Sam Debruyn

Cloud Data Solution Architect

Specialized in Microsoft Azure, Fabric & modern data stack. Microsoft Data Platform MVP. Public speaker & meetup organizer. FOSS contributor.

Sam Debruyn

Create App Previews with the iOS Simulator

2 minutes

I don’t always have a ton of iOS devices lying around when I submit iOS apps to iTunes App Store Connect.

So I take my screenshots on the simulators. At the time of writing Apple requires screenshots made with an iPhone 8 Plus and an iPad Pro. You can optionally add screenshots from an iPhone XS Max. Apple then downscales them to all other iPhones or you can add screenshots for the other models yourself.

Apple recently introduced App Previews . These are short videos that demonstrate how your app works. These can also be created using the simulator.

Screen recording from the simulator

This records the screen of your simulator and saves it to the current directory. Use CTRL+C to stop recording.

Make sure your video is between 15 and 30 seconds long.

xcrun simctl io booted recordVideo

Convert to the required format

For a 5.5 inch iPhone, Apple requires 30 full HD frames per second, a stereo audio stream and the H264 format.

Use homebrew to install ffmpeg:

brew install ffmpeg

Convert your video to the correct format using ffmpeg:

ffmpeg -f lavfi -i anullsrc=channel_layout=stereo:sample_rate=44100 -i -vf scale=1080:1920 -map 0:0 -map 1:0 -shortest -strict experimental -r 30 -y apppreview.mp4

Now upload your video using Safari and you’re done.

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Optimize memory usage in Xamarin apps

10 minutes

This post has been translated to Russian by Denis Gordin . You can read the Russian version on the Russian website TechMedia . Thanks, Denis! Xamarin is amazing in how it allows .NET developers to write apps for Android, iOS, MacOS… in C#. But that amazing capability comes with a prize and even the most simple apps can suffer from high memory usage.

Diagnosing memory issues with the Xamarin profiler

5 minutes

The Xamarin profiler is a must-have tool for every Xamarin developer. The profiler comes with a Xamarin business or enterprise license and is available as a standalone installer at . To get started, make sure a debug version of your app is installed on a device or a simulator (works both for Android and iOS).