Decryption error in c++ program - c++

Question

I have created a program which decrypts tracks using bento4 but I am stuck at writing file to disk. The program crashes when writing decrypted tracks, because the size of the encrypted and decrypted samples are not the same.
The problem is in main.cpp in FragmentedSampleReader::ReadSample() after this comment :
// Write initialisation & data into decrypted file.
AP4_Result FragmentedSampleReader::ReadSample()
{
AP4_Position pos_init, pos_after_sample;
m_FragmentStream->Tell(pos_init);
AP4_Result result;
if (!m_codecHandler || !m_codecHandler->ReadNextSample(m_sample, m_sampleData))
{
bool useDecryptingDecoder = m_protectedDesc && (m_decrypterCaps.flags & SSD::SSD_DECRYPTER::SSD_CAPS::SSD_SECURE_PATH) != 0;
bool decrypterPresent(m_decrypter != nullptr);
if (AP4_FAILED(result = ReadNextSample(m_track->GetId(), m_sample, (m_decrypter || useDecryptingDecoder) ? m_encrypted : m_sampleData)))
{
if (result == AP4_ERROR_EOS)
{
if (dynamic_cast<AP4_DASHStream*>(m_FragmentStream)->waitingForSegment())
m_sampleData.SetDataSize(0);
else
m_eos = true;
}
return result;
}
//Protection could have changed in ProcessMoof
if (!decrypterPresent && m_decrypter != nullptr && !useDecryptingDecoder)
m_encrypted.SetData(m_sampleData.GetData(), m_sampleData.GetDataSize());
else if (decrypterPresent && m_decrypter == nullptr && !useDecryptingDecoder)
m_sampleData.SetData(m_encrypted.GetData(), m_encrypted.GetDataSize());
// Make sure that the decrypter is NOT allocating memory!
// If decrypter and addon are compiled with different DEBUG / RELEASE
// options freeing HEAP memory will fail.
if (m_decrypter)
{
m_sampleData.Reserve(m_encrypted.GetDataSize() + 4096);
result = m_decrypter->DecryptSampleData(m_poolId, m_encrypted, m_sampleData, NULL);
}
else if (useDecryptingDecoder)
{
m_sampleData.Reserve(m_encrypted.GetDataSize() + 1024);
result = m_singleSampleDecryptor->DecryptSampleData(m_poolId, m_encrypted, m_sampleData, nullptr, 0, nullptr, nullptr);
}
}
// Write initialisation & data into decrypted file
std::vector<char> buffer;
int pos_decrypted = file_decrypted_data.tellp();
if(pos_decrypted < pos_init)
{
buffer.reserve(pos_init - pos_decrypted);
file_fragment.seekg(pos_decrypted, std::ios::beg);
file_fragment.read(buffer.data(), pos_init - pos_decrypted);
file_decrypted_data.write(buffer.data(), pos_init - pos_decrypted);
}
m_FragmentStream->Tell(pos_after_sample);
int metadata_length = pos_after_sample - m_sampleData.GetDataSize() - pos_init;
buffer.reserve(metadata_length);
file_fragment.seekg(pos_init, std::ios::beg);
file_fragment.read(buffer.data(), metadata_length);
file_decrypted_data.write(buffer.data(), metadata_length);
file_decrypted_data.write((const char*)m_sampleData.GetData(), m_sampleData.GetDataSize());
return result;
};
I have a official git repo : https://github.com/x-hgg-x/video_decrypter
It gives me below error.
std::bad_alloc error