I'm attempting to implement better multi-track audio/stem export for Kdenlive, and have some questions about implementation details


  • Audio stem export is currently unusable, and has some strange behavior such as exporting silent tracks from non-selected sequences, and not working with nested sequences at all.

Changes I’d like to make:

  • Add “selected timeline only,” option, which will only export tracks from the selected timeline
  • Mix down nested sequences into the appropriate track

Questions I have:

  • Is this already being worked on?
  • Do these features align with the goals of Kdenlive?
  • What does a “tracktor,” represent in the codebase? From what I can tell it represents a sequence, but I just want to double check before I start working with incorrect assumptions.
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Hi @zachthefrog, welcome to Kdenlive. I’ll ask the team and let you know.

Hi, and thanks for getting in touch!

What you see is likely a regression caused by the new sequence feature, which we were not aware of so far.

As I understand you are willing to contribute code for this? You are very welcome to do so!

Concerning the details:

  • Exporting the tracks of the current timeline only should be the default behavior as it aligns with the normal (non multi-track) render behavior.
  • The current behavior is a bug, not sure we need it at all
  • tractors are not only sequences, but also tracks. Please see dev-docs/fileformat.md · master · Multimedia / Kdenlive · GitLab for a detailed description

BTW for questions closely related to the code base and maybe with the intention to contribute code, you can also use Issues · Multimedia / Kdenlive · GitLab or maybe even draft merge requests.

I hope that helps!

Great! Thank you so much for your detailed reply. I’ll check it out this weekend and see what I can do.

If you don’t mind, could you mention the update which added the “new sequence feature,” you said might be contributing to the bug? It might help narrowing it down (even just an approximate date might be helpful).

With “sequence feature” I mean what you may also know as “nested timelines”. This was one of the biggest code changes in the past months maybe even 1-2 years.

Nested timelines (!378) · Merge requests · Multimedia / Kdenlive · GitLab is the initial merge request which was merged to the master branch on 10th February 2023

FYI: A commit has just been made to fix stem export:

Great! Good to see I was on the right track with my thought process. I was also having major issues getting Kdenlive to build/run on Windows so it was probably going to be a while before I could actually do anything.

Where you using Craft? Btw, in these kind of situations you may contact the team for support in matrix/telegram.

If you are still interested in contributing we have a list of simple tasks for new comers to get acquainted with the code base.