On Saturday, July 16, 2016 7:02:25 PM CEST, Brian Matherly wrote: > I think this would be a good optimization. > > QImage::Format_RGBA8888 is not available in Qt 4.8. So we would > need some pre-processor conditionals to use either the previous > way or the new way depending on version.
Oh, right. I used it in my qtblend transition - than I guess I will enable it only on Qt5. > Are you sure that line order is the same between Qt and MLT > image formats? For some reason I was thinking that line 0 is the > bottom for MLT and the top for Qt. If that is the case, the new > method can not be used for services that need to draw on the > image because, for example, text would be written upside down. > It may not matter for some services like your transition that > don't have any directional component. Maybe the difference could > be compensated by applying a transform to the painter. Could you > check this out and report back? I can confirm that you can draw text directly on the QImage (Format_RGBA8888) through a QPainter and it displays correctly in MLT. > The documentation it a little confusing. It states: "The order > of the colors is the same on any architecture if read as bytes > 0xRR,0xGG,0xBB,0xAA.". I think what they are trying to say is > that the color order will be the same on any architecture if you > look at the bytes, but if you look at each pixel as an int, the > order will appear differently depending on the endianess of the > system. So I think this will work for us on big or little endian > systems since. If we find that it does not work on big-endian > systems, we can just put a check in place and either convert the > easy way or the hard (current) way. Ok for me. regards, jb > From: Jean-Baptiste Mardelle <j...@kdenlive.org> > To: mlt-devel@lists.sourceforge.net > Sent: Saturday, July 16, 2016 8:56 AM > Subject: [Mlt-devel] Optimizing Qt functions > > Hi, > > Following my tests with the qtblend transitions, I realized that the QImage > format Format_RGBA8888 allows for a much simpler conversion between MLT and > QImage, avoiding the need to copy data. We can in fact simply create a > QImage directly from MLT's image buffer (with format=mlt_image_rgb24a): > > QImage img( *image, *width, *height, QImage::Format_RGBA8888 ); > > We can then use a QPainter to draw directly on the buffer. > So for instance, in filter_audiowaveform we currently do (line 214): > > QImage qimg( *width, *height, QImage::Format_ARGB32 ); > copy_mlt_to_qimage_rgba( *image, &qimg ); > draw_waveforms( filter, frame, &qimg, audio, channels, samples ); > copy_qimage_to_mlt_rgba( &qimg, *image ); > > This can be replaced by: > > QImage qimg( *image, *width, *height, QImage::Format_RGBA8888 ); > draw_waveforms( filter, frame, &qimg, audio, channels, samples ); > > In my tests, this results in a 8% speedup when rendering a simple video > with the audiowaveform filter. > > My only concern is that in the doc ( > http://doc.qt.io/qt-5/qimage.html#Format-enum ) it says that > QImage::Format_RGBA8888 behaves differently on big endian systems, and I am > not sure if this would affect us... > > Can anyone with a better understanding or a big endian system tell me if > this works on such systems ? > > Seems like something we might want to use in our Qt producers/filters, what > do you think? > > regards, > > jb > > > > > > > > > ------------------------------------------------------------------------------ > What NetFlow Analyzer can do for you? Monitors network bandwidth and traffic > patterns at an interface-level. Reveals which users, apps, and > protocols are > consuming the most bandwidth. Provides multi-vendor support for NetFlow, > J-Flow, sFlow and other flows. Make informed decisions using > capacity planning > reports.http://sdm.link/zohodev2dev ------------------------------------------------------------------------------ What NetFlow Analyzer can do for you? Monitors network bandwidth and traffic patterns at an interface-level. Reveals which users, apps, and protocols are consuming the most bandwidth. Provides multi-vendor support for NetFlow, J-Flow, sFlow and other flows. Make informed decisions using capacity planning reports.http://sdm.link/zohodev2dev _______________________________________________ Mlt-devel mailing list Mlt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mlt-devel
