To find out what video codecs are and why they are used, take a coffee and reserve about 45 minutes of your life to watch this comprehensive video: How Codecs Work (Vimeo)
When compressing a video, you will be asked to enter a 'bitrate'. This is what determines how much information is stored for every second of video. The more information, the higher the quality of the video. The tradeoff is file size. The more information, the larger the file. So setting a bitrate is striking a balance between limiting the file size without losing too much quality. The smarter the compression format, the easier this is to achieve.
If you are using H.264 compression, you can calculate a ballpark estimate for your target bitrate using the Kush gauge:
Target Bitrate (kbps) = Frame Width (px) * Frame Height (px) * Frame Rate (fps) * Motion Factor * 0.07 / 1000
"Motion Factor" is an arbitrary value (typically 1, 2 or 4) that you can assign to your video based on the amount of (fast) movement in the video. Higher amounts of movement require a higher amount of information to be stored in order to prevent quality loss. Example calculation for a typical 720p video:
1280 * 720 * 25 * 2 * 0.07 / 1000 = 3225.6 kbps (= 3.2 Mbps)
Bitrate can be set to Constant (CBR) or Variable (VBR). A variable bitrate can help decreasing file size when your video has a combination of high and low amounts of movement, as it will optimize the distribution of information storage for those parts in your video. The downside is that your video player has to sometimes suddenly decode a lot more information than the previous frame, resulting in possible lag. For this reason, we advise using a constant bitrate.
|Recommended formats||Non-Recommended formats|
|Container||.webm .mkv||.ogv .ogg||.mp4||.avi|
|Advantage||libre||libre||Industry Standard||Works in Presentation|
1 Windows version requires careful installation.
2 Recommended output for Presentation only. See documentation below for conversion options.
Note: This list is incomplete and will be updated as soon as we have tested all the common and recommended video formats with all supported stimuli software.
|Name||Download Location||Supported formats||Supported containers|
|Handbrake||https://handbrake.fr/||H.264, MPEG-4, MPEG-2, VP3||mp4, mkv|
|Freemake1||http://www.freemake.com/||H.264, MPEG-4, XVID, MPEG-2, MPEG-1, WMV3, FLV||avi, wmv, mpeg, mp4, 3gp, mkv, flv, swf, webm|
1 Freemake adds a watermark to videos longer than 5 minutes.
|K-Lite Codec Pack||http://www.codecguide.com/download_kl.htm|
|Noldus Mainconcept Codec (Noldus Media Recorder)||Media:Noldus MainConcept Codec Package 8.5.26.zip|