Digital Signage with the Raspberry Pi

Raspberry Pi 3
Raspberry Pi 3

If you look at the specifications, you can legitimately ask whether it is possible to use the Raspberry Pi for digital signage. The open-source software support is exemplary and there are inexpensive starter kits. The community is huge, has a lot of experience, and you can get easily support. The device plays beneath pictures and websites, Full-HD videos and now even works with WLAN.

Nevertheless, in my view, there are some conceptual drawbacks which limit the Digital Signage with the Raspberry Pi combination severely, particularly in a network.

Foremost, it was designed as a learning computer and not for media player purposes. For example, the network use a USB hub to save costs and the overall performance is just satisfactory.

Some Models

Specifications Raspberry Pi 3.0 B (February 2016)

  • 1200 MHz 64 Bit ARMv8-A Quad-core CPU
  • 1024 MB RAM
  • Bluetooth 4.1
  • WLAN b/g/n
  • 10/100 MBit Ethernet
  • MicroSD-Reader

The Raspberry Pi Zero

I only list this model for completeness. The Raspberry Pi Zero has been available since November 2015 for just under 5 EUR. In the variation from February 2017 even with Wi-Fi. The Zero has only 512 MB of working memory and the CPU from the first Raspi model with only one core. Despite the video acceleration, it works much too slowly to be used as a media center or even in digital signage projects.

In the summer of 2016, I ported my garlic-player to the Zero as part of a customer project out of curiosity. It ran and even HD videos played. However, the operation was tough, and it was not really fun to administrate the device. As a technology study, it was of course impressive for the customer. However, this hardware was not created for serious projects in the field of media.

Update: Raspberry Pi Version 4

In June 2019, the Foundation released the Raspberry Pi in version 4. The new CPU is much more powerful and the network no longer runs over USB. The performance has been greatly improved overall, and the device even runs two 4K monitors simultaneously. Moreover, it even addresses 8 GB of main memory in a slightly more expensive variant since May 2020. It seems at first glance with a good heat sinking case, even less problems for use in digital signage projects to give.

Unsatisfactory Hardware Acceleration for Videos

Unfortunately, appearances are misleading, and a second look reveals some issues. The Raspberry Pi 4 still does not accelerate 4K videos currently (April 2021). Only the LibreElec project manages to play a certain video profile. Otherwise, 4K content stutters unacceptably and leads to overheating.

To completely address partially up to 8 GB large main memory, it requires a 64-bit operating system. The official 64 bit Raspberry Pi OS (formerly Raspbian) has been in the test phase since May 2020. However, the hardware acceleration for videos is completely missing there.

It is true that during one of my tests, an impressive four videos ran almost smoothly at the same time. However, since a processor that gets quite hot bears the main load instead of the video accelerator, this causes questions regarding long-term stability. Apart from the fact, of course, that there is no question of using test operating systems in productive signage projects under any circumstances.

For several months (as of April 2021) nothing significant is happening there, unfortunately. From my perspective, this is sad. In the field of low-cost digital signage projects, the Raspberry Pi 4 could set standards. Being able to display content on two 4K monitors without any problems is unique in the price category.

The most critical disadvantage: The lack of eMMC memory

Usually, a CMS operates the network in Digital Signage projects to change the content repeatedly quite promptly. So, the players are centrally operable and should be able to submit logs for play or error statistics. For a media player, this means lots of writing accesses to its internal storage in addition to reading accesses. A standard Raspberry Pi does not have any internal storage, so it needs to be upgraded.

Pitfalls in storage purchasing

There are two ways to install this memory; with a microSD card or a USB stick. However, one should not use the cheap consumer-storage. A low-price sd flash memory, which is primarily for reading only. It is optimized for usage in a smartphone or as mobile storage. For such a flash memory, writing accesses for such a large amount of data can be excruciatingly slow.

Apart from this, such types of flash memory are limited. Depending upon the technology of storage, blocks can allow a maximum of 1,000 to 1,000,000 of erasing and write cycles (P/E cycles) approximately. (Source Wikipedia). Expensive models differ from the cheaper SD cards in the number of these cycles.

Experiences

In a network-based Digital Signage project, a lot of daily content changes and log statistics occur. Hence, you can reach this limit quickly in cheaper consumer-storage.

Theoretically, since eMMC memory blocks have the same technology, they also have the issue of limited erase/write cycles. However, hardware manufacturers are aware of this issue and hence usually incorporate chips of higher quality. However, a user underestimates the risk of low-priced product and takes advantage of the seemingly favorable cheaper variant for his Raspberry Pi.

