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Diffraction Grating: How Thousands of Slits Turn Light into a Spectrum

Tilt a CD or DVD under a desk lamp and a band of color sweeps across its surface. The disc is not painted; it is a spiral of microscopic pits, packed so tightly that they act on light the way a finely ruled scientific instrument does. Each wavelength of white light leaves the surface at its own angle, and your eye sees the result fanned out as a rainbow. That is a diffraction grating at work. The same principle that decorates a CD is the engine inside spectrometers that identify chemical elements, tune lasers, and read the composition of distant stars. This article explains how a grating spreads light, how to compute the angles, and where the analysis goes wrong. Why this calculation matters A prism also splits white light, but a grating does it with far more control and far more precision. Because the spreading depends on a countable number — the spacing between lines — a grating can be designed to send a chosen wavelength to a chosen angle. That predictability is what makes it the heart of the spectrometer. Spectroscopy underpins a remarkable range of work. Astronomers read a star's chemistry and velocity from the dark lines in its spectrum. Chemists identify unknown compounds by the wavelengths they absorb. Telecommunications engineers use gratings to combine and separate the many wavelengths sharing a single optical fiber. In every case the first task is the same: given the grating and the light, predict the angle at which each wavelength emerges. Get that wrong and a spectral line lands on the wrong detector pixel, and the measurement is meaningless. The core formula A diffraction grating is a surface ruled with a large number of equally spaced, parallel lines. When light passes through or reflects off it, each line acts as a source of secondary waves. Those waves interfere, and they reinforce each other only in specific directions — the directions where waves from neighboring lines arrive exactly in step. The condition for that reinforcement is the grating equ

2026-07-07 原文 →
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How to Use FFmpeg with Pipedream (No Timeout Errors, No Binary Setup)

Originally published at ffmpeg-micro.com If you've tried running FFmpeg inside a Pipedream workflow, you've probably hit one of two walls: the step timed out before processing finished, or the FFmpeg binary wasn't available. These are the most common complaints in Pipedream community threads, and neither has a clean workaround. Why FFmpeg Breaks in Pipedream Pipedream workflows run Node.js steps with a 30-second default execution timeout . Paid plans extend that to 300 seconds. But even five minutes isn't enough to transcode most videos. A 10-minute 1080p file can take 3-8 minutes to process depending on the codec and output settings. Longer videos or higher-quality encodes blow past that limit every time. The timeout kills your step mid-execution. No partial output. No graceful failure. Just a dead workflow. Then there's the binary problem. FFmpeg isn't available in Pipedream's runtime environment. Developers on the Pipedream community forums have tried downloading the static binary at runtime, setting PATH variables, and running chmod inside a Node.js step. Some of these hacks work intermittently. Most break the next time Pipedream updates its execution environment. And even if you solve both problems, Pipedream steps have memory constraints that make video processing unreliable. A single high-resolution transcode can exhaust available RAM and crash silently. The Fix: Call an FFmpeg API Instead The timeout issue goes away when you stop running FFmpeg inside the workflow. Make an HTTP request to an external API instead. The API processes the video on its own infrastructure with no time limit. Your Pipedream step sends the request, gets back a job ID, and moves on. FFmpeg Micro processes video through a standard REST API, so any Pipedream HTTP step can call it. No marketplace plugin to install. No binary to configure. Just a POST request and a polling loop. This is different from tools like Rendi or Renderio.dev that require a native Pipedream marketplace integratio

2026-07-07 原文 →
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How to Use FFmpeg with Swift (No Installation Required)

Originally published at ffmpeg-micro.com You need server-side video processing in your Swift app. Maybe you're building a Vapor backend that transcodes user uploads, a macOS utility that batch-converts media files, or a command-line tool that generates thumbnails. FFmpeg is the standard tool for the job, but getting it into a Swift project isn't as simple as adding a package dependency. Running FFmpeg from Swift with Process Swift's Foundation framework provides the Process class for running external commands. If FFmpeg is installed on the machine, you can shell out to it directly: import Foundation let process = Process () process . executableURL = URL ( fileURLWithPath : "/opt/homebrew/bin/ffmpeg" ) process . arguments = [ "-i" , "input.mp4" , "-c:v" , "libx264" , "-crf" , "23" , "-preset" , "medium" , "-c:a" , "aac" , "-b:a" , "128k" , "output.mp4" ] let pipe = Pipe () process . standardOutput = pipe process . standardError = pipe try process . run () process . waitUntilExit () let data = pipe . fileHandleForReading . readDataToEndOfFile () let output = String ( data : data , encoding : . utf8 ) ?? "" print ( output ) guard process . terminationStatus == 0 else { fatalError ( "FFmpeg failed with exit code \( process . terminationStatus ) " ) } This works on macOS and Linux. Install FFmpeg with brew install ffmpeg on macOS or apt-get install ffmpeg on Ubuntu, point executableURL at the binary, and you're running. But you own that FFmpeg install on every machine. On Linux servers, you're managing the binary across deploys. On macOS CI runners, you're adding Homebrew steps to your build pipeline. And on iOS, Process doesn't exist at all. Processing Video via Cloud API (No FFmpeg Install) Skip the local binary entirely. FFmpeg Micro exposes full FFmpeg capabilities through a REST API. Send a video URL, pick your settings, get processed video back. If you're familiar with how this works in Node.js or Kotlin , the pattern is identical. Here's the basic flow using URLSe

2026-07-07 原文 →
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Show HN: InstantVideos.org – short documentaries in ~30 seconds

Hiya! So I've been playing around with having Claude make videos for a bit now even had some success posting the results to TikTok (and setup a whole pipeline so Claude can generate and post autonomously). With the release of Nano Banana 2 Lite, I was curious show fast I could make the generation, so last night I gave it a whirl and got down to around 30s for short-form video. It uses GLM-5.2 fast via Fireworks to generate the scripts and image prompts and, like I said, Nano Banana 2 Lite for th

2026-07-07 原文 →
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The ‘first’ AI-run ransomware attack still needed a human

An AI agent carried out the technical execution of a real-world ransomware attack for the first known time, but new details show a human still chose the victim, set up the infrastructure, and supplied stolen credentials — meaning it wasn't quite the fully autonomous cybercrime debut that last week's headlines suggested.

2026-07-07 原文 →