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      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 
     41     virtual int getMaxChannels()   const { return 5 + 1; } // 5.1 surround
     42 
     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