1/* ------------------------------------------------------------------
2 * Copyright (C) 1998-2009 PacketVideo
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
13 * express or implied.
14 * See the License for the specific language governing permissions
15 * and limitations under the License.
16 * -------------------------------------------------------------------
17 */
18#include "mp4dec_lib.h"
19#include "vlc_decode.h"
20#include "bitstream.h"
21#include "zigzag.h"
22
23PV_STATUS PV_DecodePredictedIntraDC(
24    int compnum,
25    BitstreamDecVideo *stream,
26    int16 *INTRADC_delta)
27{
28
29    /*----------------------------------------------------------------------------
30    ; Define all local variables
31    ----------------------------------------------------------------------------*/
32    PV_STATUS status = PV_SUCCESS;
33    uint DC_size;
34    uint code;
35    int first_bit;
36
37    /*----------------------------------------------------------------------------
38    ; Function body here
39    ----------------------------------------------------------------------------*/
40    /* read DC size 2 - 8 bits */
41    status = PV_VlcDecIntraDCPredSize(stream, compnum, &DC_size);
42
43    if (status == PV_SUCCESS)
44    {
45        if (DC_size == 0)
46        {
47            *INTRADC_delta = 0;
48        }
49        else
50        {
51            /* read delta DC 0 - 8 bits */
52            code = (int) BitstreamReadBits16_INLINE(stream, DC_size);
53
54            first_bit = code >> (DC_size - 1);
55
56            if (first_bit == 0)
57            {
58                /* negative delta INTRA DC */
59                *INTRADC_delta = code ^((1 << DC_size) - 1);
60                *INTRADC_delta = -(*INTRADC_delta);
61            }
62            else
63            { /* positive delta INTRA DC */
64                *INTRADC_delta = code;
65            }
66            if (DC_size > 8) BitstreamRead1Bits_INLINE(stream);
67        }
68    }
69
70    /*----------------------------------------------------------------------------
71    ; Return nothing or data or data pointer
72    ----------------------------------------------------------------------------*/
73    return status;
74}
75
76