omxVCM4P2_EncodeVLCZigzag_IntraDCVLC.c revision 78e52bfac041d71ce53b5b13c2abf78af742b09d 
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_EncodeVLCZigzag_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 encoding
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 * Function:  omxVCM4P2_EncodeVLCZigzag_IntraDCVLC   (6.2.4.5.2)
47 *
48 * Description:
49 * Performs zigzag scan and VLC encoding of AC and DC coefficients for one
50 * intra block.  Two versions of the function (DCVLC and ACVLC) are provided
51 * in order to support the two different methods of processing DC
52 * coefficients, as described in [ISO14496-2], subclause 7.4.1.4, "Intra DC
53 * Coefficient Decoding for the Case of Switched VLC Encoding".
54 *
55 * Input Arguments:
56 *
57 *   ppBitStream - double pointer to the current byte in the bitstream
58 *   pBitOffset - pointer to the bit position in the byte pointed by
59 *            *ppBitStream. Valid within 0 to 7.
60 *   pQDctBlkCoef - pointer to the quantized DCT coefficient
61 *   predDir - AC prediction direction, which is used to decide the zigzag
62 *            scan pattern; takes one of the following values:
63 *            -  OMX_VC_NONE - AC prediction not used.
64 *                             Performs classical zigzag scan.
65 *            -  OMX_VC_HORIZONTAL - Horizontal prediction.
66 *                             Performs alternate-vertical zigzag scan.
67 *            -  OMX_VC_VERTICAL - Vertical prediction.
68 *                             Performs alternate-horizontal zigzag scan.
69 *   pattern - block pattern which is used to decide whether this block is
70 *            encoded
71 *   shortVideoHeader - binary flag indicating presence of
72 *            short_video_header; escape modes 0-3 are used if
73 *            shortVideoHeader==0, and escape mode 4 is used when
74 *            shortVideoHeader==1.
75 *   videoComp - video component type (luminance, chrominance) of the current
76 *            block
77 *
78 * Output Arguments:
79 *
80 *   ppBitStream - *ppBitStream is updated after the block is encoded, so
81 *            that it points to the current byte in the bit stream buffer.
82 *   pBitOffset - *pBitOffset is updated so that it points to the current bit
83 *            position in the byte pointed by *ppBitStream.
84 *
85 * Return Value:
86 *
87 *    OMX_Sts_NoErr - no error
88 *    OMX_Sts_BadArgErr - Bad arguments:
89 *    -    At least one of the following pointers is NULL: ppBitStream,
90 *              *ppBitStream, pBitOffset, pQDctBlkCoef.
91 *    -   *pBitOffset < 0, or *pBitOffset >7.
92 *    -    PredDir is not one of: OMX_VC_NONE, OMX_VC_HORIZONTAL, or
93 *         OMX_VC_VERTICAL.
94 *    -    VideoComp is not one component of enum OMXVCM4P2VideoComponent.
95 *
96 */
97
98OMXResult omxVCM4P2_EncodeVLCZigzag_IntraDCVLC(
99     OMX_U8 **ppBitStream,
100     OMX_INT *pBitOffset,
101     const OMX_S16 *pQDctBlkCoef,
102     OMX_U8 predDir,
103     OMX_U8 pattern,
104     OMX_INT shortVideoHeader,
105     OMXVCM4P2VideoComponent videoComp
106)
107{
108    OMX_S16 dcValue, powOfSize;
109    OMX_U8  DCValueSize, start = 1;
110    OMX_U16 absDCValue;
111
112    /* Argument error checks */
113    armRetArgErrIf(ppBitStream == NULL, OMX_Sts_BadArgErr);
114    armRetArgErrIf(*ppBitStream == NULL, OMX_Sts_BadArgErr);
115    armRetArgErrIf(pBitOffset == NULL, OMX_Sts_BadArgErr);
116    armRetArgErrIf(pQDctBlkCoef == NULL, OMX_Sts_BadArgErr);
117    armRetArgErrIf((*pBitOffset < 0) || (*pBitOffset >7), OMX_Sts_BadArgErr);
118	armRetArgErrIf((videoComp != OMX_VC_LUMINANCE) && (videoComp != OMX_VC_CHROMINANCE), OMX_Sts_BadArgErr);
119	armRetArgErrIf((predDir != OMX_VC_NONE) && (predDir != OMX_VC_HORIZONTAL) && (predDir != OMX_VC_VERTICAL) , OMX_Sts_BadArgErr);
120
121    if (pattern)
122    {
123        dcValue = pQDctBlkCoef[0];
124        absDCValue = armAbs(dcValue);
125
126        /* Find the size */
127        DCValueSize = armLogSize (absDCValue);
128        absDCValue = armAbs(dcValue);
129
130        /* Insert the code into the bitstream */
131        if (videoComp == OMX_VC_LUMINANCE)
132        {
133
134            armPackVLC32 (ppBitStream, pBitOffset,
135                          armVCM4P2_aIntraDCLumaIndex[DCValueSize]);
136        }
137        else if (videoComp == OMX_VC_CHROMINANCE)
138        {
139
140            armPackVLC32 (ppBitStream, pBitOffset,
141                          armVCM4P2_aIntraDCChromaIndex[DCValueSize]);
142        }
143
144        /* Additional code generation in case of negative
145           dc value the additional */
146        if (DCValueSize > 0)
147        {
148            if (dcValue < 0)
149            {
150                /* calulate 2 pow */
151                powOfSize = (1 << DCValueSize);
152
153                absDCValue =  absDCValue ^ (powOfSize - 1);
154            }
155            armPackBits(ppBitStream, pBitOffset, (OMX_U32)absDCValue, \
156                        DCValueSize);
157
158            if (DCValueSize > 8)
159            {
160                armPackBits(ppBitStream, pBitOffset, 1, 1);
161            }
162        }
163    }
164
165    return armVCM4P2_EncodeVLCZigzag_Intra(
166                ppBitStream,
167                pBitOffset,
168                pQDctBlkCoef,
169                predDir,
170                pattern,
171                shortVideoHeader,
172                start);
173}
174
175/* End of file */
176