In 2012, I supervised a project in which the same thing happened due to cost reasons. The service installed consumer USB storage into the media player. These USB storage were not even the cheapest available. Nevertheless, in less than a year, the devices failed, and the screen became black. In all cases, a technician of service was called to replace the USB stick with a higher quality model. This exceeded the actual price by multiple times.

You don’t want such a thing to happen in your Digital Signage project.

Industrial Memory-Cards as Alternative

You can avoid such a mishap by using an industrial memory in case of Digital Signage and Raspberry Pi. SLC components are one of the highest quality components. You can also use a cheaper industrial MLC flash of a higher capacity, which allows the erase/write cycles to be evenly distributed. But, it comes with a price:

For industrial usage, microSD cards with SLC memory. For example, on ATP, the cost of 8 GB capacity is about 93 EUR (as of January 2018) Source ATP

Industrial MicroSD cards having 8 GB of cheaper MLC memory, depending upon the order amount the cost caries between 30-40 EUR Source for Panasonic

We would need a higher capacity to use MLC memory, 16 GB being the least recommended. So, at the end of the day, you’d be paying approximately the same cost as that of SLC memory.

The cost aspect of thigh quality USB memory is quite comparable. There are two disadvantages also; a stick requires more power than a microSD card. The Raspberry Pi, having a standard power supply of 2.5 amperes only, could get overwhelmed with that. Furthermore, a USB stick extrudes out of the device, requiring space which may not be available.

In addition, this represents a mechanical source of error that must be secured in signage projects. Someone could come up against it or remove the stick maliciously.

Cost with Industrial SD-Cards

Raspberry Pi 3 Starter Kit with power supply and housing: approximately 60 EUR (Source Amazon)
8 GB SLC MicroSD: 93 EUR (Source DigiKey)
The pure hardware costs of operating Digital Signage with Raspberry Pi securely in a network are approximately 153 EUR! (As of January 2018)

We can get much more powerful and 4K-capable digital signage hardware of at least 8 GB eMMC memory or higher for less than 100 EUR.

For completeness: the Compute Module

Bild vom Compute Module
Raspberry Pi Compute Module

A Raspberry Pi Compute-Module 3 with a 4 GB eMMC memory is currently available for 30 EUR (Source Raspishop – As of January 2018). However, this module doesn’t come with a WLAN chip, and 4 GB memory is only suitable for SD videos and short HD playlists.

Update: Compute Module 4 (CM4)

In October 2020, the Raspberry Pi Foundation released the CM4. This also has two HDMI outputs, up to 8 GB of RAM and, like the CM3+ presented in January 2019, it can drive up to 32 GB of flash memory. This should make space worries for HD or 4K content a thing of the past. Furthermore, the CM4 even has a PCIe 2.0 interface. It can do Bluetooth, but still no Wi-Fi. The price ranges between 25 and 90 EUR.

Furthermore, you need a carrier board if there’s no slot with the I/O interfaces. This again costs you around 100-110 EUR. Only a few NEC monitors have an onboard Computer Module.

This means that the cost reaches to at least 130-140 EUR, which unfortunately makes it unappealing.

Summary on Digital Signage with the Raspberry Pi

On paper, the Raspberry Pi, especially version 4 with its two HDMI outputs, looks great. It is very reasonably priced and the Linux operating system is maintained for the long term.

Is the Raspberry Pi suitable for professional digital signage?

No! I think using a Raspberry Pi in larger digital signage projects is a mistake. As much as I am impressed by the version 4 hardware and its price, I would not advise anyone to run networks with it without eMMC-Flash.

What problems can occur with the Raspberry Pi?

The lack of local eMMC storage is a tangible disadvantage. MicroSD memory cards have limited write cycles that are quickly exceeded in professional use cases due to logging and regular content swapping. The cards break and have to be replaced. For distributed devices, frequent technician visits blow up any maintenance budget.

When you can a Raspberry Pi?

If the content does not change and no playback statistics are necessary. For example, to run a tool demonstration in an endless loop in a hardware store. Or in a furniture store, an image video for kitchen equipment. For this, theoretically, even a 5 EUR Raspberry Zero without Wi-Fi is enough.

However, as soon as the digital signage requirement includes weekly or even daily content changes or playback statistics, this changes. To upgrade the Raspberry Pi with industrial memory is not worth it financially. In this case, it makes more sense to consider alternatives.

A way out may be offered by the Compute Module 3, 3+ or 4. Provided the necessary slots, such as some NEC monitors, are already available, the contents of the CM3 do not require too much memory and integrated Wi-Fi can be dispensed with.


Gravatar Nikolaos Sagiadinos
Author: Niko Sagiadinos
Developer & Co-Founder SmilControl – Digital Signage
Visit me on: LinkedIn or GitHub

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