A few months ago I didn't know much about coding. Today I have a full stack marketplace running with a real API, a live database, user authentication, image uploads, messaging and a React frontend. The Idea Kisumu has a huge secondhand clothes market. Mitumba is everywhere — Kibuye market, roadside stalls, WhatsApp groups. But there is no dedicated digital platform for it. If you want to sell a jacket in Kondele you have no easy way to reach buyers in your area. If you want to find size L shoes in CBD you have to physically go and look. I wanted to build something that solved a real local problem. Not another todo app. Not another weather app. Something that could actually help people in my city. That is how Kisumu Marketplace was born. The Tech Stack I Chose I built the backend in Go using the Gin framework. The database is PostgreSQL hosted on Neon.tech — a free cloud database that saved me more than once when my laptop broke. Authentication uses JWT tokens and bcrypt for password hashing. Images are uploaded to Cloudinary. The frontend is React with Tailwind CSS. I chose Go because Zone 01 teaches it and I wanted to go deep on one language rather than shallow on many. I chose PostgreSQL because it is the industry standard and learning it properly matters. I chose React because it is the most in-demand frontend framework and I wanted to build something real with it. What I Learned I learned Go from scratch while building this. I learned React from scratch while building this. I learned PostgreSQL, JWT, bcrypt, Cloudinary, Tailwind, axios, React Router and more — all by needing them for this project. The most valuable thing I learned is that you understand something properly only when you build with it. Reading about JWT is nothing like debugging a 401 Unauthorized error at midnight. I also learned that documentation is a skill. Writing this article, explaining how things work, is making me understand my own project better.

📦 Code: github.com/USER/hls-multi-audio - replace before publishing TL;DR We'll add a working language picker to an HLS player. The hard part isn't the dropdown, it's the manifest. We'll author alternate audio with EXT-X-MEDIA audio groups, package it correctly, debug the classic "zero audio tracks" bug, and wire a switcher on hls.js v1.7 . Adaptive video, captions, the whole pipeline already works. Now someone wants an English/Spanish audio toggle. In HLS, "which audio can the viewer pick" is decided at packaging time and written into the master playlist. The player just displays it. Let's build it in that order. 1. Understand the structure (audio groups) HLS decouples video variants from audio renditions: Each audio rendition is an #EXT-X-MEDIA:TYPE=AUDIO entry pointing at its own media playlist. Renditions are bundled into a named audio group via GROUP-ID . Each video variant ( #EXT-X-STREAM-INF ) references a group with AUDIO="..." . A correct master playlist: #EXTM3U #EXT-X-VERSION:6 #EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="aud",NAME="English",LANGUAGE="en",DEFAULT=YES,AUTOSELECT=YES,CHANNELS="2",URI="audio/en.m3u8" #EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="aud",NAME="Espanol",LANGUAGE="es",DEFAULT=NO,AUTOSELECT=YES,CHANNELS="2",URI="audio/es.m3u8" #EXT-X-STREAM-INF:BANDWIDTH=2128000,CODECS="avc1.640028,mp4a.40.2",AUDIO="aud" video/720p.m3u8 #EXT-X-STREAM-INF:BANDWIDTH=1128000,CODECS="avc1.640020,mp4a.40.2",AUDIO="aud" video/480p.m3u8 Every attribute earns its place: LANGUAGE - BCP-47 code, used for the label. DEFAULT - plays when the viewer has no preference. AUTOSELECT - may be auto-picked from the OS language. CHANNELS - needed so the player can reason about stereo vs surround. BANDWIDTH on each video variant must include the audio group's bitrate , or your ABR logic works from a wrong total. 2. Author the renditions with FFmpeg Extract/encode each language's audio, then package. First, encode video-only and audio-only renditions: # video only (no audio), two ladder rungs

📦 Code: github.com/USER/nvenc-vs-cpu-bench - replace before publishing TL;DR A GPU encodes faster than a CPU, but "faster" and "cheaper" are different claims. We'll build a small FFmpeg + VMAF harness that times software (libx264/SVT-AV1) against hardware (h264_nvenc/av1_nvenc), then plug the results into a dollars-per-encoded-minute formula so you find your break-even instead of trusting a benchmark blog. We're using FFmpeg 7.1.x (current stable line) and an NVIDIA GPU with NVENC. Same approach works for Intel QSV ( *_qsv ) and AMD AMF ( *_amf ) if you swap the encoder names. Why this isn't obvious NVENC is a fixed-function hardware block, not "the GPU doing x264 in parallel." It's extremely fast and barely touches the CPU, but it exposes fewer rate-control knobs and gives up a little compression efficiency versus a slow software preset. The gap has narrowed a lot, but it's still there at the quality-obsessed end. So the decision is per-job, and it comes down to one number: dollars per encoded minute = (instance $/hr) ÷ (minutes encoded/hr) . GPU instances cost more per hour but encode many streams in parallel, so the answer depends on whether you can keep the encoder saturated. Let's measure instead of argue. 1. Set up the encoders Three contenders. One representative source file (use real footage, not a synthetic clip). # software H.264, quality-leaning preset ffmpeg -y -i source.mp4 -c :v libx264 -preset slow -crf 21 -an out_cpu.mp4 # NVENC H.264, quality-tuned ffmpeg -y -hwaccel cuda -i source.mp4 -c :v h264_nvenc -preset p6 -tune hq \ -rc vbr -cq 23 -an out_gpu.mp4 # AV1: software (SVT-AV1) vs hardware (needs Ada / RTX 40+) ffmpeg -y -i source.mp4 -c :v libsvtav1 -preset 6 -crf 30 -an out_svtav1.mp4 ffmpeg -y -hwaccel cuda -i source.mp4 -c :v av1_nvenc -preset p5 -cq 30 -an out_av1nvenc.mp4 💡 Tip: -preset p1 (fastest) through -preset p7 (slowest/highest quality) for NVENC. p6 / p7 is where it competes on quality; p1 - p3 is where it competes on raw throughput.

