AudioVideoEditing

Aegisub

A free, cross-platform open source tool for creating and modifying subtitles

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Ciano

A multimedia file converter

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EasyTAG

Edit audio file metadata

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Gaupol

Editor for text-based subtitles

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Gnome Subtitles

Video subtitling for the GNOME desktop

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Kdenlive

Video Editor

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Kid3

Edit audio file metadata

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Kid3

Edit audio file metadata

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MKVToolNix

Matroska files creator and tools

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MediaInfo

Convenient unified display of the most relevant technical and tag data for video and audio files

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MuseScore

Create, playback, and print sheet music for free

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MusicBrainz Picard

MusicBrainz's music tagger

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Pitivi

Create and edit your own movies

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Shotcut

Video editor

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Sound Converter

Converts audio files into other formats

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Subtitle Editor

GTK+3 tool to edit subtitles for GNU/Linux/*BSD

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Transmageddon Media Transcoder

Easy to use audio and video transcoding application

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VidCutter

Media Cutter + Joiner

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