Difference between revisions of "Video Codecs"

Revision as of 15:49, 17 August 2015

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.

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.
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. Instead, you can convert your H.264 encoded .mp4 videos to the .avi container using the MP4Cam2AVI Easy Converter, as recommended by Neurobs. Be sure to uncheck 'preview On' before opening your files, because the program might crash otherwise. Alternatively, if your videos are under 5 minutes, you can use Freemake instead. Both programs can be downloaded via the links below.

Downloads

Converters

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
MP4Cam2AVI Easy Converter	http://sourceforge.net/projects/mp4cam2avi	H.264	avi, mp4

¹ Freemake adds a watermark to videos longer than 5 minutes.

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/

@@ Line 100: / Line 100: @@
 === 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) you need.
+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.
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