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/**
*
* File Name: omxVCM4P2_DecodeVLCZigzag_IntraDCVLC.c
* OpenMAX DL: v1.0.2
* Revision: 9641
* Date: Thursday, February 7, 2008
*
* (c) Copyright 2007-2008 ARM Limited. All Rights Reserved.
*
*
*
* Description:
* Contains modules for zigzag scanning and VLC decoding
* for intra block.
*
*/
#include "omxtypes.h"
#include "armOMX.h"
#include "omxVC.h"
#include "armVC.h"
#include "armCOMM_Bitstream.h"
#include "armCOMM.h"
#include "armVCM4P2_Huff_Tables_VLC.h"
#include "armVCM4P2_ZigZag_Tables.h"
/**
* Function: omxVCM4P2_DecodeVLCZigzag_IntraDCVLC (6.2.5.2.2)
*
* Description:
* Performs VLC decoding and inverse zigzag scan of AC and DC coefficients
* for one intra block. Two versions of the function (DCVLC and ACVLC) are
* provided in order to support the two different methods of processing DC
* coefficients, as described in [ISO14496-2], subclause 7.4.1.4, Intra DC
* Coefficient Decoding for the Case of Switched VLC Encoding.
*
* Input Arguments:
*
* ppBitStream - pointer to the pointer to the current byte in the
* bitstream buffer
* pBitOffset - pointer to the bit position in the current byte referenced
* by *ppBitStream. The parameter *pBitOffset is valid in the
* range [0-7].
* Bit Position in one byte: |Most Least|
* *pBitOffset |0 1 2 3 4 5 6 7|
* predDir - AC prediction direction; used to select the zigzag scan
* pattern; takes one of the following values:
* - OMX_VC_NONE - AC prediction not used;
* performs classical zigzag scan.
* - OMX_VC_HORIZONTAL - Horizontal prediction;
* performs alternate-vertical zigzag scan;
* - OMX_VC_VERTICAL - Vertical prediction;
* performs alternate-horizontal zigzag scan.
* shortVideoHeader - binary flag indicating presence of
* short_video_header; escape modes 0-3 are used if
* shortVideoHeader==0, and escape mode 4 is used when
* shortVideoHeader==1.
* videoComp - video component type (luminance or chrominance) of the
* current block
*
* Output Arguments:
*
* ppBitStream - *ppBitStream is updated after the block is decoded such
* that it points to the current byte in the bit stream buffer
* pBitOffset - *pBitOffset is updated such that it points to the current
* bit position in the byte pointed by *ppBitStream
* pDst - pointer to the coefficient buffer of current block; must be
* 4-byte aligned.
*
* Return Value:
*
* OMX_Sts_NoErr - no error
* OMX_Sts_BadArgErr - bad arguments, if:
* - At least one of the following pointers is NULL:
* ppBitStream, *ppBitStream, pBitOffset, pDst
* - *pBitOffset exceeds [0,7]
* - preDir exceeds [0,2]
* - pDst is not 4-byte aligned
* OMX_Sts_Err - if:
* - In DecodeVLCZigzag_IntraDCVLC, dc_size > 12
* - At least one of mark bits equals zero
* - Illegal stream encountered; code cannot be located in VLC table
* - Forbidden code encountered in the VLC FLC table.
* - The number of coefficients is greater than 64
*
*/
OMXResult omxVCM4P2_DecodeVLCZigzag_IntraDCVLC(
const OMX_U8 ** ppBitStream,
OMX_INT * pBitOffset,
OMX_S16 * pDst,
OMX_U8 predDir,
OMX_INT shortVideoHeader,
OMXVCM4P2VideoComponent videoComp
)
{
/* Dummy initilaization to remove compilation error */
OMX_S8 DCValueSize = 0;
OMX_U16 powOfSize, fetchDCbits;
OMX_U8 start = 1;
/* Argument error checks */
armRetArgErrIf(ppBitStream == NULL, OMX_Sts_BadArgErr);
armRetArgErrIf(*ppBitStream == NULL, OMX_Sts_BadArgErr);
armRetArgErrIf(pBitOffset == NULL, OMX_Sts_BadArgErr);
armRetArgErrIf(pDst == NULL, OMX_Sts_BadArgErr);
armRetArgErrIf(!armIs4ByteAligned(pDst), OMX_Sts_BadArgErr);
armRetArgErrIf((*pBitOffset < 0) || (*pBitOffset > 7), OMX_Sts_BadArgErr);
armRetArgErrIf((predDir > 2), OMX_Sts_BadArgErr);
/* Insert the code into the bitstream */
if (videoComp == OMX_VC_LUMINANCE)
{
DCValueSize = armUnPackVLC32(ppBitStream,
pBitOffset, armVCM4P2_aIntraDCLumaIndex);
}
else if (videoComp == OMX_VC_CHROMINANCE)
{
DCValueSize = armUnPackVLC32(ppBitStream,
pBitOffset, armVCM4P2_aIntraDCChromaIndex);
}
armRetDataErrIf(DCValueSize == -1, OMX_Sts_Err);
armRetDataErrIf(DCValueSize > 12, OMX_Sts_Err);
if (DCValueSize == 0)
{
pDst[0] = 0;
}
else
{
fetchDCbits = (OMX_U16) armGetBits(ppBitStream, pBitOffset, \
DCValueSize);
if ( (fetchDCbits >> (DCValueSize - 1)) == 0)
{
/* calulate pow */
powOfSize = (1 << DCValueSize);
pDst[0] = (OMX_S16) (fetchDCbits ^ (powOfSize - 1));
pDst[0] = -pDst[0];
}
else
{
pDst[0] = fetchDCbits;
}
if (DCValueSize > 8)
{
/* reading and checking the marker bit*/
armRetDataErrIf (armGetBits(ppBitStream, pBitOffset, 1) == 0, \
OMX_Sts_Err);
}
}
return armVCM4P2_DecodeVLCZigzag_Intra(
ppBitStream,
pBitOffset,
pDst,
predDir,
shortVideoHeader,
start);
}
/* End of file */
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