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/*
* 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;
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
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