Audio/Video Documentation

Distribution Formats

Audio Formats

We distribute most of our audio files in the Ogg Vorbis format. Unlike MP3, this format has always been completely free and unencumbered by patents. The Vorbis wiki provides lists of software and hardware that support it.

A few recent audio files are encoded in Opus, which is a low-delay, free format that supports high audio quality.

Video Formats

We distribute most of our video files encoded with the Theora video codec, encapsulated in an Ogg transport layer. They share the .ogg extension with the audio files (or occasionally have the .ogv or .ogm extension).

The Theora video codec was designed as a free video codec unencumbered by patent licensing restrictions. Its technical brilliance and superb compression rates should not be allowed to overshadow its most important asset: it respects users' freedom! Visit the Theora wiki at xiph.org for more information or to download players and codecs.

We use WebM (with the VP8 or VP9 video codec) instead of Ogg Theora for some videos; WebM is a more recent format, also unencumbered by known software patents.

Accessing Recordings

Most of the ogg files have been encoded in a stream of 20 kb/s. Most Internet users, including those with slow connections, should be able to listen to the files streaming from our server.

Our media files can be streamed by the major browsers (e.g., Firefox), and streaming will start automatically by default. You can also stream them with VLC. For example:

vlc https://audio-video.gnu.org/audio/file.ogg

Another possibility is to download the media file, and play it later:

wget -q https://audio-video.gnu.org/audio/file.ogg

Wget with the -c switch will continue a transfer if a smaller file of the same name exists in the download location. For example,

wget -c https://audio-video.gnu.org/video/file.webm

Request for Recordings

If you are planning to attend a GNU event, please make a recording. It is polite to ask permission from the event organizer. If you wish to make the recording publicly available in a digital format, please choose one that is accessible to free software. Theora or Vorbis are the best choice as using one of these will add support to free, open, unencumbered formats. Please choose the license we use for the speech recordings, and remember to embed the license into the digital file so that people who receive a copy of the file are aware of their freedoms.

If you have a good recording from a GNU event, and you would like to share it with us, please send an email to <[email protected]>. We are interested in both audio and video recordings, and can accept the source in a wide range of formats (e.g., those supported by ffmpeg). We will transcode to a standardised codec for the site, and optimize the encoder settings.

When submitting recordings, please provide the following information:

• who recorded the speech and who owns the copyright;
• the name of the event where the speech was recorded, including city and country;
• the date the recording was made;
• confirmation our usual license is OK to use: Creative Commons Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0);
• the names of introductory speakers;
• the title of the speech.

We prefer to handle speech recordings as a single file rather than split into sections, but if the original is in many parts, we can join it as required. If the original is compressed with a lossy compression format such as mpeg, divx or a proprietary format, please don't transcode the recording before sending it to us. Given that we may transcode it to a different bit rate and frame size, and insert copying information, inserting yet another transcoding stage will simply degrade quality.

We don't have a public uploading facility for large media files. So, the best way to send us the recording is to place it on a website and send us the link. You can also use a free (as in freedom) file-sharing service. If you experience any difficulty in this respect, we can probably find a solution.

Audio

We prefer original recordings in the original recorded sample rate up to 44100Hz. Monophonic is generally adequate for speech recordings and saves a lot of space over stereo. We will accept the recording in the original file type. If the original file is large, you may wish to transcode to 64 kb/s mono Ogg Vorbis.

Video

The same is true for video as for audio. Send the recording in the original frame size. If already compressed with a lossy codec, please send the original. If your original is uncompressed or has a very low compression/ large file size, please compress using Theora with video quality set to 5 or more.

Transcription

If you have a transcription of a speech by a GNU speaker, or would like to make one, please contact <[email protected]>.