Enable original video file
In some cases, you may want to use the original video (not transcoded by RealEye) file as a stimulus.
By default, RealEye prepares (transcodes) video files to work best on a wide range of devices.
If for some reason you need to use the original video file, please make sure it's encoded properly for the web browsers and the devices you want people to participate from.
Video Player used in study
RealEye works in web browser, without any additional plugin or software needed.
To show video stimuli, RealEye uses regular HTML <video> element.
Encoding video file
To encode your video files, you might also use free tools like Handbrake.
Here are our recommendations for video and audio encoders.
Video and audio stream container:
- Use MP4 as a container.
For video encoding:
- Use the H.264 video codec (also known as AVC codec).
- "Main" profile is recommended.
- Fast-decoding is recommended if you know study will be run on old/slow mobile devices.
- Resolution up to 1080p is recommended. The newest devices support up to 4K UHD resolution (horizontal or vertical). We strongly advise AGAINST using videos over 4K UHD resolution. NOTE: Higher video resolution may result in lower eye-tracking sampling rate.
- 8-bit color depth.
- For 1080p bitrate up to 3 Mbps. For 4K UHD bitrate up to 10 Mbps.
- 30 FPS or less is recommended.
- No DRM.
Video encoding with x264 tips:
- Use "fast start".
- For the best quality/size ratio use at least the "medium" preset.
- For the best quality/size ratio use the "2-pass encoding".
- To improve the compatibility with various devices/players you might want to consider using the "4:2:0 chroma subsampling". Please be aware that this will most likely result in a "blurry text".
For audio encoding:
- Use the AAC codec. 44 or 48 kHz, 16-bit, stereo, up to 160 kbps bitrate.
4k UHD Video
Supported mobile devices:
- iPhone 6 or later. With iOS 11 or later.
- Android 8 or later with 2 GB RAM, e.g. Samsung Galaxy A8.