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_FRAME_SCANNER_H 18 #define ANDROID_AUDIO_FRAME_SCANNER_H 19 20 #include <stdint.h> 21 22 namespace android { 23 24 25 /** 26 * Scan a byte stream looking for the start of an encoded frame. 27 * Parse the sample rate and the size of the encoded frame. 28 * Buffer the sync header so it can be prepended to the remaining data. 29 * 30 * This is used directly by the SPDIFEncoder. External clients will 31 * generally not call this class. 32 */ 33 class FrameScanner { 34 public: 35 FrameScanner(int dataType, 36 const uint8_t *syncBytes, 37 uint32_t syncLength, 38 uint32_t headerLength 39 ); 40 virtual ~FrameScanner(); 41 42 /** 43 * Pass each byte of the encoded stream to this scanner. 44 * @return true if a complete and valid header was detected 45 */ 46 virtual bool scan(uint8_t byte); 47 48 /** 49 * @return address of where the sync header was stored by scan() 50 */ getHeaderAddress()51 const uint8_t *getHeaderAddress() const { return mHeaderBuffer; } 52 53 /** 54 * @return number of bytes in sync header stored by scan() 55 */ getHeaderSizeBytes()56 size_t getHeaderSizeBytes() const { return mHeaderLength; } 57 58 /** 59 * @return sample rate of the encoded audio 60 */ getSampleRate()61 uint32_t getSampleRate() const { return mSampleRate; } 62 63 /** 64 * Some formats, for example EAC3, are wrapped in data bursts that have 65 * a sample rate that is a multiple of the encoded sample rate. 66 * The default multiplier is 1. 67 * @return sample rate multiplier for the SP/DIF PCM data bursts 68 */ getRateMultiplier()69 uint32_t getRateMultiplier() const { return mRateMultiplier; } 70 getFrameSizeBytes()71 size_t getFrameSizeBytes() const { return mFrameSizeBytes; } 72 73 /** 74 * dataType is defined by the SPDIF standard for each format 75 */ getDataType()76 int getDataType() const { return mDataType; } getDataTypeInfo()77 int getDataTypeInfo() const { return mDataTypeInfo; } 78 79 virtual int getMaxChannels() const = 0; 80 81 virtual void resetBurst() = 0; 82 83 /** 84 * @return the number of pcm frames that correspond to one encoded frame 85 */ 86 virtual int getMaxSampleFramesPerSyncFrame() const = 0; 87 virtual int getSampleFramesPerSyncFrame() const = 0; 88 89 /** 90 * @return true if this parsed frame must be the first frame in a data burst. 91 */ 92 virtual bool isFirstInBurst() = 0; 93 94 /** 95 * If this returns false then the previous frame may or may not be the last frame. 96 * @return true if this parsed frame is definitely the last frame in a data burst. 97 */ 98 virtual bool isLastInBurst() = 0; 99 100 /** 101 * Most compression types use a lengthCode expressed in bits. 102 */ convertBytesToLengthCode(uint16_t numBytes)103 virtual uint16_t convertBytesToLengthCode(uint16_t numBytes) const { return numBytes * 8; } 104 105 protected: 106 uint32_t mBytesSkipped; // how many bytes were skipped looking for the start of a frame 107 const uint8_t *mSyncBytes; // pointer to the sync word specific to a format 108 uint32_t mSyncLength; // number of bytes in sync word 109 uint8_t mHeaderBuffer[32]; // a place to gather the relevant header bytes for parsing 110 uint32_t mHeaderLength; // the number of bytes we need to parse 111 uint32_t mCursor; // position in the mHeaderBuffer 112 uint32_t mFormatDumpCount; // used to thin out the debug dumps 113 uint32_t mSampleRate; // encoded sample rate 114 uint32_t mRateMultiplier; // SPDIF output data burst rate = msampleRate * mRateMultiplier 115 size_t mFrameSizeBytes; // encoded frame size 116 int mDataType; // as defined in IEC61937-2 paragraph 4.2 117 int mDataTypeInfo; // as defined in IEC61937-2 paragraph 4.1 118 119 /** 120 * Parse data in mHeaderBuffer. 121 * Sets mDataType, mFrameSizeBytes, mSampleRate, mRateMultiplier. 122 * @return true if the header is valid. 123 */ 124 virtual bool parseHeader() = 0; 125 126 }; 127 128 129 } // namespace android 130 #endif // ANDROID_AUDIO_FRAME_SCANNER_H 131