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
PV_DecodePredictedIntraDC(int compnum,BitstreamDecVideo * stream,int16 * INTRADC_delta)23 PV_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