MLT Multimedia Framework

Author, manage, and run multitrack audio/video compositions.
The engine of a non-linear video editor that can be used in all sorts of apps, not just desktop video editors.
MLT is an open source multimedia framework, designed and developed for television broadcasting. It provides a toolkit for broadcasters, video editors, media players, transcoders, web streamers and many more types of applications. The functionality of the system is provided via an assortment of ready to use tools, XML authoring components, and an extensible plug-in based API.
Download source code. The easiest way to try out and learn MLT is by downloading Shotcut.

Recent News

v6.6.0 released

Jan 22, 2018

You can download it from GitHub.

This version builds upon the previous release with performance improvements using the sliced image processing framework. It also improves compatibility with dependencies (FFmpeg, Qt 5, SDL 2, NDI, OpenCV, libebur128).

Framework

  • Added a thread pool to mlt_slices:
    • mlt_slices_run_normal()
    • mlt_slices_run_rr()
    • mlt_slices_run_fifo()
    • mlt_slices_count_normal()
    • mlt_slices_count_rr()
    • mlt_slices_count_fifo()
    • MLT_SLICES_COUNT environment variable
  • Added mlt_log_timings_now() to mlt_log.
  • Added mlt_image_yuv422p16 image format.
  • Added mlt_image_format_planes() and mlt_image_format_id() to mlt_frame.
  • Added mlt_service_disconnect_all_producers() and Mlt::Service::disconnect_all_producers()
  • Fixed accuracy of mlt_time_format conversions.
  • Fixed mlt_filter_get_progress() never reaching 1.0.
  • Fixed divide by zero in mlt_filter_get_progress().

Modules

  • Added sdl2 module!
  • Added sum property to mix transition for simple mixing without dynamics.
  • Added TLD and KCF tracking modes to opencv module.
  • Added CSV (comma-separated values) simple slideshow to pixbuf producer.
  • Added jack filter to jackrack module.
  • Added sliced processing to frei0r.
  • Added sliced processing to composite transition.
  • Added sliced processing to avformat producer pixel format conversion.
  • Added sliced processing to affine transition and filter.
  • Converted volume and pan filters to floating point.
  • Added rotate_center property to qtblend transition and filters.
  • Added meta.media.variable_frame_rate (VFR detection) to avformat producer.
  • Added support for external libebur128.
  • Updated internal libebur128 to latest.
  • Added 10-bit capture to decklink producer.
  • Added mlt_image_yuv422p16 to fieldorder filter, avcolour_space filter, and avformat consumer.
  • Added no_profile property to xml consumer.
  • Various ndi module fixes and improvements.
  • Fixed setting color_trc in multi consumer.
  • Fixed kdenlive title transparency.
  • Fixed incorrect alpha channel breaking freeze filter with qtblend transition.
  • Fixed transparency of pixbuf images with qtblend transition.
  • Fixed some crashes in new qtblend transition.
  • Fixed building qt module with C++11 for Qt 5.7+.
  • Fixed reporting accurage length for image sequences in qimage and pixbuf.
  • Fixed extra audio samples added to end of file in avformat consumer.
  • Fixed rawvideo export in avformat consumer.
  • Fixed multi-threading wtih FFmpeg 3.2+ in avformat module.
  • Fixed JPEG album art in avformat producer.
  • Removed filter_avresample (dropped by FFmpeg).
  • Stop flushing audio buffer in decklink consumer.
  • Fixed field order handling in decklink consumer.
  • Make composite transition field order aware.
  • Fixed nesting mlt_tractor with opengl module.
  • Fixed kdenlive titler crash on resized frame.

Other

  • Various memory leak fixes.
  • Fixed opening files with extended chars on Windows (framework and modules).

v6.4.1 Hot-fix Release

Nov 15, 2016

There was a problem in the symbol version declaration for the new Mlt::Profile::is_valid() method that was breaking some scripting language bindings including Python. You can download it from GitHub.

v6.4.0 released

Nov 11, 2016

You can download it from GitHub. This is both a bugfix and enhancement release:

Framework

  • Added functions for multi-threaded slice-based image processing: mlt_slices_init, mlt_slices_close, and mlt_slices_run.
  • Added Mlt::Profile::is_valid().
  • Added MLT_DIRLIST_DELIMITER to mlt_types.h.
  • Renamed mlt++/config.h to mlt++/MltConfig.h.
  • Fixed mlt_properties_set_lcnumeric() on macOS.
  • Fixed address of Free Software Foundation in comment headers.

