| /* |
| * Copyright 2014, The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #ifndef ANDROID_AUDIO_FRAME_SCANNER_H |
| #define ANDROID_AUDIO_FRAME_SCANNER_H |
| |
| #include <stdint.h> |
| |
| namespace android { |
| |
| |
| /** |
| * Scan a byte stream looking for the start of an encoded frame. |
| * Parse the sample rate and the size of the encoded frame. |
| * Buffer the sync header so it can be prepended to the remaining data. |
| * |
| * This is used directly by the SPDIFEncoder. External clients will |
| * generally not call this class. |
| */ |
| class FrameScanner { |
| public: |
| FrameScanner(int dataType, |
| const uint8_t *syncBytes, |
| uint32_t syncLength, |
| uint32_t headerLength |
| ); |
| virtual ~FrameScanner(); |
| |
| /** |
| * Pass each byte of the encoded stream to this scanner. |
| * @return true if a complete and valid header was detected |
| */ |
| virtual bool scan(uint8_t byte); |
| |
| /** |
| * @return address of where the sync header was stored by scan() |
| */ |
| const uint8_t *getHeaderAddress() const { return mHeaderBuffer; } |
| |
| /** |
| * @return number of bytes in sync header stored by scan() |
| */ |
| size_t getHeaderSizeBytes() const { return mHeaderLength; } |
| |
| /** |
| * @return sample rate of the encoded audio |
| */ |
| uint32_t getSampleRate() const { return mSampleRate; } |
| |
| /** |
| * Some formats, for example EAC3, are wrapped in data bursts that have |
| * a sample rate that is a multiple of the encoded sample rate. |
| * The default multiplier is 1. |
| * @return sample rate multiplier for the SP/DIF PCM data bursts |
| */ |
| uint32_t getRateMultiplier() const { return mRateMultiplier; } |
| |
| size_t getFrameSizeBytes() const { return mFrameSizeBytes; } |
| |
| /** |
| * dataType is defined by the SPDIF standard for each format |
| */ |
| int getDataType() const { return mDataType; } |
| int getDataTypeInfo() const { return mDataTypeInfo; } |
| |
| virtual int getMaxChannels() const = 0; |
| |
| virtual void resetBurst() = 0; |
| |
| /** |
| * @return the number of pcm frames that correspond to one encoded frame |
| */ |
| virtual int getMaxSampleFramesPerSyncFrame() const = 0; |
| virtual int getSampleFramesPerSyncFrame() const = 0; |
| |
| /** |
| * @return true if this parsed frame must be the first frame in a data burst. |
| */ |
| virtual bool isFirstInBurst() = 0; |
| |
| /** |
| * If this returns false then the previous frame may or may not be the last frame. |
| * @return true if this parsed frame is definitely the last frame in a data burst. |
| */ |
| virtual bool isLastInBurst() = 0; |
| |
| /** |
| * Most compression types use a lengthCode expressed in bits. |
| */ |
| virtual uint16_t convertBytesToLengthCode(uint16_t numBytes) const { return numBytes * 8; } |
| |
| protected: |
| uint32_t mBytesSkipped; // how many bytes were skipped looking for the start of a frame |
| const uint8_t *mSyncBytes; // pointer to the sync word specific to a format |
| uint32_t mSyncLength; // number of bytes in sync word |
| uint8_t mHeaderBuffer[32]; // a place to gather the relevant header bytes for parsing |
| uint32_t mHeaderLength; // the number of bytes we need to parse |
| uint32_t mCursor; // position in the mHeaderBuffer |
| uint32_t mFormatDumpCount; // used to thin out the debug dumps |
| uint32_t mSampleRate; // encoded sample rate |
| uint32_t mRateMultiplier; // SPDIF output data burst rate = msampleRate * mRateMultiplier |
| size_t mFrameSizeBytes; // encoded frame size |
| int mDataType; // as defined in IEC61937-2 paragraph 4.2 |
| int mDataTypeInfo; // as defined in IEC61937-2 paragraph 4.1 |
| |
| /** |
| * Parse data in mHeaderBuffer. |
| * Sets mDataType, mFrameSizeBytes, mSampleRate, mRateMultiplier. |
| * @return true if the header is valid. |
| */ |
| virtual bool parseHeader() = 0; |
| |
| }; |
| |
| |
| } // namespace android |
| |
| #endif // ANDROID_AUDIO_FRAME_SCANNER_H |