ppPosCoefBuf) is updated upon return, unless
 *            there are only zero coefficients in the currently decoded block.
 *             In this case the caller is expected to bypass the
 *            transform/dequantization of the empty blocks.
 *   pOffset - *pOffset is updated after each block is decoded
 *   pNumCoeff - Pointer to the number of nonzero coefficients in this block
 *   ppPosCoefBuf - Double pointer to destination residual
 *            coefficient-position pair buffer
 *
 * Return Value:
 *    OMX_Sts_NoErr, if the function runs without error.
 *
 *    OMX_Sts_BadArgErr - bad arguments: if one of the following cases occurs:
 *    -    ppBitStream or pOffset is NULL.
 *    -    ppPosCoefBuf or pNumCoeff is NULL.
 *    -    sMaxNumCoeff is not equal to either 15 or 16.
 *    -    sVLCSelect is less than 0.
 *
 *    OMX_Sts_Err - if one of the following is true:
 *    -    an illegal code is encountered in the bitstream
 *
 */

OMXResult omxVCM4P10_DecodeCoeffsToPairCAVLC(
     const OMX_U8** ppBitStream,
     OMX_S32* pOffset,
     OMX_U8* pNumCoeff,
     OMX_U8**ppPosCoefbuf,
     OMX_INT sVLCSelect,
     OMX_INT sMaxNumCoeff
 )
{
    int nTable;

    armRetArgErrIf(ppBitStream==NULL   , OMX_Sts_BadArgErr);
    armRetArgErrIf(*ppBitStream==NULL  , OMX_Sts_BadArgErr);
    armRetArgErrIf(pOffset==NULL       , OMX_Sts_BadArgErr);
    armRetArgErrIf(*pOffset<0          , OMX_Sts_BadArgErr);
    armRetArgErrIf(*pOffset>7          , OMX_Sts_BadArgErr);
    armRetArgErrIf(pNumCoeff==NULL     , OMX_Sts_BadArgErr);
    armRetArgErrIf(ppPosCoefbuf==NULL  , OMX_Sts_BadArgErr);
    armRetArgErrIf(*ppPosCoefbuf==NULL , OMX_Sts_BadArgErr);
    armRetArgErrIf(sVLCSelect<0        , OMX_Sts_BadArgErr);
    armRetArgErrIf(sMaxNumCoeff<15     , OMX_Sts_BadArgErr);
    armRetArgErrIf(sMaxNumCoeff>16     , OMX_Sts_BadArgErr);

    /* Find VLC table number */
    if (sVLCSelect<2)
    {
        nTable = 0;
    }
    else if (sVLCSelect<4)
    {
        nTable = 1;
    }
    else if (sVLCSelect<8)
    {
        nTable = 2;
    }
    else /* sVLCSelect >= 8 */
    {
        nTable = 3;
    }

    return armVCM4P10_DecodeCoeffsToPair(ppBitStream, pOffset, pNumCoeff,
                                         ppPosCoefbuf, nTable, sMaxNumCoeff);
}