https://bugs.documentfoundation.org/show_bug.cgi?id=157440
--- Comment #11 from Dan Dennedy <[email protected]> --- What an interesting bug that appeared to me in my "Shotcut" Google Alert. I found the problem and a workaround. The problem occurs when the aspect ratio of the image does not match the video project - 16:9 in this case. In fact, neither JPEG is exactly 16:9, but the `img0 single slide export.jpeg`is close enough while `img0 group export as HTML.jpg` is not. When the aspect ratio does not match, Shotcut pads the source image with transparent black before any transition mixing or track compositing/blending. Both the transition mixer and track compositor are sensitive to the alpha channel. This is how one can transition between two pieces of text or images with transparent parts over a video track below. There is some behavior difference when the transition receives an image with or without an alpha channel. In the single slide export case, the transition does not receive an alpha channel and in the HTML export case it does due to this padding from a mismatching aspect ratio. I am not certain this is a bug for either project. It is somewhat an artifact of something that is paper document oriented such as Impress (Slide Properties) mismatching the video/screen paradigm, although that concept for a presentation program is dated. Maybe one can workaround this problem in Impress by slightly changing the dimension in slide properties, but I cannot tell you how. But in Shotcut, the workaround is to add to each transition the **Alpha Channel: Adjust** video filter and set its **Mode** to **Threshold**. This makes the transition's output opaque. -- You are receiving this mail because: You are the assignee for the bug.
