Stan Larroque's Blog

Category: Technical

  • Prototyping any stereo camera with StereoCam

    This post is for any person in AR/VR/drones and beyond who want to quickly prototype with stereo cameras.

    Our StereoCam prototyping platform

    At Lynx, we are big on passthrough for Mixed Reality and thus we always had a need to test various setup of stereo cameras. We even built a passthrough MR headset with 140dB+ HDR cameras (probably not the HDR you think about).

    In order to test various lenses and sensors when tinkering future HMD configurations, I built as a weekend project a prototyping platform for the team where the goal was to be as simple and effective as possible to have quick results.

    The result is a platform built on top of the latest Raspberry Pi 5. The Raspberry Pi 5 has 2 dedicated MIPI ports, and all the bells and whistles you can expect from a small yet powerful ARM computer. There is even a 16Go RAM version now, pretty cool.

    What you’ll need to assemble this:

    The casing is separated in 3 volumes (CamHolder, Case, Lid). You can 3D print these with standard PLA very easily.

    CamHolderDownload
    CaseDownload
    LidDownload

    The CamHolder was designed to hold the High Quality Camera from Raspberry Pi. It is a camera module based on a high-res Sony IMX477 sensor. So you can add two of these to the BOM.

    The case is designed to hold the Raspberry Pi 5 and its active cooling add-on. If you’re just streaming the cameras over the network to do processing somewhere else, then the whole system should only consume 5-6W, which could be fine without a cooler. Otherwise the active cooler is greatly encouraged.

    The case supports all RPi interfaces and its active cooler.

    To connect the MIPI cameras to the Raspberry Pi, you’ll need this kind of FPC: https://www.digikey.fr/fr/products/detail/raspberry-pi/SC1128/21658272. It also exists in 300mm and 500mm length.

    You also need to pick the right lens for your camera. Here is a vendor with a conveniant tool to pick the right FOV based on your resolution requirements.

    In Lynx use-case, we dump the RAW frames over the network so we can process them later and on a more powerful computer. We use the Raspberry Pi strictly as a “networked capture card”. The board is connected over Ethernet and we can start streaming the cameras with simple commands thanks to the Raspberry Pi incredible software support for cameras. You should find there your preferred ffmpeg/streaming command lines and if you don’t, you can always dig deeper with libcamera.

    Now you have in your hands a very capable stereo camera setup that can do a little bit off onboard processing (not any heavy AI stuff, but OpenCV distortion correction etc is largely feasible). You could even mount it as a payload on a drone and do some cool stereo FPV!

  • My personal setup

    A short article about what I use to manage my digital life.

    Computer

    It took me some time to find the right setup for me. I tried Mac, Windows and Linux and still own machines with these OS and my daily driver is finally Ubuntu 22.04. I mainly use a Dell XPS 13 running Ubuntu 22.04.

    It allows me to take calls from Webex/Google Meet/Teams/Zoom/Skype etc, and use professional software like the Jetbrains suite, Unity3D and Fusion360. It’s also great because most of my work on server-side stuff is also running on Ubuntu server or Debian.

    For the webcam I’m using OBS with my iPhone (modern smartphones have great cameras, might as well be useful with the computer as well?)

    I have a small Windows 10 virtual machine that I only use to run iTunes to backup my phone since I own an iPhone but don’t use iCloud.

    My browsing experience is simply Firefox with uBlock Origin.

    Phone

    I use an iPhone 12 13 mini. I owned an iPhone SE (2016) before for some years. I like being able to use it with only one hand, and having a smaller screen incentivize me to use it less (at least that’s my belief). I’m not a big user of my smartphone because I don’t want to be too dependent. To give you an idea, this is my home (and only) screen:

    Yep, not much.

    I only have notifications enabled for SMS/Signal and Gmail (the last one doesn’t have sound/vibration).

    I don’t have accounts for Facebook/Whatsapp/Snap/TikTok etc… for Linkedin and Twitter I use Safari or my desktop as the apps consume too much battery and are generally doing more tracking than the mobile web experience. My background is black because the phone display is OLED-based so it consumes less battery.

    The only thing I don’t like on my phone is Signal not providing a good backup system for iOS.

    I highly recommend the “DS File” app if you have a Synology server, see next paragraph. I use it to backup my photo as well as having my music and some important files (ID, passport scan etc) at hand. Also thank God for Adguard.

    Servers

    I own a Synology DS220+ at home that I use for:

    • Backing up my computer and email, photos, files… as well as some of my family members data
    • Backing up my phone (DS File for photo backup, and for everything else the backup file from iTunes)
    • Hosting this website
    • a VPN when I’m abroad or when I need
    • My addressbook server

    As it’s quite sensitive, it’s using the highest security possible. It also syncs weekly with a distant cloud in an encrypted manner, so if my house burns down or someone breaks in and steals the server (useless without the keys to decrypt content on disks of course), I still have a backup. I highly recommend this product.

    I also operate some servers, mainly rented from OVH (<3).

    HMDs

    Of course I own various AR & VR HMDs, and at Lynx we have most of what’s on the market.

  • Surviving the Hacker News “hug of death”

    A quick article to mention that one of my articles on the DNS requests made by iPhones made the front page of Hacker News for a few hours. (and it got a lot of interesting comments!)

    When your post gets on the front page, there is what we call in the community the “HN hug of death”. It describes the huge traffic you will see on the URL you shared, and sometimes your site becomes unresponsive because the server is bloated.

    To be totally honest, I didn’t suffer from it because this blog is running with a very tiny CMS (almost a static website), the server is not a small VM and the front end is not bloated with dozens of requests.

    I got 10 114 unique visitors to the blog post from Hacker News on that day, so with a well-optimized website, everything should be fine!

  • High number of DNS requests made by iOS devices

    I run a simple ad blocker based on AlgoVPN. It is a simple adblocker for iOS devices. It blocks requests at the DNS level, so it is network-wide and thus very efficient.

    The connections are strictly anonymous and very secure (the code is here), but I anonymously log the DNS requests. It is a way of monitoring the usages of my servers.

    When I tested the service on my device, I discovered that iOS communicated non-stop with Apple servers. I thought it was linked to the Push services, but I looked into the logs and here are the concerned domains that are iOS-related:

    apple.com
icloud.com
akamaiedge.net
akamadns.net
apple-dns.net
akamai.net
akadns.net
cdn-apple.com
aaplimg.com

    Here is a screenshot showing the unexpected number of requests your phone makes. Notice the activity between 3AM and 5AM (I swear I was sleeping haha).

    I haven’t tried on Android devices, but it should be interesting as well. Another experiment would be to block these domains and see the impact on your battery life 😉

    UPDATE:

    Here is what it looks like with more devices. Observe the difference of requests between the two graphs.

    Here is a breakdown of all concerned hosts in a light csv file.

    Read more on the Hacker News discussion.