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

v6.12.0 released

Nov 26, 2018

You can download it from GitHub.

This version has many important fixes plus a few new filters and support for encoding using VA-API.


  • Changed buffer property to be mutable and adaptive to speed property in mlt_consumer.
  • Changed macOS RELOCATABLE build to use standard app bundle layout:
    • lib/mlt -> ../PlugIns/mlt
    • lib/frei0r-1 -> ../PlugIns/frei0r-1
    • lib/ladspa -> ../PlugIns/ladspa
    • share/mlt -> ../Resources/mlt
    • share/movit -> ../Resources/movit
  • Fixed a_track of transitions matching deleted track in mlt_tractor_remove_track().
  • Fixed multi-thread race crash in mlt_properties_clear().
  • Fixed possiblle null pointer crash in mlt_property_get_rect() and mlt_property_get_time().
  • Fixed non-animated strings containing ‘;’ or ‘=’ in mlt_animation_parse().
  • Fixed crash in clear_property() with mlt_animation.


  • Added a generic text filter to the plus module.
  • Added a timer filter to the plus module.
  • Added audio timeout handling to sdl2 consumers.
  • Added spot_remove filter to the plus module.
  • Added dds, ico, and webp filename extensions for qimage producer.
  • Added support for color_range property in avformat consumer: “pc” or “jpeg” for full range, otherwise limited range.
  • Added a window property to the audiowaveform filter.
  • Added MM:SS.SS to the timer filter.
  • Added query string param “multi” to the xml producer to force using the multi consumer.
  • Improved WebP image support in avformat producer.
  • Integrated hwupload filter in avformat consumer if using VAAPI codec.
  • Changed count producer to use pango if qtext not available.
  • Changed qt moduled to not call XInitThreads()
  • Changed color producer to only set alpha on frame if rgb24a requested or not opaque.
  • Changed the xml producer to pass quality and performance parameters to the multi consumer.
  • Fixed sdl2_audio distortion (regression in v6.10.0).
  • Fixed dynamictext filter to not error on empty text.
  • Fixed dynamictext aliased (regression in v6.10.0).
  • Fixed qimage outputs premultiplied if scaled internally.
  • Fixed crash in cbrts consumer if running property was never set.
  • Fixed rendering edges of some typefaces in qtext producer.
  • Fixed qimage fails to load with wrong filename extension.
  • Fixed affine dark right and bottom edge artifacts regression in (v6.10.0).
  • Fixed support for vp8 and vp9 with alpha channel in avformat producer.
  • Fixed interpolation mode selection in qimage producer.
  • Fixed crash in qimage with alpha channel.
  • Fixed some AAC MP4 files start playing from middle in avformat producer.
  • Fixed crash in avfilter if initialization fails.
  • Fixed crash in mix when frame rate is very low.
  • Fixed crash on missing luma file in composite transition.
  • Fixed A/V sync on some files in avformat producer.
  • Fixed seeking on audio filter with album art in avformat producer.
  • Fixed colorspace conversion in avformat consumer.


  • Added more avformat consumer presets:
    • alpha/Quicktime Animation
    • alpha/vp8
    • alpha/vp9
    • alpha/Ut Video
    • lossless/Ut Video
  • Added square video profiles:
    • square_1080p_30
    • square_1080p_60
  • Added support for nodejs to the swig bindings.
  • Changed configure script to require opencv module be explicitly enabled.
  • Numerous spelling fixes in source code and comments thanks to codespell.

v6.10.0 released

Jul 2, 2018

You can download it from GitHub.

This version fixes bugs and supports serializing animation keyframes with a specified time format (previously only frame number).


  • Reverted mlt_pool change in v6.8.0 pending further testing.
    (USE_MLT_POOL compiler define is now a 0/1 boolean, defaults to 1.)
  • Fixed crash regression in v6.8.0 “parsing non-animated string as an animation.”
  • Added pointer checks to mlt_animation.
  • Changed producer cache size heuristic in mlt_multitrack to be more liberal.
  • Fixed handling reserved characters in names for YAML in mlt_properties.
  • Added clamping to prevent computing negative in and out points to mlt_producer.
  • Added functions to serialize animation with a time format:
    • mlt_animation_serialize_cut_tf()
    • mlt_animation_serialize_tf()
    • mlt_property_get_string_tf()
    • mlt_property_get_string_l_tf()
    • mlt_properties_get_value_tf()
    • Mlt::Properties::get(int, mlt_time_format)
    • Mlt::Animation::serialize_cut(mlt_time_format, int, int)
  • Added functions to clear a property to mlt_properties:
    • mlt_property_clear()
    • mlt_properties_clear()
    • Mlt::Properties::clear()


