There are several possible reasons for this:
You have installed the codecs after Kdenlive’s installation. To force Kdenlive to check available codecs on your system, run the configuration wizard:. Complete the wizard and restart Kdenlive to be sure that codecs have been detected.
The codecs are not available on your system. Kdenlive uses the codecs from your FFmpeg or Libav library. Due to licensing issues, some distributions do not provide all codecs by default and you might need to install an extra package. On Ubuntu/Mint for example, you must install a package called libavcodec-extra-xx. After that, check the codecs again as explained in the first step.
Last possibility is that your FFmpeg or Libav version is buggy and does not report all supported codecs. Kdenlive releases after 0.9.2 have an option to try using codecs even if they seem unsupported:and check the option.
This usually happens when too many widgets are open. Each widget label takes a minimum amount of space in width. Close some (e.g. via thebutton) and consider using layouts ( ).
You cannot do this with Kdenlive. (Please try Avidemux instead.) The reason is that, for splitting, files need to be treated in a very different manner (the file itself needs to be edited, whereas Kdenlive renders frames into a new file). See also: https://forum.kde.org/viewtopic.php?f=272&t=116144&p=286144&hilit=clips+without+render+angain#p286144.
I want to apply an effect, for example a watermark, to the whole project. What is the best way to do this?¶
Create a new project with the same project profile and import the project on which you want to apply the effect as a clip (How to: Add a Watermark in Kdenlive on Vimeo.). See also:
Please check yoursettings. Try to disable OpenGL if it is enabled, or use a different driver. Kdenlive may need to be restarted.
See Notes at Installation.