This page covers the content requirements, abilities, and restrictions of the HTML rendering engine on BrightSign players.
The following are content restrictions associated with HTML pages:
BrightSign players are not intended for use as general-purpose web browsers. It is best to think of BrightSign units as HTML players with interactive capabilities, not web-surfing tools: Each page should be thoroughly tested before being used as digital signage.
BrightSign players do not support Flash content. Any HTML pages that have embedded flash content will not display correctly. Most Flash authoring applications, including the Adobe Creative Suite, have tools that allow you to export flash content as HTML.
See the HTML Video page for usage rules regarding HTML video.
While many BrightSign models can output 4K video modes (3840x2160 or 4096x2160), not all of these models can render HTML at 4K:
The XTx44 and XTx43 models support a native 4K HTML graphics plane (see this page for more details). Note the following performance restrictions when using native 4K HTML graphics:
- Animations will not exceed 20 FPS (and intensive animations may exhibit very low framerates).
- Non-HWZ video is likewise limited to 20 FPS, so HWZ should be enabled for video elements in native 4K.
- We recommend displaying only one or two 4K images at a time (for example, a slideshow with one image displayed and next image preloaded). Images should not exceed 4096x2160 in size.
- We recommend using swap memory if possible.
- Pages that use many layers may run out of memory in native 4K. Enabling the
gfxmemlargesetting may help mitigate this issue.
4Kx42, XDx34, XDx33, HDx24
The 4Kx42, XDx34, XDx33, and HDx24 models support graphics up to 1920x1200 (see this page for more details), which can then be upscaled to a 4K video mode. Pages must be specified as 1920x1080 (or 2048x1080 for DCI 4K); they can then be upscaled to 4K.
Pixel Sizes and Coordinates with 4K Modes
As noted above, webpages are often upscaled when outputting a 4K video mode. Relative CSS property values will scale automatically, but pixel values may need to be modified to account for differences between 4K video and graphics. See here for more information about using coordinates with upscaled video modes.
Images larger than 2048x1280x32bpp (or 4096x2160x32bpp for XT, 4K, XTx34, and XDx33 players) will not be displayed by default. If a 4K video mode is used, the player will upscale images from HD resolution accordingly (though native 4K graphics can be enabled on the XTx43). The default limit can be increased in BrightScript using the roVideoMode.SetImageSizeThreshold() method.
Without altering the default maximum resolution, you can increase the maximum width of images by sacrificing height (e.g. using a 4096x640x32bpp image on non-4K players is allowed). You can also increase the maximum width/height by reducing the bpp value (e.g. using a 4096x1280x16bpp on non-4K players is allowed).
For performance reasons, we recommend against downscaling images. This consumes considerably more resources than either displaying images at their native size or upscaling them.
Memory and Performance
The amount of memory available for HTML applications varies by model:
XTx43, XTx44: 512MB for graphics; 512MB for JavaSript
- The memory available for graphics can be reduced by a number of factors, including the number of CSS layers, the complexity of animations, and the use of WebGL.
Often, the best way to improve graphics performance is to ensure that images are scaled to the desired output resoultion before they are rendered in HTML.
Use the Chromium Web Inspector to determine the amount of resources being used by a webpage.
If a font file is not included and referenced by the HTML page, text will be rendered using a default system font. While functional, the default font has little aesthetic appeal, so we recommend including font files for most digital-signage applications. Supported font types include TrueType Font files (.ttf), OpenType Font (.otf), and Web Open Font files (.woff, .woff2).
We recommend using
setAttribute() to manipulate the DOM, rather than using "x.value=y":
Creating HTML Pages
Follow these steps when creating HTML pages:
- Make sure the HTML page has the same aspect ratio as your signage display. If you are using HTML content in a BrightAuthor zone that is smaller than the screen, fit the page to the same aspect ratio as the zone.
- Use a master Div aligned to 0,0 when building an HTML page. This will ensure correct alignment.
- When creating an HTML site, make sure that all webpage assets (image files, video files, etc.) are contained within the same folder on your local disk. This folder is a “site folder,” meaning that all assets in this folder and its subfolders will be used in the production of the webpage. If these assets are not in the folder, they will not display when the project is published.
- You can test the layout and appearance of a page locally by opening it with Google Chrome, which has similar rendering capabilities to BrightSign players.
- If you want to publish resource-intensive presentations (e.g.
<video>elements or multiple transforms) using HTML, we recommend using a Class 10 (10Mb/s) SD card.
The BrightSign implementation of the Chromium engine includes several platform-specific extensions. Extensions for <video> elements are covered on the HTML Video page.
GPU rasterization is enabled by default in firmware versions 6.2.x and later.
