Hi, Why not construct the image object from the shared memory buffer to begin with? Then lock the sm while drawing. Look for example this constructor: http://doc.qt.io/qt-5/qimage.html#QImage-3
On Mon, Dec 12, 2016 at 11:45 PM, Joshua Grauman <jnf...@grauman.com> wrote: > Hello all, > > I have been able to generate a screen capture of my program by rendering a > window into a QImage at 30fps (called from QTimer), and then copying the > QImage to shared memory (QSharedMemory) where another program grabs the > frames and outputs them to ffmpeg. It all works great. > > However, my cpu is barely keeping up if I do much on my app. > > One of the ways I thought of to speed it up is to avoid the memcpy from > the QImage (img) to QSharedMemory (sharedMemory) by deriving from QImage to > a new class (QSharedMemoryImage) which allocates its image data in shared > memory to begin with so that the window->render() function renders the > window right into shared memory so the copy isn't necessary. QImage was a > bit too complex for me to figure out how to do this. > > For you experts, is this possible? How hard would it be? > > Here's the relevant code in the QTimer: > > window->render(&img, QPoint(), QRegion(), QWidget::DrawChildren); > sharedMemory.lock(); > char *to = (char*)sharedMemory.data(); > const unsigned char *from = img.constBits(); > memcpy(to, from, sharedMemory.size()); > sharedMemory.unlock(); > > Josh > _______________________________________________ > Interest mailing list > Interest@qt-project.org > http://lists.qt-project.org/mailman/listinfo/interest >
_______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
