Kdenlive/Manual/Troubleshooting and Common Problems

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How to file a bug report, and where? How to do debugging if necessary (link gdb tutorials) when using a dev version?

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Troubleshooting and Common Problems

Kdenlive warns me about missing codecs, I cannot render in some formats.

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: Settings -> Run Config 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 some 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 again the codecs 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: Settings -> Configure Kdenlive and check the Bypass codec verification option.

Kdenlive is too large on my screen. I cannot make it smaller.: 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 the View button) and consider using layouts (View -> Save Layout As).

I want to trim videos without re-encoding them. How can I do this?: 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, whileas Kdenlive renders frames into a new file).
See also: [1], [2]

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 to as a clip (Project -> Add Clip).
See also: How to: Add a Watermark in kdenlive on Vimeo.

My monitor plays distorted images, or generally something it really should not.: Please check your Settings -> Configure Kdenlive -> Playback settings. Try to disable OpenGL if it is enabled, or use a different driver. Kdenlive may need to be restarted.