Modules

  • Added crop_to_fill property to composite transition.
  • Added sliced_composite property to composite transition.
  • Added peak and true peak properties to loudness_meter filter.
  • Added qtblend transition and filter to qt module.
  • Added ndi (NewTek NDI) module with producer and consumer.
  • Added opencv module with opencv_tracker filter.
  • Added line_spacing, strech, wrap_width, and wrap_type properties to pango producer.
  • Added oblique value for style property to pango producer.
  • Added fontmap-reload event to pango producer.
  • Added support for pkg-config to sdl module.
  • Added .kra (Krita Image) file name extension to loader.dict.
  • Improved performance of kdenlivetitle producer.
  • Improved decklink producer and consumer.
  • Improved accuracy of seeking on lossy compressed audio in avformat producer.
  • Improved mix transition using 32-bit floating point.
  • Fixed avfilter when image format changes.
  • Fixed loading relative file name in vidstab filter.
  • Fixed crash on Windows with avfilter.
  • Fixed parsing LADSPA_PATH with semi-colon delimiter on Windows.
  • Fixed parsing FREI0R_PATH with semi-colon delimiter on Windows.
  • Fixed reading relative path with backslash (Windows) in xml producer.
  • Fixed loading relative file name for av.file (avfilter).
  • Fixed loading multiple LADSPA plugins on some systems.
  • Fixed compile error when not configured with –enable-gpl.
  • Fixed loading in avfilter.lut3d in locales with comma decimal point.
  • Fixed a possible crash in resample filter.
  • Fixed alpha channel in kdenlivetitle producer.
  • Fixed possible crash in pixbuf and qimage producers.
  • Fixed count when counting down in count producer.

Other

  • Moved some avformat presets from lossless to new intermediate folder.
  • Added a YouTube avformat consumer preset.
  • Changed metadata.rb metadata publisher to output Markdown.

v6.2.0 released

Apr 20, 2016

You can download it from SourceForge or GitHub. The major announcement is the introduction of support for libavfilter! This is still a work-in-progress. It is limited to FFmpeg 2.3 and up, and there are a number of filters that are black-listed because they are known to not integrate with MLT, which is not a full libav* environment or simple wrapper for it. There are likey avfilters that are not yet black-listed but might not work because they have not been completely tested. Also, they do not support MLT's keyframable property animation nor its frame-threaded parallelism due to architectural or integration limitations. However, some avfilters are slice-threaded (internal parallelism), and that works. Finally, libavfilter filtergraph syntax is not supported either.

All of the supported libavfilters are exposed as MLT filters beginning with the prefix "avfilter." All of the avfilter parameters are exposed as MLT properties with the "av." prefix to prevent clashes with MLT properties. You can run
melt -query filters to see the new avfilters, and
melt -query filter=avfilter.rotate, for example, to view generated documentation for an individual filter.

Here is a list of notable fixes and enhancements in this release:
  • Added support for libavfilter to avformat module.
  • Added auto-rotate support to avformat producer.
  • Added animated GIF preset for avformat consumer.
  • Prevent serializing and deserializing mlt_type property to xml module.
  • Fixed relative paths for WebVfx "plain:" resources in xml module.
  • Updated libebur128 to v1.1.0 in plus module.
  • Added dynamic_loudness filter to plus module.
  • Added loudness_meter filter to plus module.
  • Qt 5 fixes for kdenlivetitle producer.
  • Added gradients and text shadows to kdenlivetitle producer.
  • Added support for building rtaudio against external build of lib.
  • Upgraded bundled RtAudio to v4.1.2.
  • Added status parameters to ladspa producer and filters.
  • Added 5.1 surround to stereo downmix to audiochannels filter in core module.
  • Fixed compiling SWIG bindings for Ruby 2.0.

v6.0.0 released

Feb 17, 2016

This is a bugfix and minor enhancement release. Note that our release versioning scheme has changed. We were approaching 1.0 but decided to synchronize release version with the C library ABI version, which is currently at v6. You can download it from SourceForge or GitHub. Here are some of the notable changes and enhancements:

Framework

  • Added unit tests for tractor, multitrack, and field.
  • Deprecate mlt_frame_get_alpha_mask().
  • Added drop_count readable property to mlt_consumer.
  • Added mlt_factory_repository().
  • Added mlt_properties_to_utf8().
  • Define MIN, MAX, CLAMP in mlt_types.h in not already defined.
  • Switched to __APPLE__ and _WIN32 defines throughout codebase.

Modules

  • Added UDP and SMPTE 2022-2 support to cbrts consumer.
  • Fixed build against latest FFmpeg versions - now requires v1.1 and up.
  • Added audiospectrum filter to qt module.
  • Added meta.media.0.codec.rotate property to avformat producer to let apps and other services get the media orientation.
  • Make the avformat producer handle animated images.
  • Added style property to dynamictext filter.
  • Added timewarp producer to core module.
  • Fixed slowly accumulating A/V sync drift in mix audio transition.
  • Added width_crop and width_fit properties to pango producer.

Melt
  • Added -abort option to simply exit without full cleanup.
  • Fix key-press handling on Windows.

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MLT enables you to author, manage, and run multitrack audio/video compositions.
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