1/*
2 * Copyright (C) 2007-2008 ARM Limited
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 *
16 */
17/**
18 *
19 * File Name:  omxVCM4P2_DecodeVLCZigzag_IntraDCVLC.c
20 * OpenMAX DL: v1.0.2
21 * Revision:   9641
22 * Date:       Thursday, February 7, 2008
23 *
24 *
25 *
26 *
27 * Description:
28 * Contains modules for zigzag scanning and VLC decoding
29 * for intra block.
30 *
31 */
32
33#include "omxtypes.h"
34#include "armOMX.h"
35#include "omxVC.h"
36
37#include "armVC.h"
38#include "armCOMM_Bitstream.h"
39#include "armCOMM.h"
40#include "armVCM4P2_Huff_Tables_VLC.h"
41#include "armVCM4P2_ZigZag_Tables.h"
42
43
44
45
46/**
47 * Function:  omxVCM4P2_DecodeVLCZigzag_IntraDCVLC   (6.2.5.2.2)
48 *
49 * Description:
50 * Performs VLC decoding and inverse zigzag scan of AC and DC coefficients
51 * for one intra block.  Two versions of the function (DCVLC and ACVLC) are
52 * provided in order to support the two different methods of processing DC
53 * coefficients, as described in [ISO14496-2], subclause 7.4.1.4,  Intra DC
54 * Coefficient Decoding for the Case of Switched VLC Encoding.
55 *
56 * Input Arguments:
57 *
58 *   ppBitStream - pointer to the pointer to the current byte in the
59 *            bitstream buffer
60 *   pBitOffset - pointer to the bit position in the current byte referenced
61 *            by *ppBitStream.  The parameter *pBitOffset is valid in the
62 *            range [0-7].
63 *            Bit Position in one byte:  |Most      Least|
64 *                    *pBitOffset        |0 1 2 3 4 5 6 7|
65 *   predDir - AC prediction direction; used to select the zigzag scan
66 *            pattern; takes one of the following values:
67 *            -  OMX_VC_NONE - AC prediction not used;
68 *                             performs classical zigzag scan.
69 *            -  OMX_VC_HORIZONTAL - Horizontal prediction;
70 *                             performs alternate-vertical zigzag scan;
71 *            -  OMX_VC_VERTICAL - Vertical prediction;
72 *                             performs alternate-horizontal zigzag scan.
73 *   shortVideoHeader - binary flag indicating presence of
74 *            short_video_header; escape modes 0-3 are used if
75 *            shortVideoHeader==0, and escape mode 4 is used when
76 *            shortVideoHeader==1.
77 *   videoComp - video component type (luminance or chrominance) of the
78 *            current block
79 *
80 * Output Arguments:
81 *
82 *   ppBitStream - *ppBitStream is updated after the block is decoded such
83 *            that it points to the current byte in the bit stream buffer
84 *   pBitOffset - *pBitOffset is updated such that it points to the current
85 *            bit position in the byte pointed by *ppBitStream
86 *   pDst - pointer to the coefficient buffer of current block; must be
87 *            4-byte aligned.
88 *
89 * Return Value:
90 *
91 *    OMX_Sts_NoErr - no error
92 *    OMX_Sts_BadArgErr - bad arguments, if:
93 *    -    At least one of the following pointers is NULL:
94 *         ppBitStream, *ppBitStream, pBitOffset, pDst
95 *    -    *pBitOffset exceeds [0,7]
96 *    -    preDir exceeds [0,2]
97 *    -    pDst is not 4-byte aligned
98 *    OMX_Sts_Err - if:
99 *    -    In DecodeVLCZigzag_IntraDCVLC, dc_size > 12
100 *    -    At least one of mark bits equals zero
101 *    -    Illegal stream encountered; code cannot be located in VLC table
102 *    -    Forbidden code encountered in the VLC FLC table.
103 *    -    The number of coefficients is greater than 64
104 *
105 */
106
107OMXResult omxVCM4P2_DecodeVLCZigzag_IntraDCVLC(
108     const OMX_U8 ** ppBitStream,
109     OMX_INT * pBitOffset,
110     OMX_S16 * pDst,
111     OMX_U8 predDir,
112     OMX_INT shortVideoHeader,
113     OMXVCM4P2VideoComponent videoComp
114)
115{
116    /* Dummy initilaization to remove compilation error */
117    OMX_S8  DCValueSize = 0;
118    OMX_U16 powOfSize, fetchDCbits;
119    OMX_U8 start = 1;
120
121    /* Argument error checks */
122    armRetArgErrIf(ppBitStream == NULL, OMX_Sts_BadArgErr);
123    armRetArgErrIf(*ppBitStream == NULL, OMX_Sts_BadArgErr);
124    armRetArgErrIf(pBitOffset == NULL, OMX_Sts_BadArgErr);
125    armRetArgErrIf(pDst == NULL, OMX_Sts_BadArgErr);
126    armRetArgErrIf(!armIs4ByteAligned(pDst), OMX_Sts_BadArgErr);
127    armRetArgErrIf((*pBitOffset < 0) || (*pBitOffset > 7), OMX_Sts_BadArgErr);
128    armRetArgErrIf((predDir > 2), OMX_Sts_BadArgErr);
129
130    /* Insert the code into the bitstream */
131    if (videoComp == OMX_VC_LUMINANCE)
132    {
133        DCValueSize = armUnPackVLC32(ppBitStream,
134                            pBitOffset, armVCM4P2_aIntraDCLumaIndex);
135    }
136    else if (videoComp == OMX_VC_CHROMINANCE)
137    {
138        DCValueSize = armUnPackVLC32(ppBitStream,
139                            pBitOffset, armVCM4P2_aIntraDCChromaIndex);
140    }
141    armRetDataErrIf(DCValueSize == -1, OMX_Sts_Err);
142    armRetDataErrIf(DCValueSize > 12, OMX_Sts_Err);
143
144
145    if (DCValueSize == 0)
146    {
147        pDst[0] = 0;
148    }
149    else
150    {
151        fetchDCbits = (OMX_U16) armGetBits(ppBitStream, pBitOffset, \
152                                           DCValueSize);
153
154        if ( (fetchDCbits >> (DCValueSize - 1)) == 0)
155        {
156            /* calulate pow */
157            powOfSize = (1 << DCValueSize);
158
159            pDst[0] =  (OMX_S16) (fetchDCbits ^ (powOfSize - 1));
160            pDst[0] = -pDst[0];
161        }
162        else
163        {
164            pDst[0] = fetchDCbits;
165        }
166
167        if (DCValueSize > 8)
168        {
169            /* reading and checking the marker bit*/
170            armRetDataErrIf (armGetBits(ppBitStream, pBitOffset, 1) == 0, \
171                             OMX_Sts_Err);
172        }
173    }
174
175    return armVCM4P2_DecodeVLCZigzag_Intra(
176                ppBitStream,
177                pBitOffset,
178                pDst,
179                predDir,
180                shortVideoHeader,
181                start);
182}
183
184/* End of file */
185
186