Difference between revisions of "Video Codecs"

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We advise users to contact the Technical Support Group to discuss which codec and export settings are best suited for your video stimuli. This page functions only as reference.
 
We advise users to contact the Technical Support Group to discuss which codec and export settings are best suited for your video stimuli. This page functions only as reference.
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For a guide on recording your screen, see [[Screen Recording with OBS]].
  
 
== Information ==  
 
== Information ==  

Latest revision as of 17:09, 18 July 2019

We advise users to contact the Technical Support Group to discuss which codec and export settings are best suited for your video stimuli. This page functions only as reference.

For a guide on recording your screen, see Screen Recording with OBS.

Information

Codecs

To find out what video codecs are and why they are used, grab a cup of coffee (or other non-alcoholic beverage of choice) and reserve about 45 minutes of your life to watch this comprehensive video: How Codecs Work (Vimeo).

Bitrate

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, a helpful formula written by a guy named Kush:

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, potentially causing laggy playback. For this reason, we advise using a constant bitrate.

Software support

Recommended formats Non-Recommended formats
Codec VP8/VP9 Theora H.264 XVID
Container .webm .mkv .ogv .ogg .mp4 .avi
Advantage Open Source Open Source Industry Standard Works in Presentation
Software
Chrome/Firefox/Opera Yes Yes Yes No
VLC Yes Yes Yes Yes Yes
PsychoPy Yes1 Yes1 Yes1
Neurobs Presentation No No No Yes2 Yes

1 Windows version requires careful installation, consult the TSG for help.
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.

Neurobs Presentation

Neurobs Presentation does not support the .mp4 container, so you will have to convert your H.264 encoded .mp4 videos to the .avi container. Neurobs recommends using MP4Cam2AVI Easy Converter[1]. Be sure to uncheck 'preview On' before opening your files, because the program might crash otherwise.

Downloads

Converters

Name Download Location Supported formats Supported containers
Handbrake https://handbrake.fr/ H.264, MPEG-4, MPEG-2, VP3 mp4, mkv
MP4Cam2AVI Easy Converter http://sourceforge.net/projects/mp4cam2avi H.264 avi, mp4

Codec Packs

Note: Below is just a list of several codec packs. Please do not attempt to install all packs together, but only choose the one(s) your playback-software requires.

Name Download Location
Libavcodec https://libav.org/
LAV Filters https://github.com/Nevcairiel/LAVFilters/releases
K-Lite Codec Pack http://www.codecguide.com/download_kl.htm
FFmpeg Encoder https://www.ffmpeg.org/
FFDshow http://sourceforge.net/projects/ffdshow-tryout/

Media Players

Name Download Location
VLC https://www.videolan.org/
Noldus Mainconcept Codec (Noldus Media Recorder) Media:Noldus MainConcept Codec Package 8.5.26.zip
AVBin (Psychopy) http://avbin.github.io/AVbin/Home/Home.html
Gstreamer (Matlab) http://gstreamer.freedesktop.org/

References

  1. http://www.neurobs.com/wiki/Presentation/Video#Video_Encoding