1 /*
2  * Copyright 2014, The Android Open Source Project
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 #ifndef ANDROID_AUDIO_AC3_FRAME_SCANNER_H
18 #define ANDROID_AUDIO_AC3_FRAME_SCANNER_H
19 
20 #include <stdint.h>
21 #include <system/audio.h>
22 #include <audio_utils/spdif/FrameScanner.h>
23 
24 namespace android {
25 
26 #define AC3_NUM_SAMPLE_RATE_TABLE_ENTRIES          3
27 #define AC3_NUM_FRAME_SIZE_TABLE_ENTRIES          38
28 #define AC3_PCM_FRAMES_PER_BLOCK                 256
29 #define AC3_MAX_BLOCKS_PER_SYNC_FRAME_BLOCK        6
30 #define EAC3_RATE_MULTIPLIER                       4
31 #define EAC3_NUM_SAMPLE_RATE_TABLE_ENTRIES         3
32 #define EAC3_NUM_BLOCKS_PER_FRAME_TABLE_ENTRIES   38
33 #define EAC3_MAX_SUBSTREAMS                        8
34 
35 class AC3FrameScanner : public FrameScanner
36 {
37 public:
38     explicit AC3FrameScanner(audio_format_t format);
39     virtual ~AC3FrameScanner();
40 
getMaxChannels()41     virtual int getMaxChannels()   const { return 5 + 1; } // 5.1 surround
42 
getMaxSampleFramesPerSyncFrame()43     virtual int getMaxSampleFramesPerSyncFrame() const { return EAC3_RATE_MULTIPLIER
44             * AC3_MAX_BLOCKS_PER_SYNC_FRAME_BLOCK * AC3_PCM_FRAMES_PER_BLOCK; }
45     virtual int getSampleFramesPerSyncFrame() const;
46 
47     virtual bool isFirstInBurst();
48     virtual bool isLastInBurst();
49     virtual void resetBurst();
50 
51     virtual uint16_t convertBytesToLengthCode(uint16_t numBytes) const;
52 
53 protected:
54     // Keep track of how many of each substream blocks have been accumulated.
55     // We need all of each substream before sending block data burst.
56     uint8_t   mSubstreamBlockCounts[EAC3_MAX_SUBSTREAMS];
57     int       mAudioBlocksPerSyncFrame;
58     // The type of EAC3 stream as per EAC3 spec paragraph 2.3.1.1
59     uint32_t  mStreamType;
60     // substream index
61     uint32_t  mSubstreamID;
62     audio_format_t mFormat;
63 
64     // used to recognize the start of an AC3 sync frame
65     static const uint8_t  kSyncBytes[];
66     // sample rates from AC3 spec table 5.1
67     static const uint16_t kAC3SampleRateTable[AC3_NUM_SAMPLE_RATE_TABLE_ENTRIES];
68     // frame sizes from AC3 spec table 5.13
69     static const uint16_t kAC3FrameSizeTable[AC3_NUM_FRAME_SIZE_TABLE_ENTRIES]
70             [AC3_NUM_SAMPLE_RATE_TABLE_ENTRIES];
71     // sample rates from EAC3 spec table E2.3
72     static const uint16_t kEAC3ReducedSampleRateTable[AC3_NUM_SAMPLE_RATE_TABLE_ENTRIES];
73     // audio blocks per frame from EAC3 spec table E2.4
74     static const uint16_t kEAC3BlocksPerFrameTable[EAC3_NUM_BLOCKS_PER_FRAME_TABLE_ENTRIES];
75 
76     virtual bool parseHeader();
77 };
78 
79 }  // namespace android
80 
81 #endif  // ANDROID_AUDIO_AC3_FRAME_SCANNER_H
82