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Commit 862f8455 authored by Chong Zhang's avatar Chong Zhang
Browse files

handle emulation_prevention_three_bytes for AVC 

bug: 15917805
Change-Id: I824fe7eea807f8faba6b149c31890b7a5df87825
parent e8f2c6cf

include/media/stagefright/foundation/ABitReader.h

+19 −3
Original line number Diff line number Diff line
@@ -25,8 +25,10 @@ 


namespace android {



struct ABitReader {

class ABitReader {

public:

    ABitReader(const uint8_t *data, size_t size);

    virtual ~ABitReader();



    uint32_t getBits(size_t n);

    void skipBits(size_t n);
@@ -37,18 +39,32 @@ struct ABitReader { 


    const uint8_t *data() const;



private:

protected:

    const uint8_t *mData;

    size_t mSize;



    uint32_t mReservoir;  // left-aligned bits

    size_t mNumBitsLeft;



    void fillReservoir();

    virtual void fillReservoir();



    DISALLOW_EVIL_CONSTRUCTORS(ABitReader);

};



class NALBitReader : public ABitReader {

public:

    NALBitReader(const uint8_t *data, size_t size);



    bool atLeastNumBitsLeft(size_t n) const;



private:

    int32_t mNumZeros;



    virtual void fillReservoir();



    DISALLOW_EVIL_CONSTRUCTORS(NALBitReader);

};



}  // namespace android



#endif  // A_BIT_READER_H_

media/libmediaplayerservice/nuplayer/NuPlayerDecoder.cpp

+2 −2
Original line number Diff line number Diff line
@@ -674,9 +674,9 @@ bool NuPlayer::CCDecoder::extractFromSEI(const sp<ABuffer> &accessUnit) { 


    bool hasCC = false;



    ABitReader br(sei->data() + 1, sei->size() - 1);

    NALBitReader br(sei->data() + 1, sei->size() - 1);

    // sei_message()

    while (br.numBitsLeft() >= 16) { // at least 16-bit for sei_message()

    while (br.atLeastNumBitsLeft(16)) { // at least 16-bit for sei_message()

        uint32_t payload_type = 0;

        size_t payload_size = 0;

        uint8_t last_byte;

media/libstagefright/foundation/ABitReader.cpp

+68 −0
Original line number Diff line number Diff line
@@ -27,6 +27,9 @@ ABitReader::ABitReader(const uint8_t *data, size_t size) 
      mNumBitsLeft(0) {

}



ABitReader::~ABitReader() {

}



void ABitReader::fillReservoir() {

    CHECK_GT(mSize, 0u);
@@ -99,4 +102,69 @@ const uint8_t *ABitReader::data() const { 
    return mData - (mNumBitsLeft + 7) / 8;

}



NALBitReader::NALBitReader(const uint8_t *data, size_t size)

    : ABitReader(data, size),

      mNumZeros(0) {

}



bool NALBitReader::atLeastNumBitsLeft(size_t n) const {

    // check against raw size and reservoir bits first

    size_t numBits = numBitsLeft();

    if (n > numBits) {

        return false;

    }



    ssize_t numBitsRemaining = n - mNumBitsLeft;



    size_t size = mSize;

    const uint8_t *data = mData;

    int32_t numZeros = mNumZeros;

    while (size > 0 && numBitsRemaining > 0) {

        bool isEmulationPreventionByte = (numZeros >= 2 && *data == 3);



        if (*data == 0) {

            ++numZeros;

        } else {

            numZeros = 0;

        }



        if (!isEmulationPreventionByte) {

            numBitsRemaining -= 8;

        }



        ++data;

        --size;

    }



    return (numBitsRemaining <= 0);

}



void NALBitReader::fillReservoir() {

    CHECK_GT(mSize, 0u);



    mReservoir = 0;

    size_t i = 0;

    while (mSize > 0 && i < 4) {

        bool isEmulationPreventionByte = (mNumZeros >= 2 && *mData == 3);



        if (*mData == 0) {

            ++mNumZeros;

        } else {

            mNumZeros = 0;

        }



        // skip emulation_prevention_three_byte

        if (!isEmulationPreventionByte) {

            mReservoir = (mReservoir << 8) | *mData;

            ++i;

        }



        ++mData;

        --mSize;

    }



    mNumBitsLeft = 8 * i;

    mReservoir <<= 32 - mNumBitsLeft;

}



}  // namespace android