I suspect the last frame exported to JXL has a duration of 0, because after converting the jxl to png (animated) with `djxl` the last frame has an erratically short frame time in Firefox and doesn't show up at all in IrfanView. You can use the test file in https://bugs.kde.org/show_bug.cgi?id=455361
A possibly relevant merge request was started @ https://invent.kde.org/graphics/krita/-/merge_requests/1481
Git commit f9da97e2d87f3dc2ade94cf4d60699d8b57bad17 by L. E. Segovia. Committed on 28/06/2022 at 17:31. Pushed by lsegovia into branch 'master'. JPEG XL: fix animations with keyframes not in the tail end There are two compounded issues with frame timing: - last frames lasting more than a single frame would get trimmed - once fixed, these would also get a tick chopped off M +4 -1 plugins/impex/jxl/JPEGXLExport.cpp M +4 -3 plugins/impex/jxl/JPEGXLImport.cpp A +- -- plugins/impex/jxl/tests/data/sources/animated/animation_test.jxl M +35 -0 plugins/impex/jxl/tests/kis_jpegxl_test.cpp M +1 -0 plugins/impex/jxl/tests/kis_jpegxl_test.h https://invent.kde.org/graphics/krita/commit/f9da97e2d87f3dc2ade94cf4d60699d8b57bad17
Git commit e82fc0fd026a2068a86244a71824c108ac651659 by L. E. Segovia. Committed on 28/06/2022 at 18:51. Pushed by lsegovia into branch 'krita/5.1'. JPEG XL: fix animations with keyframes not in the tail end There are two compounded issues with frame timing: - last frames lasting more than a single frame would get trimmed - once fixed, these would also get a tick chopped off (cherry picked from commit f9da97e2d87f3dc2ade94cf4d60699d8b57bad17) M +4 -1 plugins/impex/jxl/JPEGXLExport.cpp M +4 -3 plugins/impex/jxl/JPEGXLImport.cpp A +- -- plugins/impex/jxl/tests/data/sources/animated/animation_test.jxl M +35 -0 plugins/impex/jxl/tests/kis_jpegxl_test.cpp M +1 -0 plugins/impex/jxl/tests/kis_jpegxl_test.h https://invent.kde.org/graphics/krita/commit/e82fc0fd026a2068a86244a71824c108ac651659