Started: October 23rd, 2015
Last update: November 9th, 2015
 Written by Peter B.,

 

Introduction

The following list provides guidelines in cases where audiovisual material is produced, but more as a side product. Long-term preservability is desirable, but not the main objective of the production.

A typical example would be: Recordings of speeches, conference talks, meetings, etc.

The information here lists options to choose that should facilitate long-term preservation of externally recorded materials. These suggestions are not intended for long-term preservation per-se, but sticking to some of these guidelines make it easier to preserve the created audiovisual recordings. Wherever possible, use Open Standards when selecting a digital file-format or encoding.

It is preferred to have at least one Free Software (Open Source) implementation that can read/write that format - such as FFmpeg. In that case, the chances of irreversible format obsolescence are improved by definition.

For details about codecs/containers for archiving, see the other "Audio/video encoding in archiving context" articles.

Video Encoding

Video-codec whitelist

These codecs are preferred in order of appearance.
All of them are either standardized and/or have a Free and Open implementation in FFmpeg.

The lossy codecs listed here are mentioned only as interim solution, in case of insufficient storage capacities.
Codecs which are not on this list, will be transcoded to lossless for preservation.

Framerate

Please use a linear, non-fractional framerate if possible.
The framerate is usually listed as "frames-per-second" (fps).

Standard for TV/video in Europe is 25 fps.
NTSC (U.S. standard) is fractional per definition: 30000/1001 fps.

Avoid variable framerates.
Variable framerates are common with some modern consumer devices, such as foto-cameras, smartphones, etc.

Group-Of-Pictures (GOP)

Most digital videos are stored in GOPs, to increase compression.

Frames that can be decoded standalone are called "keyframe" (or "I-Frame"). The majority of frames in a GOP however, are non-keyframes and require the images before or after for proper decoding.

Therefore, if possible, try to record in keyframes (I-Frames) only.

This results in larger video files, but makes the video more robust and facilitates transcoding/segmenting/editing later on.

Audio-Encoding

Audio-codec whitelist

When dealing with video, the data size of audio has become less relevant. Therefore, it is always advised to record and store audio uncompressed (PCM) or lossless if possible.

The following audio encodings are listed in order of preference.

Containers (Wrappers)

These video containers are listed in order of being least-problematic for handling.