Hi, I've recently been testing image decoding and scaling with FFmpeg (compiled with mingw as dlls on Windows 7 x64), and everything has been working smoothly with the exception of two problems.
Both problems are seemingly related to down-scaling of large images. As mentioned in the subject, I experienced these issues while testing bmp files. 1. The first issue happens, when I try down-scaling a large bitmap (4608x3328) to a much smaller size (e.g. 256x185). The resulting image resembles the original, however all colours have become slightly more green during the scaling. Basically the output looks as if it has gotten a green tint/overlay. Initial testing was done with sws_scale via a small test application I've written. The conversion was from BGR24 to BGR24. After noticing the problem, I consequently tried to reproduce the issue with FFmpeg.exe (Zeranoe's build), and the results were identical. To reproduce: Get a large bitmap such as this: http://wa8lmf.net/MapCaptureTool/Google-Terrain-SoCal-Zoom-12.htm Use FFmpeg.exe with the following command: ffmpeg.exe -i path\to\image -s 256x185 path\to\output.bmp To see a properly coloured output, change the output extension to .jpg instead. Am I doing something wrong here, or could this be an sws_scale bgr2bgr error? 2. The second issue has to do with extreme down-scaling. If we use the linked image from above as an example. If I were to scale it down to something as small as 64x46, I would get an error telling me to increase the MAX_FILTER_SIZE, to accomplish such extreme scaling. Now, if I increase the MAX_FILTER_SIZE, the extreme scaling works, but the output is corrupt, and normal scaling of other images results in a crash. I simply doubled the size of MAX_FILTER_SIZE, to keep the format. Perhaps that was the wrong action? Would it be better to simply perform consecutively smaller down-scale operations on the image until the destination size has been reached? Oh! And one very interesting note: Both issues were resolved, when I used FFmpeg dlls compiled with the MSVC toolchain (same config). Hmm... I will happily provide additional information if required (build configuration etc). Thanks for your help, and for FFmpeg.
_______________________________________________ Libav-user mailing list [email protected] http://ffmpeg.org/mailman/listinfo/libav-user
