Video Edition

From Elvanör's Technical Wiki
Jump to: navigation, search

Formats and conversion tools

  • recordmydesktop saves exclusively to Free formats (Theora for video and Vorbis for audio).
  • A general tool to convert from one format to another is ffmpeg. You can use it like this:
ffmpeg -i input-file.ogm -vcodec libx264 -b 2000k -t 5 output.mp4

Note that the -ss option does not seem to work with Theora encode streams.

  • Avidemux is a nice application to split and edit streams, with a GUI. It cannot read Theora encoded videos yet though.
  • To split or generally work with Theora videos, the applications are in the Gentoo package liboggz. Extracting part of a Theora video does not reset the time counter to 0 which is strange. Also, mplayer does not read well "non-canonical" Theora videos (for example ones extracted and that do not start with a keyframe). VLC is better, but generally speaking, support for Theora is quite buggy in a lot of tools.

Applications for video edition

Kdenlive

  • Kdenlive (requiring KDE 4) seems to be a very good application. It can export to a lot of different formats, and take any format as input.
  • Reading from Theora seems to be buggy though.
  • A very important concept in Kdenlive are the project profiles. Here you define the target resolution, Pixel Aspect Ratio and Display Aspect Ratio.

Exporting to Flash video (.flv)

  • When exporting to Flash video from Kdenlive, it is crucial to create a project profile that has the exact same data as the original source. Eg, PAR, DAR and resolution should exactly match those of the original source. This is because Flash video are not anamorphic (eg, rescaling is not possible to adapt to some given size).

Obtaining information about a movie file

  • The best way seems to be to use ffmpeg -i filename.avi. It gives you lots of useful data, such as resolution, DAR and PAR.


Online services

  • Youtube limits the duration of a video to 10 minutes and upload size to 1Gb. You can add fmt=22 as a parameter to the URL to get the video in HD. When embedding you need to use "&ap=%2526fmt%3D22" in the URL.
  • blip.tv seems a very good service. There is an upload counter when you upload a video, which is very nice, and they accept Theora videos.