Creating content for multiple screens can be less straight-forward then creating content for a single screen. The resolution and aspect ratios of the content can be very non-standard and even finding applications that support these irregular resolutions can be difficult.
This solution will explain the different considerations and specifications around creating content for a multiple screen scenario; however it does not cover the details of the using encoding and video production software. The specifications in this solution are purely a “guide” and are not the hard rules that must be followed. Use these specifications for a starting point and modify as necessary.
When creating or encoding content, keep in mind that the quality of the video can only be as good as the original content. Re-encoding content at a higher resolution will not increase the quality and in fact may decrease the quality since the encoder will have add pixels to the video to increase the resolution.
Testing
Content creation and video encoding is not an exact science to get the optimal visual quality on the screens. The many factors of video can require “tweaking” and testing to get the content to play just right. Content being played back on a design computer with a single screen will have significantly different playback qualities compared to the EnGage player with multiple screens attached.
Note: Ultimately, the playback quality of the content will be dependent on the hardware resources of the EnGage player. Be sure to test all content on a test player prior to deploying the content onto a player in the field.
1.) Aspect Ratio
The most important factor in having content that looks good on a multiple screen system is to have content created at the proper aspect ratio. Ideally, the content will be the same resolution and aspect ratio as the zone in which it was designed to play. By default content will be scaled to fit the zone in which it has been programmed to play. However, having the content scale to fit a zone is not necessarily a bad thing and in some case can be very helpful.
Having the player scale the content more in one direction (horizontally or vertically) will cause stretching or squishing of the content which can be very noticeable on the screens. Although the content doesn't need to be created at the same resolution as the zone, creating in at the same aspect ratio will allow it scale into the zone and avoid any vertical or horizontal stretching or squishing.
2.) Video Bitrates
A general “rule of thumb” is 5 megabits per second, per screen on which the video will play up to 40MB/sec. Over encoding content can result in poor playback due to the player hardware straining to play back the content. Under encoding content can reduce the quality of the content and create pixelation on the screens. Determining the optimal bit-rates will be a balance between the size of the file, the playback quality and the hardware resources of the player.
The bitrate of content will also be dependent on the type of content being encoded. Video content with heavily moving objects and lots of colors will need to be encoded at higher bitrates, such as a car race. Video content that has slow moving objects can be encoded at lower bitrates, such as a person talking with a static background, like a newscast.
3.) Video Resolutions
The resolution of the content playing on a video wall will be dependent on the size of the video wall, the resolution of the zones and the distance of which the audience is viewing the screens. In the best case scenario, the content resolution should be the exact same size of the zone in which it is going to play. This will avoid and scaling of the content.
However, due size of the videos, the resources of the player and the irregular size zones possible in multiple screen arrangements, the video resolution may need to a different resolution than the zone.
It’s also not always required to have content that is pixel-for-pixel the same size as the zone, depending on the view distance of the audience. The audience may not be able to see the difference between 720p videos vs 1080p videos, in which case encoding the content at 1080p will unnecessarily increase the file size and put extra strain on the player resources. Since 720p is easier for the player to playback compared to 1080p, the playback quality may even be better at 720p.
When content is being created that will span multiple screens, it may be required to use video editing software to combine multiple videos together to achieve the aspect ratio and resolutions required to look good on the screens. For example, having a video that spans two landscape mounted screens will be heavily stretched to fit the zone if standard 16x9 content is used. In this scenario, two videos should be combined, side-by-side, in video editing software should be used in the zone. If the two videos are encoded at 720p (720H X 1280W) then the end resolution would be 720x2560. Depending on the arrangement of the screens, videos may need to be combined to create content with the same aspect ratio as the zone. Determine the size of the videos based on the resolutions of the screens and the arrangement. Some manual calculations will be required to work out these details.
The maximum resolution that the EnGage player can play back on a dual output player is 2048 pixels in either horizontal or vertical direction. If the combined screens create a resolution larger then 2048, use 2048 as the maximum horizontal or vertical resolution and calculate the opposite resolution dimension depending on the aspect ratio. On a four output player (or greater), the dimensions increase to 8192.
Typical consumer video cameras can record video at a maximum resolution of 1920x1080. Special higher end video cameras can record video at 4,096 X 2,304, which is known as 4K. Any content required at a resolution larger the 4096px will have to be scaled up or combined with other videos to match the required resolutions.
4.) Image Resolutions
Images can have any resolution and the player will scale the image to fit the zone in which it is programmed to play. As with video, the aspect ratio of the image should be the same as the zone otherwise stretching may occur. It’s recommended that images are re-sized to properly fit the zone to avoid unnecessary player scaling in order to archive optimal image quality. There is no practical limit to the resolution of an image, but it should not be bigger than the combined resolution of your screen layout.
Suggested Codec
Although there are many audio and video codecs that the EnGage player can play, it is a good practice to standardize on one format. ComQi suggests the following:
MPEG-4 (*.MP4)
Video: H.264 @ baseline profile, 3-5Mbps @ 23.976 fps, constant quality
Audio: AAC (LC) 128kbps 44.1Khz, 2 Channel
Best Practices
· Add an audio track even if there is no audio in the video
· Encode content without B-frames
Limitations
· Not all video encoders can output very high (greater than 1080p) resolution content. ComQi has been successful using “MPEG Stream Clip” or “Handbrake”.
· Adobe flash content it not currently supported by multiple output EnGage players
· Playing a single content asset spanning multiple screens put more strain on hardware resources then separate videos on individual screens.