📦 Code: github.com/USER/video-api-bench - replace before publishing TL;DR The per-minute delivery rate is the easiest number to compare and the least useful. The real cost lives in encoding, analytics, and the player. This post compares Mux, Cloudflare Stream, api.video, FastPix, and AWS on what each includes by default, then gives you a tiny script to benchmark upload and time-to-ready on your own files so you stop trusting marketing pages. I have shipped video on four managed APIs across three jobs, and every single time the invoice surprised someone. Not because the delivery rate was wrong, but because encoding, analytics, and the player turned out to be separate line items on some platforms and free on others. Let's compare the parts that don't show up in the headline number. ⚠️ Note: pricing pages move. Everything here was checked in June 2026; verify the links before quoting numbers. 1. Encoding: free or metered? This is the widest spread in the whole comparison. Platform Encoding Delivery Storage Cloudflare Stream Free $1 / 1,000 min delivered $5 / 1,000 min stored api.video Free (unlimited) $0.0017 / min $0.00285 / min FastPix Free on standard plan ~$0.00096 / min @1080p Per-minute, tiered Mux Metered per minute Per minute Per minute AWS (DIY) Per minute (MediaConvert) Per GB (CloudFront) Per GB (S3) If your catalog is upload-heavy (lots of assets encoded once, watched rarely), metered encoding is not a rounding error. It can flip which platform is cheapest, even when the delivery rates look identical. 2. Analytics: included or a $499 floor? QoE analytics is the feature teams forget to price until playback breaks in production. Platform QoE analytics Entry cost FastPix (Video Data) Session-level, 50+ signals/session Free up to 100K views/month Mux (Mux Data) Mature, broad device SDKs $499/month (Media plan, 1M views, +$0.50/1K) Cloudflare Stream Basic Included, limited depth api.video Available Usage-based AWS Build it yourself (CloudWatch + logs) Engineerin

TL;DR If your product lets strangers upload video, you need moderation before launch, not after the first bad upload. We will build a small-team pipeline: extract frames with FFmpeg, score them with NudeNet (ONNX Runtime, CPU-friendly), route uploads into approve / human-review / block by confidence, and log every decision. No trust-and-safety department required. 📦 Code: github.com/USER/ugc-moderation, replace before publishing ⚠️ Note: this is a sensitive area. The goal here is the engineering shape (sampling, scoring, routing, auditing), not detection of any specific content. Keep test fixtures clean and lawful. A model does not decide what is allowed. It produces a score. You decide where the lines go. The whole design is about routing scores sensibly and sending the uncertain middle to a human. The architecture 🧠 upload ──> extract sample frames (ffmpeg) ──> score frames (NudeNet / ONNX) ──> aggregate to one confidence ──> route: high-confidence clean -> auto-approve uncertain middle band -> human review queue high-confidence violation -> auto-block ──> write an audit record for every decision The economics only work if the middle band is small. A decent model makes most uploads obviously fine or obviously not, so a human only ever sees the genuinely ambiguous slice. 1. Sample frames, do not score every frame You cannot afford every frame and you do not need it. Pull one frame per second (or scene-change keyframes) with FFmpeg. # extract 1 frame per second into ./frames mkdir -p frames ffmpeg -i upload.mp4 -vf "fps=1" -q :v 3 frames/frame_%05d.jpg Prefer scene changes to catch more variety with fewer frames: # keyframes where the scene actually changes ffmpeg -i upload.mp4 -vf "select='gt(scene,0.3)',showinfo" -vsync vfr frames/scene_%05d.jpg 💡 Tip: a 30-minute upload at 1 fps is ~1,800 frames. Scene-change sampling often cuts that by an order of magnitude with little loss for moderation purposes. 2. Score frames with NudeNet NudeNet runs on ONNX Runtime on pla