  • Fixed enabling sliced pix_fmt conversion in avformat producer.
  • Fixed incorrect seek and sync on audio files with discard packets.
  • Added support for avcodec_send_frame() API to avformat consumer.
  • Fixed compile errors with Libav master.
  • Fixed a crash in affine transition.
  • Fixed a crash in ladspa filters when consumer frame rate is low (e.g. <= 8).
  • Fixed a crash in boxblur filter.
  • Added animation support to boxblur hori and vert properties.
  • Fixed a crash in movit.convert.
  • Fixed incorrect alpha in affine transition blending routine.
  • Converted frei0r from deprecated mlt_geometry to mlt_animation API.
  • Fixed tilde in text string for pango producer.
  • Fixed using more than one channelcopy filter.
  • Fixed the mono filter reducing volume level.
  • Fixed degraded audio scrubbing in sdl2_audio consumer.
  • Converted dynamictext filter to use affine transition for more correct alpha compositing and sub-pixel positioning.
  • Added time format support for animation keyframes to the xml consumer.
  • Added animation support to more affine transition properties:
    • fix_rotate_x
    • fix_rotate_y
    • fix_rotate_z
    • fix_shear_x
    • fix_shear_y
    • fix_shear_z
    • ox
    • oy
    • scale_x
    • scale_y
  • Fixed gaps in text when characters overlap in qtext and kdenlive producers.
  • Fixed a crash in pixbuf producer with multiple render threads.
  • Converted the oldfilm vignette filter from mlt_geometry to mlt_animation.


  • Numerous updates to mlt-xml.dtd.
  • Categorized many of the encode presets (using

v6.8.0 released

May 10, 2018

You can download it from GitHub.

This version improves support for multi-channel audio and adds some new manipulation functions to the mlt_animation API.


  • Added support for musl C library.
  • Added functions for audio channel layouts:
    • mlt_channel_layout_name()
    • mlt_channel_layout_id()
    • mlt_channel_layout_channels()
    • mlt_channel_layout_default()
  • Added channel_layout property to mlt_consumer.
  • Added mlt_channel_layout enum.
  • Disabled memory pooling by default and require compile macro USE_MLT_POOL to re-enable it.
  • Fixed reliability of keyframed properties serializing properly.
  • Fixed parsing non-animated string as an animation.
  • Added more functions to mlt_animation:
    • mlt_animation_key_set_type()
    • mlt_animation_key_set_frame()
    • Mlt::Animation::key_set_type()
    • Mlt::Animation::key_set_frame()


  • Fixed some crashes in qimage producer especially with alpha channel.
  • Fixed >2 channel audio output in the SDL consumers.
  • Fixed >2 channel audio output in the rtaudio consumer on Windows.
  • Fixed vorbis encoding with FFmpeg v3.4+.
  • qimage and qtext are now higher priority than gtk2 pixbuf and pango by the loader producer.
  • Added support for more channel counts to decklink consumer.
  • Added swresample filter based on libswresample from FFmpeg. This is now the preferred channel count normalizing filter used by the loader producer.
  • Fixed the strange “Undefined constant” and “Unable to parse option value” log messages in the the avformat consumer.
  • Fixed GIF and DPX writing in avformat consumer.
  • Reduced the memory usage of the affine transition and filters.
  • Fixed a crash in kdenlivetitle producer.
  • Fixed a crash in the rotoscoping filter.
  • Fixed frame rate reported in Matroska and WebM files produced by the avformat consumer.
  • Added sdl2_audio consumer.
  • Fixed alpha channel support for more pixel formats in the avformat producer.
  • Converted the affine transition to use mlt_rect and mlt_animation.
  • Fixed LADSPA plugins with mono channel audio.


  • Fixed a melt command line parsing bug when argument supplied to -transition.
  • Fixed melt with SDL2 on Windows not using stdio and stderr.
  • Improved speed of the vp9 avformat consumer preset.

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).


  • 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().


  • 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 (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.


  • 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.


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