Optimized Image Rendering
image-rendering CSS property can be assigned the
optimizeSpeedBS value. Using this value ensures that Chromium uses lower-quality but faster bilinear filtering when scaling images to 50% or less. We recommend using this value with pages that scale a lot of images at runtime.
Renderer Versions and Support
The following table describes which version of web-rendering engine is used in each version of BrightSign firmware:
|Rendering Engine||Version||BrightSign FW Versions|
|Chromium||45||7.1.x, 7.0.x, 6.2.x|
|WebKit||--||5.1.x, 5.0.x, 4.8.x, 4.7.x|
You can use this page to determine if specific function calls and extensions are supported in a corresponding version of Chrome.
Animations and Add-on Libraries
This section outlines support for animations and add-on libraries for the Chromium engine on BrightSign players.
For best results when animating images, we recommend using images at their original size instead of scaling them first. For example, a 480x270 icon will rotate more smoothly if you use an image that is originally 480x270, rather than scaling down a 1280x720 image and then attempting to rotate it.
The SVG protocol should be used to specify vector animations.
Bitmap animations display smoothly when they are 1/3 or less of a 1080p HTML canvas. Setting the canvas size to 720p allows for larger high-quality animations to occupy the screen.
The long polling technique has been tested and proven to work on BrightSign players.
The Websocket protocol is fully supported via the Node.js implementation on the BrightSign Chromium instance. In production environments, we recommend using HTTPS to initiate Websocket connections with a server (i.e using a WSS connection rather than a WS connection).
An example Websocket application is available on the BrightSign Github page.
All CSS transforms should be specified as WebKit transforms. When performing a transform on a <div> or graphics element, you should not specify the transform in-line.
The following code shows an example of an effective CSS transform for a BrightSign player:
BrightSign players are compatible with touchscreens that use standard HID drivers. Note that some manufacturers claim support for HID but still use custom drivers. See this FAQ for further discussion and a list of touchscreen models that have been tested with BrightSign players.
You can use the Web Inspector to debug webpages over the local network. The Web Inspector can be enabled using BrightAuthor or BrightScript:
BrightScript: When creating the roHtmlWidget instance, include the
inspector_serverinitialization parameter and specify a port number. You can then use Chrome to access the Web Inspector at http://playerIPAddress:<port>.
If you don't know the player IP address, power on the player with the SD/microSD card (and other storage devices) removed. After a few moments, the IP address will be displayed on screen.
The Web Inspector creates a security vulnerability on the BrightSign player and should be disabled in production environments.
Because BrightSign players use an older version of Chromium than recent desktop versions, newer desktop Chrome releases may not work with the Web Inspector. If you're having trouble using the Web Inspector with your version of Chrome, download and install one of these versions:
- Linux: https://www.googleapis.com/download/storage/v1/b/chromium-browser-snapshots/o/Linux_x64%2F338389%2Fchrome-linux.zip?generation=1436570329817000&alt=media
- Windows (unofficial portable release): https://sourceforge.net/projects/crportable/files/ChromiumPortable_45.0.2453.0.paf.exe/download
When trace events are enabled on a BrightSign player, Chromium captures trace messages to a circular buffer. The player takes regular snapshots of this buffer and writes them to the root directory of the microSD card or SSD as JSON files.
The TraceEvent system can easily generate gigabytes of log data on local storage, so we recommend disabling it in production environments.
Creating a TraceEvent Directory
Before enabling the TraceEvent system, create a directory named "brightsign-webinspector" in the root directory of the microSD card or SSD on the player. If this directory is missing, the player will not record trace events when they are enabled in the registry. Conversely, you can disable trace events by deleting the "brightsign-webinspector" directory from the storage device.
Enabling the TraceEvent System
html section of the registry:
[string] tracecategories: A comma-separated list of trace event categories to enable. The category names are documented in the link below.
[int] tracemaxsnapshots: The maximum number of JSON-trace snapshot files in the "brightsign-webinspector" directory. When the limit is reached, the counter wraps around and begins writing over the oldest trace file.
[int] tracemonitorinterval: The frequency (in seconds) with which the player will take snapshots of the TraceEvent buffer. We recommend 60 seconds as a default value.
Viewing Trace Events
Follow these steps to view the trace events:
- Transfer the JSON trace files from the "brightsign-webinspector" directory to your PC.
chrome://tracingon your PC Chromium instance.
- Import the JSON trace files.
You can merge multiple trace files; however, in a long trace capture, there will be too many trace events to view at once (you'll likely need to write a script to process them).
See the following links for further explanation of trace events:
Disabling Staged ES6 Features
To bypass such issues, you can disable all staged (i.e. experimental) ES6 features using the