Traverse an raw video more efficiently - c++

Question

I have a raw video file , and i make in qt , an app that reads frame by frame from this file .At large raw files when i press an button that goes to the next frame there is a big delay almost one sec .
Here is my code that returns an frame from raw file :
void RawVideoReader::getFrame(int offset)
{
std::cout<<"getFrame"<<std::endl;
file.seek((unsigned long long int)(((unsigned long long int)width * (unsigned long long int)height) * (unsigned long long int)offset));
QByteArray array = file.read(width * height);
const std::size_t count = array.size();
hex = std::unique_ptr<unsigned char>(new unsigned char[count]);
std::memcpy(hex.get(), array.constData(), count);
}

Answer 1

You can read directly into the buffer you desire - the question is: why do you want to manage this memory buffer using unique_ptr? QByteArray already does that job. Furthermore, you probably want to keep the same buffer, and not reallocate it over and over.
class RawVideoReader : ... {
QByteArray frame;
uint8_t *frameData() const { return frame.size() ? static_cast<uint8_t*>(frame.constData()) : nullptr; }
size_t frameSize() const { return static_cast<size_t>(frame.size()); }
...
};
bool RawVideoReader::getFrame(int frameNo) {
qDebug() << __FUNCTION__;
frame.resize(width * height * 1);
file.seek(qint64(frame.size()) * qint64(frameNo));
auto const hadRead = file.read(frame.data(), frame.size());
return hadRead == frame.size();
}