TL;DR Converting HDR10 to SDR with a naive FFmpeg command gives you grey, washed-out video. The fix is tone mapping. We will detect HDR with ffprobe , run two working tone-map chains ( zscale on CPU, libplacebo on GPU) in FFmpeg 8.0, compare operators, and batch it. Test the commands on your own build before shipping. 📦 Code: github.com/USER/hdr-to-sdr, replace before publishing If you have ever run an HDR clip through your normal pipeline and gotten back something flat and foggy, this post is for you. The bug is that HDR and SDR are different color systems, and "just converting" reinterprets one as the other. We will use FFmpeg 8.0 "Huffman" (8.0.2 is current as of May 2026). Why naive conversion fails HDR10 SDR Transfer function PQ (SMPTE ST 2084) gamma 2.4 / BT.1886 Color primaries Rec.2020 (wide) BT.709 (narrow) Peak luminance ~1,000 to 4,000 nits ~100 nits A command that ends in -pix_fmt yuv420p with no tone mapping reads PQ-encoded, Rec.2020 values as if they were SDR. The gamut gets crushed with no intelligence and the brightness curve is misread. Hence the fog. 1. Detect whether a file is even HDR 🔍 Do not tone-map SDR files. Check first: # detect transfer characteristics and primaries ffprobe -v error -select_streams v:0 \ -show_entries stream = color_transfer,color_primaries,color_space \ -of default = noprint_wrappers = 1 input.mkv HDR10 content reports something like: color_space = bt2020nc color_transfer = smpte2084 color_primaries = bt2020 If color_transfer is smpte2084 (PQ) or arib-std-b67 (HLG), you have HDR and you need to tone-map. If it says bt709 , leave it alone. 2. The libplacebo path (GPU, my default) 🚀 libplacebo is the Vulkan-accelerated filter in FFmpeg 8.0. It follows the ITU tone-mapping recommendations and handles the color conversions internally, so the command is short: ffmpeg -i input.mkv \ -vf "libplacebo=tonemapping=bt.2390:colorspace=bt709:color_primaries=bt709:color_trc=bt709:format=yuv420p" \ -c :v libx264 -crf 20 -c :a copy \ ou

"It works on my test input" is the most dangerous sentence in on-device AI development. I typed that sentence - or some version of it - a dozen times while building Redacto, our on-device PII redaction app running Gemma 4 E2B on a Samsung Galaxy S25 Ultra. The model would redact a patient name from a clinical note, I would nod, and I would move on. Then I would hand the phone to a teammate, they would type a police report, and the model would redact the suspect description instead of the victim name. The problem is not the model. The problem is that manual spot-checking is not validation. You are testing a single input against your own expectations, with all the confirmation bias that entails. When you have five domain modes (HIPAA, Financial, Tactical, Journalism, Field Service), three difficulty levels, and two candidate models, you need something systematic. You need a benchmark suite. This post covers how I built one - from dataset curation to scoring methodology to on-device infrastructure - for a hackathon app running entirely on a phone. No cloud. No API calls. No data leaving the device. Why Not Use an Existing Framework? The LLM evaluation space has mature tools. EleutherAI's lm-eval-harness is the community standard for evaluating language models against academic benchmarks like MMLU, HellaSwag, and ARC. Stanford's HELM (Holistic Evaluation of Language Models) provides a multi-metric evaluation framework with standardized scenarios. Google's BIG-bench offers hundreds of tasks for probing specific capabilities. These frameworks are excellent for what they do. They are also completely wrong for this problem, for three reasons. First, they assume server-side inference. lm-eval-harness expects to call a model through an API or load it in PyTorch on a GPU server. Redacto's model runs on a Qualcomm Hexagon NPU inside a phone. There is no Python runtime, no HuggingFace tokenizer at evaluation time, no way to hook into the framework's inference loop. Second, their

Plenty of SEO audits end with a single tool report. You run Lighthouse, screenshot Search Console coverage, save a "12 issues found" panel, and call it done. The trouble is that most audits finished that way silently revert within three months. Someone publishes a new post, refactors a component, swaps a font, and the issue quietly comes back. Nobody notices. Over the last five days I actually audited my four-language blog (ko/ja/en/zh, 298 posts per language). Five items, all fixed. But what I really want to talk about isn't what I fixed. It's that the five fixes mattered less than the build gates that keep them from ever returning. An audit should be a loop, not an event. Why a one-report audit always comes back Most technical SEO issues aren't "the code is wrong." They're "an invariant was never enforced anywhere." Take a clear rule: a published post must not link internally to a draft. Obvious enough. But if a human has to remember that every time, then the moment a recommendation generator pulls in one draft slug, a 404 is born. The report catches that 404 and shows it to you, but it does nothing to prevent the next one. So I ran the audit as a three-step loop. Measure. Fix the biggest item first. Then turn that item into a checker and nail it to the build . Skip the third step and the first two become a chore you repeat every six months. Once a gate is in place, the same class of problem makes npm run build fail. A pipeline enforces the rule, not human memory. This isn't a new invention. It's the same logic by which tests prevent bug regressions, applied to the content and markup layer. It's just oddly rare in SEO, where most teams leave "SEO checks" as a quarterly manual task. The five items I actually ran over five days Measurement first. Each item got a before/after in numbers, not a vibe that "things feel better" but reproducible figures. (The raw log of all five lives on the improvement history page too.) Date Item Before After Gate 07-02 relatedPosts int

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