v6.20.0 released

Feb 16, 2020

You can download it from GitHub.

This version adds support for low resolution Preview Scaling and adds a module based on the Rubber Band Library for audio pitch-shifting. An official docker image is now available on Docker Hub as mltframework/melt.


  • Added consumer scaling:
    • mlt_profile_scale_width()
    • mlt_profile_scale_height()
    • Mlt::Profile::scale_width()
    • Mlt::Profile::scale_height()
    • support for a double scale property to melt and the xml producer
  • Fixed mlt_properties_set() with an invalid expression.
  • Added new functions that do not evaluate expressions:
    • mlt_properties_set_string()
    • Mlt::Properties::set_string()
  • Improved the service-caching heuristic in mlt_multitrack.
  • Fixed possible crashes in mlt_playlist get_frame() and mlt_filter_process().


  • Added the rubberband module with a rbpitch filter.
  • Added pitch compensation to timewarp producer.
  • Added the invert_scale property to the affine filter and transition.
  • Added the reverse property to the shape filter.
  • Added support for text keyframes to the text and qtext filters.
  • Added support for the CSRT and MOSSE algorithms in opencv.tracker filter.
  • Fixed a crash on empty algo property in the opencv.tracker filter.
  • Changed vorbis module to no longer be deprecated.
  • Improved colorspace conversions in the avformat module.
  • Fixed audio artifacts on initial seek to in point in avformat producer.
  • Fixed the colorspace of the cached image in avformat producer.
  • Fixed white video flashes on property changes in the qtext filter.
  • Fixed a crash in the rotoscoping filter with large spline deviations.
  • Fixed a crash in the sdi consumer if the driver is not loaded.
  • Improved support for a video clip as luma producer to the luma transition.
  • Fixed a crash in the matte transition.
  • Fixed a crash when using invert property =1 in the composite transition.


  • Added a Dockerfile and integrated docker build into Travis CI.
  • Added more avformat consumer presets:
    • intermediate/DNxHR-HQ
    • intermediate/ProRes HQ
    • ALAC
    • FLAC
  • Fixed some parameters in the XDCAM and D10 avformat presets.
  • Fixed link failure on some CPU architectures.



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