armVCM4P2_CheckVLCEscapeMode.c revision 0c1bc742181ded4930842b46e9507372f0b1b963 
1/**
2 *
3 * File Name:  armVCM4P2_CheckVLCEscapeMode.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 module for VLC escape mode check
14 *
15 */
16
17#include "omxtypes.h"
18#include "armOMX.h"
19
20#include "armVC.h"
21#include "armCOMM.h"
22
23/**
24 * Function: armVCM4P2_CheckVLCEscapeMode
25 *
26 * Description:
27 * Performs escape mode decision based on the run, run+, level, level+ and
28 * last combinations.
29 *
30 * Remarks:
31 *
32 * Parameters:
33 * [in] run             Run value (count of zeros) to be encoded
34 * [in] level           Level value (non-zero value) to be encoded
35 * [in] runPlus         Calculated as runPlus = run - (RMAX + 1)
36 * [in] levelPlus       Calculated as
37 *                      levelPlus = sign(level)*[abs(level) - LMAX]
38 * [in] maxStoreRun     Max store possible (considering last and inter/intra)
39 * [in] maxRunForMultipleEntries
40 *                      The run value after which level
41 *                      will be equal to 1:
42 *                      (considering last and inter/intra status)
43 * [in] pRunIndexTable  Run Index table defined in
44 *                      armVCM4P2_Huff_Tables_VLC.c
45 *                      (considering last and inter/intra status)
46 *
47 *
48 * Return Value:
49 * Returns an Escape mode which can take values from 0 to 3
50 * 0 --> no escape mode, 1 --> escape type 1,
51 * 1 --> escape type 2, 3 --> escape type 3, check section 7.4.1.3
52 * in the MPEG ISO standard.
53 *
54 */
55
56OMX_U8 armVCM4P2_CheckVLCEscapeMode(
57     OMX_U32 run,
58     OMX_U32 runPlus,
59     OMX_S16 level,
60     OMX_S16 levelPlus,
61     OMX_U8  maxStoreRun,
62     OMX_U8  maxRunForMultipleEntries,
63     OMX_INT shortVideoHeader,
64     const OMX_U8  *pRunIndexTable
65)
66{
67    OMX_U8 escape = 0, fMode = 0, entries;
68
69    level = armAbs (level);
70    levelPlus = armAbs (levelPlus);
71
72    /* Check for a valid entry with run, level and Last combination
73       Mode 0 check */
74    if (run <= maxStoreRun)
75    {
76        entries = pRunIndexTable[run + 1]
77                  - pRunIndexTable[run];
78        if (run > maxRunForMultipleEntries)
79        {
80            entries = 1;
81        }
82        if (level > entries)
83        {
84            escape = 1;
85        }
86    }
87    else
88    {
89        escape = 1;
90    }
91    if(escape && shortVideoHeader)
92    {
93        escape = 0;
94        fMode = 4;
95    }
96    /* Check for a valid entry with run, levelPlus and Last combination
97       Mode 1 check */
98    if (escape)
99    {
100        escape = 0;
101        fMode = 1;
102        if (run <= maxStoreRun)
103        {
104            entries = pRunIndexTable[run + 1]
105                      - pRunIndexTable[run];
106            if (run > maxRunForMultipleEntries)
107            {
108                entries = 1;
109            }
110            if (levelPlus > entries)
111            {
112                escape = 1;
113            }
114        }
115        else
116        {
117            escape = 1;
118        }
119    }
120
121    /* Check for a valid entry with runPlus, level and Last combination
122       Mode 2 check */
123    if (escape)
124    {
125        escape = 0;
126        fMode = 2;
127        if (runPlus <= maxStoreRun)
128        {
129            entries = pRunIndexTable[runPlus + 1]
130                      - pRunIndexTable[runPlus];
131            if (runPlus > maxRunForMultipleEntries)
132            {
133                entries = 1;
134            }
135            if (level > entries)
136            {
137                escape = 1;
138            }
139        }
140        else
141        {
142            escape = 1;
143        }
144    }
145
146    /* select mode 3 --> FLC */
147    if (escape)
148    {
149        fMode = 3;
150    }
151
152    return fMode;
153}
154
155/*End of File*/
156
157